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.
Thanks you.
Peter
--
He spoke with a certain what-is-it in his voice, and I
could see that, if not actually disgruntled, he was far
from being gruntled.
P.G. Wodehouse 1881 -1975
"Peter James" <pfjames2000@googlemail.com> wrote in message
news:1ij93e2.zmhufg1i5j64sN%pfjames2000@googlemail .com...
>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.
>
> Thanks you.
>
> Peter
>
Peter,
It may be a good idea to use batteries that are close in capacity, but exact
matching is not necessary if you use the right charger.
The most important thing (from my experience) is to use a charger that
charges each cell individually. The less expensive chargers will take
shortcuts and charge two at a time. This can cause problems if one (of the
two) has different characteristics than the other. This can cause problems
such as cell voltage reversal.
One example of a good separate-charger-circuit-per-battery charger is the
Maha MH-C401FS, but there are other good ones, too. I've been using a couple
of them for years they've never let me down.
On Sat, 28 Jun 2008 15:17:38 +0100, Peter James wrote:
> 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?
For several reasons, you really should replace all four.
> 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 shouldn't mix 'n match *any* type of batteries, whether
alkaline or NiMH. The main thing that you want is that all four of
the NiMH cells should have approximately the same capacity.
Assuming that those Hama batteries are fairly old, if you bought two
more, they'd probably be rated near to 2,500mAh. Continuing with
that assumption, your old batteries (at least the better 2 of the 4)
probably now have *much* less than their original 1,850mAh capacity,
possibly 1,000mAh or less. Add two new 2,500mAh NiMH cells and the
combination will perform almost as if all four were 1,000 mAh cells,
so battery life will not only be terrible, it will decline as the
two old cells get even older. Best to get four new NiMH cells now,
rather than two now and another two soon after.
>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.
>
>Thanks you.
>
>Peter
As I understand it, you should not mix NiMH batteries that have
different levels of discharge. You end up over-charging some of the
batteries, which can damage the batteries or even the charger.
You also don't want to mix different types of batteries or batteries
with different capacities.
> 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.
I'm not sure that it is a myth or fact, but I keep my sets of 4 together
and run 'em down and charge 'em up as a set.
If you can buy 2 + 4, then use the 2 to try to match the working 2 and
the other 4 as a new set.
I've had poorly performing sets turn around and become reliable. No
idea why. If you go through a half dozen cycles as a set, you might get
there:
Same manufacturer and model of battery.
Same nominal capacity (Ah).
Charge the two "good old" batteries to max and SEPERATELY charge the two
new batteries to max. Start using them as a set of 4.
(Charge the other new 4 as a separate set).
Run them through several cycles. If by the 5th or 6th run through
you've gotten nowhere, then abandon them.
I tape colored electricians tape around mine to keep the sets identified.
NOTE: Store your NiMH's with the positive end UP. You'll notice there
are vents at the top of the battery.
In article <1ij93e2.zmhufg1i5j64sN%pfjames2000@googlemail.com >,
Peter James <pfjames2000@googlemail.com> 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@radagast.org> 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!
> Can I just replace two batteries, or must they all be replaced by a
> "matching" four pack?
Use NiMH batteries in sets composed of batteries of the same brand,
rated capacity, and manufacturing date. Some users like to test the
capacity of batteries to match sets even closer.
> 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.
Nothing terrible will happen if you do this, but it will mean that the
weakest battery determines how long the device will operate between
recharges.
For information on caring for NiMH batteries go to
"http://batterydata.com/" and click on "Care and Feeding of NiMH
Batteries" in the table of contents.
> 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.
>snipped
Thank you for all of the replies to my original posting. They have been
most informative and useful.
I'll dispose of the old set of NIMH batteries and buy new. I have had
them some time, so it's not the end of the world.
Thanks again.
As Isidor Buchmann writes (http://www.buchmann.ca/), NiMH cells are
considered high maintenance batteries.
Here are some tips to maximize capacity and longevity of NiMH batteries:
1. Prime your New NiMH Batteries with five discharge/charge cycles.
2. Use NiMH batteries in sets composed of batteries of the same brand,
rated capacity, and manufacturing date. Some users like to test the
capacity of batteries to match sets even closer.
3. Do not store NiMH batteries in a discharged condition.
4. Do not trickle charge NiMH batteries with a current higher than 10mA.
5. Orient the charger properly. The temperature sensor will not operate
properly if the charger is not properly oriented. Some charger
instructions explicitly warn about this (i.e. the Sanyo NC-MQN05 which
comes in the Sanyo eneloop pack from Costco.
6. Try to completely discharge the batteries prior to charging. Some
chargers can do this automatically (LaCrosse BC-900) and some can do it
manually (Maha MH-C9000).
7. Do not use the "discharge" button on your charger (if it has one) for
every charge cycle, because this unnecessarily shortens the battery life.
8. Do a full discharge/charge of NiMH batteries every few months (most
cameras won't completely discharge the batteries)
9. To keep NiMH batteries topped up, store them in the charger, with a
timer that comes on for about thirty minutes per day. This will
counteract the self-discharge. Since most NiMH chargers do not trickle
charge after the battery is fully charged, the only way to turn the
charger back on automatically is to unplug it then plug it back in using
a timer. Alternately, you can build a very low rate trickle charger.
10. Keep track of the number of cycles. 500 cycles is very optimistic.
Consider replacing NiMH batteries after 250 cycles.
11. As with all batteries, store in a cool place.
12. Choose a good charger, with independent charging for each cell. See
"http://nordicgroup.us/chargers/" for advice on chargers.
13. Avoid the extremely high rate chargers (don't go over 2000 mA)
And finally....don't worry too much about all of this, because
high-capacity, high-quality NiMH batteries (at least AA cells), cost
only about $2 to $2.50 each. If you mistreat them, you may only get 150
cycles rather than 300 cycles out of them, which is no big deal.
From "http://batterydata.com/", Earth's Independent Source for Digital
Camera Battery Information.
Problems with digital camera batteries 
Linear Mode
