DIY battery coupler for DC/battery power

TimeScience

« on: 10 / March / 2010, 19:26:23 »

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I'm building a simple solar powered camera system using powershot cameras and CHDK (Info: http://timescience.wordpress.com/projects/). Since the camera will be battery powered, it doesn't need the AC adapter but for the Powershots cameras there doesn't seem to be any way to buy just the plastic battery coupler that the DC power goes into to run the camera. (I've seen them for DSLR's but not for powershots... anyone know where you can buy these without the AC adapter part?)

Since those power supplies are a ripoff anyway I thought I'd see if I could build the fake battery part myself. Turns out it was pretty easy to do and worked way better than I expected. I thought others might appreciate knowing this can be done so we don't have to keep paying $40 for the cheap hollow battery couplers.

Tutorial is here:
http://www.flickr.com/photos/timescience/sets/72157623581979614/

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NewbieToobie

Re: DIY battery coupler for DC/battery power

« Reply #1 on: 11 / March / 2010, 05:06:13 »

You might want to look into a "DigiPower" DPS-9000 Li-Ion battery pack (approx. $30-$40). I used one with a folding solar-panel for years on extended photography expeditions into many remote places where roads were days away, powering whichever camera I wanted to use that day. They used to come included with a couple of DC-DC voltage converters and an array of plug adapters. But I think now you have to buy them with one adapter per camera. It's compact, screws onto the base of your camera using the tripod socket (with an external female thread for further mounting of both on a tripod.). In any case, it was one of the best investments I've ever made for remote extended digital photography situations. The included DC-DC converters and adapters almost worth the price itself. I made a male-male adapter to plug the "charging interface" voltage converter (12-24vdc to 8.4vdc 600ma, the perfect range for all solar-panels) between the solar-panel and DigiPower pack to charge it at the proper rate. As well as using that DC-DC converter and solar-panel to charge my other Li-Ion batteries that charged right in the camera.

I can't seem to get to their site at the moment, it must be under maintenance or something. But here's an old review I found http://www.imaging-resource.com/ACCS/DPS9000/DPS9000.HTM It seems you can still get them at Amazon and other places for about $25-$40.

For those requiring compact extended power without access to AA's or mains supplies, this is about the simplest, most adaptable, affordable solution I have ever found.

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TimeScience

Re: DIY battery coupler for DC/battery power

« Reply #2 on: 11 / March / 2010, 17:23:13 »

Great suggestions, thanks. That's just the kind of thing I've been looking for, for the power system.
Do you know if you can charge it while it is plugged in to the camera? One of the main issues I've been trying to solve is that it seems like most power packs or batteries aren't designed to be charged while in use.

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NewbieToobie

Re: DIY battery coupler for DC/battery power

« Reply #3 on: 11 / March / 2010, 22:32:40 »

« Last Edit: 11 / March / 2010, 23:07:09 by NewbieToobie »

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NewbieToobie

Re: DIY battery coupler for DC/battery power

« Reply #4 on: 11 / March / 2010, 23:00:07 »

Correction! I remember now, it's been so long since I charged it ...

(Yet, all 5 lights are still lit from over a year ago.) The charge-limit is determined by the 24-12v to 8.4v 600mA DC-DC converter, the module that plugs between the switching power-supply and the battery (or in your needed case, between solar-panel and battery + camera). When its small red light turns from red, to yellow, to green, then it's done charging. So ... no, it won't overcharge with the above scenario. The power from the solar-panel will only go through when the battery is under-charged.

« Last Edit: 11 / March / 2010, 23:03:12 by NewbieToobie »

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TimeScience

Re: DIY battery coupler for DC/battery power

« Reply #5 on: 11 / March / 2010, 23:30:48 »

I ordered a DPS-9000 to test, so I'll be able to see if that works soon enough. Thanks for looking into it. Looks like it might just work.

After reading your post I started looking around for other battery power systems like that one. Amazon has a bunch of very cheap 5v USB charging systems with both AC input and a mini solar panel (e.g. http://www.amazon.com/SunPlug-Solar-1350-rechargable-battery/dp/B0019ZH5N0/ref=sr_1_1?ie=UTF8&s=electronics&qid=1268367867&sr=1-1). I'm wondering if I can use one of those as a super cheap charge controller. Since the AC charging input is actually just a DC input from an AC wall wart, I wonder if I could run my solar panel (with a voltage regulator) into that AC input on the battery as an external power source, then splice the a USB charging cable from the output for a nicely regulated power source for my camera. For $11 its probably worth trying out.

I haven't had a chance to test what the full tolerance range on the SD990 I'm using. On the Rebel T1i, the minute you go over 8.2v input it just shuts off and gives an error message but there isn't any damage to the camera (I didn't go that far over), so its nice to know they build in some internal controls to give us some leeway on up our hacking efforts.

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TimeScience

Re: DIY battery coupler for DC/battery power

« Reply #6 on: 12 / March / 2010, 00:17:27 »

Ok, so I tested the voltage tolerance range on my SD950.
If the camera is on, it turns off at a low voltage of 2.7, but it can't turn on from being off until it is getting at least 3.2v.
At the high end, it appeared to be fine at 5v. At 5.5v a new graphic appears on the screen. The graphic is the same as the func/set ISO/macro button on the back camera face. It disappears if you drop back below 5.5v. Curious. I didn't leave it at that level for more than a few seconds for fear of damaging the camera. Anyone else out there who has had the nerve to test their cameras for longer? (Note, I'll cross post this as a new topic since I think this would be useful info for people to put out there if they have experience with their cameras.)

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NewbieToobie

Re: DIY battery coupler for DC/battery power

« Reply #7 on: 12 / March / 2010, 07:22:02 »

Quote from: TimeScience on 11 / March / 2010, 23:30:48

After reading your post I started looking around for other battery power systems like that one. Amazon has a bunch of very cheap 5v USB charging systems with both AC input and a mini solar panel (e.g. http://www.amazon.com/SunPlug-Solar-1350-rechargable-battery/dp/B0019ZH5N0/ref=sr_1_1?ie=UTF8&s=electronics&qid=1268367867&sr=1-1). I'm wondering if I can use one of those as a super cheap charge controller. Since the AC charging input is actually just a DC input from an AC wall wart, I wonder if I could run my solar panel (with a voltage regulator) into that AC input on the battery as an external power source, then splice the a USB charging cable from the output for a nicely regulated power source for my camera. For $11 its probably worth trying out.

I find no specs on what input voltage those use. I suspect that it being advertised as charging from AC or USB that input voltage might be limited to ~5v, same as its own solar-cell specs. Keep in mind too that if you use a standard voltage regulator to drop the voltage from the typical solar-panel array (15-18v) that this is a lossy process. The nice thing about the DC-DC converters with that DigiPower unit is that they don't waste energy as heat. Miniature DC-DC converters are also very pricey, if you've ever tried to hunt some down, even as bare-bones electronics components. As I said, those were worth the price of the unit alone. But you say you already ordered a DPS-9000 so you'll have your bases covered in either case.

The main problem I see is whichever battery you plan on using. And this will all depend on how much solar-panel you use as well as the frequency of shots taken, and the power-draw for each shot which depends on which camera features they are using. I find no mAh specs on my battery here, but searching online I see estimates of 1850-2200 mAh for the DPS-9000. (Which seems about right, when compared to the size of my Li-Ion battery in one of my cameras which rates at about 1250mAh.) With the semi-lossless DC-DC converter going from 7.2v (8.2v on full charge) to 5v, that's probably around 2700-3000 mAh of useful charge at 5v from the DPS-9000. If you are going to use a standard voltage regulator at any spot in your current path, then after the 5v to lower it to your camera's input will be the most energy-efficient spot to use one. Though in the end I think it will take a few days of tests in sunlight and cloudy conditions to be certain if solar-panel and battery-capacity will be enough for your required shooting rate. (From your blog: "Frame rate: 12 images an hour, ~200 per day (One image every five minutes, +/-16hrs a day)") For my trips I used three 1-watt solar panels. One of them being compact and foldable which was used/carried most often to the more remote places. It could charge a depleted DPS-9000 in about 3-5 hours of bright sunlight. Keeping the charge curve well ahead of daily photography uses, clear-skies permitting.

I recall seeing a CHDK page somewhere of them doing a test on all camera functions and how much current that each one will draw. It might be worth trying to find that. Then you'll be able to gauge how much solar-panel and battery-capacity is needed to keep up with whatever time-lapse task you choose. The surprise in that list is that manual-focus mode drew much more current than auto-focus modes.

So many variables to consider.

« Last Edit: 12 / March / 2010, 07:45:49 by NewbieToobie »

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