Battery level indicator with NiMH AA cells in the BG-E2 ?

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SMS - 04 Feb 2006 08:41 GMT

When I use one or two BP511A battery packs in the BG-E2, the battery
indicator level is fine. When I use six AA cells in the battery tray,
the level quickly falls to the second to lowest level. I'm wondering if
this is because of the the slightly lower voltage of the six AA cells
(7.2V) versus the voltage of the Li-Ion pack (7.4V). When the batteries
are hot out of the charger, they are at around 1.25V each would account
for the battery indicator being okay until a couple of shots are taken.

These are new Sanyo 2500 mAH cells that came with the charger. They test
as good (charger has a test function to test the AA cells under load).

The BG-E2 is one of the early ones, and was serviced by Canon.

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C J Southern - 04 Feb 2006 11:11 GMT

I always got pretty much the same result - and never did get a satisfactory
answer.

The good news is that with a couple of bp-511a clones it's almost impossible
to run them flat in a day.

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SMS - 04 Feb 2006 17:07 GMT

> I always got pretty much the same result - and never did get a satisfactory
> answer.
>
> The good news is that with a couple of bp-511a clones it's almost impossible
> to run them flat in a day.

I would never actually rely on AA cells, too much trouble, but I wanted
to just try them. I could still take plenty of pictures even with the
battery indicator that low.

My theory is this:

Since the voltage discharge curve is very flat on Li-Ion, the battery
meter is designed to measure very small voltage differences on a Li-Ion
battery, i.e. anything less than 7.4 is full, 7.3 is half empty, and 7.2
is 3/4 empty. Since six NiMH will be 7.5V immediately off the charger (6
x 1.25V) they show full when first inserted, but as soon as you put a
real load on them, by taking a picture, they drop to 1.2V, and 6 x 1.2V
= 7.2V. I guess I could try seeing how many photos I could take on them.

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C J Southern - 04 Feb 2006 21:46 GMT

The bit I don't get is that if you put something like 6x Eveready Alkalines
(ie 6 * 1.5v = 9v) you only get (per the "manual") around 60 shots - whereas
your close to 1000 with the double bp511a combo.

Also says it's not compatible with Lithium batteries (as in the 1 shot
variety, not Li-on rechargeables).

I also have the same issue with my hand-held aviation transciever - but on
the correct battery pack and all is sweet - put in lithiums (after extending
the house mortgage) and I'm immediately in a battery low situation.

Hmmm

My advice is to grab a couple of clones (1.5 times the capacity, 1/3 the
price of the original) and use them - and also keep your original as a
standby (just don't forget to charge it once a month at the outside).

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SMS - 04 Feb 2006 22:23 GMT

> The bit I don't get is that if you put something like 6x Eveready Alkalines
> (ie 6 * 1.5v = 9v) you only get (per the "manual") around 60 shots - whereas
[quoted text clipped - 12 lines]
> price of the original) and use them - and also keep your original as a
> standby (just don't forget to charge it once a month at the outside).

Yes, I have plenty of BP-511 clones, I just wanted to try the NiMH
batteries when I got the grip back from Canon. I was a little worried
that the battery level indication meant that there was still a problem.

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