any way to change Low Battery voltage threshold ? - Feature Requests - CHDK Forum
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any way to change Low Battery voltage threshold ?

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Offline tgt

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any way to change Low Battery voltage threshold ?
« on: 07 / January / 2009, 11:03:03 »
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Hi, I was wondering if there is andy way to change the battery voltage level, at which the battery indicator starts blinking and the camera goes to shutdown. The A570 IS has it set very high and likes to suddenly turn off, especially, when the flash is charging. This issue has been reported by a lot of users:
http://www.digitalcamera-hq.com/digital-cameras/canon-powershot-a570is_question.html?qid=15701
but there was no response by official Canon support. When watching the voltage meter with chdk is seems that falling below 2,2V is
I know, that the internal battery resistance can cause a huge voltage drop when theer is a need for power (zoom, flash etc.), but after that the voltage slowly rises and reaches the actual battery level.
My idea is to let the user set a voltage threshold wyth hysteresiss, according to his own observations. New Ni-MH batteries have a small internal resistance, which causes amost no problems. While aging (or discharging of course) the internal resistance rises, so the voltage readouts are incorrect. Also, a new type of Ni-MH rechargeable batteries (Panasonic Infinium or Sanyo Eneloop)  have smaller self-discharge effect, but also greater internal resistance compared to typical Ni-MH.
Changing the voltage threshold level can help get longer lifetime of a set of batteries, because they can be now discharged
deeper (in my case with a570 were at discharged only about 50% with new Infinum batteries). Theere is of course a side effect: discharging batteries too deeply decreases their overall lifetime. In theory, a Ni-MH cell is discharged, when the voltage reaches 1.0V for a single one. That is the voltage (multiplied by the number of cells) , which should be set as the default threshold level. However, this should be detected ONLY in the stable state (no zooming, flash charging or other mechanic actions - much less power drain).

Maybe it's too complicated on the first look, and my english isn't as good as should be.
Allowing to set the voltage threshold level somewhere around (n_cells * 1.0V) would be very useful, at least for a570 owners (and maybe others)
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Offline fudgey

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Re: any way to change Low Battery voltage threshold ?
« Reply #1 on: 07 / January / 2009, 13:00:06 »
It's possible that there is a way, but so far it hasn't been found. I also have the a570is and the battery indicator annoys me greatly, especially when using Varta Ready-to-Use cells (sometimes starts blinking minutes after installing a fresh pair, and yes, I have a good charger). With regular good quality 2700 mAh NiMHs things are much better, but battery warning is still way too trigger happy to my taste especially considering I have CHDK voltage display to refer to.

My camera is sometimes too eager to power off too, even though this part usually works well and the cells really are empty (I always have the voltage reading on display).


There are lots of strings in the Canon firmwares dealing with battery capacity tests. I have no idea if all of it is actually operational in our cameras, but some of it gives the impression that the battery indicator and/or shutdown feature is more complex than you might think... it just doesn't work well. :(
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Offline tgt

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Re: any way to change Low Battery voltage threshold ?
« Reply #2 on: 07 / January / 2009, 20:35:38 »
Well, if it is too complicated, let's just disable this feature as an advanced option . The "voltage-aware user ":) should turn off the camera when it's level becomes too low. No more red battery indicator and automatic shutdown, that would be nice...
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Offline pavel7nl

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Re: any way to change Low Battery voltage threshold ?
« Reply #3 on: 08 / January / 2009, 03:53:54 »
FYI: I've raised an incident to turn the original power indicator off, but don't know if it is possible: https://chdk.kernreaktor.org/mantis/view.php?id=160

I don't think the single threashold solution would always work, becase different batteries (I carry 3 types with me - 2x Alkaline, 2x1800mah GP, 2x2000mah Eneloop) have different threashold values. In my situation nothing is better than human brain and CHDK battery voltage indicator :)
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Offline Hacki

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Re: any way to change Low Battery voltage threshold ?
« Reply #4 on: 08 / January / 2009, 04:31:15 »
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Offline tgt

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Re: any way to change Low Battery voltage threshold ?
« Reply #5 on: 08 / January / 2009, 07:59:48 »
Hi, thanks for suggestions.
As for me, as an electronics engineer, I tried to define and analyze the problem in theory, assuming that the internal camera voltage measurements are accurate. With CHDK I reveive readings about 2,25V when the red indicator starts to blink. Recently I've build an automated rechargeable battery diagnostics system (including advanced pulse charging methods and reamining charge estimation) and with Eneloop/Infinium batteries (freshly charged) on A570 IS  I get discharge up to around 70%, while the same batteries left at least one week unused (fully charged) can be dischargewd only about 50%. On typical GP Ni-MH in any conditions (excluding very low temperatures) the discharge is at least 90%. In my opinion, is is a battery issue, but looking for a better charger won't solve the problem. So, the only way to cope with this problem would be to FORCE the camera software to ignore the voltage measurements and let the user decide, when the batteries are depleted.
I agree, that every battery finally reaches full discharge, and the camera will stop responding or start to do some weird mechanical operations, but that's not the point. I just KNOW, that in most cases (as stated earlier) there is still some charge available in the batteries. This is especially irritating, when i.e. the batteries were charged 2 weeks ago and the camera made only some photos. Everyting looks fine, but after a few shots with flash suddenly everythoing goes dark and You get thew "Replace Batteries" message.
The wole problem is caused by he battery internal resistance, which increses with depth-of-discharge, and is also NON-LINEAR.  When the camera is in idle state (no shutter pressed, no zooming/flash) it drains some current (few hundred mA), and the voltage drop is small. When the camera starts to drain higer currents (above 1A) the voltage drop becomes larger, but not proportionally. Increasing battery current causes also internal battery resistance to increase. This is some kind of an avalanche effect - increasing current 2 times makes the internal resistance increase several times. This is mostly observable with high battery current (1C or more), and could be dealt with use of parallel connection of large electrolytic capacitors. However, it is not applicable in small portable devices such as pocket cameras. The whole device and software relies on the performance of a battery and I guess, the prototypes are tested with standard types of batteries. The technology used in Infinium/Eneloop Ni-MH leads to extension of storage time without self discharge at the expense of increased internal resistance. In such case, those batteries are best suited for low power devices, and NOT for digicams.
Eventually - solution the problem is to forget about the problem and buy a high performance Ni-MHs. I just wondered, if such an advanced team developing CHDK would have any means to address this issue. Regards
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Offline PhyrePhoX

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Re: any way to change Low Battery voltage threshold ?
« Reply #6 on: 08 / January / 2009, 08:26:44 »
i ordered a 8-pack of eneloops a few days ago, will see how my s3is handles these.
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Offline fudgey

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Re: any way to change Low Battery voltage threshold ?
« Reply #7 on: 08 / January / 2009, 13:14:48 »
Quote from: tgt on 07 / January / 2009, 20:35:38
Well, if it is too complicated, let's just disable this feature as an advanced option.

Exactly what I've been wanting for a year, but I'm sorry to say we currently don't know how to do that either. Likely possible, though, one way or another.

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Offline dzsemx

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Re: any way to change Low Battery voltage threshold ?
« Reply #8 on: 09 / January / 2009, 06:05:43 »
this "feature" will lead only to camera crahes, stops and/or filesystem corruption...
« Last Edit: 09 / January / 2009, 06:07:31 by dzsemx »
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Offline fudgey

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Re: any way to change Low Battery voltage threshold ?
« Reply #9 on: 09 / January / 2009, 12:46:41 »
Quote from: dzsemx on 09 / January / 2009, 06:05:43
this "feature" will lead only to camera crahes, stops and/or filesystem corruption...

Only if the emergency shutdown algorithm/levels are tampered with. Definitely not if the annoying blinker is the only thing modified.
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