PT Wang said:
Is there any negative consequences, other than longer time, for recharging a
battery (Li-Ion or NiMH) with current lower than the specification but
similar voltage? For example, to charge with 12V x 100mA while the
specification states 12V x 1A.
Battery technology isn't quite that simple. firstly, Li Ion batteries
generally have embedded electronics to protect the cells. That makes it
hard to charge them unless you know what the protection circuit is doing.
Bypassing the circuitry can cause a real risk of damage to the cells and to
you. Most others such as NiMH use current based charging. This means that
you don't charge a battery at a specific voltage but at a specific current.
For example, one pack I have been using recently is an 8.4V NiMH 3.5Ah unit.
This gets charged at 2A and during the cahrge cycle, the voltage at the
battery terminal rises from about 9.3V at the start of the charge to 10.5V
at the end. The current remains at 2A for the complete charge process.
However, a small voltage drop at the end of the charge indicates a full
charge, and at a lower charging current, this won't be detected
Using a fixed voltage will either overcharge batteries, damage the power
supply or perhaps won't ever fully charge the battery. A well designed
charging circuit doesn't have to be complex, but I would suggest you look at
the battery specifications carefully before doing anythig with your own
charger
Peter