Canon S45 external battery pack	Search WWW Search www.moz.net.nz email moz

I bought an S45 knowing that it has a tiny internal battery, and that I'd possibly need to recharge a couple of times to fill the CF card I was buying. As well, there's no socket to take external DC. My plan was to get the mains power adaptor and see if I could make up some sort of external battery pack.

A little research produced evidence that James Jin had already done this, as his photo to the right shows. That's simply 6 AA NiMH batteries in a holder, attached to the cord that comes with the Canon mains adapter. The camera takes nominal 7.4V (two lithium cells in series), and 6 NiMh give 7.2V nominal. It works just fine.

The mains adaptor looks like this, and you have two choices - if you can find a compatible plug to go into the fake battery, just wire that onto your external battery and you're away. Otherwise you need to cut the wire somewhere to insert some plugs. There's a ferrite on the cord near this end, and you don't really need that with batteries, and it's bulky so I plan to move my one to the end near the mains adaptor while I have the wire cut.

Plug selection is trivial if you just go with the 9V battery style connectors that are normally on those six cell holders, but they have one minor problem - they don't release reliably when you pull on them. This could be an issue for me, as I'm prone to forgetting that there's two parts to the camera (I do this with my cell phone fairly often - pictured).

So rather than those plugs, I'll go for a line plug and socket just outside the camera that have the other problem - they tend to release unexpectedly. I'll address that by crushing the socket slightly to increase friction. But at least I'm not going to be ripping the camera apart by dropping the battery (or putting the camera in my bag with the battery pack still in my pocket).

Here's the wee port in the right hand side of the camera that the cable comes out.

I've been asked whether the common 7.2V battery packs for radio controlled cars (etc) would be suitable: yes! So if you own one of these, just buy a matching plug for it (available from most electronic hobbyist shops). I'd be tempted to put a fuse in that circuit, because the bigger batteries can deliver enough power to melt the copper wires if there's a short circuit - and if they do that inside your camera, it might not work afterwards. Since the camera draws about 2A maximum, use a 2A or 5A, slow blow fuse. That plus an inline holder will cost about a dollar.

Later

I've now built my own battery pack and been using it for a couple of weeks. I'm happy to report that it works jush fine, and the comera recovers well from the infrequent loss of power when I pull the plug out... but I have done that a few times, which I think justifies putting the plug next to the camera. I moved the ferrite (the lump on the cable) back down to the mains adapter end of the cable by unclipping it from the cable and re-installing it. Which was easy to do.

Battery life with 1650mAH NiMH cells is considerable - I have only run them flat once, and that was at a peace rally where I shot about 500 photos over 6 hours, with the camera and display running fairly continuously. Towards the end of that time I had to change over to the internal battery. Photos from the peace rally are here.