Cannon Battery Mod to run from 12VDC - Page 1
Forum section: electronics / projects

author: ssagerian
author_rank: Newbie
timestamp: December 23, 2016, 05:59:54 pm
content: So, I want to run my Cannon DLSR from 12VDC. I use it for astro imaging, and its a pain to have to replace the batteries several times a night.So I disassembled a battery and found that it has a 8 pin micro and a battery management chip (S-8241ACOMC-GCOT2G) on a small board.There are 2 battery cells connected in series, and it looks like the micro must monitor the bottom voltage to ensure both cells are charging (or discharging) properly. The board battery inputs are marked B+, B-, BM which I take to be B+ = combined voltages of both cells, BM= voltage of bottom cell, B-= ground reference.The board connector to the camera has three pins, 7.2VDC, a mystery pin (I assume some 1 wire serial comms) and ground.I want to mod this battery to be able to run 12V into the mod and get 7.2 VDC at the camera. So far, I have tried the follow..I used the camera battery connector to run 7.2VDC to the camera directly but the camera indicates that the battery is not functional so it must communicate with the battery, via the mystery pin.I thought I might be able to remove the two battery cells and substitute a 12V to 8.4V regulator ( 2 x 4.2V normal Li/ion battery cell??) with a voltage divider going to the BM signal (so the battery management IC would always see 1/2 the total voltage of the "battery"). I tried this but see 8.4 on the out put of the battery to the camera.Any ideas? Anybody made this mod already?Guess I could buy an AC to DC version on ebay but how fun is that?Thanks in advance and happy holidays to all!

author: KhronX
author_rank: Frequent Contributor
timestamp: December 23, 2016, 06:07:10 pm
content: 8v should be close enough to a full battery, but here's a thought:1) first, just to be on the safe side, set your DMM to the volts range, and make sure you've got (close enough to) 0v between the negative of the battery and the 3rd terminal2) if that's confirmed, set it to resistance and measure the same two pins again - there's a reasonable chance it's only the "free" leg of an NTC, and since the camera can't sense the "battery" temperature that way, it signals that something's wrong.

author: ssagerian
author_rank: Newbie
timestamp: December 27, 2016, 12:08:42 am
content: I took a second battery, charged it up, cut the plastic case away and measured the voltages on the B+,B-,BM and Vout pins all measured as I would expect (8.2 on the B+, B+/2 on BM, and 7.4 on Vout). Once I removed the battery from the pcb and connected a 8.2 Voltage source on B+, B-, the output now is 8.2V (no regulation, pass thur).Is it possible that the firmware is programmed to no longer function (charge the battery or deliver regulated voltage to the output) if it passes thru a power ON reset?I am not familar with the processor, and a google search of the PN turned up nothing, If I took a pic of the logo and attached it, would that be a good way to identify it?thanks in advance.

author: KhronX
author_rank: Frequent Contributor
timestamp: December 27, 2016, 12:10:47 am
content: Which processor do you mean? Inside the camera, or inside the battery?

author: alsetalokin4017
author_rank: Super Contributor
timestamp: December 27, 2016, 01:24:54 am
content: Hmmm... I can see why you want to DIY... the commercial 12VDC adapter is about 100 bucks.http://www.telescope.com/Astrophotography/Astrophotography-Accessories/Orion-12V-DC-Power-Adapters-for-Canon-EOS-DSLR-Cameras/c/4/sc/61/e/93.utsBut if you have AC available in your observatory, you can get an AC adapter set for your Canon for 15-25 dollars.(I too use my Canon Xti for astrophotography.)

author: ssagerian
author_rank: Newbie
timestamp: December 27, 2016, 02:14:06 am
content: I was talking about the processor on the battery. I think the mystery pin on going to the camera is a 1 wire bus so that the camera can interrogate the battery for battery level.

author: KhronX
author_rank: Frequent Contributor
timestamp: December 27, 2016, 02:21:28 am
content: Assuming this isn't a huge emergency, there's one thing i could maybe help with.I've got an EOS 550D back at my place, and i've got a mains adapter for it (off eBay), complete with a battery "placeholder".This latter item feels real lightweight, and i'm willing to bet it's just a straight feedthrough, from the barrel-connector socket to the contact terminals.I could crack it open and see if there's anything else in there, apart from a couple wires, but only after i get back there (which would be around the 10th of next month).You actually never mentioned the camera model you're dealing withCanon make / have made more than a few DSLR's

author: ssagerian
author_rank: Newbie
timestamp: December 27, 2016, 03:33:16 am
content: No please dont crack your adapter, I can afford to go buy one one ebay if this fails..I thought it would be a simple, cheap and cool (and quick ) hack to replace the internal battery with a 12V to 8V DC to DC regulator, that would allow people to run their astro modded (or non modded) DLSR on 12v with out having to constantly replace batteries.My DLSR is a T3I, I modded it to run full spectrum.I can not figure out what the one IC is (the processor) it has a A4 half enclosed in a oval for its mark BV3R18 and 8830 markings. I tried taking a pic of it using the magnify app on my phone but its too small.If your adapter doesn't have a small processor board in it then perhaps my theory of how the battery and camera interact is wrong. I guess I do a bit more googling for clues, wait a day or two to see if anything comes to me, or someone steps up with some other info..

author: wasyoungonce
author_rank: Frequent Contributor
timestamp: December 27, 2016, 09:08:09 am
content: Finally a topic I have some experienceDaniel Mccauley made a switchmode buck converter PSU for a canon many years ago, 8.2VDC out. He also did a linear PSU for the same which is the basic obvious.http://www.easternvoltageresearch.com/dan/equipmods.htmlI've made and used variants for many years. The original had no fold-back protection for current voltage but is more than use able. You can buy cheap ebay Chinese converters....don't they are a mess! I also made a system that used a canon remote canon adaptor (DR-E5 for 450D) PSU with my remote PSU...to keep heat out of the camera. Works a treat.If you use the traditional outside pins for power, the centre pins represent charge. So some astronomy camera software like APT might not read the PSU power correctly but that's not an issue.

author: KhronX
author_rank: Frequent Contributor
timestamp: December 27, 2016, 10:14:33 am
content: For what it's worth, the one i got is (something like) this:http://www.ebay.de/itm/Netzteil-AC-Adapter-DC-Coupler-fuer-Canon-EOS-550D-600D-650D-700D-Ladekabel-/401126277696The mains adapter itself i had already opened up and re-capped. There's no "smart" circuitry in there, just the positive & ground wires coming out.I was talking about opening up the battery "placeholder" thing, i'm reasonably sure it's only clipped together anyway, so it's no biggieQuote from: ssagerian on December 27, 2016, 03:33:16 am

author: ssagerian
author_rank: Newbie
timestamp: December 27, 2016, 12:52:05 pm
content: Wasyoungonce, how is the center pin "charge" signal used ?KhronX, that is similar to my "fall back option" (http://www.ebay.com/itm/282015040907?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT)The image shows the mains adapter as providing 7.4VDC, combined with your comments makes me think I have this all wrong, if the battery place holder is just a shell with leads then there may not be any smarts in the battery, perhaps I will go back and try once more with my original setup and triple check that I have things setup correctly. I will give it a try this week and post my results. BTW, I spent some time (weeks) in Oulu (and Helsinki ) loved it.Thanks to both of you.Steve

author: KhronX
author_rank: Frequent Contributor
timestamp: December 27, 2016, 02:04:20 pm
content: Like i said, if you can wait another couple weeks until i get back to my place, i'll gladly crack open the battery placeholder to make surePS: I'm not a native, i've "only" moved to Finland back in '08** Later edits **PS2: If memory serves, the last time i looked into the battery compartment in my camera, despite the 4-slot battery connector, i seem to recall seeing only 3 blade-contacts inside the camera.PS3: i googled for "eos 600d battery compartment" (600D = non-US name of the T3i), and i came across this site:http://www.camerahacker.com/myink/ViewPage.php?file=docs/Canon+Battery+Pack+LP-E8+PinoutBetween the aftermarket battery's pin labeling, and the camera contacts, it would appear the "D" pin is used only for charging (if even there).

author: ssagerian
author_rank: Newbie
timestamp: December 27, 2016, 02:40:08 pm
content: I can wait, thanks for the effort.you are correct, there are only 3 blade connections. I assumed that the camera processor asks the battery for its percent charge over that third pin (one wire comm ). I am unsure now.Smart move going to finland, beautiful people, great country

author: KhronX
author_rank: Frequent Contributor
timestamp: December 27, 2016, 02:42:34 pm
content: Nah, the charge is sensed most likely just from the battery pack voltage, via some sort of ADC and some voltage-vs-charge "map". Just like most (if not all) phones do

author: Twoflower
author_rank: Frequent Contributor
timestamp: December 27, 2016, 03:04:26 pm
content: If I remember correctly Canon released a FW which also transformed third party batteries into paperweights. That was for the EOS 5DIII, but probably they do similar things with the smaller DSLR models. So I wouldn't wonder if just feeding power to the Cam isn't working. The battery needs to say the magic words. Maybe if you have a dead battery you can cheat by replacing just the cells with the supply and keep the electronics in there. Even if you do so, there is a chance that they have some kind of protection in there.For the bigger DSLR models the Cam can even identify individual batteries and display some statistic.

author: KhronX
author_rank: Frequent Contributor
timestamp: December 27, 2016, 03:56:50 pm
content: I've had the latest (1.0.9) firmware on my Eos 550D (aka T2i) since soon after i bought it (used, last year), and at least with the aftermarket mains adapter, i've had zero issues.It seems Canon released some new versions within the last couple of months though.Either way, aftermarket batteries arenotwhat this particular topic's about anyway, as far as i knowQuote from: Twoflower on December 27, 2016, 03:04:26 pm

author: Twoflower
author_rank: Frequent Contributor
timestamp: December 27, 2016, 04:10:12 pm
content: Yes, I'm also not talking about after marked batteries. But the acceptance of something connected to the Cam. For example a power supply. Which uses the same connectors like a battery which needs for some models at least some authorization.Of course the after marked manufacturers reacted fast andcircumworked the problemvery fast.ButI don't think just apply a voltage to the contacts was not the solution. The cam needs to accept the supply before it uses the juice coming in (no matter it it came from LiIon or 12V).Again, this may apply only to the big bodies and the smaller ones ain't be that protective.

author: KhronX
author_rank: Frequent Contributor
timestamp: December 27, 2016, 04:22:44 pm
content: That's pretty much my hunchLike i said, i've used my mains adapter with my camera, for on-location video recording, on more than a few occasions - camera didn't complain, shows a "full battery", and works just as you'd expect.Quote from: Twoflower on December 27, 2016, 04:10:12 pm

author: Twoflower
author_rank: Frequent Contributor
timestamp: December 27, 2016, 04:42:49 pm
content: That sounds legit. So probably feeding in the right voltages to the cam is enoughFunny thing: Just checked my 5DIII. It has also only 3 pins in the battery compartment. I can't identify if it goes to the C or T connector on the battery as the connectors are totally different than yours. Still they're able to receive the serial number inside of the cam. So the lack of the fourth pin is no guarantee that they don't do strange stuff there.

author: wasyoungonce
author_rank: Frequent Contributor
timestamp: December 27, 2016, 11:09:23 pm
content: Quote from: ssagerian on December 27, 2016, 12:52:05 pmI really didn't look too much into it suffice to say it the std battery has 2 cells and it only used one of them thru a small ccrt brd to these pins.

author: KhronX
author_rank: Frequent Contributor
timestamp: January 25, 2017, 10:55:19 pm
content: Real sorry about the delayPictured is my "dc coupler". Unfortunately it seems to be glued together (or ultrasonically welded), not just clipped together, as i had hoped. Sorry, but i'm not too eager to risk literally cracking it openOn the other hand, it's really lightweight, and sounds pretty hollow if you tap it.