For optimum longevity, at which stage of drainage is it best to recharge a battery?

Question

I've heard every opinion from people of various qualifications including it doesn't matter, only when it's ~99% dead, if you let it die completely it'll never hold the same maximum charge. Perhaps the answer is different for different types of batteries.

Answer 1

It is different for different types. Ni cad are best discharged completely, lead acid should not be discharged completely. NiMH and lithium don't care.

Answer 2

As far as I know Lead-Acid (Car batteries) should not be completely run down. This is because when being charged up it is more likely that lead particles will fall to the bottom, becoming useless. This is how car batteries eventually die anyway, but doing full charges will deplete their capabilities faster.

On the other hand with Li-Ion batteries (Digital cameras, cell phones) it is best to completely run them down regularly and then charge them completely so as to avoid them developing a 'memory'. I'm not exactually sure how they develop a memory, but the end result is that they 'forget' that they could hold so many Amp hours and thus can hold less power.

Answer 3

For cordless phones, cell phones, etc. let them get run down as far possible before recharging.
Those batteries have a "memory", and if you recharge them when they only half discharged they will use the half discharge point as the new "zero" point and you will have to recharge the battery twice as often as it will only hold half the original charge.

Answer 4

Years ago (1990) the theory was that it's best to let it fully discharge. I don't know if that's still the case. I would just keep recharging it anytime you want (I do this with my laptop battery) and its life hasn't degraded noticeably.

Answer 5

It really matters on what type of battery. Try asking again later with the type.