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Author Topic: NimH life of charge  (Read 2229 times)

Tug-Kenny RIP

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NimH life of charge
« on: July 11, 2014, 09:25:13 pm »


How long should a fully charged NimH battery stay charged please.

I fully charged my Spektrum transmitter and it read 11.2 volts but when I came to it the following day the charge level was down to 10.6 volts on the power indicator. I keep checking it by switching on the radio for one minute each day and it's progressively going downwards. It's now settled on 10.2 but the length bar (shown as black line) is only at 3/4. I did start out with a new battery originally so find this surprising as i figured it would stay close to full for longer than this.

Your thoughts please.

Ken

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Stavros

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Re: NimH life of charge
« Reply #1 on: July 11, 2014, 10:44:30 pm »

Arnt they 9v rated anyway Ken usually after being charged they will be around 10v................My futaba is doing the same as yours and I dont get any probs
 
 Checked some batts tonight that I havnt charged for over 12mnths and they were 1.5v down on what thye should have been so I cylcled them and recharged them tonight
 

Dave
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malcolmfrary

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Re: NimH life of charge
« Reply #2 on: July 12, 2014, 08:26:23 am »

8 NiCads are nominally 9.6 volts, so settling down from a peak charge voltage is normal.  Transmitters are probably designed and its meter calibrated around the user using alkaline dry cells, eight of them will give 12 volts plus a bit for newness.
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Tug-Kenny RIP

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Re: NimH life of charge
« Reply #3 on: July 12, 2014, 09:46:17 am »



Ah !!  Thank you for that. I can see the logic and will check if it goes down any more over the next few weeks.

Cheers

ken

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NFMike

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Re: NimH life of charge
« Reply #4 on: July 12, 2014, 10:33:40 am »

Most batteries 'lose' a chunk of voltage immediately after coming off charge - sometimes called surface charge. It doesn't come off the core capacity.

A downside of NiMH is high self discharge rates. Originvally they could be near 5%/day but modern ones are more like 1%. But you really need to recharge every month or two if you want to keep them 'ready'.
If that's a problem use NiCd or possibly lithium (not LiPo) instead.
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