Hello enscor
Welcome at CPF
Since the Silva L1 is build for 6V, it works great with 4xnimh cells, AA or Baby.
When you don't want to risk the driver or the led, don't do it.
Your LiIon-pack will come more than 8V out of the charger and I guess, something will go bad.
Try the new Sanyo eneloop's for less selfdischarge.
Best regards
____
Tom