Author Topic: Voltage from factory Ni-Mh Batteries  (Read 869 times)

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Offline made2hack

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Voltage from factory Ni-Mh Batteries
« on: February 02, 2016, 05:13:05 am »
Hello all,

I recently bought 24 Ni-Mh batteries from a seller on ebay (see this post).

13 have a voltage of close to 1V (around 0.95V), 1 has around 0.67V and 11 have voltage close to 0.2V.

What should be the factory voltage? Should there be a factory charge? Are the 0.2V Ni-Mhs dead?

Offline Gyro

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Re: Voltage from factory Ni-Mh Batteries
« Reply #1 on: February 02, 2016, 05:48:41 am »
That does sound like quite a variation for new(?) batteries. If NiMh behave the same way as NiCd the it is ok to discharge them to 0V (In fact large capacity single cell aviation cells used to be supplied with a shorting clip fitted)..What kills them is where you have multiple cells in series and one cell gets forced reverse polarity by the other cells as the whole pack gets discharged.

The important thing (I assume you're going to be using them in series stacks) is that their capacities match well. If not, the above situation can occur. They will at least need constant current charging at C/10 rate for longer than 14 hours to ensure that they all become fully charged and the cell voltages equalize.

Edit: To answer your middle question - always assume that new batteries are discharged and require a full charge before use. There are some special 'low self-discharge' cells that are retail packed as 'pre-charged' now, but that's not what you have bought.
« Last Edit: February 02, 2016, 05:53:44 am by Gyro »
Chris

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Offline DivineChaos

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Re: Voltage from factory Ni-Mh Batteries
« Reply #2 on: February 03, 2016, 10:04:33 am »
If they are AA nimh batteries, you can refresh them with a LaCrosse BC-700. Best Nimh charger and restorer period. Keep in mind that it will in some cases take DAYS to restore them.

The charger will also tell you the capacity of the batteries so you can pair them up
 


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