Using same battery bank for starter and house

Hey guys, I am buying a bus that was converted to a party bus (sound system, tv’s, inverter) and will be continuing it to build a full time 4 seasons house (we live in Canada). Currently the electrical system is plugged to the starter batteries. I was wondering if it would be possible keep this system but upgrade the batteries to lithium and move them inside. In the case that the batteries get drained too low we have a backup generator if ever we were not paying attention. Since this is the main reason people keep them seperate, is this a viable option or is there another metric to take into consideration?

This would simplify the work, give us an overall bigger battery bank, and allow us to charge directly from the alternator without getting extra systems.


You could install a battery isolator between the starting battery(ries) and house batteries. That way you’ll always be able to start the bus, but once the engine is running it will charge the house batteries.

If I have a backup generator for charging in case it drops too low then having all the batteries together could just give me an overall bigger battery bank. I was thinking of having all AGM or relay them into the bus for all Lithium batteries. Seems to me like it will be good unless there is something I’m missing.

Starting batteries can’t handle very many deep cycles. You’ll kill them. Starting batteries have thin plates that are good for one purpose: supplying a lot of amps to crank the engine for just a few seconds. Then they get charged right away while the engine is running. If you slowly draw them down it damages them.

AGM deep cycle batteries might not supply enough instantaneous amps to start an engine, especially a diesel engine. Diesels require fast cranking to start.

Lithium batteries made for starting are fine, but good luck finding them big enough to start your bus (where they can supply enough cranking amps). I have lithium starting batteries in a couple motorcycles, but have never heard of them for cars/trucks/buses. One drawback with lithium starting batteries is they don’t work well when cold. For my motorcycles they won’t crank when cold, so I have to heat them up by turning the lights on; then they’ll start, but sometimes just barely. If you have a diesel it may turn over, but won’t start.

Also, deep cycle or not, if you draw AGM (or any other lead-acid battery) down past around 50% it will damage the battery. A 100 amp battery is really only 50 amps if you want it to last. That’s why we install low voltage shutoffs in our electrical systems.

Would it not work if there were like 6 batteries together? I will have to shop around

Good luck…

For safety ad performance I would leave the starter battery dedicated to your engine and install Lithium for your “house”. You can run an isolator between your alternator to your lithium to provide charge when the engine is running.