I'm working on resolving some potential issues on our 1976 GMC Motorhome. One issue is battery charging. The engine alternator charges the engine battery and the house battery via a battery isolator – both batteries charge, but the loads are isolated.
The house batteries are also charged by a solar panel or a 120VAC (North America) – 12v charger which can be operated from 'shore power' or the generator.
There's a continous-duty boost solenoid that ties house and chassis batteries together. If the chassis battery is dead, this may allow the engine to start by paralleling the batteries.
The downside of this system is that the chassis battery can't charge from the solar panel or on-board battery charger. My thought to fix this issue was to replace the battery isolator with a battery combiner – in simple terms a relay to tie the batteries together if either side is charging.
Then I realized my boost solenoid is already most of a battery combiner. If the voltage on the house battery is greater than around 13 volts, closing the boost solenoid will charge the chassis battery.
And so my question: Got any unique way to monitor battery voltage for some level over 13 volts and provide an output to activate a relay? I'll probably use an "Arduino relay module" that includes a transistor driver as I believe the boost solenoid draws a fair bit of current. Ideally, the circuit should be very low power so as not to drain the house battery during days when no solar or shore power charging is available. Hard to believe that days or weeks could go by with no appreciable solar charging in Seattle
The house batteries are also charged by a solar panel or a 120VAC (North America) – 12v charger which can be operated from 'shore power' or the generator.
There's a continous-duty boost solenoid that ties house and chassis batteries together. If the chassis battery is dead, this may allow the engine to start by paralleling the batteries.
The downside of this system is that the chassis battery can't charge from the solar panel or on-board battery charger. My thought to fix this issue was to replace the battery isolator with a battery combiner – in simple terms a relay to tie the batteries together if either side is charging.
Then I realized my boost solenoid is already most of a battery combiner. If the voltage on the house battery is greater than around 13 volts, closing the boost solenoid will charge the chassis battery.
And so my question: Got any unique way to monitor battery voltage for some level over 13 volts and provide an output to activate a relay? I'll probably use an "Arduino relay module" that includes a transistor driver as I believe the boost solenoid draws a fair bit of current. Ideally, the circuit should be very low power so as not to drain the house battery during days when no solar or shore power charging is available. Hard to believe that days or weeks could go by with no appreciable solar charging in Seattle