Battery Basics

Questions and Answers – What you need to know.

A battery is a source of electrical energy. Its smallest unit is called a (galvanic) cell. A battery usually consists of several individual cells electrically connected in series. The chemical energy as stored in each cell is converted directly into electrical energy when its terminals are connected to an electrical consumer.

A galvanic cell also needs two substances for energy conversion, represented by two electrochemically active electrodes of different composition, both of which are immersed in an electrolyte which provides a conductive medium between them.

One of the electrodes uses a metal such as zinc or lithium. Within the electrolyte it establishes a negative potential and consequently represents the negative electrode. The other electrode consists of an electron conducting compound which is rich in oxygen, e.g. manganese dioxide, silver oxide, nickel hydroxide or atmospheric oxygen in combination with a suitable oxygen electrode. This electrode establishes a positive potential within the electrolyte and consequently represents the positive electrode of the electrochemical system. Depending on the electrochemical system, the cell voltage will be between 1.2 V and 4 V. When connecting the system to an external load, electrical energy will be taken out of the system, while the chemical energy stored inside the cell or battery will be used up.

The smallest electrochemical unit of a battery is called a cell. The cell does not yet have a completed housing or ready-to-use contacts, and is usually connected with its neighboring cell within the battery via soldered or welded contacts.

In contrast to a cell, a battery is easily recognized by its completed housing fitted with ready-to-use contacts. Furthermore the housing is clearly labeled with the manufacturer's name, type designation, battery voltage, etc. Since single cells are frequently offered with the above attributes of a battery, it has also become customary to refer to this type of single cell as a battery

The kind of electrochemical system decides whether the system is a rechargeable one or not. Truly rechargeable systems are reversible systems with regard to their electrochemistry and the structure of their electrodes. In an ideal system, this reversibility must not be affected by the number of charges and discharges (cycles). Since charges and discharges also cause a reversible change in electrode volume and structure, the design of a rechargeable battery must be adequate to accommodate these changes. Since a primary battery undergoes just one discharge, its internal construction is generally more simple as it does not have to accommodate reversible volume changes. No attempt should be therefore made to recharge primary batteries. This is both dangerous and uneconomical.

If a rechargeable system is required, the only sensible choice is to select a truly rechargeable system which permits more than 1,000 safe cycles. Batteries of this type are also referred to as Secondary Batteries or Accumulators.

Other marked differences between rechargeable (secondary) and primary battery systems are their weight-related energy content, the weight-related load capability and the rate of self-discharge.

The weight-related and volume-related energy density of primary batteries is generally far higher than secondary batteries, whereas their load capability is relatively small. Secondary batteries have a higher load capability. Rechargeable lithium-ion batteries, as developed in recent years, boast a high weight-related energy content. The rate of self-discharge is favorably low for all primary batteries, regardless of system.

Different devices operate at different voltages and power levels. They all require batteries that provide the necessary power output at a minimum discharging voltage. The voltage of a given battery depends on the number of single cells connected in series and on their electrochemical system. For instance, a lithium-manganese-dioxide cell has a nominal voltage of 3 V, a rechargeable lead-acid cell offers 2 V, while an alkaline-manganese cell has an initial voltage of approx. 1.5 V, that decreases during discharge to 0.9 V and below.

The capacity of a battery is determined by the amount of chemical energy stored inside its housing. It determines - for a given current of a given device - the service life of the battery.

In order to properly operate a specific electrical device,

• the battery's operating voltage must be matched to that of the device;
• the correct battery capacity must be selected in order to provide the necessary operating time for the device;
• the battery must be able to deliver the power required: its internal resistance must be smaller than that of the device.

In principle, no battery can be stored without loss of energy, although some battery systems may be stored for longer periods of time than others. Processes inherent to the battery's electrochemical system cause a gradual, but unavoidable loss of usable energy which, however, is predictable. The best known process is "self-discharge". This generally has to do with the electrolytic solubility of the positive electrode material or its thermodynamic instability (e.g. spontaneous decomposition).

Self-discharge in rechargeable batteries (secondary batteries, accumulators) is particularly high in comparison to primary batteries. At room temperature the rate of self-discharge is in the range of 15% to 25% per month, depending on the system. Of the rechargeable systems, solar batteries have an unusually low self-discharge rate of only 10% per month.

Electrochemical self-discharge in primary batteries is considerably lower, and may even be below 2% per year at room temperature. However, various processes take place in parallel with this which lead to an increase of the battery's internal resistance during storage. These processes lead to a reduction in load capability. Loss of usable energy becomes noticeable only at relatively high discharge rates (e.g. motor applications, flashlights etc.). This effect, however, has nothing to do with self-discharge. At low discharge rates the increased internal resistance which occurred during storage will not be detectable.

Under normal storage conditions, the following approximate values apply to self-discharge:

A general rule is: The higher the storage temperature, the worse the capacity retention and vice versa. A refrigerator, with a temperature range from 0°C to 10°C, is a good place for storing batteries, especially primary batteries. The refrigerator may, of course, also be used to store secondary batteries, but since they are rechargeable, their loss of capacity during storage may be better compensated by recharging, particularly as they can take up substantial space in the refrigerator (e.g. automotive batteries)

The electrical energy E delivered by a battery to an electrical device may be computed by formula

E = V x I x t, where V is the battery's discharging voltage (in volts), I is the discharging current (in amperes) and t is the time of discharge (in hours). The unit of energy E as computed by the above formula is given in watt x hours.

A battery's power output refers to its ability to deliver a specific amount of energy within a fixed period of time. The power output P of a battery is calculated from the product of the discharging current I (measured in amperes) and the discharging voltage V (in volts), thus : P=I x V. The power output is expressed in watts.

The smaller a battery's inner resistance, the higher its possible power output. Its inner resistance must always be smaller than that of the electric device to be operated. Otherwise the battery voltage would break down, i.e. the battery would be unable to operate the device. At a given discharging voltage, a battery's power output increases with increasing electrode surface and operating temperature, and vice versa.

The terms "dry battery" and "liquid battery" are restricted to primary systems and date from the early development of galvanic elements. At that time, a liquid cell consisted of an electrolyte-filled glass container into which electrochemically active electrodes were immersed. It was only later that unspillable cells which could be used in any position and had a completely different construction were introduced, these being similar to today's primary batteries. These earlier cells were based on paste electrolytes. At that time they were known as dry batteries. In this sense today's primary batteries are also dry batteries.

The term "liquid battery" is in principle still applicable to certain modern secondary batteries. For large stationary lead-acid or solar batteries, liquid sulfuric acid is preferred for the electrolyte. For mobile applications unspillable, maintenance-free lead-acid batteries are recommended and have been available for many years. Their sulfuric acid is immobilized by a gel (or a special microglass mat).

Of all environmental factors, the temperature has the greatest effect on battery charge and discharge behavior. This has to do with the temperature- dependent electrochemical reactions occurring at the electrode/electrolyte interface, which may be considered the heart of the battery. If the temperature decreases, the rate of electrode reaction decreases too. Assuming the battery voltage remains constant, the discharging current drops and thus the power output of the battery. The opposite effect occurs if the temperature rises, i.e. the power output of the battery increases.

The temperature also affects the speed of transport processes within the electrolyte and its porous electrode. A rise in temperature accelerates transport processes, a decrease in temperature slows them down. The charge / discharge performance of the battery may also be affected.

The effect of the relative humidity depends on the battery system. It plays a key role in "open" battery systems (unlike closed battery systems). Its effect can also be crucial, as in zinc-air batteries (most frequently used for powering hearing aids). The unique feature of a zinc-air cell is that it is in direct contact with the surrounding atmosphere. It will therefore begin to dry out if the atmosphere is too dry. If the relative humidity of the environment is too high, the system will begin to pick up water. Both scenarios have an adverse effect on the performance of the zinc-air cell.

An "external short circuit" can occur if the external terminals of a battery are bridged by any kind of conducting material. Depending on the battery system, a short circuit may have serious consequences. For example, the temperature of the electrolyte may rise, thus building up an internal gas pressure which may open the pressure valve of the battery and eject electrolyte from the battery. This can cause injuries. In extreme cases a detonation may even occur if the safety vent fails to respond (due to e.g. a molding defect during production).

You should therefore ensure that, for example, you do not carry charged or fresh batteries in the same pocket as coins or bunches of keys. Otherwise they may bridge the battery's terminals.

It is also important to avoid mechanical impacts which could deform the battery and result in internal electrode short circuits with the consequences described above.

A portable battery is primarily a battery which provides electrical energy to operate portable, cordless equipment. In a more generalized definition it also includes batteries that only operate certain sub-devices within a larger system (which may be operated by the mains), e.g. a desktop computer. Sub-devices of the above kind may be a computer's internal clock or a memory backup. Larger batteries (e.g. four kilograms and above) are no longer considered portable. Today's typical portable batteries will weigh several 100 grams. The portable battery family includes both primary and rechargeable (secondary) batteries. Button cells belong to a special group of their own.

"Leakage" (visible loss of electrolyte) was an annoying, discharge-related phenomenon of zinc-carbon batteries, which were one of the most popular battery types until the end of the 1970s. The zinc can of this system, which serves as the anode, was perforated by the electrochemical oxidation of the zinc, thus causing the electrolyte leakage. Furthermore, zinc chloride was chosen as the prevailing electrolytic component. This produces a reaction product that absorbs water. Under extreme conditions, however, a zinc-carbon battery may still leak, if e.g. a flashlight is left switched on for weeks or months. Even if it no longer provides any light, the electrochemical reaction continues as long as positive electrode material is available.

A further improvement in the area of leak-proof batteries was achieved by the development of the alkaline-manganese battery (also called ALKALINE). For some years now, Varta has been selling only alkaline-manganese and zinc-carbon primary batteries of improved design and chemistry. Today, all portable batteries are leak-proof under normal operating conditions.

Yes, they do. The alkaline-manganese battery has nearly twice the energy content of a zinc-carbon battery of the same size, even at higher loads. This battery is particularly suited for continuous discharge. For low power applications (such as transistor radios) or applications using discontinuous discharge regimes (e.g. flashlights), the zinc-carbon battery still represents an interesting and inexpensive alternative. The on-load period should preferably not exceed five minutes at higher loads. This limitation does not apply for the more expensive alkaline-manganese batteries.

Batteries standardized by the IEC (International Electrotechnical Commission) have a clear, internationally valid designation. However, the use of this designation is voluntary, so it will not necessarily appear on every primary battery. Nevertheless, the manufacturer's designation and the battery voltage are always printed on the battery housing. Reference is often made to the battery's electrochemical system. The way it is specified, however, may vary from manufacturer to manufacturer.

An alkaline-manganese round cell can be "recharged" about 20 times. In reality, however, this is not a true recharge process as offered by secondary batteries, because they do not permit a normal deep discharge like a true rechargeable battery, but only a partial discharge. Consequently, the recharge process is also only a partial one, and which therefore should be better called "regeneration" to differentiate it from a true recharge as offered by secondary batteries. The serious limitation of its charge/discharge behavior and its very short "cycle life" renders the regeneration of an alkaline-manganese battery rather uneconomical.

Various conditions must be met in order to ensure the successful regeneration of alkaline-manganese batteries:

1. A "regeneration" is possible only if a maximum 30% of the battery's initial capacity is withdrawn at moderate discharge rates, whereby the discharging voltage should not drop below 0.8 V. When removing more than 30% of the capacity, an irreversible manganese dioxide structure will develop that prevents any further "regeneration". The "30% capacity point" and the 0.8 V discharging voltage can only be monitored by use of proper measuring instruments, which the average consumer does not possess.

2. Alternatively, the user would need to buy a recharger for performing regeneration. Other charging devices like chargers for rechargeable nickel-metal-hydride or nickel-cadmium accumulators should never be used, because their charging current may be too high and may lead to gas generation inside the battery, which in turn may lead to the safety vent opening and electrolyte being ejected. In extreme cases an explosion may even occur if the safety vent fails to respond (due to e.g. a molding defect during production). Cases like this happen very rarely, nevertheless they can happen, especially if the battery is not used properly.

3. The length of time needed for "regeneration" (approx. 12 hours) is out of all proportion to the discharge time (approx. 1 hour).

4. After about 20 partial cycles at the very latest, the battery's capacity will have dropped to about 50% of its initial value.

5. If a given device needs more than three batteries connected in series, an additional problem will arise if the batteries have differing capacities as a result of "regeneration". This can lead to a voltage reversal of the weakest battery. This danger is particularly likely if regenerated batteries are used together with fresh ones. A battery reversal leads to hydrogen evolution inside the battery, with the danger that unacceptably high pressures will build up. This can result in electrolyte being ejected and even an explosion!

Every battery constitutes an electrochemical energy converter capable of converting stored chemical energy directly into electrical energy. In the case of a secondary battery (also called "accumulator") - a technology which also includes rechargeable portable batteries - the chemical energy - as converted into electrical energy during discharge - may be restored by a charging process during which electrical energy is reconverted into chemical energy. This procedure (cycle) can be repeated for more than 1,000 times.

Rechargeable portable batteries are available in various electrochemical systems, i.e. the lead-acid system (2 V/cell), the nickel-cadmium system (1.2 V/cell), and the nickel-metal-hydride system (1.2 V/cell). One new development is the rechargeable lithium-ion battery (3.6 V/cell), which is not yet generally available, however. This system has both a relatively high energy density and a high load capability. Its discharging voltage decreases with the discharge depth. Typical for rechargeable portable batteries with alkaline or acid electrolyte is their relatively constant discharging voltage. This breaks down rapidly at the end of the discharge procedure.

Rechargeable batteries have the advantage of a long service life. They can be recharged more than 1,000 times. Even though they are somewhat more expensive than primary batteries, they become quite economical for frequent use.

Rechargeable portable batteries have a lower capacity than same-sized alkaline-manganese or zinc-carbon batteries, i.e. they discharge faster. Another disadvantage of the "rechargeables" is that due to their nearly constant discharging voltage, it is difficult to predict when end of discharge will come. When end of discharge is finally reached, its voltage may collapse unexpectedly - a fact that can have particularly annoying consequences, e.g. when using cameras. On the other hand, rechargeable batteries offer a higher load capability than most primary batteries. For Example, the latest NiMH technology in the most popular AA size battery is typically aimed at the once non-feasible high drain consumer applications such as digital cameras. This is coupled with the fact that primary batteries are usually disposable and secondary batteries may be recharged and used in some cases more than 1,000 times. (insert discharge curves)

Recently developed rechargeable lithium-ion power packs may provide additional opportunities for camera applications. Their characteristics include high load capability, high energy density and a decrease in discharging voltage with increasing discharge depth (from 4 V to about 3 V).

The answer is no. The alkaline-manganese battery discharges over the voltage range 1.5 V (fresh) and 0.9 V (final discharging voltage according to IEC), whereas rechargeable portable batteries (nickel-cadmium or nickel-metal-hydride) discharge at a virtually constant voltage of 1.2 V/cell. This voltage level is roughly equivalent to that of the average discharging voltage of an alkaline-manganese battery. Therefore, exchanging a rechargeable, portable battery for an alkaline-manganese battery or vice versa should never be a problem.

Rechargeable batteries are particularly well-suited for devices requiring a relatively high power, i.e. for devices requiring high energy development over a short period of time, e.g. portable cassette players, portable Compact Disc players, portable cassette radios, electronic games, motor-driven toys, various household appliances, professional cameras, camcorders, mobile telephones or cordless telephones, notebooks, and other equipment having medium to high power requirements.

Rechargeable portable batteries are not recommended if a device is rarely used (a rechargeable battery loses up to 1% of its capacity every day). On the other hand, a rechargeable battery may be necessary if the device's power consumption is too high to be met by an alkaline-manganese battery. Rechargeable batteries have far higher power reserves than alkaline-manganese batteries. In general it is wise to follow the appliance manufacturer's guidelines for battery selection as given in the operating instructions.

Yes, this depends on the system. At temperatures below -15°C a drop in power output is quite noticeable for nickel-cadmium and nickel-metal-hydride batteries. At -20°C the alkaline electrolyte reaches its freezing point. The maximum permissible temperature for the charging process is +45°C. Above this temperature the charge acceptance is reduced.

The charger must meet the requirements of the battery system (see description). A low price is not necessarily the best argument for buying a charger. Low-quality or unapproved chargers of unknown makes may damage the battery, thus obliterating the original savings.

A good charger has the following features:

• Quick charging mode: In order to use battery operated devices extensively, it is often important to be able to recharge batteries in one or two hours.
• Overload protection: Good chargers have a timer or a temperature sensor. With these features, the charging process ends as soon as the battery has been fully charged. Unnecessary overloading can thus be avoided.

Furthermore, good chargers carry the manufacturer's name and type designation and are sold together with a relevant technical data sheet and instructions.

Some practical tips:

• Never charge primary batteries! High currents could lead to leakage or even an
• Insert the rechargeable battery correctly into the charger - note the polarity!.
• Charge secondary batteries to 100% of their rated capacity prior to first use (they are uncharged at the time of purchase). It is best not to use the quick-charge mode when charging them the first time.
• Make sure that secondary batteries are always fully charged. In order to achieve the maximum operating time (i.e. maximum capacity), it is essential that nickel-cadmium batteries are discharged completely before being recharged. Maximum capacity may not be realized after initial charging or when charging the batteries after a longer idle period. The battery's maximum capacity will be restored following repeated cycling (full discharge and recharge).
• Do not charge rechargeable batteries at temperatures below 0°C. After charging, however, they may be discharged at lower temperatures.
• As a general rule with NiCd and NiMH 1.2V per cell technology you have to input 140% of the batteries rated capacity to fully charge that battery.(i.e. 140% in to get 100% out allowing for a condition known as thermal runaway). This is usually why batteries are charged at the 0.1C rate for 14-16 Hours on standard charging parameters. (10% of cells rated capacity (0.1C) for 14-16 hours).
• When charging at rapid rates ( e.g. 1C rate = 100% of rated capacity) it is usually recommended that 120 – 130% input is only needed.

At -20°C discharge becomes difficult because the electrolyte freezes at this temperature.

If nickel-cadmium batteries are recharged before they have been fully discharged, cadmium crystals can form at their negative electrodes. This results in an unwanted second discharge stage. The battery stores this stage as a discharge stage for the next cycle in its memory, even though capacity is still available 'below' this. During the next discharge process, the battery only remembers this reduced capacity. Any further incomplete discharge cycles which follow will aggravate this situation still further and the performance of the battery will continue to fall. Nickel-cadmium cells should therefore be discharged fully at occasional intervals. This prevents the 'memory effect' from occurring and prolongs the service life of the cell or battery. This effect does not occur with nickel-metal-hydride batteries. Consequently, these batteries can be discharged and recharged without problem.

The memory effect is a phenomenon which can quickly end the useful service life of a Ni-Cd battery if handled incorrectly. The technical explanation for this is as follows: If you trickle charge a Ni-Cd battery (with low current) or charge it before it is fully* drained (i.e.perform only partial discharges), certain chemical compounds are formed on the negative electrode. If you continue to charge the battery like this, the compounds build up. This has the effect of gradually reducing the available energy until the battery only supplies the required voltage for a few minutes.

The memory effect is linked with the properties of the negative Cadmium electrode, and thus only occurs with Nickel-Cadmium batteries. You should never recharge these on an ongoing basis, but should always allow them to be drained until the device ceases to operate.

* The expression "fully" implies draining the battery until the device cut-off voltage is reached. With round cells, this is between 0.8 and 1.0 Volt. Draining a battery completely to the voltage of 0.0 V may destroy the battery.

No, because each charger employs a specific charging technology which is matched to a given electrochemical system, e.g. lithium-ion, lead-acid or nickel-metal-hydride. They differ not only in their voltage characteristics, but also in their charging mode, e.g. only quick chargers which have been specially developed for nickel-metal-hydride batteries will ensure optimal charging results for this system. Former chargers for nickel-metal-hydride batteries can continue to be used, but may need more time to fully charge the battery. Care must be taken when using a charger that does not meet the required charging conditions for a given electrochemical system, even if it carries a label that seems to signal "officially approved". A label of this kind may only state that the device was wired according to the county of manufactures standards and approval ratings. This type of label does not make any reference to the charger's suitability for a specific battery system, but only complies with the laws and standards of the country that the charger is sold in. With cheap devices of this kind, charging nickel-metal-hydride batteries can be both dangerous and lead to unsatisfactory results. This warning also applies to chargers developed for other systems (e.g. lead-acid accumulators).

No - not if a high-quality charger is employed. High-quality chargers have either a timer or thermo-sensor to ensure that the charging process is terminated as soon as the battery is fully charged. This eliminates any risk of overcharge.

Yes - if chargers of unknown quality and with insufficient instructions may not meet these requirements. If used, the battery may overheat due to overcharging and may be damaged as a result.

A "button cell" should actually be better called a "button battery", because it has the external attributes of a battery. Its popular name, however, is "button cell". A button cell may be defined as a battery whose diameter is equal to or larger than its height. Present dimensional limits for button cells using an aqueous electrolyte range from a) diameter: 4.8 mm to 11.4 mm, b) height: 1.05 mm to 5.4 mm. Depending on the electrochemical system their nominal voltage is either 1.2V, 1.35V, 1.4V, 1.5V or 1.55V. Batteries of this family were given this name because of their visual similarity to buttons. Coin Cells also belong to the group of button cells.

Certain cameras and electronic devices have specific voltage requirements and rely on the use of mercury button cells to work properly as they need a more stable voltage during discharge. Nevertheless, because of the battery's mercury content (30% pure mercury) the composition of these cells is considered a danger to the environment if not disposed of in a correct manner. For this reason all battery manufacturers will have ceased production of mercury cells by the turn of the century. With the development of the zinc-air button cell, manufacturers like Varta have achieved their goal for one essential application: hearing aids.

The zinc-air battery is activated if exposed to air. The activation occurs as soon as the self-adhesive film is removed, thus opening the battery's air access hole(s) to the atmosphere. The oxygen in the air is electrochemically activated via an air electrode inside the battery. As the air electrode requires far less volume than, e.g. a silver-oxide electrode, far more zinc can be accommodated inside the button cell housing. Thus the zinc-air cell has a very high capacity, far more than all other button cells and even lithium cells. In addition the zinc-air battery offers a high load capability.

Button cells should preferably be used in a temperature range from +10°C to +35°C. Permissible minimum and maximum temperatures are -10°C and +65°C respectively. The temperature range for zinc-air button cells is more restricted.

Coin cells (coin-shaped cells) are also button cells. However, their diameter/height ratio is particularly large. All coin cells use lithium

systems. Their smallest diameter is 10 mm, their largest 30 mm. Heights range from 1.2 mm up to 5.4 mm.

Yes, there are various types of rechargeable button cells available, primarily using nickel-cadmium and nickel-metal-hydride technologies. Rechargeable lithium button cells have recently been introduced to the market. At present they are generally sold with their devices they are used in. It is currently difficult to purchase them through normal retail channels.

Automotive Batteries (SLI-Batteries)

An SLI battery is an automotive battery and stands for Start, Light and Ignition. Two substances dominate a standard SLI battery: lead and sulfuric acid. The positive electrode consists of lead-dioxide, the negative electrode is composed of finely distributed sponge lead. The sulfuric acid forms the electrolyte, ensuring the flow of ionic current between the battery's electrodes. The sulfuric acid's maximum conductivity is obtained at a gravimetric density of 1.28 kg/l. This is a typical acid density.

In an SLI battery, positive and negative electrodes are alternately welded to electrode stacks and set into the battery housing. A separator is placed between them to electrically isolate the positive and negative electrodes from each other. Six of these series-connected electrode stacks form a 12V battery.

As soon as the engine starts running, the battery charging process is initiated by means of the alternator. The result of the recharging process is that the lead sulfate formed during the discharge process will again become lead dioxide, lead and sulfuric acid, thus restoring the necessary chemical energy to be converted into electrical energy in future use.

The optimal charging voltage of the car's voltage regulator is 14.2V. If the regulator voltage is set too high, water will be electrolyzed. This lowers the electrolyte level over time. If the regulated voltage is set too low, the battery will not be charged properly, this also shortening its life span.

Audio/Video/Photo Equipment

If a portable cassette player or portable Compact Disc player is used only occasionally, it is preferable to use alkaline-manganese primary batteries instead of accumulators because of the letters' relatively high self-discharge. However, if this type of equipment is to be used more frequently, e.g. on a daily basis, it may be advantageous to use rechargeable nickel-metal-hydride batteries. However, it is important to remember that they need to be recharged regularly, since they cannot match the single-charge capacity levels of alkaline-manganese primary batteries. When using accumulators intensively it is advisable to ensure you always have a fully charged spare set at hand.

This depends very much on the type of camcorder and the kind of usage. The operating time of nickel-metal-hydride accumulators is up to 40% longer than that offered by traditional nickel-cadmium accumulators of the same weight and volume. This is due to the higher capacity. Typical operating times for the latest nickel-metal-hydride range from 1 hour to 6.5 hours dependent on the wattage, accessories and age of the camera and the capacity of the battery.

This is a rechargeable battery designed for both 8 mm and VHS video camcorders. One side of this battery carries the contacts for an 8 mm camcorder and the other side those for the VHS system. These universal accumulators or "multifits" were developed to fit about 1,000 different camcorder models; there are some 8 mm or VHS camcorders, however, which cannot use these "multifits". In this case, an expert should assist in selecting an appropriate power pack.

If the video camcorder is not in use for an extended period of time it is better to remove the power pack from the camcorder and to store it in a dry and cool place. If this is not done, a minimum amount of current will continue to be taken out of the battery by the camcorder system - even if the camcorder is switched off - which may shorten the battery's service life.

An accumulator standing idle for a long period of time may be totally discharged due to its inherent self-discharge. The accumulator must be cycled a number of times (charged and discharged) to restore its original capacity, i.e. operating time.

Lithium batteries offer relatively high volume-specific energy (approx. 800 mWh/cm³). In addition, lithium batteries which have spirally wound large-surface electrodes have a high load capability and high capacity retention during storage. Both the lithium battery's longer operating time and its higher cell voltage of 3V are important in camera applications. The latest generation of cameras is fitted out with numerous automatic functions, which means increased energy coupled with relatively high load requirements. Lithium batteries of this type are a particularly good choice for today's cameras.

A sudden voltage break-down at the end of discharge is typical for accumulators. When an accumulator is used to operate a camera, especially those of former design, this can lead to an annoying situation if the flashlight suddenly stops working, and an important scene to be photographed remains undocumented. A situation of this kind can of course easily be avoided by checking the battery's state of charge well in advance. Another way of avoiding such an unexpected situation is to use alkaline-manganese batteries (ALKALINE). Typical for this primary system is that - during discharge - its voltage and thus load capability decrease gradually, so that the user recognizes the end of discharge in good time and has the opportunity to change the battery. Some of the newer generation of cameras have eliminated the above problem with accumulators.

A remote control device should only be operated by the battery stipulated in its battery compartment. Different zinc-carbon batteries are available for different remote control devices. They can be identified by their IEC designation. Commonly used batteries include the R03 (AAA, "Micro"), R6 (AA, "Mignon") and the 9V Bloc 6F22. A better choice is the alkaline versions of these batteries which offer twice the operating time of the zinc-carbon battery. They can be identified by their IEC designations LR03, LR6 and 6LR61. Nevertheless, because of the relatively low current required by this application, zinc-carbon batteries still remain a good and economical alternative.

Interchangeable accumulators may - in principle - be used as well. They are, however, less recommendable for this application because of their relatively high self-discharge, which requires repeated charging, thus rendering this type of battery rather impractical.

Watches / Hearing Aids

There is a wide range of button cells available for watches. The preferred electrochemical system is silver oxide. Varta offers 40 different types of this system. The type of battery to be used is listed in the watch's operating instructions. In general, it is important to remember that analog watches (watches with hands) and simple digital watches are powered by "low drain" batteries. They are extremely leakage-proof. However, due to their higher internal resistance, they do not comply with the current requirements of multi-functional watches, which need "high drain" batteries to operate their multiple functions (i.e. alarm, illumination of the watch's face etc.).

In addition to the silver-oxide system, alkaline-manganese and lithium-manganese systems are also used in watches. The alkaline-manganese button cell is most commonly used for low price watches. This battery can later be replaced by an identical sized silver-oxide button cell. The advantage of the silver-oxide button cell is its constant operating voltage (highly accurate time-keeping) and higher capacity (longer operation).

Another category of watches uses lithium coin cells, which may also be equipped with multiple functions. A typical coin cell for this purpose is the CR2025, with a diameter of 20 mm and a height of 2.5 mm. In total there are more than 12 different sizes (different diameter and height).

Yes, Varta has launched a new zinc-air battery on the market, named "ZincAir Top", which can unquestionably replace mercury batteries in all hearing aids. The load capability of this battery is higher than that of the traditional zinc-air battery and even higher than that of the mercury battery. "ZincAir Top" batteries from Varta can only be purchased from authorized hearing aid dealers.

This depends on the type and usage of the hearing aid. On a 12 hours/day "on" and a 12 hours/day "off" regime, the "ZincAir Top 675" button cell (IEC: PR44) provides enough energy to operate a hearing aid for two weeks, whereas the small battery of type 10 or 230 (IEC : PR70) can be used for only a few days following activation.

Small-sized rechargeable button cells for hearing aids would not be practical for the consumer. The operating time would be quite short and the button cell would need recharging several times a day. An exception is battery type 675, which may be replaced by an interchangeable accumulator. The accumulator must, however, be recharged after eight hours' use.

This depends on the type of power pack, and the age and type of mobile telephone. This is measured in standby time and talk time, where actual conversation needs more energy than keeping the telephone in standby mode.

High-capacity accumulators deliver a longer operating time than slimline accumulators; however, they are heavier and larger. Slimline accumulators are lighter and are especially designed to fit mobile telephones, but offer a shorter operating time. This aspect should be kept in mind when selecting an accumulator for a mobile telephone.

The service life is 2 to 3 years, sometimes longer. The accumulator needs to be replaced if:

• the talk time falls from charge to charge;
• the reception becomes indistinct;
• the allowable range between cordless phone and base unit is reduced.

With cordless telephones equipped with conventional nickel-cadmium accumulators, putting the telephone back onto the base unit after each single use builds up the battery's memory effect and thereby cuts the operating time. Nickel-metal-hydride batteries from Varta have virtually no memory effect. The same is true for button cells. Nevertheless an occasional complete discharge is to be recommended in order to restore the battery's original capacity and discharge behavior.

An increasing number of electrical consumers used in modern automobiles depend on just one SLI battery. This is particularly problematic if the engine is not running, i.e. if the battery is not being charged. Such installations include heated seats, heated rear window, electric window openers, air conditioner, radio, mobile telephone, reading lights etc. The demand for inside comfort is rising constantly. As a result, the performance requirements for an efficient SLI battery are also increasing. However, a battery whose primary task is to ensure a reliable engine start cannot be expected to carry unlimited additional loads.

Concepts are therefore being developed which, in the future, will provide vehicles with several batteries and cable networks.

• Prior to installation or removal: switch off all electrical consumers.
• Essential for installation: the battery must be installed in such a way that it is mechanically secured. Its degassing vents must not be covered. In the case of centrally vented batteries, the ventilation hose must be connected.
• Essential for removal: when detaching the electrical connections, first remove the ground cable from the negative terminal. Then disconnect the cable from the positive terminal. This avoids short-circuits.

Two things are necessary - a second car and two jump leads for the positive and negative terminals. An electrical connection via jump leads from an SLI battery being charged by the running motor to the SLI battery of the car that won't start is normally the simplest solution. The start procedure is to be carried out in six steps.

First step: switch off all electrical devices in the car to be started.

Second step: connect one end of one lead to the negative terminal of the charging battery and the other end to the chassis of the vehicle which won't start.

Third step: use the other lead to connect the positive terminals of the two batteries.

Fourth step: wait a few minutes to allow the flat battery to be charged a little.

Fifth step: start the engine of the troubled car.

Sixth step: disconnect the two jump leads in precisely the reverse order. The car bodies must not touch each other when performing this procedure.

Note: please refer to the operating manual for your vehicle!

If an SLI battery is not properly maintained, battery failure may be the result. Unclean terminals may cause leakage currents, leading to energy loss. If a car is predominantly used in "stop and go" traffic while using installations like air conditioning systems, heated seats, heated front and rear window etc., the battery may be discharged excessively, thus causing difficulties, e.g. when trying to start the car in winter!

All automotive batteries require a certain amount of maintenance.

1. The surface of the battery should be kept clean and dry, otherwise leakage currents can build up, causing additional loss of charge. Batteries and terminals should be periodically checked to ensure a tight fit, and should be tightened if necessary. For automotive batteries with vent plugs, the following should be noted:

2. Battery fluid levels should be checked regularly. During the warmer months of the year, water consumption is normal. If consumption increases noticeably, the control voltage should be checked by a specialist. If the battery fluid level is too low, it should be topped up with purified water. Acid should never be used. When storing automotive batteries, the following should be noted:

3. Batteries should always be kept as fully charged as possible to prevent the formation of large lead sulphate crystals. Batteries should never be stored in discharged (or partially discharged) state!

4. Charged batteries in storage should be checked regularly, and should be charged when the acid density falls below 1.20 kg/l.

Deep Cycle Batteries For Mobile Applications

Vehicle electrical systems can be found on airplanes, ships, house trailers and cars. It encompasses all kinds of electrical installations, consumers, wiring and cables, as well as the battery, generator and starter.

SLI batteries are used repeatedly for applications they never were made for, e.g. as power supplies for house trailers, to provide extra electrical energy for mobile ambulances (lights etc.), as energy supplies for boats, or as backup batteries for computers.

An SLI battery's primary task is to provide a high power output for a short period of time necessary to start a combustion engine. In order to provide these high current outputs, large electrode surface areas are necessary. This is realized by using many thin electrodes connected in parallel.

Permanent cycling, i.e. charging and discharging, of 60-80% of the rated capacity at medium currents over a longer period of time can produce strong mechanical forces within the thin plates of the SLI battery. These forces may cause the active mass to separate from the electrode grid and thus lead to premature wearing of the battery.

Therefore, when discharging 60-80% of a battery's rated capacity, special batteries should be used which are designed for this type of application.

For the "semi-traction" application area, Varta offers two distinct technologies, i.e. sealed batteries using a gelled electrolyte and wet batteries employing specially designed electrode stacks with liquid electrolyte.

In order to guarantee optimal battery life, "gel" batteries may be discharged (cycled) up to 60%, whereas wet batteries may be discharged up to 80%. Thus - depending on technology - 60% or 80% of the rated capacity will be available.

Deep discharges should also be avoided with these batteries. Deep discharges which occur when capacity is withdrawn beyond the minimum voltage limit cause the battery's service life to be shortened. In order to protect the battery from deep discharge a "deep discharge protector" should be used.

Yes. They use a gelled electrolyte and are leak-proof even when stored upside down. These batteries are used in boats, in house trailers or in small electric vehicles (golf buggies, wheelchairs etc)

The choice of the correct battery capacity is best made with the help of a checklist. Make a list of all the electrical consumers on your house trailer or boat. The power consumption of the individual installed units can be found in the relevant manufacturer's data sheet and should be given in watts. Dividing the power consumption by the voltage (12V or 24V) gives you the current in amperes. Now estimate the usage of the individual consumers in hours, total these and calculate the capacity required in ampere hours.

In order to determine the battery capacity actually needed, the estimated result should be multiplied by a safety factor. A safety factor of 1.5 is recommended for "wet" batteries, i.e. batteries using liquid electrolyte. For gel batteries, as in our example, a safety factor of 1.7 should be used. In this way the risk of a deep discharge can be avoided provided the battery is properly maintained.

When applying the safety factor, the resulting capacity may lie in-between two existing Varta battery types. In this case the battery offering the higher capacity ought to be chosen.

Example:

Capacity requirement/day 51.5 Ah x safety factor 1.7 = 87.55 Ah (K20)

Capacity (K20) 89.25 Ah x conversion factor 0.85 = 74.4 Ah (K5)

Note: When comparing batteries, keep in mind that K5 or K20 means a capacity with a 5 or 20 hours discharge rate.

Use of Solar Energy

During recent years, use of environmentally benign solar energy has increased. Solar energy systems are easy to install, easy to expand, and easy to disassemble. They are economical as well, since there are no energy costs during operation. In addition, solar energy systems are subject to virtually no mechanical wear. A solar energy system requires a reliable solar battery for charge acceptance and storage. The solar battery from Varta is characterized by:

• high charge acceptance
• durability in cycle operation
• good rechargeability
• virtually no maintenance

Compared with other rechargeable systems, solar batteries with a liquid electrolyte have a remarkably low self-discharge of only 10% per month (approx. value, determined at 25°C).

Which components are needed to operate a solar energy system?

The two basic components of a solar energy system are the storage battery and the solar cells. The solar battery from Varta is a grid plate battery with liquid electrolyte. Its performance characteristics (e.g. cycle life and deep discharge capability) are tailored to the requirements of a small solar-electrical system. Solar cells are available in thin rectangular-shaped elements (10 x 10 mm). Depending on the voltage needed to charge the solar battery system, a relevant number of solar cells are connected in series (module).

The efficiency of solar energy conversion into electrical energy is currently 11%-14%. The charging efficiency is approx. 90%, meaning that when X ampere hours are removed from the battery a charge of 1.1 X ampere hours must be recharged into the battery in order to maintain the original level of charge.

Small solar power systems can be used in cottages, vacation homes, trailers and boats, as well as in isolated areas to operate e.g. an emergency telephone. Solar systems offer a useful, environmentally benign, low-maintenance and silent source of energy.

During normal use, the battery should be checked and maintained only once a year. To ensure that the charge conditions meet the requirements, the electrolyte should be checked with a hydrometer (acid density of the charged battery: 1.28 kg/l at 25°C). Also to be checked is the battery’s open circuit voltage, which should be 2.12 V/cell (if fully charged).

Batteries and Environmental Protection

Today nearly all consumer batteries, especially primary batteries, are free of mercury and cadmium. On the other hand, heavy metals are still essential components in mercury batteries, rechargeable nickel-cadmium batteries and lead-acid accumulators. These metals may cause damage to the environment if disposed of improperly and in large quantities.

The battery industry is working to develop alternatives to replace mercury, cadmium and lead wherever possible. Alternatives are already available for a large number of applications (e.g. nickel-metal-hydride and zinc-air systems). Other new technologies are already in an advanced stage of development.

Mercury oxide, nickel-cadmium and lead batteries are already being collected and recycled in Europe. Some of the raw materials are reused in the manufacture of new batteries. Varta has been recycling used lead batteries in its own recycling plant for many years. For example almost 100 % of lead batteries in Germany are collected and recycled.

Rechargeable batteries of any type should only be placed in dealers' collection boxes or returned to the local authorities when they are discharged. When the equipment stops working and says "battery dead", or if it fails to work properly after a long period of use, then the batteries are discharged. If you are not sure whether the battery is completely discharged, you should cover the poles of the battery with a piece of sticky tape or return the battery in a plastic bag. It is the responsibility of the dealer and manufacturer to dispose/recycle the various electrochemical systems as per the country of sale regulations.

The future of Batteries

Yes - although there are limits - the trend towards smaller batteries is continuing. Among standard round cells the smaller sizes, i.e. the Penlight (R6, AA) and small Penlight (R03, AAA) are becoming more and more popular. These two battery types currently account for 70% of sales, while the demand for larger standard round cells like Baby (R14, C) and Mono (R20, D) is decreasing. New rechargeable battery systems like nickel-metal-hydride and lithium-ion enable the use of smaller batteries which offer the same amount of energy. In addition, more and more devices are being operated with button cells. Rechargeable button cells can be expected to gain more and more in importance in future.

By the year 2000, rechargeable portable batteries will probably have a larger market share than primary batteries. The dramatic growth predicted for the years to come will be primarily in the area of rechargeable power packs. Camcorders, mobile and cordless telephones, notebooks and multimedia devices with picture, sound, and speech transmission will have found their place in the majority of households

Intelligent accumulators are equipped with an electronic chip which is not only responsible for the device's energy supply, but also controls its main functions. This type of accumulator indicates the charge remaining, the number of times the accumulator has been charged already, its temperature etc. Intelligent accumulators are not yet available on the market, but will most definitely play a major role in the not too distant future - particularly in the field of power packs for camcorders, cordless and mobile telephones and notebooks.

There is no alternative to a battery for storing and providing electrical energy. It will remain our most important mobile energy source, together with solar energy (via solar cells). No other energy system offers the convenience of the battery. The battery for a wrist-watch, for instance, can in principle be replaced by kinetic energy created by body movement; however, if the wrist-watch is not used for a certain period of time, it will cease to work, i.e. the hands won't move.

Each one of today's battery systems is a specialist in its own right, able to fulfill a specific task better than any other battery system. They all are specialists either in terms of value for money, high capacity, high energy density, long shelf life, high or low operating temperatures, environmental compatibility or economical, environmentally benign recyclability. A battery system capable of combining all such characteristics is unlikely ever to be available.

• Keep batteries out of the reach of children, especially those that may be ingested (IEC).
• In the case of ingestion of a cell or battery the person involved should seek medical assistance promptly (IEC).
• Equipment intended for use by children should have battery compartments which are tamper-proof (IEC).
• The circuits of equipment designed to use alternative power supplies should be such as to eliminate the possibility of a primary battery being charged (IEC).
• It is of extreme importance that batteries be inserted into equipment correctly with regard to polarity (IEC).
• Do not attempt to revive used primary batteries by heating or other means. Primary batteries must not be charged as this can cause leakage, explosion or fire (IEC).
• Recharge and maintain accumulators according to the manufacturer’s instructions; employ only approved, high quality chargers designed for the intended battery system.
• Do not immerse batteries into water* and do not store them in a damp place; instead store them where it is dry and cool (*unless the packaging is absolutely water-tight) (IEC).
• Do not dispose of batteries in fire; do not try to open batteries or to solder or weld batteries yourself (IEC).
• Only use the type of battery recommended by the equipment manufacturer. Follow the instructions and symbols on the battery compartment.
• Do not short-circuit batteries (IEC).
• Replace all batteries of a set at the same time (IEC).
• Newly purchased batteries should not be mixed with used ones, batteries of different electrochemical systems, grades or brands should not be mixed either (IEC). This also applies to rechargeable batteries.