NiMh Battery Question

[GPB]

What is the recommended usage pattern for Nimh rechargeables. I like to change out the battery before I notice a decline in light output. For me this will be every 4 or 5 days on my edc ( single AAA light ). Will I shorten the life of the battery if I only use up 50-60% of the juice before I swap it out for a fresh one ? Will I be better off if I leave the light on for an hour or so to drain the battery before I swap it out.

Thanks

 

[FILIPPO]

I have heard that you should charge batteries when you see light dimming...

I'd like to know something more about this...


PS: I think it isn't the correct place for this thread...
http://www.candlepowerforums.com/vb/forumdisplay.php?f=9

 

[turbodog]

Nicd or nimh in a SINGLE cell light just about can't be damaged. You can use them part way and recharge and you'll be fine, and this is actually the preferred method.

Full discharge is ok also, but only in a single cell light. Otherwise the remaining cells will reverse charge the first cell to run down. This reverse charging is very bad for a cell and will usually kill it in very short time as well as create a fire/leak hazard.

 

[SilverFox]

Hello Greg,

NiMh cycle life is based on a full discharge every time. If you do shallow discharges, you can expect an improvement on cycle life.

I will move this over to the batteries section of the form.

Tom

 

[GPB]

Thanks everyone ( for the responses and for putting the thread where it belongs.....sorry about that )

 

[Curious_character]

Hello Greg,

NiMh cycle life is based on a full discharge every time. If you do shallow discharges, you can expect an improvement on cycle life.
Tom

But do you get more total energy? That is, if you discharge the cells 50% each time, do you get more than twice as many cycles as when you discharge them fully? If not, what's the point?

c_c

 

[SilverFox]

Hello Curious character,

Yes, you get more total energy.

Tom

 

[TorchBoy]

Re: NiMH Battery Question

Yes, you get more total energy.

Is that why NiMH batteries like in the Toyota Prius last so long? They're normally only used for partial cycles?

 

[SilverFox]

Re: NiMH Battery Question

Hello Ian,

Yes, that is how it works.

I don't remember what the cycle is on the Prius, but I seem to remember something about only charging to 80%.

Tom

 

[Mr Happy]

Actually there are two different cases here:

1) Charging to 80% and discharging completely each cycle
2) Charging to 100% and discharging to 50% each cycle

I believe the first case leads to longer battery life than the second.

 

[shadowjk]

I wonder what Prius uses as end-of-charge signal to achieve 80%, and how well the cells stay in balance over time...