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Battery life

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Offline PhyrePhoX

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Re: Battery life
« Reply #10 on: 25 / April / 2008, 21:13:40 »
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thats odd. what makes you sure it started around the time you started to use chdk? i mean i guess you left the batteries in there for longer periods and they werent empty, eh? strange. i know my s3is does have a kind of deep-suspend-sleep, at least when using the built-in intervalometer. but the a720is doesnt have that feature. hm. maybe the batteries are defect?
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databoy

Re: Battery life
« Reply #11 on: 25 / April / 2008, 22:52:55 »
NiMH batteries can exhibit peculiarities. Trickle chargers may or may not charge your NiMH fully. Make certain that your batteries are fully charged. This can take a number of cycles on new batteries. Use a one hour fast charger and deep cycle your batteries; ie make sure they are flat before the next recharge. DO NOT use any of the 15 or 30 minute fast chargers on the market on NiMH batteries. They will shorten the life of your batteries and they can die instantly. Fully charged NiMH batteries if not used can go flat in two to three weeks. That is normal. NiMH batteries are designed for instant use and not for shelf storage.
« Last Edit: 26 / April / 2008, 02:40:31 by databoy »
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Offline jonnythe

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Re: Battery life
« Reply #12 on: 26 / April / 2008, 18:44:36 »
Quote from: databoy on 25 / April / 2008, 22:52:55
Trickle chargers may or may not charge your NiMH fully.
Not only that but trickle charging NiMH is not good for them. And there's usually no need to fully discharge NiMH's before charging. A decent charger would help to prevent overcharging however. Once a month or so you should deep-cycle the cells though, depending on how much they're being used.

15 minute chargers? Yeah I've had many new cells die after one charge in my Varta quick charger. I think it's the high temperature the cells exhibit from the >10A charge current.

As for the OT, I find my batteries lasting longer with CHDK, because the battery meter allows me to know when things are getting bad and if I want to squeeze several more shots out, it's time to turn the LCD off or put it in playback mode to reduce current drain.  :) The S5 sucks a huge amount of juice in record mode.
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Offline fudgey

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Re: Battery life
« Reply #13 on: 27 / April / 2008, 05:55:25 »
NiMH manufacturers do recommend trickle, but only for keeping an unused cell at full charge at very low current (such as C/300, which means nominal charge transferred in 300 hours). Also, there's a surprising dead-zone in recommended currents; for example Duracell doesn't recommend NiMH charging currents between C/3 and C/10, apparently because in that range it's harder to figure out when to stop charging (simple timer is not safe enough any more, there is no sharp rise in temperature and the voltage dip may not be very clear).

This means you should ideally charge in 1 to 4 hours (with a good charger) OR >11 hours but not for example in 6 to 8 hours. If you do, it's possible that your charger doesn't charge the batteries fully or that it slightly harms them by overcharging or that it doesn't handle old batteries as well as it could.

Those 10--20 minute chargers can indeed be harmful, and all cells aren't born equal in withstanding those high charging currents even though these chargers (always?) have active cooling.

If self-discharge is a problem (and it is not caused by the camera drawing the current), you may want to try Sanyo Eneloop batteries (or one of the other brands they sell them under); they are 2000 mAh NiMH cells, sold pre-charged and ready to use. They can be used in regular NiMH chargers (probably not those 15 minute ones, though), but their self discharge is supposedly closer to alkaline batteries than NiMH.  Also, for what I've read, normal 2800 mAh cells lose the extra 800 mAh very quickly after charging to self-discharge, so unless you use them instantly, the difference in capacity is not as large as it seems.

Oh, almost forgot one more thing: I've noticed that there are cheap quick charger + NiMH cell combos on the market who claim to charge faster than they physically can. They often come equipped with a separate DC wall power supply with a rated output power significantly lower than what is required to output the energy that needs to be transferred to the cells.
These chargers will either charge batteries slower than advertised (if you're lucky) or fail to fully charge them (if you're less lucky).
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Offline jonnythe

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Re: Battery life
« Reply #14 on: 27 / April / 2008, 07:39:53 »
Quote from: fudgey on 27 / April / 2008, 05:55:25
NiMH manufacturers do recommend trickle, but only for keeping an unused cell at full charge at very low current (such as C/300, which means nominal charge transferred in 300 hours).
I don't know if they recommend it, but this is basically true. However I wouldn't bother without an expensive charger. As you mentioned full charge is usually detected by monitoring delta-V. Trying to detect a several mV change over a several hours time period with a wall charger having cruddy line filtering is very difficult.  :) It just doesn't seem worth it when fast charging works so well.
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Offline fudgey

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Re: Battery life
« Reply #15 on: 27 / April / 2008, 08:27:24 »
Quote from: jonnythe on 27 / April / 2008, 07:39:53
I don't know if they recommend it, but this is basically true. However I wouldn't bother without an expensive charger. As you mentioned full charge is usually detected by monitoring delta-V. Trying to detect a several mV change over a several hours time period with a wall charger having cruddy line filtering is very difficult.  :) It just doesn't seem worth it when fast charging works so well.

Yes, basically I see trickle useful for two kinds of uses:

1) To always keep your spare set of batteries at 100% charge (when you're at home) for devices like cameras which may not need recharging every month. This means trickle must be a robust feature of the charger (be it a quick one or not) so that you can leave it plugged as long as you wish.

2) For appliances in which batteries are only for backup or for short term use away from a regular mains connected setup and the appliance includes a built-in charger.
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databoy

Re: Battery life
« Reply #16 on: 27 / April / 2008, 11:46:54 »
I live in Perth, Western Australia. The reason I mention it is that depending on where on the planet you live, you may or may not find the ideal NiMH batteries or charger. Duracell and Energizer NiMH batteries and chargers are reasonable but not the best quality available on the international market. At least the performance is reasonably guaranteed. Some of the funny named Chinese brands have a snub positive nose which will cause a short circuit on the S3IS cameras.

In Australian, the analogue mobile phone network is redundant. It is all digital. I have a number of fast and trickle chargers for the NiMH batteries which I opened and examined the circuit. The fast chargers all have a smart chip, sometimes a PIC chip or dedicated smart charging circuit. From the information circulating on technical sites on the net, I can determine that the chips monitor the NiMH voltage and may even put an intermittent current load on the battery to determine the charging current and voltage. The charging current and voltage is then applied and monitored. Mobile phone battery packs also have an over temperature sensor to protect the battery pack from overheating. The trickle chargers are only a diode and current limiting resistor. Some of them are only half wave DC. They rely on the ripple current for charging.

On a mass production scale the manufacture of and sale fast chargers is relatively cheap. I would not even bother to buy the components to build one. Locally the price difference between a fast charger and trickle charge is a maximum of $30. Not worth the time wasted waiting for a trickle charger. I have 3 sets of 2650mah cells. The chances of having flat batteries is remote. My Energizer fast charger comes with a 12 volt cigarette lighter cable; therefore the chances of flat batteries is very rare.   

NiMH batteries do not have a memory like NiCad batteries.; you can deep cycle them and probably trickle charger them to prevent them going flat. I don't bother. If the batteries are 50% or less, I stick them in the fast charger. So far no problems.

You may find that even though the camera says the batteries are flat, the batteries are not fully discharged. The electronics manufacturers will switch off the appliance to prevent spurious operation when the electronic equipment is approaching under the voltage operation thresh hold.

My opinion is buy the best fast charger and batteries you can obtain in your locality. In relative terms they are cheap and disposable items. Your photos are more important. In local costs a blister pack of 4 Duracell or Energizer cells are about $25 AUD. The Charger is about $40 to $50. Over the year your petrol costs will be the main overhead. Adding $125 to $150 per annum operating costs is neglible overheads. The chances are you will get  2 years out of the cells.   

     
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Offline jonnythe

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Re: Battery life
« Reply #17 on: 27 / April / 2008, 18:59:56 »
Quote from: databoy on 27 / April / 2008, 11:46:54
NiMH batteries do not have a memory like NiCad batteries.; you can deep cycle them and probably trickle charger them to prevent them going flat. I don't bother. If the batteries are 50% or less, I stick them in the fast charger. So far no problems.
I do the same. They do have memory (practically all rechargeable batteries do to some extent) but it's negligible. I just make sure to give them a full discharge/charge cycle every now and then.

BTW Databoy, seeing you are an Aussie, have you ever tried the cheap Dorcy NiMH's that BigW sell,  in your camera? They are around half the price of most others. I've been using the AAA's in my mp3 player for a couple of years. Although they don't get a high current drain, I absolutely kill them in a Varta 15min charger, whether they are flat or not, and I'm getting the same amount of usage as when they were new.

To the OP, you may also have to recalibrate the battery meter for your batteries. With my S5, new energizer batteries would drop to around 60% in less than 20 seconds but then stay there, whereas another worn-in brand stayed above 80% for several shots.
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Offline triaged

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Re: Battery life
« Reply #18 on: 29 / April / 2008, 10:11:32 »
Thanks for all the responses.

I have a LaCrosse BC-900 charger and charge at 200mA...
It is a very nice charger other then the fact that the first one came DOA.

Now I can't get it to do it again.  Maybe I have a few bad batteries or they didn't get fully charged?

Is there any way I could have done something stupid with CHDK settings (allbest a720.100c) to cause the batteries to discharge?  The only script I have tried is a bracketing one and I used the reset option as part of my troubleshooting.
« Last Edit: 29 / April / 2008, 10:16:34 by triaged »
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Offline PhyrePhoX

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Re: Battery life
« Reply #19 on: 29 / April / 2008, 10:19:23 »
no, there no such setting. only way to lose much power is by either lot of i/o (writing data to sd card) or cpu intensive calculations (raw average, etc). other than that: taking pictures or video. so if this wasnt the case with your camera, i guess it was the batteries' fault.
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