I'm not usually a person to go into the techie "tool" stuff - there are plenty of blogs out there for that! But, I feel like this is one of those things that might make your life easier if you knew a little more about it, so here we go!
NiMH: Nickel-metal hydride
The most common rechargeable battery when it comes to standard AAA and AA batteries. NiMH batteries come in a variety of mAh (milliAmp hours = aka power time), the higher the number, the more battery life you can get out of them. Some of the best mAh on the market right now for a standard AA rechargable battery is about 2700mAh- look for this info, usually clearly marked on the battery, before purchasing because it will make the biggest difference in how long you can use those batteries during a single charge.
When it comes to getting the most life out of NiMH batteries, you will want to use these batteries until they are completely drained, and then only charge them immediately before they are going to be used again. If you can't completely drain them, than simply let them sit uncharged until you need to use them again. If you charge them 24 hours before they'll be used, you should get a decent battery life out of them. If you try to charge them one week before they'll be used, you'll find that significant draining has occurred and lessened the battery life. The first few times you use this battery, it's strongly recommended that you let it completely charge and completely discharge a few times in order to get the most out of the battery.
Li-ion: Lithium Ion
This battery type is often found in cell phones, small digital devices, and professional cameras and video cameras. It is not currently available as a rechargeable battery in standard (AA) battery sizes. It has a higher capacity for mAh, and can produce a higher voltage than the NiMH batteries. Li-ion batteries are also much better at holding a charge over a long period of rest. When properly cared for, these batteries can last a very long time.
Li-ion batteries perform best when they are not fully drained. These batteries like to be charged regularly and perform best when maintained at a full to medium charge. Li-ion batteries do a MUCH better job of holding a charge over a long period of time, but only if they have a partial or full charge left before leaving them on the shelf to sit. If you do let a Li-ion battery fully discharge and then let it sit for a long time, you may find that it is unusable after it has been discharged below it's safe level. Li-ion batteries don't tend to develop a "memory" in the way that NiMH batteries do, therefor it is not necessary to fully charge and discharge this battery regularly, but it is recommended to complete the cycle from time to time.
All Rechargeable Batteries are affected by extreme temperatures and different types of chargers. It is recommended that you use a medium speed charger in order to prevent your battery from overcharging or undercharging too quickly. Rechargeable batteries should be replaced when their performance life has significantly decreased. If you have a device that is only used sporadically, you may prefer the life of a Li-Ion battery (even if it isn't rechargeable) over that of a NiMH. However, rechargeable batteries are ultimately better for the environment and for your finances when well-cared for.
*Special thanks to my Dad, aka "Battery Dave" for helping me pull together this info.
If your house gets taken over by your need to charge many batteries the night before a wedding, check out this awesome battery and charger storage and organization solution featured on Laura Eaton's blog! Click any image to see the original post..
