Update - Sanyo brand name has been closed down by it's mother company, Panasonic. So now these batteries come to market under the new name Panasonic Eneloop Batteries.
Sanyo Eneloop Rechargable Batteries are cheap but better than most of other expensive rechargeable battery types. Sanyo Eneloop Rechargeable Batteries are pre-charged and ready to use right out of the pack Also these rechargeable batteries preserves charge for long periods of time. According to Sanyo, the new eneloop LSD (low self-discharge) NiMH batteries can maintain 85% of its original charge after 1 year of storage. In lower temperatures percentage would be lower still this is pretty good. Sanyo Eneloop Rechargeable Batteries have an Over-voltage protection system and foldaway AC plug offers worldwide voltage for traveling. Also Batteries can be charged up to 1,000 times.
One of the biggest problems I have with Rechargeable Batteries are self-discharge. This means that a charged battery slowly discharges itself without any equipment consuming any current. It's a pretty annoying when you want to take photo of something suddenly and finding batteries are dead.When you need them, the energy is gone ! Sanyo Eneloop batteries have an extremely low rate of self-discharge, which means they hold their stored energy for a very long time. But self-discharge rate would be different in different areas depending on temperature. Low the temperature get faster batteries would self-discharge.
Its always use 4 batteries of same brand for your Canon SX10 IS camera. Also its better use 4 batteries which charged same time in a charger. Thats good for life time of batteries as well as for your camera. You can find lot of positive reviews about Sanyo Eneloop Rechargable Batteries at Amazon.com. Some of those reviews are very informative so you will learn a lot about Rechargeable Batteries by reading those.