House Battery Replacement Procedure

[Jeff Watt]

Ed, Joel,

I have a Big Boy system in my coach. What is puzzling to me (and many things are), is the solar controller. In the photo you can see there are + leads coming off of it to the house batteries and to the engine batteries. I am thinking that maybe the engine battery lead is connected somewhere I can't see it, such as on the main switch?

Ed, if the solar charges the house and once they are full then through the Big Boy or BIRD the chassis are charged, then it seems to me that with enough drain on the house batteries the chassis will never get charged. By charging the house batteries first seems somewhat backwards as I'd have thought the main priority is to keep the engine batteries charged so they are available to start the engine and/or the generator. But what do I know!

Thanks for the info. If I can get at hooking the batteries up today instead of dealing with other life issues (lots the last few days), then I'll post my success or failure.

Jeff

[Edward Buker]

Jeff,

I was not aware that the solar charger had an output for the chassis battery also. I do not know if that unit contains circuitry that sets a priority of one vs the other bank or just gives a little to each. I think the issue has always been that the chassis batteries were expected to have very little draw (radio clocks etc) and therefor like in a car with the ignition off you might be able to go a month or so without an issue. Beaver, for reasons that have never been clear, wired the engine ECM directly to the chassis batteries and a constant approximate 1.75 amps is pulled all the time.

I would check the voltage on both banks with the solar charger on and see if you do get charging to both banks. You may have to use a blanket to turn them on and off so that you can tell what is happening at the battery banks with the solar charger.

The main charging is always done with the charger/inverter unit using a power post or the genset. With that charger the house will always be brought up in voltage relatively quickly and the coupling charger of some sort will connect the chassis batteries to the charger. If for some reason the chassis batteries are down and will not crank the engine then you have the emergency start that ties the banks together (do that for several minutes before you crank) to allow you to get things running. The solar charger should be looked at as a trickle charger for the house bank and will not play a big role for heavy charging or power use out of the house banks.

Later Ed

[Joel Ashley]

Scratching my head over this, I checked the manufacturer's website and to quote,

"Charges both the House and Engine Battery Banks Simultaneously
(Up to 30 amps heads to the House Battery while up to 5 amps head to the Engine Battery!)".

So I reckon that answers that.

Joel