My experience.
Batteries : Sanyo 2300 and 2500
Charger : Sanyo Charger
Method : Slow charge / flash charge
Usage : Canon Flash 580.
Comments : I can only manage less than 5 to 10 flash before battery is unusable.
After 3-4 days of not using the fully charged batteries, Sanyo 2500 indicate 0% on my flash, totally flat. Sanyo 2300 is a little better, indicate 50% on bar. Batteries discharge too very fast.
Using Maha charger, this is worse of the lot I hate this charger!
Slow charge on my sanyo 2300 and 2500 which took the entire 12 hours! After less than 2 days of not using the fully charged battery, both models are unusable! Sanyo2300 indicated 25% on the bar, 2500 is 0%.The maha charger cannot be used on the sanyo batteries, the batteries discharge too fast.
The old Sanyo 2100 was much better, slow discharge, I could use the batteries even after 7 days and its still usable. I stopped buying Sanyo rechargeables as it is impossible to use.