Hello,
I have 4 x 175W Victron panels on the Ducato roof, Victron MPPT 100/50 regulator, Victron Orion 30 A, Victron MultiPlus 12/1600/70-16 and 2 x 200 Ah LifePo4 (not Victron).
What do I need to make a DC-DC starter battery charger that will only work when hotel batteries are fully charged?
What is the Victron Orion DC-DC 30A doing now? Anything? Is it connected at all?
So, you want to charge the Starting Battery, using the House / Hotel batteries, but only when the House Battery reaches 100% SOC.
What condition will stop this charging?
May I ask, why do you need a 30 amp charger to "trickle charge" the Starting Battery? What is draining your Starting Battery?
You can configure a second small Orion to charge the starter battery.
But automatic on off will be driven by voltage, so the starter battery will start charging as soon as house battery voltage rises from charge. This shouldn't be a problem as starter batteries don't need much charging when charged frequently. So no point in worrying about house battery being at 100%.
