have a 96 CTD. It has a stock block heater that i plug in on a timer. Last night i left my interior and cargo lights on by mistake, and they were on all night. I expected the batteries would be drained, at least so you would notice it, but it was fine. Is there some mechanism within the block heater that also recharges the battery?

 

Nope, you just have strong batteries.

 

Thats why I like the dual battery set up , I left the door open the other night & forgot to plug in [ 20* ] , started just fine .

 

thanks! I appreciate it.