A recent post, “Recharged Batteries” concluded that rechargeable batteries do not have a memory effect but other factors have been charged with that fraility.
How do rechargeable batteries die or become unusable, and is there a way of predicting when they have reached the end of their usable life?
Which size, model, type of battery are you looking at? Nimh are different than Nicad, different from lithium, lead, etc.
My benchmark for replacement of alarm panel standby batteries is 5 years. They are rarely discharged, and towards the end of the 5 year span will not deliver the standby rating in Amp/hours as when new.
NiMh is an improvement over NiCd, but they still suffer when not cycled. My fire company has made an investment in a battery cycler, given the number of portable radios we own. This way, the batteries aren’t cooked in a charger all the time or left in slow drain by standby status.
The best thing to do with a battery is use it. Cycling is better for long term battery health regardless of chemistry than constant charge or lack of use.
To really keep things short, there are several common causes for the death of any battery, including non-rechargable ones.
The electrolyte dries up. Very common on NiCads. Some people have injected water to revive NiCads. I do stupid stuff with batteries but nothing that desperate.
The anode or cathode gets eaten away. This seems to be how LiIons usually die. Very corrosive stuff in those, even by battery standards.
The anode or cathode gets gunked up. The chemical processes are not perfect and unintended compounds get created, usually around a terminal. Very common on NiCads and NiMhs.
For Nicads, there can also be “spikes” develop in the electrolyte that (nearly) shorts out the battery. There are also supposedly ways to revive these, I’ve tried it, but it doesn’t really work well enough to be worth it.
There’s a link to some battery info at the repairfaq.org site that Q.E.D. links to in the other thread. (Q.E.D. links to the repair FAQ, I never thought I’d see the day!)
Note that all these batteries contain Very Bad Stuff and every precaution should be taken to keep you and the Very Bad Stuff safely apart. Acids, alkalines, heavy metals, etc. Some can even produce fumes that will hurt you bad enough to ruin an ER doctor’s day.