Battery: “A battery is a device that converts the chemical energy contained in its active materials into electrical energy by means of an electrochemical reaction. While the term “battery” is often used, the basic electrochemical element being referred to is the cell. A battery consists of two or more cells electrically connected in series to form a unit. In common usage, the terms “battery” and “cell” are used interchangeably.
Batteries are either primary or secondary. Primary batteries can be used only once because the chemical reactions that supply the electrical current are irreversible. Secondary (or storage) batteries can be used, charged, and reused. In these batteries, the chemical reactions that supply electrical current are readily reversed so that the battery is charged.
“Primary batteries are common since they are cheap and easy to use. Familiar primary battery uses are in flashlights, watches, toys, and radios. The most common use for secondary (storage) batteries is for starting, lighting, and ignition (SLI) in automobiles and engine-generator sets. Other applications include uninterruptible power supplies (UPSs) for emergency and backup power, electric vehicles (traction), telecommunications, and portable tools.” (From Engineers Edge – Solutions by Design)
Batteries and Heat: Heat is the enemy of all batteries. Even Lithium photo batteries function better and have a longer shelf life if kept at moderate temperatures. (Moderate temperatures means the same temperatures that you find comfortable.) Automobile batteries that will last for three or four years in Maine average about 18 months in Florida.
Batteries, especially Nickel Metal Hydride (NiMH) and Lithium-ion (L-ion) types, need to be kept away from high temperatures as much as possible — period. This is especially important when they are in use. You’ve gotta do what you’ve gotta do, so obviously this isn’t going to be possible at all times. Be aware, though. For example, leaving a L-ion battery in the passenger compartment of a parked car on a sunny day in Florida will probably ruin it in a few hours. Put it in the trunk, where temperatures at least stay well below the boiling point.
- Store batteries in the proverbial cool, dry place. Don’t freeze them.
- The back of the top shelf in the fridge is a good spot to keep spares that won’t be cycled in service.
- Seal them in a plastic bag with all possible air squeezed out — in an air-conditioned room, if possible — to minimize moisture in the bag.
- When removing them from the fridge, allow them to reach room temperature before opening the bag to avoid condensation.
Common Primary Batteries/Cells
Carbon Zinc
- Cheap.
- Poor capacity and service life.
- Suitable for the least-demanding applications, but generally inferior performance compared to other primary batteries.
- How to know them: they don’t read Alkaline, NiCad, NiMH, Lithium or Li-ion someplace on the battery. They will probably read Carbon Zinc someplace in really tiny letters.
- Cannot be recharged.
- Charging: Do Not Attempt to Charge!
Alkaline
- Widely available in common sizes.
- Excellent capacity and life compared to cost.
- Can be used for most applications, but do best in low-drain situations such as remote controls, toys, MP3 players, etc.
- How to know them: they will read Alkaline on the side of the cell.
- Environmental hazard due to mercury content, other waste products when discarded.
- Charging: Do Not Attempt to Charge!
Lithium
Ordinary “lithium” batteries, such as the Energizer e2 cells, C123 cells, and “button cells” sold for photo purposes and use in watches, are not rechargeable. They are not the same as Lithium-Ion batteries, and will explode if placed in a charger.
- Specialized applications, mostly photo and flashlights
- Excellent shelf life (up to 10 years)
- Superior resistance to heat, the big enemy of most batteries
- Functional over a wide range of temperatures
- Excellent service life, flat discharge curve; Maintain voltage until nearly depleted, then die quickly
- Ideal for extreme service applications: watches, other items that must remain powered up for years but use little of the battery’s capacity, flashlights to be kept in survival kits, and applications where reliability and performance are the concerns, and price is not an issue
- Incredibly expensive, for disposable batteries.
- How to know them: they will read “Lithium” on the battery case
- Charging: Do Not Attempt To Charge!
Common Secondary Batteries/Cells
Lead-Acid (wet cell)
Used in vehicles: autos, motorcycles, electric wheelchairs, computer UPS applications, and others where long life, capacity and efficiency outweigh portablilty. Lead/acid batteries are also used to stabilize circuits and store extra output from generator systems, as in cars and other motor vehicles. They may someday be surpassed by Li-ion or similar technology, because they’re heavy, bulky, contain liquid acid, and can be dangerous if damaged or overcharged. Their fumes are dangerous as well.
- Excellent service life
- Can be recharged constantly
- Excellent heat resistance
- No memory problems
- Extremely heavy for size
- Presently the best option for applications requiring the ability to deliver high levels of electrical energy over prolonged periods.
Rechargeable Alkaline
- For the last few years there has been available a type of alkaline battery that can be recharged and reused. These are not common, and they are generally inferior in performance to other rechargeable cells. They are clearly marked “Rechargeable”, whereas other alkaline batteries are marked with instructions not to charge them. Their chief advantage is/was cost, but NiMH batteries are so superior in terms of service life that they are far more economical for most purposes.
- Charging: Require a special charger.
Nickel Cadmium (NiCad)
NiCads were the first widely-available rechargeable batteries for portable applications. They were first used in portable radios, large flashlights and similar items. As the technology matured they became common in many applications, and were for a number of years about the only secondary battery technology (apart from lead-acid) available for consumer use. They have been largely supplanted by Nickel Metal Hydride (NiMH) technology.
- Lightweight
- Good for several hundred charge/discharge cycles
- Do not hold charge well; must be recharged often if left unused
- Develop “memory,” requiring that they be fully discharged and then completely recharged (preferably each cycle) to enable them to keep their capacity.
- Decent capacity
- Will not a hold charge for very long if left unused. Not suitable for applications such as flashlights that must be ready for use over extended periods.
- Charging: Discharge completely, then charge to full capacity — preferably every cycle, but as often as practical. Failure to do so will result in the battery losing the ability to be brought to full charge. This can sometimes be partially reversed by several full cycles.
Nickel Metal Hydride (NiMH)
Currently (2010) the most common type of secondary battery, but quickly being overtaken by Li-ion technology.
- Lightweight
- Relatively inexpensive — dirt cheap when compared to the cost of primary batteries
- Readily available in common sizes
- Good for applications requiring battery changes, such as digital cameras, flashlights and music players that lack built-in batteries
- High capacity and relatively flat power delivery curve
- Minimal memory problems*
- Excellent service life; good for hundreds of cycles
- Heat-sensitive — keep ‘em cool
- Do not hold a charge well over time, but surpass NiCads in that respect; don’t depend on a NiMH to be ready to use out of the box or after storage for any period of more than a few days. (See: Hybrids, below)
- Charging: generally, recharge before you notice the capacity diminishing. Try to avoid frequent discharges to cut-off.
*Some sources say that NiMH’s have no memory, and that reduction of capacity is due to overcharging, deep discharge and heat. Others say that it is still necessary to do a full discharge every 10 to 15 cycles. If you choose to do that, discharge the battery to cut-off in the device if at all possible. If you use a “conditioning” charger, make sure that it is designed to condition NiMH cells. Total “deep” discharge of NiMH cells will damage them, and will quickly reduce their capacity. It may even make them impossible to recharge.
Unused NiMH batteries should be stored in a cool place, with a full charge at the time of storage. Don’t expect a “standard” NiMH to have much useful charge if left unused for more than a couple of weeks.
NiMH “Hybrid” Batteries
The biggest failing of small rechargeable batteries has been their inability to hold a charge over time. Until recently their use was limited to applications that did not require long periods without charging. This not only caused inconvenience, but resulted in the purchase and eventual discard of billions of mercury-containing alkalines into landfills and elsewhere, with environmental results that will be with us for a long time.
That all changed in September of 2006, when Sanyo introduced their Eneloop® hybrid cells. Where previous NiMH chemistry had been optimized for greater capacity, Sanyo’s breakthrough was twofold: at the cost of 10-15% of a cell’s capacity, they were able to develop the first small rechargeables that would hold a charge over time: approximately 85% of the cell’s total capacity is retained after a year of storage (under optimum conditions). These batteries are sold pre-charged, as “ready to use” rechargeables.
As a byproduct of the chemistry change, the new batteries are able to deliver power more uniformly, which to some degree makes up for the reduced capacity in high-drain applications such as digital cameras. Since then, Ray-O-Vac Hybrid®, Uniross Hybrio® (and possibly others) have come on the scene. (When I switched to Hybrio® from standard NiMH in my camera, battery life went from days to “Gee, I’d better take these things out and charge them some time soon.” I’m now in the process of testing some Ray-O-Vac Hybrids®, which seem comparable, and I have some Eneloops® on order.) [Later: Eneloops® kick butt!]
Available in AA and AAA sizes, the new hybrids have moved secondary batteries into applications (such as flashlights) where they were previously not practical, and have resulted in superior service in some other applications. They’re definitely worth a look.
- Sold “ready to use” and pre-charged
- Can be charged in any NiMH charger
- Lightweight
- Not yet available in sizes other than AA and AAA to my knowledge
- Rather more expensive than ordinary NiMH batteries (about 50%)
- Up to 1,000 cycles claimed; deterioration seems to be over time as much as use
- Less theoretical capacity than other NiMHs
- Superior service in some applications
- Heat sensitive — keep ‘em cool.
- Major positive environmental impact due to potential to replace primary batteries in many applications.
- Claims of no memory (see comments under Nickel Metal Hydride above)
- Charging:
same as any other NiMH: generally, recharge before you notice the
capacity diminishing. Try to avoid frequent discharges to cut-off.
Lithium Ion (Li-ion)
Lithium Ion technology is, at present, the best combination of energy density (storage capacity v. weight) and cost. They have the additional advantage they they can be molded into various shapes, making them ideal for use in phones, music players and other appliances that need to pack their batteries into small places with odd shapes.
- Very light
- No memory problems
- May vent smoke or flame if overcharged*
- Extremely heat-sensitive
- May be damaged by excessive discharge
- Relatively expensive due to built-in protective circuit
- High capacity
- Very flat discharge curve
- Charging: charge early and often; ok to charge continuously as long as there is no heat buildup.
*Li-ion cells are very sensitive to overcharging and overheating. The latter will cause them to fail, the former to vent (some people might say “explode”). For that reason most (but not all) Li-ion cells and batteries have built-in circuitry to limit charging. Chargers meant for Li-ion application also have special circuitry. In the absence of that circuitry, charging a Li-ion is very dangerous.
Such problems can occur if both the circuit in the charger and in the battery fail at the same time. They can also occur if either the battery or the charger was built without the circuits in order to keep the price down, and then the other device’s protection fails. This is most likely to happen with after-market phone chargers that are sold for ten bucks at the convenience store. Few of them have the protective circuitry, and depend on the circuit in the battery to protect the charging cycle. If the battery is subjected to too much heat, shock from being dropped, etc., that circuit may fail as well. Imagine your phone bursting into flames on the car seat beside you. Scary.
Li-ion batteries do not require conditioning. The “exception” can occur with laptop batteries (and some phone batteries). If they are left on charge for long periods, the device “fuel gauge” can lose calibration and indicate a lower charge than is actually in the battery. If yours is indicating low, allow the battery to discharge to cut off in the device, then completely recharge before using. If that was the problem, you should notice an increase in capacity. If not, you will probably need a new battery soon.
Some laptops permit you to remove the battery after it is charged and run the machine on the AC converter when using it on the desktop. This is a good idea, to keep the heat down. The devices that cool the bottom of a laptop are also a good investment.
Recommendations
I like the hybrids for just about everything requiring AA or AAA cells. What’s not to like? They’re environmentally friendly (one hybrid will replace hundreds of alkalines), they perform much better than other AA and AAA rechargeables, and considering their service life the cost is negligible. I find little or no difference between them and the “regular” NiMH cells, and in some applications they seem to perform better. Add to that the fact that they hold their charge for months, and they immediately become the battery of choice for most purposes.
Lithium Ion batteries are excellent for applications where the absolute maximum must be squeezed out of the battery or — obviously — for equipment that came with Li-ions. When it comes to high loads like those imposed by electric-powered vehicles (real or model) and small appliances like phones that need teeny batteries, they’re hard to beat. They’re great for cramming maximum capacity into restricted areas because of the ability to mold the battery to the shape of the appliance. However their sensitivity to heat and need for careful charging is not likely to endear them to the masses even if they become widely available in common sizes.
The exception: power-out emergencies that last for long periods, such as hurricanes and other natural disasters. You can charge batteries in the car, but that’s a bit iffy for me. I plan to keep a 24-pack of cheap alkalines from Costco in the back of the refrigerator, just in case. Those and our LED lighting devices should handle anything of that nature that arises. I won’t even have to warm them up. About the time I really need them, the refrigerator will have taken care of that for me. ;=)
6-month follow up:
The hybrids seem to be working better for me than the regular NiMH batteries for camera applications. The power delivery curve is a bit flatter, which seems to give adequate performance at the beginning and slightly better at the end of the discharge cycle. That’s consistent with other findings I’ve researched.
The downside: capacity is limited to the neighborhood of 2000 mAH instead of the 23-2500 of a conventional NiMH cell. This is a function of the chemistry change that allows hybrids to retain their charge for much longer periods than the “normal” cells. I haven’t found this to be a problem. I think the flatter discharge curve somewhat compensates for it. Your mileage may vary.
All in all, I like them better than the “old” NiMH’s. They perform adequately, and their slow self-discharge allows them to be substituted for alkalines in many applications, such as flashlights, media players and so forth. This means you’re getting, in effect, about 200 alkalines for the price of one hybrid.
I will continue to use alkalines or lithium in long-running installations such as smoke detectors and appliances that have to be subjected to temperature extremes (such as flashlights that live in the glove compartment) because heat is the enemy of all rechargeable batteries, especially NiMH and L-ion, and even hybrids will self-discharge over long periods (roughly 50 – 80%/year). Non-rechargeable lithium is still the choice for extreme performance and extremes of temperature.
Remarks on charging: when charging any battery, of any type, it is best to bring it to a full charge whenever possible before removing it from the charger.
