Is there a way to...

[Mtrdrms]

Wire my interior lights so my ignition key doesn't have to be turned on to operate them? I am going to a battery bank with an inverter for AC but I want to use my existing lights in the bus. How do I do that?
Thanks!

[somewhereinusa]

You don't say what kind of bus. The simple answer is find the circuit breaker that feeds the lights you want to change and simply change the feed to it from the source you want to use.
If it's a full size bus probably located in door beside the driver on outside.

[Mtrdrms]

Ok, so I found the hot lead to the light switches. However, when I apply an alternate power source (my house batteries), the lights don't work. I think this is due to a grounding issue. So, if I ground my house batteries to the bus, will that work or do I have to reground the lights to the house batts?
Thanks

[alpine44]

Best setup for a 12V house system is to have both the house and starter battery grounded. The house battery is connected on the + side to the vehicle battery via an isolator relay that closes when the alternator charges. This way, the house battery gets charged from the alternator but house loads do not drain the starting battery when the engine is off. Every consumer, whether on house or starter battery, is grounded for the current return path.

A isolator diode can be used in lieu of the isolator relay but you need to compensate for the voltage loss in the diode with a separate sense lead to the alternator. That's a little trickier especially if the alternator is monitored/controlled by the ECU.

[Mtrdrms]

Ok, so I should ground both sets of batteries to the chassis and connect a positive lead of the house batteries to a positive of the start batteries with and isolator in between? I can do that. Sorry if its a silly question, I'm no electrician...

[alpine44]

Originally Posted by Mtrdrms

Ok, so I should ground both sets of batteries to the chassis and connect a positive lead of the house batteries to a positive of the start batteries with and isolator in between? I can do that. Sorry if its a silly question, I'm no electrician...

Yes, the isolator relay prevents the house loads from draining the starting battery when parked, which would be very annoying. When the alternator is charging, both house and starter battery are connected in parallel (house + to start +) via the closed relay contact.

[Mtrdrms]

Thats great! Can you point me to a good isolator? I see lots out there...

[peteg59]

Are there any other stats needed to figure out the correct isolator relay?

[alpine44]

Originally Posted by peteg59

Are there any other stats needed to figure out the correct isolator relay?

The relay and connecting wires need to be rated for the maximum current flowing between the batteries.

There is a configuration where the house battery contributes to the cranking current. That is great for diesels in the winter but you need a beefier relay for this.

The other high current scenario is when you drain a large house bank way down and then the relay connects it to a fully charged starting bank.

I would contact the tech support of the isolator manufacturer and tell them your battery configuration and sizes to have them suggest a suitable model. I never had any issue with several products from Sure Power.