Battery Power Supply Page

Battery information and circuits

    General battery information

    Batteries are all over the place: in our cars, our PCs, laptops, portable MP3 players and cell phones. A battery is essentially a can full of chemicals that produce electrons. Chemical reactions that produce electrons are called electrochemical reactions.

    If you look at any battery, you'll notice that it has two terminals. Electrons collect on the negative terminal of the battery. If you connect a wire between the negative and positive terminals, the electrons will flow from the negative to the positive terminal as fast as they can. Normally, you connect some type of load to the battery using the wire. Inside the battery itself, a chemical reaction produces the electrons. The speed of electron production by this chemical reaction (the battery's internal resistance) controls how many electrons can flow between the terminals. Normal batteries have generally 1.5V per cell voltage (except some Lithium cells which have 3V voltage). The batteries which have higher voltage output are built genrally from many 1.5V cells in series all put inside same "case". Since there are no real industry standards, many terms used by battery manufacturers have become misleading marketing hype.

    Although the terms battery and cell are often used interchangeably cells are the building blocks of which batteries are constructed. Batteries consist of one or more cells that are electrically connected.The world of batteries divides into two major classes: primary and secondary batteries. Primary batteries such as the common flashlight battery are used once and replaced. The chemical reactions that supply current in them are irreversible. Secondary batteries (for example, car batteries) can be recharged and reused. They use reversible chemical reactions. By reversing the flow of electricity i.e. putting current in rather than taking it out, the chemical reactions are reversed to restore active material that had been depleted. Secondary batteries are also known as rechargeable batteries, storage batteries or accumulators.

    As a battery is used, the amperage is consumed and the voltage drops. There is a formula for a ballpark estimate for battery life:
    Estimated total battery life = (Ib / Id) x 0.7
    Where: Ib = Total Capacity Rating of battery (mAh) and Id = Current Consumption of the device in milliamps (mA)
    Use of this formula does not guarantee that you will get the determined battery life. Other factors such as weather condition (temperature, humidity, etc.), and battery condition can extend/shorten the battery life. This formula cannot be used to calculate battery life for alkalines. Battery state can be somewhat determined with the battery voltage. Please note that batteries do not show their correct voltage unless under a load. Battery testers are designed to provide this load; however, when testing batteries with a multimeter, you must have the meter set to measure DC voltage and place the battery under load by using a resistor in parallel with the test leads of the meter. How the battery voltage drops during the use varies from battery type to another.

    Carbon Zinc based single-use batteries are those "regular" batteries you get from a normal shop. Those are cheap batteries. Typical cell voltage is 1.5 volts. This kind of batteries are available in conventional form factors like AA, AAA, C, D and 9-volt. Carbon Zinc batteries are usually the cheapest battery type you can find (cheapers per battery unit, propably not cheapest per capacity unit). The term Heavy Duty battery was used to refer to Zinc chloride batteries which had about 50% more capacity than traditional carbon zinc batteries (that was tens of years years ago). Calling zinc chloride batteries heavy duty became misleading once alkaline batteries (with 300% more capacity than zinc chloride batteries) became available.

    Alkaline batteries are single-use batteries, but provide a higher start voltage and longer life than many other single use batteries. The capacity rating for alkaline batteries is not a fixed number on alkaline batteries, although it can be safely assumed that an alkaline battery will last significantly longer (2-3 times as long) as a same-size rechargeable under the same conditions. Alkalines do not have a fixed capacity rating because where the discharge rate of rechargeable batteries is a straight line, the discharge rate for alkalines slopes depending on the current drain. The higher the current drain, the faster the battery discharges. In alkaline batteries, the sloping discharge curve makes it impossible to accurately provide a mAh rating; the rating would vary depending on discharge rate and temperature. Alkaline batteries are significantly heavier than many other battery types for the same size, but they can store lots of energy (few times more than "regular" batteries). Alkaline batteries can take storage nicely when not used. Alkaline batteries stored at "room temperature" self discharge at a rate of less than two percent per year. However, if alkaline batteries are stored at higher temperatures they will start to lose capacity much quicker. At 85 degrees F they only lose about 5% per year, but at 100 degrees they lose 25% per year.

    There is a variation of alkaline cell that can be charged with a limited number of times: Rayovac sells rechargable akaline batteries. Rechargeable alkalines are really just normal alkalines with a beefy casing to reduce leakage, but the full charge drops off significantly even after the first recharge cycle and gets worse from there.

    There are also other single-use batteries. Lithium Manganese Dioxide (Li/MnO2) is used in some high capacity single use batteries (for example some camera batteries). Silver Oxide Zinc is used in some small batteries used to power watches and tiny electronics gadgets like digital thermometers. Silver Oxide technology features one of the greatest capacities to store electricity for a certain volume. Silver Oxide technology also provides a near constant voltage over the entire life of the battery. This is essential to ensure watch accuracy, and could not be attained easily with alkaline battery technology.

    Rechargeable batteries tend to have a lower start voltage and shorter usage cycle; however, they make up the difference by being reusable. They are lighter in weight than alkaline batteries.Normal alkalines are 1.5V each, but Ni-Cd batts are only about 1.2V each. If you use four of them for instance, you only get 4.8V instead of 6V. By standard, the NiCad battery type nominal voltage is 1.25 V. This has to do with the chemistry of the battery. When shopping around, take care that many dealers will call the standard 1.25 V batteries a 1.5 V battery type, because people generally use them as 1.5 V batteries. If you have a consumer device that was made to use rechargeable batteries, it would be designed to use the standard 1.25 V rechargeable battery. The voltage difference is that's probably why some equipment instructions don't allow them. Another reason could be that NiCd batteries have enormous short-circuit current capability (easily tens of ampreres or more) compared to many traditional batteries (causes greater risk of fire in case of short circuit). On some applications the small internal resistance is a benefit. That high resistance combined with high current load causes voltage drop and this power lost in voltage drop causes the batteries to heat quickly, and because resistance increases with heat, it gets worse the longer you use the device. The voltage drop across the resistance causes the output voltage to drop, and before long it can drop below a useful voltage. In high-current devices, NiMH and NiCd batteries work much longer than alkaline batteries, in part because they don't heat as much. Ni-Cd batteries are the most popular type of rechargeable battery. They are quick to charge and work well in extreme temperatures. They will last up to 500-700 charge/discharge cycles. NiCd batteries are easy to charge at slow charge mode. Just applya charging current, typically around 50 mA for 500mah cells, for 12-14hours to change them. It does not hurt the batteries if you charge thebatteries at the current with somewhat longer times (even few times longer)than needed. When batteries are are charged after they are full,the applied power is converted to heat, so NiCd batteries should start to become warm then. Some will say sinking C/10 (50mA for500 mAh battery) indefinately into NiCd is acceptable but thisis not a recommended practice. NiCd batteries can also be charged faster with special"smart chargers" which use controlled higher current to the batteriesuntil they are charged and stop this current when batteries are full(the charger has special sense circuitry for this). You want the -deltaV controlled, which monitor the voltage on the battery to sense when they're fully charged. The timer controlled chargers, will overcharge the battery, and nothing kills batteries like overcharging. Ni-Cd batteries can suffer from what is called the "memory effect", although some people cailm this effect is just a myth. If a Ni-Cd battery is recharged before it is fully discharged, the recharge process can create a layer of bubbles in the battery which will eventually prevent the battery from discharging beyond that point. To avoid this problem, we recommend that Ni-Cd batteries be fully discharged before recharging. If they are only partially discharged and then recharged, then after several such recharge cycles, the batteries may not be able to recharge to full capacity. Exercise extreme precaution when handling and testing NiCd batteries.NiCd batteries include some amount of cadmium (Cd), which is dangerousmaterial for enviroment. Do not throw NiCd batteries away with your trash.You should bring those batteries to recycling. When discharging NiCd battery packs be cautious about over-discharge. Individual NiCd cells can go to zero volts but in a battery pack letting them drop below 1V each may reverse and ruin a weak cell since they are in series. Rechargeable batteries might not be right solution for all battery applications, for example in applications where normal batteries last many months. The rechargeable battery will loose its charge more quickly than a standard alkaline battery. You will find that after a month or two, you may have to recharge the batteries. When on the shelf, rechargeable batteries will loose their first 10% of charge within the first 24 hours. After that they will self discharge at a rate of about 5% for the next 24 hours. After about 24 to 48 hours, the rate of loss would be about 1% per day. If you were to charge a NiCad battery and put it on the shelf, you would have to re-charge the battery before use, if you let it sit for about a week, and want to have optimum performance.

    In many modern applications NiCd batteries are replaced with higher capacity NiMH batteries. Those batteries have pretty much similar characteristics to NiCd (except that they need somewhat different charger).NiCad and NiMh cell voltages are identical. I like NiMH as it is relatively easy (and safe) to recycle. NiMH batteries are great but they have the downside of losing charge very quickly "on the shelf". A NiMH battery can lose up to 2% of its charge per day sitting on the shelf. So it is not a good choice for that emergency flashlight application. NiMh are sensitive to overcharge. NiMh should be preferably be always charged with "smart chargers" designed to charge NiMh batteries. There is some difference at end of charge and used by sophisticated chargers compared to NiCd, that's why an intelligent NiCd charger does not work with NiMH battery. NiMh batteries can also be charged with constant currentC/10 (50mA for 500 mAH cell) current, but you should avoidexcessive overcharge because this will shorten battery life. Compared to Nicad NiMh are nearly twice the capacity, can berecharged from any level, selfdischarge more tha twice as fast,have about half the full cycle number life, and are not as robust when charging. Some sources say that charging NiMH batteries will reduce their life, but for practical purposes with batteries that are designed to be quick charged, for example, Sanyo, GP, POWERhaus, that is not true. It is important to use a battery charger that has been specifically designed to rapid charge NiMH cells. Actually there is a much greater likely hood of reducing the life of a NiMH battery by using an "overnight" charger than by using a smart fast charger. Overnight chargers rely on the fact that you will unplug them after a number of hours. If you forget to unplug them they can continue to charge the batteries longer than they should. Overcharging WILL reduce the life of batteries.

    NiMH is a superior battery compared to NiCd in many situations - just to inject a note of realism and take care of differences. A great deal of the raw materials for NiMH batteries comes from China (and Russia), regardless of what the "made in ..." sticker says. NiMH and NiCd batteries self discharge at a MUCH faster rate than alkaline batteries. In fact, at "room temperature" (about 70 degrees F) NiMH and NiCD batteries will self discharge a few percent PER DAY. Storing them at lower temperatures will slow their self discharge rate dramatically. NiMH batteries stored at freezing will retain over 90% of their charge for full month (so it might make sense to store them in a freezer in some applications). If you store you batteries in very cold place, it's best to bring them back to room temperature before using them (cold batteries perform poorly). Even if you don't freeze your NiMH batteries after charging them, you should store them in a cool place to minimize their self discharge.

    By standard, the NiCad and NiMH battery type nominal voltage is 1.25 V. This has to do with the chemistry of the battery. The lower voltage cna be problem sometimes and that's why there are also battery types that give 1.5V out. There are some expensive industrial type chargeable batteries that are 1.5 V. These are not made the same way as the reasonable cost consumer batteries. For consumer markets Rayovac makes a rechargable alkaline that is the usual 1.5V (there could be also other makers). They like to be re-charged often and seem to have about the capacity of regular alkalines, perhaps a little less. They can take only about 50 charges to a set before they started to degrade, and ff you deep discharge them, they die. Those rechargeable alkaline batteries need a special charger (sold by battery manufacturer).

    Lithium-ion batteries are the latest technology for portable use. Many new small gadgets like cellular phones use Li-ion batteries.Li-ion batteries have a high energy density. Compared with a Ni-Cd battery, these batteries will deliver twice the runtime on each charge. It is available only in a limited number of sizes and models. They have a life expectancy of 300-400 charge/discharge cycles. Generally, lithium batteries are designed to be recharged in the device rather than in an external charger. Exercise extreme precaution when handling and testing Li-ion batteries.Do not short circuit, overcharge, crush, drop, mutilate, penetrate,apply reverse polarity, expose to high temperature or disassemble them. Only use the Li-ion battery with the designated protection circuit(cellular phone batteries usually have this). Abuse of Li-ion can cause "explosion" like happening, because in short circuitthe case temperature can get very high and the electrolyte insideLi-ion battery is highly flammable. Lithium-ion Polymer battery is a special way built Lithium-ion battery. There are three main advantages to a lithium-ion polymer battery -- lighter weight, a wide range of possible shapes and greater performance at high and low temperatures. A lithium-ion polymer is lighter than a standard lithium-ion battery because it uses a plastic electrolyte instead of an electrolyte solution, as is used by lithium-ion batteries.

    Lead-acid batteries are used for a vast number of purposes, but all batteries provide either starting or deep cycle power. The only difference is how much power is delivered and how long it needs to be delivered. When people think about lead-acid batteries, they usually think about batteries that start their cars. These are starting batteries. They deliver a short burst of high power to start the engine. Car batteries are built using lead acid cells. They have a cell voltageof around 2 volts (means 6 cells in series makes 12V battery). Normal 12V car battery is designed to be quite robust. It canbe carged with almost any reasonably current limited constantvoltage source of around the nominal voltage of the battery(for example 13.5V for 12V car battery). It supplies power to the starter and ignition system to start the engine, supplies the extra power necessary when the vehicle's electrical load exceeds the supply from the charging system and acts as a voltage stabilizer in the electrical system. Car batteries are built for heavy currents but DO NOT deep discharge them, only shallow discharge. If you repeatedly run a car battery down tomuch below 50% of capacity you will seriously shorten its life. Warnings on car batteries: Car batteries contain dangerous acid hare heavy, so handle carefully.Charging car batteries can generate highly flammabble hydrogen,so it is best to charge those only in well ventilated spaces. Car batteries have very large short circuit current (hundreds of amperes), so do not short circuit them (a fuse near battery terminal is essential for safety to avoid wire fires in short circuithappens).

    There are also other types of lead acid cells than car batteries. Some are designed for deep discharge use and some for some otherapplications. Generally lead acid batteries don't like to be discharged below 1.67 volts per cell (10V for a 12V battery) and their full capacity can only be extracted if the load current is something like C/10 or C/20 (where C is the barrery capacity in Ah and resulting current is in A). There also are deep-cycle batteries. You'd find these on boats or campers, where they're used to power accessories like trolling motors, winches or lights. They deliver a lower, steady level of power for a much longer time than a starting battery. There are very many applications that use lead-acid batteries for stationary applications. Here is a list of some standards relevant to this application area:

    • IEEE 1189-1996, IEEE Guide for Selection of Valve-Regulated Lead Acid (VRLA) Batteries for Stationary Applications
    • IEEE 1187-1996, IEEE Recommended Practice for Installation Design and Installation of Valve Regulated Lead -Acid Storage Batteries for Stationary Applications
    • IEEE Std 450-1995, how to maintain batteries
    • IEEE Std 485-1997, reference how to size batteries

    Short list of most common battery characteristics:

    • Lead Acid: most economical for larger power applications where weight is of little concern (cars, boats, wheelchairs, emergency lighting, UPS systems), low energy density (30-50 Wh/kg), available in low cost versions, cell voltage 2V, voltage limiting rather than current limiting is used for charging
    • Sealed lead acid (SLA,Gelcell): maintenance-free lead acid battery with electrolyte in moistened separators, enclosure is sealed, used for wheeled mobility, typical charge times are 8 to 16 hours, must always be stored in a charged state, 200 to 300 discharge/charge cycles
    • Nickel Cadmium (NiCd): mature and well understood technoogy used in chargeable batteries used in many applications (power tools, two-way radios, video cameras), standard against which other batteries are usually compared, not very good energy density (45-80 Wh/kg), cell voltage 1.25V, life cycle 1000-1500 charges
    • Nickel-Metal Hydride (NiMH): higher energy density (60-120Wh/kg) compared to the NiCd at the expense of reduced cycle life, no toxic metals, used in mobile phones and laptop computers, cell voltage 1.25V, life cycle 300-500 charges
    • Lithium Ion (Li-ion): fastest growing battery system, high-energy density (110-160 Wh/kg) and lightweight, technology is fragile and a protection circuit is required to assure safety, applications in notebook computers and cellular phones, cell voltage 3.6V, life cycle 500-1000 charges
    • Lithium Polymer (Li-polymer): uses a dry solid polymer electrolyte, cell thickness measuring as little as one millimeter, suffers from poor conductivity (high internal resistance)
    • Lithium Ion Polymer (Li-ion polymer): uses a combination of dry polymer electrolyte combined with some gelled electrolyte, ultra-slim geometry, high energy density (100-130 Wh/kg), used in mobile phones, cell voltage 3.6V, life cycle 300-500 charges, promotional reasons most battery manufacturers mark this kind of battery simply as Li-polymer
    • Reuasable Alkaline: Special alkalinen battry which can be charged few times (energy density 80 Wh/kg), cell voltage 1.5V, life cyle around 50 cyled of 50% charge/recharge
    Here are some data of some common battery types in everyday use:
    Name     Size            Alkaline      NiCd        Ni-MH       Weight         
    (dia x len mm) (V / mAH) (V /mAH) (V / mAH) (alkaline/NiMH g)
    AA 14.2 x 50 1.5 / 2100 1.2 / 500 1.2 / 1250 24 / 27
    AAA 10.5 x 44.5 1.5 / 1000 1.2 / 180 1.2 / 550 12 / 13
    N 11.5 x 28 1.5 / 700 6.6 / 11
    C 26 x 46 1.5 / 7000 1.2 / 1200 65 / 80
    D 33 x 58 1.5 / 14000 1.2 / 1200 135 / 105-160
    9V 48.5x26.2x17mm 9.0 / 550 7.2 / 80 8.4 / 130 44
    LR44 11.6 x 5.4 1.5 / 105 2
    The data for battery rating is mostly based on infromation at The alkaline battery data is based on Duracell Battery Data, NiCd data is from Eveready and Ni-MH data is based in Radio Shack Ni-MH Battery data. LR batery types data is from maxel battery data at The ratings of the bateries can vary somewhat from manufacturer to manufacturer. The battery size data is from Diameter can vary as much as 1 mm between different manufacturers.Many battery types are known with many codes. Unfortunately, battery manufacturers have never agreed one standard convention for battery labels (there are few hundred different commonly used codes to identify a battery type). Here are some code names for different battery types:
    • 9V Alkaline Battery: 6LR61, 1604A, 1604AC, MN1604, 9V, 4022, 522, K9V, A1604, 6AM6, BLOC, ND65V, 1604, KA9, PP3, CLR6, 6F22, 9VOLT
    • LR44: LR44, 5244, A76, A76LR44, 1166A, V13GA, KA76, RW82, FM28F, AG13, L1154, A200, GP76A, KA, A01, G13A, WL14, LR44H, G13-A
    • LR54: L1131, LR54, 189, LR1130, V10GA, AG10, A120, GP89A, A05, RW49, 10L/122, WL10, G10, G10A, GP189
    • CR2032 Lithium Button Cell (3V cell): CR2032, DL2032, L2032, BR2332, ECR2032, 2032, EA2032C, LF1/2V, L14, BR2032, 2332, SB-T15
    • D: D, KD, MN1300, LR20, E95, 4050, AM1, MONO
    • C: C, MN1400, KC, LR14, E93, 4014, AM2, BABY, AM-2, R14
    • AA: AA, 15A, 15AC, MN1500, 4006, E91, KAA, 815, AM3, MIGNON, ND62S, LR6
    • AAA: AAA, LR03, 24A, 24AC, MN2400, 4003, E92, K3A, 824, AM4, MICRO, ND61R
    • 4LR61 Alkaline Battery: 4LR61, 539, KJ, 4AM6, 4018, 1412AP, J, 7K67
    • CRV3 Lithium Battery: KCRV3, CRV3, CR-V3, LB-O1, LB-01, LBO1, LB01
    • E10A 9V Alkaline Battery: L1021, GP-10A, GP10A, E10A, 10A
    • 27A 12V Alkaline Battery: 27A, GP27A

    When selecting a battery for a certain application many things needs to be considered. You just should not be looking at the voltage, capacity and price only. Many sources say that NiMh will last longer than alkalines in high power equipment. The capacity of an alkaline is maybe twice that of the NiMh, but the alkaline must be discharged much slower than the rechargeable in order to obtain more total energy. So, fo a low power device like a transistor radio, alkalines should last longer, but for higher power devices like digital cameras and flashlights, you are probably better off with the NiMh. But the shelf life of alkalines is much longer than NiMh since the rechargeable battery will self discharge just sitting on the shelf for a few months. So, for a flashlight that is seldom used, alkalines should be better. When powering high drain electronic devices like digital cameras, computer peripherals, or portable music players, an alkaline battery will only deliver a small fraction of its rated capacity. A NiMH or NiCd battery is likely to deliver much closer to its rated capacity when it's powering high drain devices. This means that a NiMH battery with a rated capacity of 1800 mAh can take many more photos than an alkaline battery with a rated capacity of 2,800 mAh.

    Most equipment manufacturers recommend removing batteries from the equipment if it's not to be used for a while, so as to reduce the risk of equipment damage from leakage. There are many electronic devices that have been damaged by leaked and rusted batteries. Battery leaking is quite rare occurence when you use good quality batteries and do not leave them to the devices for long time you have used them. Modern "alkaline" batteries use a liquid electrolyte which incorporates a good deal of potassium hydroxide ("lye"), a corrosive alkaline material. Over time, the electrolyte can attack the metal shell of the battery, or the seals around the upper (positive) electrode, and leak out. This corrosive action is relatively small if the battery is in its "as new" condition and has not been partially discharged, and that the electrochemical processes which occur when you draw charge out of the battery have the effect of starting or speeding up the corrosion of the shell. To clean alkaline corrosion,use ordinary household vinegar to neutralize the alkalinity,then rinse and dry.

    If you really do need to have the equipment available "on standby" for rapid use - then it's probably a good idea to swap out the batteries for fresh ones any time you've used it significantly. There are various recommendations which batteries you should use. There are some suggestions flowing around that battery-powered equipment which is used only occasionally, should be powered by "heavy duty" carbon/zinc batteries rather than by alkaline batteries. Carbon/zinc batteries have less power per cell (roughly half as much for the "heavy duty" types), but they're less expensive, and they use a chemistry with a near-neutral electrolyte pH (actually they use acidic electrolyte). If they "die of old age" it usually seems to be due to the electrolyte drying out, rather than chewing its way out of its cage and attacking innocent bystanders. Those carbon/zinc batteries are cheap too. Please also note that cheap carbon zinc (all made in China nowdays) tend to leak out much more often than "quality batteries" because they have typically vety thin casing. Heavy duty carbon zinc have somwhat better capacity than the cheap standard carbon zinc, and more importantly, are steel jacketed. Many people remember carbon-zinc cells leaking,and that's why manufacturers brought out their policies against leakage. Many manufacturers claim to replace damaged equipment. Alkalines will last in standby far longer than carbon-zinc cells. Alkaline batteries are nowadays the main product of most battery companies, leaving the carbon-zinc cells as the loss leaders. This means that they will be made as cheaply as possible. No matter how cheaply you can buy carbon-zinc cells, I'd strongly recommend that you not leave them in any device for long unless that device really had to value to you.

    Li-ion battery chargers

    Lithium ion batteries (sometimes abbreviated Li-Ion) are a type of rechargeable battery commonly used in consumer electronics. They are currently one of the most popular types of battery, with one of the best energy-to-weight ratios, no memory effect and a slow loss of charge when not in use. They can be dangerous if mistreated.

    WARNING: Exercise extreme precaution when handling and testing Li-ion batteries. Do not short circuit, overcharge, crush, drop, mutilate, penetrate,apply reverse polarity, expose to high temperature or disassemble them. Only use the Li-ion battery with the designated protection circuit(cellular phone batteries usually have this). Abuse of Li-ion can cause "explosion" like happening, because in short circuit the case temperature can get very high and the electrolyte insideLi-ion battery is highly flammable.

    Li-Ion batteries can burn, explode, and spread toxic material that inflicts human injury and damages equipment if they are overcharged. Most commercial Li-Ion batteries have several automatic protection devices built-in, because of that danger. Generally charging current is interrupted if the voltage across any cell exceeds the safe limits (4.30 volts on some types), internal pressure exceeds a preset threshold, or internal temperature rises to an unsafe level. Li-Ion batteries usually are left in an unusable state after any of those things occur. Never defeat any of the internal protection devices or otherwise try to charge a lithium-ion battery that has become unchargeable. Despite these safety features, Li-ion batteries are subject of frequent recalls. During the past decade there have been numerous recalls of lithium-ion batteries in cellular phones and laptops owing to overheating problems.

    Lithium-ion batteries can easily rupture, ignite, or explode when exposed to high temperatures, or direct sunlight. Short-circuiting a Li-ion battery can cause it to ignite or explode. Never open a Li-ion battery's casing. Li-ion batteries contain safety devices that protect the cells inside from abuse. In some cases internal contaminants inside the cells can defeat these safety devices (this was reason for millions of Laptop battery recalls in 2006).

    A unique drawback of the Li-ion battery is that its life span is dependent upon aging from time of manufacturing (shelf life) regardless of whether it was charged, and not just on the number of charge/discharge cycles. At a 100% charge level, a typical Li-ion laptop battery will irreversibly lose approximately 20% capacity per year at normal room temperature (and much faster inside hot laptop). The capacity loss begins from the time the battery was manufactured, and occurs even when the battery is unused.

    A stand-alone Li-Ion cell must never be discharged below a certain voltage to avoid irreversible damage. Therefore all systems involving Li-Ion batteries are equipped with a circuit that shuts down the system when the battery is discharged below the predefined threshold.

    Li-ion batteries are not as durable as nickel metal hydride or nickel-cadmium designs and can be extremely dangerous if mistreated. A more advanced lithium-ion battery design is the lithium polymer cell.

    Normal battery chargers

    Bascially all types of alkaline cells can be recharged, although the battery manufacturers discourage this (dangers of overcharging and battery leaking).You will need a special charger for charging alkaline cells (normal NiCd chagers are not suitable for this). There are some special alkaline cells nowadays which chan be charged better than normal alkaline cells. The best practice is not to discharge completely the cell or battery but rather to give a short charge often. Do not attempt to recharge a totally discharged cell or a cell showing even the slightest sign of damage.

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