hi, i am planing to make a charged RB with solar system, but instead of traditional acid, i want to use lithium-ion battery because of weight issues.
i was reading recently about some differences and i had 2 major points to consider:
1. if the solar voltage dropped below the source voltage, a diode is used to prevent the reverse charge from the source.
2. if the lithium-ion battery is fully charged it should disconnect (through a controller).

please if someone has tried to use lithium-ion battery i would love to hear about their experience, and what problems to expect.

thanks.

Lithium cells are quite fussy about how you charge them. If you overcharge them they can swell, vent and catch fire.

I would strongly urge you to obtain a proper charger/charging_circuit for the type of cells you intend to charge. Assuming you want a 3-cell lithium pack (11.1v), you could perhaps look at using one of the cheap chargers used in the radio control R/C hobby, and hook that up to your solar regulator?

any recommendation for a good controller?

I have looked it before on the net and I see that there are no solar powered charge controllers where it is specified to work with Lithium-Ion batteries. LiIon battery recharging needs several safety checks.