Hi,
I have a 2008 VW T5 Caravelle with a Victron MPPT 100/20. A 270watt panel on the rooftop tent.
The car has a factory option 2nd battery under the passenger seat as it has the Aux heating system fitted. This 2nd battery connects to the charging system only when the engine is running from what I can see via the ECU and diagrams.
Also as part of the factory system the fuse box under the seat runs the interior lights and aux / rear charger 12-volt outlets, so our Fridge etc goes into this battery and anything else,
Had the setup for a while and it charges the main battery with no issues. But we never connected the Load output to the 2nd battery.
I need to connect the load output to the 2nd battery so that when it sat there it can charge the 2nd battery from the solar panel.
As an idea should I connect the load output to the 2nd battery and cut that load output from the MPPT to the battery with an ignition switched relay?
So ignition on, No connection between two batteries via the MPPT - ECU controls and charges as it needs to - factory setup.
Ignition off, MPPT charges the 2nd Battery?
Big question is there any back feed through the MPPT, Could we drain the 2nd battery and the main battery if the ignition off?
Or do I need a https://www.victronenergy.com/battery_protect/battery-protect Battery protect to protect the backfeed and use a TX cable (https://www.victronenergy.com/upload/documents/VE-Direct-TX-digital-output-cable-EN.pdf) to the battery protect so the 2nd battery can only be charged when the MPPT has an output on the load? As Shown Below :-
