House batteries - swapping in 6v batts

[195pilot]

Originally Posted by PeterFTH

The big plus to two 6 volt batteries in series is there is no "weak cell" phenomenon like putting 2 12 volt batteries in parallel. I have never figured out why the engine start batteries on every big engine RV I've seen are two tiny group 24 car batteries in parallel. The plates are tiny, there is a self discharge tendency from the parallel connection - there may be a reason I'm not aware of but I'd put in one beefy 4D 12 volt or two beefier 6 volt batteries for engine start. Does anyone know why they are all manufactured this way?

Peter, the reason it's common to use two 12V starting batteries in parallel for big engines (especially diesels) is that this is an inexpensive way to provide high starting current. Batteries all have an internal resistance; this causes them to drop their output voltages as more current is drawn from the batteries. Placing two batteries in parallel divides the required current between the two batteries, hence less voltage drop for each battery (since it is only supplying half of the current).

[Bumps]

Well, based largely on information gleaned from this forum, at the end of the last season, we changed from 3x12v house batteries to 6x6volt Costco GC2 golfcart batteries (in series/parallel). I'll report back in about 5 years on how well they are doing. Can't turn back now... \ken

[CAT2000]

Does anyone know what they run for batteries on the Newell's, Prevost higher end coaches, I saw something about one that had 16 batteries but I don't know if they are 6 or 12 volt?