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Re: NiMH Battery Question

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>Hello all,
>
>Quick question.  What would the expected voltage be
>for a new VARTA 3.6vdc 70mAH NiMH rechargeable battery??

That depends on its level of charge.

>Or maybe the better question would be:
>If the voltage is at 1.76vdc would the battery be good??

Possibly, if it's newly manufactured, and had been built and shipped
in a discharged state.

NiMH cells have a nominal voltage of around 1.2 volts per cell, so a
"3.6-volt" nominal battery consists of three cells in series.

They're often rather higher when freshly/fully charged... I see around
1.45 volts when they're being charged.

A NiMH or NiCd battery should not be discharged to below around 1 volt
per cell.  Doing so risks fully discharging one cell before the
others;  as the others continue to discharge the weaker cell will be
"reverse charged" and this can permanently damage it.

So, 1.76 volts in a three-cell battery would probably indicate one of
two things:

(1) Newly made, and the cells were never charged (or were test-charged
    and then individually discharged, or were charged and then self-
    discharged over time), or

(2) A battery which has been discharged to below the safety limit, and
    might have been damaged.

Manufacturers often ship NiMH and NiCd cells and batteries in a
discharged condition.  Safer that way - less risk of fire if something
accidentally shorts one or more cells.  Older-style NiMH cells have a
high self-discharge rate - they'll lose 10% or more of their charge
every month even if not being used at all. 

You'd need to actually test it to determine.  Charge it fully
(according to the manufacturer's recommendations).  It should rise to
at least 3.6 volts very quickly, then probably to 4 or 4.2 volts as it
continues to charge.  If it doesn't behave like this, it may well be
damaged or defective.

When fully charged, discharge it at a safe rate (5-10 mA in
this case) until it drops to 3.0 volts, then disconnect.  Multiply the
discharge time by the discharge current, to get the capacity.  If it's
not in the 50-to-70 mAh range, it may be bad.

Expect that you may not get the full rated capacity until the battery
has been charged and discharged several times - NiMH cells have a
distinct "break-in" effect.

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Thread

NiMH Battery Question ABLE1 <somewhere@nowhere.net> - 2018-05-30 21:08 -0400
  Re: NiMH Battery Question ehsjr <ehsjr@verizon.net> - 2018-05-31 01:45 -0400
    Re: NiMH Battery Question Brian Gregory <void-invalid-dead-dontuse@gmail.com> - 2018-07-19 00:45 +0100
    Re: NiMH Battery Question "Ian Field" <gangprobing.alien1@virginmedia.com> - 2018-11-17 20:33 +0000
  Re: NiMH Battery Question dplatt@coop.radagast.org (Dave Platt) - 2018-05-30 22:43 -0700
    Re: NiMH Battery Question ABLE1 <somewhere@nowhere.net> - 2018-05-31 08:04 -0400
      Re: NiMH Battery Question Jon Elson <elson@pico-systems.com> - 2018-06-04 17:36 -0500
        Re: NiMH Battery Question ABLE1 <somewhere@nowhere.net> - 2018-06-04 19:26 -0400
    Re: NiMH Battery Question "Ian Field" <gangprobing.alien1@virginmedia.com> - 2018-06-11 21:38 +0100

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