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Hi
I‘m currently planning my setup for my camper van and I‘m using an AGM lead battery and want to use a lithium battery for the second one.
The second battery should be charged either via the Orion-Tr DCDC charger or MPPT and a solar panel, so far so good.
When the second battery is full, I would like the starter battery to also be charged by the MPPT charger.
The CTEK D250SE offers that functionality, but i would prefer to use a victron product if possible.
There is no Victron MPPT that has a second output for a starter battery.
Usually this is done by a DC-DC charger like the Victron Orion-Tr smart. I would like to know why you want to charge the starter battery. This is not essential if you leave your van's engine running from time to time. The starting process only puts an insignificant load on the battery and only for a very short moment. This is what starter batteries are made for, even if they are not constantly charged.
However, here's an interesting thread that has covered the topic in detail before: https://community.victronenergy.com/questions/84370/mppt-7515-charging-vehicle-battery-how.html
Presumably the AGM is your starter battery.
Standard way to do this with pure Victron is to add a second Orion. For safety use the isolated models.You'll have to play around with the setups to get it to work. Probably need to put the second Orion into constant voltage and set this to float voltage for AGM at about 12.7V.
Your starter battery shouldn't need more than a trickle charge, so a low current model is all that's needed. And as it needs so little power, you don't need to worry about switching charging to it off. I did something similar, current to my starter battery is about 0.3-0.4A and it's keeping my very tired starter battery at about 12.4V.
You've probably solved this, but my approach is going to be a little different. I'm planning to use a MPPT 75/15 with a small set of panels (100W) to charge the starter battery. I already have an Orion DC/DC to charge from the starter/alternator (12V) to the house batteries (24V).
My thinking is that as long as the starter is charged, I can get somewhere to plug in the house battery with a separate 120VAC/24VDC charger. I also carry a 120VAC/12VDC charger, but using that requires running the inverter and that sucks more power.
I'll set the Orion to charge when it detects the ignition (already wired) or the 12V input is over about 13.4V, which would indicate the starter is pretty well charged or being charged, and to shut down if the 12V rail fails below about 12.5V. This will keep the house battery topped up reasonably well. The alternator charges it at about 0.12C per hour (100Ah house pack).
Any comments? This could be a bozo idea but it seems worth a throw.
