6 Volt Chassis Batteries

[ScoobyMike]

Hello All,

My motorhome is a diesel pusher powered by a Cummins ISC. It has 4 6-volt house batteries and 2 12-volt maintenance free chassis batteries. The chassis batteries need to be replaced. Is there any reason I should not use 2 6-volt batteries wired in series?

[gemini5362]

yes there is
two different kind of uses. Chassis batteries are made for high current drain over a short period of time. They are almost never drained totally. Coach batteries are made for lower level current drain over a long period of time and are drained a lot lower. If you use two 6 volt batteries then you will get 12 volts but half as much cranking amps. Use the two 12 volt batteries in parallel for your chassis

[BFlinn181]

gemini5362 beat me to it. Before making a change like that research starting and deep cycle batteries. In addition, check the amp capacities of two 6 v compared to two 12 v starting batteries. If you've not had issues with starting before the batteries aged out and lost capacity, I don't think you have a need to change.

[ScoobyMike]

Thank you guys. I like the way 6V batteries hold up and right now I am basically starting the engine off the house batteries because the chassis batteries are so weak. I'll probably stick with 12V, but maintainable :-)

[wa8yxm]

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)