Posted: Mon Oct 06, 2008 10:41 pm
The main problem with PV as a charge source for batteries of any kind is that although the output voltage (open circuit) remains fairly constant above a certain light level it is temperature dependant (higher module temp lower voltage) and the current varies all over the shop in proportion (ish) to light level. With most PV systems being static lead acid is preferred as it is quite "tolerent" of varying charge at constant voltage, especially flooded cells, but these are pretty useless for your project. A decent BMS is obvious but as it will be very hard to get constant current at any point and at times the charge may fall to near zero it is a very different kettle of fish to a "normal" charge. Im not a BMS expert but one though is that if the PV was connected to a lead acid battery of appropriate size and voltage in a static charging point at home then it could provide a constant current/voltage charge to balance the pack and recover on the solar.
Just a thought, may not be practical.
This may be of interest to folk I had heard that PVs were a good way to recondition dodgy batteries precisely because of their variable voltage mentioned above.