This one begins with my frustration with the poor rechargeable battery performance in most Canon point-and-shoots using two AA size batteries. Canon cameras that use two AA batteries seem to be pretty much useless with normal NiMH rechargeables, as they last for about 10 shots or so, if you are lucky – that’s because they produce only 2.4 V.
Solution: Use a single LiFePO4 3.2V AA cell coupled with a dummy cell.
LiFePO4 is Lithium Iron Phosphate, a safer alternative to the usual Lithium Ion or Lithium Polymer. See http://en.wikipedia.org/wiki/Lifepo4
The dummy cell is just a chunk of wood filed down to be cylindrical and the same length as a AA cell. A hole is drilled down the center and a 2″ long wood screw is screwed in. The end of the screw would be ground down, as it is usually too sharp to put into the battery enclosure. One can also put a small amount of crushed aluminum foil over the end of the screw so that it fits nicely in the battery enclosure.
Although LiFePO4 batteries are safer than most Lithium-based batteries but this comes at a price: About half or third the power capacity. Fortunately, because they hold their voltage well over their discharge cycle, this isn’t a big problem on cameras. Plus you can carry extra as they are light and you only need one when in the past you needed two!
A few cautions
Most important – there is a small chance that the slightly higher voltage of the cell compared to Alkalines could damage your camera. If you are concerned about this, do not take the risk. I have tried this successfully with two different Canon models with no ill effect. But, I am not responsible if you destroy your favorite camera! You have been warned.
If you put two of these lithium cells in your camera, you will destroy it, thus, the need for a dummy cell. Since the cell is blue with no obvious markings, it is pretty easy to tell if you are about to do something stupid.
Where to get them
This isn’t an official endorsement, but this is the company I purchased from and the cell itself:
The cells are only $1.95 each, but you’ll need to purchase a special charger which will run you about $20. Get at least two cells for quick swapping.
Have fun saving $$$…
Update after Hack a Day feedback
Many people commented on this hack. The most significant comment was that there are now NiMH batteries that don’t have the problems of the old, mainly the self-discharge problem. But also, some older Canon cameras like mine seemed to have problems with low voltage operation whereas new ones don’t.
Also, some people were concerned about the lack of protective devices in this cell – a concern, but it appears that realistically is only an issue if the cell is misused. Others thought it would be safe to eliminate the dummy cell and wire up two cells in parallel to get double to storage. This may actually work without modifying the camera, but at the expense of some cabling and insulation trickery.
Conclusion: If you use proper NiMH and a quality charger, you get safety and performance, but if you have a camera that doesn’t like any NiMH cell, the LiFePO4 approach may be your way out.
I’ve also added a picture of my charger at the bottom, which I purchased from the link above.