EDIT: When this was written in early 2015, Canon made very little effort to publicize their AC adapter for this camera; it is almost as obscure as the access point (the rubber grip on the battery door simply flips open to reveal an access hole for the adapter plug).
Shortly after posting this article, a commenter admonished this hack and pointed me towards the correct adapter – the Canon ACK-E12. In the meantime, the market has become flooded with endless Chinese ripoffs of the ACK-E12 for $11-15, which do the job much better than anything you see written below. You should still expect to perform modifications though; the ACK-E12 adapters are meant to connect onto an AC adapter, not a DC coaxial plug. In my case, I simply cut the existing line I had built and soldered it onto the ACK-E12’s leads. With a bit of heat shrink tubing, this solution worked exceptionally well.
Please consider the above before making any such modifications. The remainder of the article here is provided for reference.
For better or worse, I’m partial to using the Canon EOS-M for shoulder-rig run-and-gun/event videography. While DSLRs or mirrorless cameras may not be the most ideal choice for the purpose, I find the EOS-M to be simple and convenient – and, unlike my Blackmagic BMCC/BMPCC cameras – it has the capability for auto ISO (and thus auto-exposure).
However, the limited battery life of the EOS-M’s LP-E12 has been the only limitation of the camera. Unlike the 5D Mark II, a dummy battery is not available for the EOS-M, and the battery door does not have a provision for an external cable – not without modification.
I happened to have two dead Wasabi LP-E12 knockoff batteries taking up space, so I decided to remove the battery core out of one and see if it would be possible to modify it.
These photos are for example purposes only. Opening up any electronic device as shown will void its warranty and most certainly cause possible injury or death to your person and/or others. Doing so will also ruin your sex life forever. Do not try this at home or on the moon. Your stupidity will never be my responsibility in a court of law, because you free me and everybody else in the world of liability if you even think of doing what you see below – or actually do it, or anything remotely similar.
The Wasabi battery casing derives most of its strength from the battery inside it. In comparison to the genuine Canon LP-E12, it is not very good. But it’s good enough for what we’re doing here.
After reinforcing the case with some styrene…
A connector from another electric accessory donated its power cable. The wires on this end were modified with brass sheet soldered to them as contacts. The other end has a female connector that interfaces with the 7.2v connection off the Chinese Gold Mount adapter for the Anton-Bauer battery.
A little more fiddling (not to mention some more Plastruct glue and some reinforcement styrene) got me to this point, with both contacts melted between two sheets of plastic to ensure that they’re not going anywhere:
Now the painful part – notching the EOS-M battery door. These doors cannot be replaced like the 5D Mark II. Has to be right the first time:
Perfect – but does the camera work without the battery ID sensor chip in the wiring?
It certainly does! The photo of success. The battery level indicator shows a full charge, which this Dionic 90 had when pulled off its base:
Ready for this Sunday:
And that completes it. We’ll see how well the setup works, but I expect it to work no different than a remote battery setup for a 5D Mark II.
-Man with the 5D