You should fully charge the battery, lead acid battery`s don`t like being flat and it can shorten there life. you should get yerself somethin like this..........
http://www.theultimatefinish.co.uk/S...?ProductId=387
there are loads of different makes out there, this is just what i have !! as for the light, it should go out after 3 heat cycles !!
hope this helps
KK