[jray3]

I'm considering running with two 8 volt deep cycle batteries on my 1987 F250 diesel (and any other vehicle with no electronics). Thinking is, I'll have more starter torque, brighter lights, and unload the alternator during most driving (for better FE and performance), but the alternator will kick in and carry the load right before the bottom discharge limit (14.0 V).
I'd grid-charge the battery when parked, floating it at 19.6V.
Anyone tried this mod? I may need a dc-dc converter and even a 12V buffer battery for 'house' loads to prevent frying the radio and lights, only using 16V for the starter.

An old-school diesel technique is a series-parallel switch to feed 24V when the starter is engaged, but that does send a voltage spike to everything else as well...

There won't be any change in weight, as the truck normally runs on two parallel 12V batteries.