Introduction: Cheap and Easy PSU for Canon EOS

Picture of Cheap and Easy PSU for Canon EOS

I think lot of guys here on Instructables know how much satisfaction is obtained building a gadget entirely by ourselves, but... sometimes it could be a clever solution opting for some nice and ready accessory. I think this is one of these cases.
I recently had the need to have a power supply for my Canon DSLR, an EOS 40D, to make some timelapse. For this pourpose I've bought an LM2596S step-down adjustable power supply module from eBay, it's very cheap, efficient, compact, and (I hope) safe... and it fits exactly inside my exhausted lithium battery case. And this instructable could be handy adapted for almost any digital camera battery, the only requirement is that the case contains the power supply module.

Step 1: Intro

Picture of Intro

The new psu is intended to work with a wall-plug transformer the same as with any DC power source between 9 and 35V, as a car battery or almost any wall-plug psu. This could be very handy in case of timelapses, gigapan shots, or long movies.

Step 2: What's Inside?

Picture of What's Inside?

I've made the same modifications on two batteries, because both of them were exhausted. They weren't Canon batteries, indeed the original ones are almost ethernal.
You have to cut/crack the plastic casing all around the perimeter, because it's glued verty sturdy. Inside you'll find two 18490 Li-ion batteries, which are very rare to find to replace.

Step 3: Keep the Shells

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Separate the battery parts unsoldering the battery contacts, and clead the case edges with a cutter, they should fit each other so we'll glue them at the end.
Maybe you wish to keep the protection circuit as replacement...

Step 4: Drill the Hole

Picture of Drill the Hole

Now take misures of the aperture which you find on your Canon. It's a little rubber door which you can bend to let the wire pass through. I've found that in battery-grip the aperture is in a different position, but if you're powering the camera by an external powersource probably you don't need the battery-grip. So I've opted for the in-camera wire position.
Drill an hole in that position and file it or cut it untill it becomes of the same shape of the wire. I've also added some heat-shrinking tubes to toughen up the cable extremity.

Step 5: Glue the Circuit

Picture of Glue the Circuit

Check that the circuit fits in the battery case, I've had to file a corner to make place for the cable.
I've insulated the two unused contacts, and also added a piece of tape to not let the pcb touch them.
Then I've used a double-tape to lock the circuit in place. I've added another layer of tape over the one you see in the pictures.
You can then begin to solder the wires on input and output terminals.

Step 6: Solder It

Picture of Solder It

You can see the glued pcb in place. You can now connect a power source to the cable ends, maybe 12 or 24 volts work good. With a multimeter misure the output voltage and turn the potentiometer until you'll obtain an (almost) exact voltage of 7.4V. 

Step 7: Label It

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Now you can add the DC input range on a label behind the battery, together with output voltage and plug's polarity scheme. I've printed some coloured labels so you can cut them and glue into the shape of the previous one.

Step 8: The Socket

Picture of The Socket

As female socket you could buy one of those nice ones which already have a cable connected. I've used a different type, and I had to solder the wires on them. Then I've enclosed them into some heat-shrinking tubes to obtain a better look.
[UPDATE] You can now see the detail of the cable coming out from the rubber cover near the battery door.

Step 9: Done!

Picture of Done!

Check another time that everything works good, let the power connected for a few time, try different input voltage, bend the cable, flex it, pull it, also chew it if you dare... it's better to get a shock now than to find your three months timelapse failed because of a bad soldering! Obviously I'm fooling with you, always pay attention to high current sources as car batteries, they're very dangerous!
Everything is ready, it's time to glue the shells pair, maybe with two elements glue, and try your new power adapter!


Mohammed AliA1 (author)2016-08-26

Hi there,thanks .i've done it but please help me I had problem err99 please shooting is not possible. Please turn off the camera or remove the battery" ? ?

check output voltage, it's probably wrong...

TimotiusR (author)2016-07-22

i know this instructables is kinda old but im curious if i can use dc-dc step up instead of a step down module. i want to connect it to a powerbank with 5v output.

the modules looks like this:

andrea biffi (author)TimotiusR2016-07-22

yes you probably can, if it supplies enough current :-)

TimotiusR (author)andrea biffi2016-07-22

how much current does it need? btw thanks for the reply

darklylit (author)2015-10-19

I recently cracked an AC adapter dummy battery and was surprised how little was inside: just a jack, two capacitors and the contacts connected to a PC board. Would you have any idea how to determine what these type of capacitors these are and their values? They're so tiny and don't seem to have any markings on them. I'm not very electronics-savvy, so if anyone might be able to give me an idea of what their values might be, or if I could substitute something else for them, I would appreciate it. Thanks a lot.

MOs7DBSV (author)darklylit2016-01-06

The reason this adaptor is so tiny, is that all the electronics andrea_biffi put into the battery casing are located in the wall adapter of your battery AC adapter.

You can measure the capacitance of the capacitors using what is called an LCR-meter. It not only measures capacitance (C), but also inductance (L), resistance (R).

The capacitors are bypass capacitors, to filter any noise, that got coupled into the cable between the wall adapter and the dummy battery. They also compensate the inductance of that wire in case of sudden changes in the current.

My guess is, that the smaller capacitor is 100nF and the larger capacitor is in the range of 1 - 10 uF. The exact values probably don't matter much. Common capacitors of this type can deviate from their labelled value by -20% to +80%(!).

vexedart (author)2015-11-11

This was a great post. Used it as a building block for creating my own PSU with a few modifications. Ended up casting my own hollow battery shell in resin you can view some of the pictures here.

mcvapes (author)2014-11-23

Thank you so much for the guide. I was just looking into using this exact converter. However, I am concerned about the heat. According to the spec sheet for the LM2596S, a heatsink should be used when over 10W. The stock batteries are rated for 7.4V at 2A. Unfortunately, I don't have the tools to measure how much power the camera uses. Have you ever checked for heat build-up in the battery enclosure after prolonged use? I

andrea biffi (author)mcvapes2014-11-23

I doubt the camera has a peak of more than 10w. Batteries are so powerful to last many hours. I never checked the heat, but I used for time lapses so there is a certain interval between pictures and certainly enough time to heat down.

Video mode on new cameras could be different, but you can always check if the psu is hot after some minutes of video.

meanpc (author)2013-02-06

Nice job! Would be nice if Canon included a DC input from the factory, wouldn't it? Especially since we are using them for video a lot now, which burns a ton of battery.
Can you show the camera with your battery installed? I would like to see how you have the wire routed.

andrea biffi (author)meanpc2013-02-07

Yes I'll take the picture soon. Canon always wants to sell more accessories, see also timelapse features or flash transmitter... :-(

archp2008 (author)andrea biffi2013-09-22

If you don't want to risk burned fingers you can order something that works like this for the Canon T2i on Ebay for around 10 bucks. If you have a larger capacity 7.4 volt power source (e.g. old canon camcorder battery) the dummy battery part of the above adapter can always be cut off and used instead of the AC adapter.

andrea biffi (author)archp20082013-09-22

Thanks for your advice, I've been using my DIY PSU with success for last seven months with not a pinkie burned ;-)
My power source is 220VAC or 12VDC, this last connected directly to my dummy battery.

tvm777 (author)2013-02-07

Its a good solution, i have a 550D, same solution for it??
wich module did you use? i find this one cheap:

andrea biffi (author)tvm7772013-03-20

that seems right, you can found other ones clicking on the link in the first step

8steve88 (author)2013-02-09

Hi there.
Great Instructable. I have an EOS40D and reckon your solution it would solve another problem as well. - Do you know if your battery has enough charge left to power a sensor cleaning session? With this solution it doesn't matter - just plug in and go.
Even with my battery grip -two batteries- I have to recharge just to be sure that the large drain of holding the shutter open won't flatten the batteries. Problem solved. Thank you.

andrea biffi (author)8steve882013-03-20

that seems right, you can found other ones clicking on the link in the first step

andrea biffi (author)8steve882013-02-11

yes, also Canon recommends using the PSU to clean sensor.

jamesobrady (author)2013-02-07

Great instructable !!
On the protection diode, have you wired it in parallel with the supply?

andrea biffi (author)jamesobrady2013-02-07

Yes, with reversed polarity.

then I decided to not add any protection diode, in parallel is too dangerous due to diode blowing, and in series it takes 0.7V (or 0.35V for a Schottky diode), so I decided to trust in circuit own protection.

lionel1024 (author)2013-02-12


andrea biffi (author)2013-02-12

Thanks! Your comment really helps me. I actually had some doubt about the way to add the diode. I didn't want to lose power (especially with an external battery supply), but you're right about diode blowing... I'd have to think about that.
Yes, maybe 0.7V are not too much, and a better protection should be good, I don't know what could happen to the circuit with a reversed voltage from a car battery with 50A... I'll update the circuit and the Instructable...

RichardBronosky (author)2013-02-07

I'd like to see how this fits into the camera.

sdtacoma (author)RichardBronosky2013-02-07

That's what I came to say. I like the idea, but no way would the batter fit back into the camera.

Andrea, can you show us how that works?

andrea biffi (author)sdtacoma2013-02-07

Of course!

sdtacoma (author)andrea biffi2013-02-11

Very cool. I don't think my camera has that little "door" so I wasn't sure how that was going to work. Thanks for the update. Great photos BTW.

RichardBronosky (author)sdtacoma2013-02-11

Yes, I have the Canon XTI and the battery tether port is different. May still be doable though. photo from:

g elliot s (author)2013-02-10

why not just buy one that's made for the camera?

Treknology (author)2013-02-08

Even when new, I've yet to see a video camera with a battery that can outlast a single cassette. My solution has been to build a bracket that holds that camera and supports an SLA battery on the shoulder (also a major improvement in stability). I never thought of publishing it because most people complain about the weight of the battery!

Helperlein (author)2013-02-07

The batteries give a voltage range between 8,4V and 6V.
Why didn't you just take a 7,5V external PSU instead of a PSU plus a Step-Down to 7,4V? At least if somebody does not have PSU yet, I would recommend just to buy a PSU with the right voltage and they are almost done. No voltage error, plus wiring is one step easier

andrea biffi (author)Helperlein2013-02-07

And with Canon unfortunately an external PSU isn't enough because Canon EOS have no DC-IN female plug.

andrea biffi (author)Helperlein2013-02-07

Hi, one reason is that I've tons of 12V DC and 9V DC PSU, because almost all devices uses that voltage (some uses 5V too) and when device breaks it left the PSU well functioning. As I've lot of them I assume many people have at least one of them. Then there is the main reason: with that you can use any battery from 9 to 35V, included a car-battery of 12V. There is more: if any device in your equipment is powered with a similar PSU you can use the SAME battery to power them all.

andrea biffi (author)2013-02-07

Here is the image of the battery in position, note the rubber door, I think every Canon EOS has it..

KT Gadget (author)2013-02-05

What you could do for the LED indicator is remove the SMD LED and replace it with a extended wired LED to point out of the pack, or get one of those bent acrylic pieces that are used to show the indication bars when the lights can't be flush with the case (not sure what they are exactly called).

Nice ible though, this might be one I will use in my Olympus when I get to more extended pic/video projects. Have you tried it through a 12V car plug to see how it performs?

andrea biffi (author)KT Gadget2013-02-07

the battery should fit inside the camera, anyway it could be useful to see if power reach the battery.
I think Olympus has a DC-IN power plug, you don't need this (if you have the right voltage power supply).
I didn't try 12V car plug, but I've tried 35V and it works good.

Helperlein (author)2013-02-07

Adding to the comment below, I think it is more important that the power supply, internal or external, can give enough amperage. It would be useful to know this for anyone who would like to use this (100mA, 500mA, 1A, 2A,..?)

andrea biffi (author)Helperlein2013-02-07

Almost all wall-plug 12V transformers have 1A amperage. These work good, maybe you could try 0.5A too, but I doubt it's enough. Any battery more than 1A is good. I think 9V 200mA are too weak.

About This Instructable




Bio: I'm an Italian freelance structural engineer, graphic designer and photographer, and I'm teaching physics in Waldorf schools. I always investigate electronics, robotics and ... More »
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