I will explain: Starting batteries, EPICALLY on a big Diesel, are designed to dump a small portion of their capacity but to do it very very very fast.. A 100 amp hour Starting battery thinks nothing of dumping 200-300 amps for up to 30 seconds. (This is only a couple percent of the capacity (300/120) but it's a lot of current)
But the most common six volt battery is a DEEP CYCLE type, This battery has 220-230 amp hours (C/20) but it does not like to dump more than 100 -200 amps ,,, However you can safely take it down to half full if you do it slow enough.
The reason is due to differences in the plate design and chemistry.
And it is the reason I favor six volt twins for house batteries.. They are designed for just that kind of service.
Stick with starting bateries for the chassis. Most all the 12 volt battery types you find in the stores are Starting type.
Exception.. The GC-12 battery at the Golf Car store. (That is a deep cycle)
Home is where I park it!