Capacity/mAH: The amount of energy a battery can store. mAH stands for milliAmp Hour or how many milliAmps are available for one hour. A 2500 mAH battery should be able to provide 2500 mA for one hour or 1250 mA for two hours.
C: Is the charge rate of a charger. 1C means that the charge current is equal to the capacity so a 3000mA battery will be charged at 3000mA for one hour. 0.5C means 1500mA for two hours.
Load current or drain: The amount of energy that can be drawn from the battery immediately. A high drain product draws a lot of current continuously.
Self Discharge: Many batteries will slowly discharge if left in storage. This is especially true for NiCd and NiMH batteries.
LSD: A newer type of NiMH called Low Self Discharge. They won’t self discharge as much while sitting on the shelf or being shipped to the customer. While convenient, I don’t think they’re worth the extra cost, yet (2011).
There are two basic types of batteries: primary and secondary.
Primary batteries are disposable. The old dry cells were zinc carbon, the more common are the alkalines.
A newer type is the lithium (not Lithium Ion). The advantage of the lithium is higher drain performance. They are not rechargeable.
Secondary batteries are rechargeable.
There are three main types of secondary (rechargeable) batteries based on chemistry:
NiCd (Nickel Cadmium)
NiMH (Nickel Metal Hydride)
Li-Ion (Lithium Ion)
Do not confuse Li-Ion batteries with Lithium batteries. Lithium batteries are not rechargeable.
Lesser known are:
Lithium Ion Polymer
NiCd and NiMH batteries
Higher drain performance. They will last longer in higher drain electronics, like digital cameras with flash and cordless power tools.
Can be recharged many times.
Self Discharge Problem: When not being used, Nickel-based batteries will lose some of their capacity over time. Wikipedia says NiMH will lose 5-10% after one day and another 1% every day after at room temperature.
Self Discharge Fix: Some suggest leaving NiMH batteries on a charger, trickle charging. I, and most websites suggest removing the battery within a day of being charged because leaving them on can lead to overcharging and overheating. However, they may require a recharge before usage which is often inconvenient.
Another possible fix is freezing or refrigerating (See separate step).
Memory Problem: NiCd batteries and to a lesser extent, NiMH batteries have something called ‘memory’. What is actually going on is controversial but what it means is that after many partial discharges and recharges, they have less capacity than before. In other words a full charged battery will not last as long.
Memory problem Fixes: To reduce this problem, most websites recommend that NiCd batteries should be fully discharged once a month. Technically, this means the battery is discharged from 1.2 V to 1.0 V. Practically, this means running the device, drill, cell phone, whatever until it no longer works or shuts off. Be careful with some products like flashlights that may discharge too far, much less than 1 V.
Another possible fix is freezing (See separate step).
Now if a NiCd or NiMH battery still has a memory problem, there often is a another way to repair it. This is called reconditioning and will be discussed in another Step.
Good: Higher drain performance.
Li-ion batteries do not have the memory problem.
Lifetime Problem: They do have another problem which is a limited life time strictly due to aging.
Lifetime Fixes: Do not fully discharge the battery.
Leave the battery or device on the charger even after it’s fully charged.
Try to keep battery cool.
Some products can use different types of batteries.
My Canon camera can use alkaline or NiMH batteries.
For some cellphones (I think), you can buy different types of batteries
Products with standard size batteries, AAA, AA, C and D can often work with different types of batteries.
One of the main advantages of using rechargeables is cost. Alkaline and lithium batteries have to be discarded after they are discharged. Rechargeables may be a little more expensive than alkalines but they can be recharged many times.
For most applications I would recommend rechargeable NiMH if they work because:
NiCd batteries contain Cadmium which is toxic. Probably for that reason, they are not as popular and harder to find.
NiMH have less of the ‘memory’ problem then NiCd.