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I've been experimenting a bit with time-lapse photography lately. Still basic stuff. Right now I have to change batteries every so often which is a pain because it's hard not to move the camera when changing the batteries. I've used the ACK-E6 power adapter to run my camera from mains, but this is only possible in some situations.

So I'm looking to somehow attach some higher capacity batteries to my camera. The regular batteries for my camera (LP-E6) deliver 7.2V. The specifications of the ACK-E6 mains adaptor list the output to the camera as 7.6V 3A.

I've read some things about buck/boost regulators (but I'm hardly an electrical engineer) that I can use to regulate the voltage to that desired 7.2V for my camera.

The goal is to attach a 12V car battery, but have other (smaller, lower weight) options if needed.

I was thinking of buying this buck/boost regulator (or one like this): 3A Power Adapter DC 3.8-32V to 1.3-35V Automatic Buck/Boost Voltage Regulator 3A Drive Power Supply #090040 http://www.aliexpress.com/item/5-PCS-LOT-3A-Power-Adapter-DC-3-8-32V-to-1-3-35V-Automatic-Buck/1609180228.html

I guess the numbers add up, and this should work. But I'm not really sure about the possible risks, because I don't want to damage my camera.

I've searched a lot but I can't really seem to find an answer, so that's why I'm asking here.

Is there a possibility that the 12V from the input goes straight to the output? Are there other risks I have to take into account before attempting this?

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    \$\begingroup\$ A 2S Li-ion battery would provide that exact voltage (in fact, the current battery would already be one) and be both smaller and lighter than a car battery even at several dozen Ah. \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Apr 26, 2014 at 21:22

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In principle, what you want to do will work. But as you say, it's a matter of risk and peace of mind. It is possible, though unlikely, that the unit you are considering (and widely available for almost nothing on ebay) could fail in such a way as to deliver a damaging voltage to the camera, which would be expensive to fix.

The main situation to avoid is over voltage. To avoid that you could add a crowbar circuit (see google if interested), but that seems like work.

The other issue is whether or not the camera presents a highly variable load, as Dave suggests. In that case the 3A rating on the ACK-E6 may be an average that doesn't represent the peak required, which the capacitors on your regulator board may not be sufficient to supply.

A possible workaround for both these problems is to take your existing ACK-E6 and interpose a connector between the brick and the "battery" block. Connect the brick for mains power, and instead connect your DC-DC converter (set to 8V I think from the spec) for alternate power. The ACK-E6 spec suggests that there's some active regulation in the "battery" block, and that would help moderate any over-voltage accident, and I would expect provide sufficient capacitance to handle transient demand.

But all of this is somewhat speculative without schematics!

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  • \$\begingroup\$ The ACK-6E consists of two parts (dummy battery and the adapter itself). So that connector is already present (yay!). I always thought the 'dummy battery' was just some plastics with the wires connected, but you might be right considering the specs. But considering Dave's experience I might just be a little too cautious. I will look into the "crowbar circuit", thanks! \$\endgroup\$
    – heisa
    Apr 26, 2014 at 21:20
  • \$\begingroup\$ A possibly less-involved project would be to just get larger 7.2V batteries. You know you won't have an over-voltage problem with them! \$\endgroup\$
    – gwideman
    Apr 26, 2014 at 21:23
  • \$\begingroup\$ On the dummy battery -- I noted the spec said something like 8V in, 7.6V out, which is what suggested something more than just wires inside. \$\endgroup\$
    – gwideman
    Apr 26, 2014 at 21:25
  • \$\begingroup\$ It will be an external solution anyway, as the space inside the camera is limited. I was thinking of using NP-970 (which are 7.2V) since I already have some of them. But if I'm rewiring like this, I'm thinking I might as well make something more flexible. \$\endgroup\$
    – heisa
    Apr 26, 2014 at 21:30
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Should be no problem. I build aerial photography camera pods for one of my clients, and I use a switching converter to power the cameras from the 12V/24V aircraft power. My design is based on the LM25005, but pretty much any chip that can handle the current (and beware of the spike drawn when the shutter fires!) should be fine. I use a separate converter for each camera.

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  • \$\begingroup\$ Thanks Dave. "Any chip that can handle the current". I assume that, if the ACK-E6 (mains adapter) can provide 3A to the camera, this will be the maximum size of the spike? And that I will be OK with a regulator that can provide 3A? Furthermore, in the occasion that the chip somehow fails, will it just stop working leaving open output? \$\endgroup\$
    – heisa
    Apr 26, 2014 at 20:53
  • \$\begingroup\$ The 2.5A LM25005 handles a Canon T1i-T5i camera just fine. I suppose it's possible for a buck regulator to fail with the switching element shorted, but it's extremely rare. I haven't put any extra protection into my converters, and I haven't had a failure (yet). If you're really worried about it, put a Zener diode and a fuse at the output. I've also found that the cameras are very good at protecting themselves -- they'll shut down if the voltage is out of spec, either too low or too high. \$\endgroup\$
    – Dave Tweed
    Apr 26, 2014 at 21:06
  • \$\begingroup\$ Thanks for the reassurance Dave. I've read some successful stories on the internet using the same components, but they never mention the risks. Seems like I should be ok then. \$\endgroup\$
    – heisa
    Apr 26, 2014 at 21:34

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