Leisure battery options - Lead acid to AGM with VSR?

[Mike Y]

Hi all - I'm after some advice...

The previous owner of my 2017 T6 Caravelle Executive had a leisure battery fitted by a conversion company... but they've used a wet lead acid leisure battery and a VSR under the driver's seat which (if I understand correctly) is not really best practice given the starter battery is AGM and has a smart alternator!





I'm not sure why they routed the wiring all the way over to the other side of the engine bay and fitted everything under the driver's seat, because under the passenger seat is pretty empty with just the standard OEM wiring/fuses etc...




Anyway, the starter battery I think might be original (Varta 75Ah AGM) and is beginning to struggle occasionally in the cold weather so I've ordered a Varta 95Ah AGM to replace this. Question is, would there be any befefit in removing the lead acid leisure battery and replacing it with the old AGM starter battery instead? - At least then both batteries would be the same chemistry (although different Ah capacities) when connected together by the VSR (altough I think the starter battery is a bit taller at 190mm vs 175mm )

It's a Caravelle not a camper, so it's only used for charging devices or plugging a powered coolbox in whilst travelling/day trips - we could probably manage without the leisure battery if I'm honest (and just have a 12V socket that's only switched live whilst driving), but seeing as the wiring is all there and the old starter battery would just be taken to the tip otherwise... obviously the ideal would be a DC-DC and small lithium battery - or even just a Eco-Flow/Bluetti power station and a way of charging it while driving - then we coud also use that camping - but can't really justify the cost at the moment!

Varta 75Ah AGM starter battery:


What would you do?!

 

[t0mb0]

Yeah, wet lead acid getting hit by regenerative braking voltage spikes probably isn’t ideal. I probably would put the old AGM in its place unless it’s completely knackered.

 

[Mike Y]

Going round and round in circles on this, and it's not worth talking to anyone at home about it as they don't care/understand! Maybe there's someone here who fancies a read and can offer any advice/guidance?!

I've got a Caravelle with the above after-market wet lead-acid leisure battery and VSR fitted under the driver's seat, connected to a couple of 12V/USB sockets on the seat base. It's questionable if we even need a leisure battery as we don't ever sleep in the van, I've now fitted a 95Ah AGM starter battery, and all we plug into the leisure battery 12V sockets is a powered coolbox when out on day trips and for charging devices. I'm aware VSR and smart alternator isn't best these days, but it seems to do ok for our modest needs, so would rather not spend extra money if I've already got the bits I need.

Either way, I want to get rid of the wet lead-acid leisure battery (maybe swap it with my old starter 75Ah AGM), but I'd also like to clear under the driver's seat so I can fit a sub in the future... so I'm thinking my options are...

1. Forget about a leisure battery altogether (given upgraded starter battery)... remove it, and configure the wiring so the seat-base 12V sockets run off the starter battery instead - maybe fit a Victron SBP-65 battery protect to shut them off when starter battery goes low. Maybe buy a small Ecoflow/Bluetti/Anker etc power station?

2. Install the old starter 75Ah AGM under the passenger seat using the factory-fitted red cable (shown in 5th photo above) under there with the VSR - Would the 10mm^2 ? factory fitted red cable be ok with the VSR? (I assume red cable is fused in the E-Box at 50A as no aux battery was installed from factory) Presumably a VSR (I believe it's rated at 140A) could see quite high currents through it - eg when connecting a fully charged starter battery to a very discharged leisure battery?

3. Install the old starter 75Ah AGM under the passenger seat using the factory red cable but buy a cheap DC-DC (Victron Orion 12/12-18A?)

What would you do?