akansaskid

How much harm, if any, is done to 1) lithium-ion and 2) Ni-MH batteries if they are left on the charger for a day or two before use?

For right now I use a simple charger for the Fenix's AA batteries which shuts off after charging. I'm assuming no harm is done leaving them in there for a couple of days even. And I'm in on the Oct 20 Magicshine shipment. I plan to put its L-ion battery pack in a front handlebar bag, and just plug in the charger straight to the bag when I return from riding. It may stay like that (plugged in) in a freezing garage for 2 or 3 days if the weather is bad. Again, will I be shortening either the battery life or its capacity (for that charge) by doing this?

ItsJustMe

In both cases, it depends largely on the charger. If you have bad chargers it could be not a good idea.

NiMH: should be no problems at all. You can leave them on for months if you have a good charger that drops to maintenance mode after charging is complete. However, if you have a non-smart charger, it's a bad idea to leave them in.

LiIon: since there's no such thing as a non-smart charger for LiIon, it shouldn't cause any trouble. What really kills LiIon batteries is leaving them discharged for very long. Ideally you should top off their charge at least every month even when you're not using them (like in the summer for bike lights).

akansaskid

Thanks. My cheap NiMH chargers just go from red light to green light when charged. I do notice that once charged and left there, the batteries quickly cool off to room temperature, making me think they are no longer receiving a charging current. I know there's no maintenance (or refresh) mode on them.

Sounds like for the L-Ion Magicshine, I'll be able to just plug the bike back in after a ride and not worry about it.

dekindy

I have a question about this as well. I have read batteryuniversity.com at lenght and used to regard it as gospel. I have been advised that it is out of date. It advised that leaving nicad and nimh batteries on trickle charge for long periods of time reduced the capacity and number of cyles of both types. If I remember correctly they recommend letting nicads run down at least once per month and nimhs quarterly. Test showed that this maximized battery capacity, number of recharge cycles and battery life.

Is this still true?

Are hybrids treated any differently?

I think it has always been true that Li-ion's can be recharged and discharged at will. However they used to begin losing permanent capacity with time and storing in cool temperatures was the only way to minimize capacity loss. Is this still true?

What is a good source for battery information now?

enine

Yes, the batteryuiniversity site is out of date and lumps NiCad and NiMH too close together. NiCad are the most tolerant of trickle charging, NiMH you can leave trickle charging but its not really recommended for them as it does tend to reduce their lifespan.

There is no such thing as a hybrid battery, thats just a marketing name from rayovac for the low self discharge NiMH, which are basically normal NiMH but with a beter insulator to reduce self discharge as the expense of a slightly lower capacity, they follow the same charging procedurs as normal NiMH. When you trickle charge NiMH at a very low level you may end up with say 500 cycles instead of 1000 but with the newer low self discharge its pointless to keep them in a charger since they hold their charge.
It really depends on the charger, if the charger does provide a "maintenance" charge and how much.
Lithium ION the chargers have to shut off when charged if now they will eventually explode. Lithium ION the typical consumer grade cells have a life of 300 cycles and partial charges add up to full charges and yes they loose 10-20% of their capacity per year. So you don;t want to cycle them as it provides no benefit and will just use up cycles.