I'm converting a VW T6 campervan, using the Orion B2B, Multiplus charger/inverter and a 3rd party MPPT which feeds just the leisure battery. These three are independently connected to the leisure battery. I've also wired the connection for the Multiplus trickle charge to the vehicle battery - this functions as I expected when AC is connected. I've been surprised to see that even with no AC connection and the Multiplus switched off, there is still a charge going to the vehicle battery when the leisure battery is being charged by solar. The vehicle battery voltage can get so high that the Orion thinks the engine is on, and says it's in bulk charge mode.
At a superficial level all of this is sort of good, because both batteries are getting charged even when off-grid. But I'm concerned that in some conditions the leisure battery might be drained in supplying a trickle charge the vehicle battery. How is this trickle getting through the Multiplus, even when turned off? Is it controlled in a sensible way, so that it only happens when the leisure battery is at high voltage (from solar charging)? I haven't found any mention of this in any documentation or discussions.
