Re: Problems with digital camera batteries
- From: dplatt@xxxxxxxxxxxx (Dave Platt)
- Date: Sat, 28 Jun 2008 10:46:29 -0700
In article <1ij93e2.zmhufg1i5j64sN%pfjames2000@xxxxxxxxxxxxxx>,
Peter James <pfjames2000@xxxxxxxxxxxxxx> wrote:
I hope this is the right NG to ask this question. If it's wrong, then I
apologize.
I use a 4 pack of NIMH Hama batteries 1.2v/1850mAh in my Canon Power
Shot A80 digital camera.
When I charged them up last night, after 3 hours two of the batteries
failed to charge and the other two charged up OK. I am assuming the two
that didn't charge are u/s or going that way.
Can I just replace two batteries, or must they all be replaced by a
"matching" four pack?
I seem to remember reading somewhere that you can't mix 'n' match NIMH
batteries like this, but I thought I would seek re-assurance here.
You *can* mix and match, but it's often considered better not to do so.
If you mix cells different capacities into a set, then the usable
capacity of the set will be that of the weakest (lowest-capacity)
cell.
To complicate things - when the weakest cell does run down, the camera
(or other device) will *probably* shut down due to low-battery before
the weakest cell runs entirely out of power. However, if it doesn't,
then the remaining cells in the battery will continue to deliver
current through the discharged cell, "reverse charging" it.
Reverse-charging will definitely damage NiCd cells and I believe it's
likely to damage NiMH cells as well. If this occurs it'll weaken the
weak cell even more, and it will soon die.
People who demand the most out of their batteries (e.g. RC racing
enthusiasts) often capacity-match the cells in their batteries to
within 5% or better.
If two of your cells out of the original four have reached
end-of-lifetime (that is, if you're sure it's not your charger that is
at fault) then the other two are probably getting long-in-the-tooth as
well and may not have much useful lifetime left.
I'd suggest replacing all four. Using some of the new ultra-low-
self-discharge NiMH types would be a good bet - Sanyo Eneloops or
Powerex Immedions or Uniross Hybrios are examples of this type.
They're typically rated at 2000 or 2100 mAh. Unlike the older NiMH
types, and unlike most current very-high-capacity NiMH (e.g. 2500-2700
mAh) they don't self-discharge very much at all, and will actually
deliver most of their rated capacity even if you don't use them for
several weeks (or months) after charging them.
--
Dave Platt <dplatt@xxxxxxxxxxxx> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
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- From: Peter James
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