Any simple solutions to make the Multiplus II trickle charger a bit... smarter?

DIY
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1

Hi guys,

So I’ve been having issues with my AGM starter battery on my campervan running flat, as everytime i open a door all the electrics boot up and if im parked up for a while and not moving its enough to give me problems.

I rather think that the starter battery is goosed, but going to at least give it a go at desulfating and seeing if i have any success before looking at replacing.

In the meantime, I’ve wired up the 4a trickle charger from my multiplus to the input side of my Orion XS so the starter battery is on a constant trickle. However due to the leisure battery being lithium and the starter battery being AGM i think the difference in voltages will mean the starter battery is at risk of constantly being overcharged. Has anyone looked at utilising one of the internal relays on the Cerbo GX to open and close the trickle charger circuit at certain voltages?

2

Have you read the FAQ I posted on the trickle charger.

https://community.victronenergy.com/t/how-does-the-multiplus-trickle-charger-work/98

I would not be worried too much about keeping the trickle charger on permanently from the AGM perspective as it will see around 13.2V which is a storage charge voltage. The issue is making sure the trickle charge is stopped on low lithium voltage which depends on your battery/BMS. Putting it through the Cerbo relay is certainly an option, or a programmable relay on the Multiplus.

3

Nice write up, its a real shame that this trickle charger isnt a true charger. I guess the easiest option is to just put a switch in the circuit and if i notice the starter battery voltage starting to drop when parked up for some time, just flick it on for a few hours.

I think leaving it on permenantly will just cause issues with the engine shutdown detection on my Orion, and as the van is now fully converted running an additional D+ signal wire will be a massive pain

4

What did you end up doing? I’m currently getting ready to move my system from a class A to a class B and am facing the same dilemma.

5

It follows the three stages that the internal vharge follows.
The AGM would technically not be overcharged since lithium needs less.

Trickle charging is for maintenance but if you need to actually charge - buy a charger.

6

You can use the remote switch of the Orion linked to the ignition key if you wish. Personally I just had a manual switch on the dash to engage the Orion when driving, and switched it off when I stopped driving.
The multiplus 4a output worked great for me with the Orion. As I say I didn’t use the engine shutdown detection, and had enough PV on the roof with battery storage not to worry about running out of power