Additional leisure battery Earth to chassis? (2 Viewers)

[Stewen]

I’ve finally got around to buying a Roamer 230AH smart4 seatbase LiFePo4 leisure battery to fit under the drivers seat of our 2015 Auto-Trail . The existing 2 AGM batteries are under a bench so we will free up some storage space. The van has a Sargent EC500 system. The existing battery wires are quite small gauge on a 20A fuse. Both positive & negative leads from the batteries connect into the Sargent unit and the negative is connected to the chassis. I have a Victron Orion XS50 dcdc charger, 75/10 MPPT solar controller and IP22 mains charger, plus a Renogy 2000w inverter. Now, Roamer advised I put a 300A terminal cube fuse on the battery and run 90mm2 cable to my positive busbar/ midi/mega fuses and same to the negative busbar & shunt. Mainly to avoid any voltage drop or ripple effect if hammering the inverter for extended periods between battery charge ups. My question is this… given that the AT negative cable to the chassis is probably 10mm2 at best, in order for the Orien XS50 to work properly, should I run a 90mm2 cable from my negative busbar to a new earth point on the chassis? Does it matter if the leisure battery is earthed to the chassis twice?

Also has anyone got any photos of their own seatbase battery set up? I’m thinking of isoloator switch & fuses at the front, shunt, neg busbar & shunt at the rear and mppt and mains charger down one side. All affixed to a 9mm ply frame around the battery. Thoughts?

 

[rod_vw]

My answer from what you have said would be NO, an additional -ve connection is not a problem. However remember that if you are introducing a Shunt (Victron or otherwise) to monitor the battery charge/discharge that should be in the ONLY connection to the battery(s) -ve pole.

Others may be along to contradict me but I think I am correct.

 

[Lenny HB]

As your battery is under the seat you will have a fairly short cable run to the starter battery and you are fitting the Orion XS near the leisure battery 16 mm² cable will be fine you connect the negative fron the XS to the negative on the leisure battery not to chassis. As you have a shunt you will connect to that not the battery.
If you connected to the chassis you would by pass the shunt.

Inverter wiring will depend on the size of the inverter and the length of cable run to it.
I have a 3000 va inverter and my cable run is 4m I used 70mm² but I rarely use my inverter at full power for more than 20 min. If I was drawing over 200 amps for extended periods I would have used at least 90mm².

 

[Stewen]

Thanks guys.
Lenny, I have a 150A negative busbar connected to the shunt which connects to the LB negative, but may need to upgrade to say 300A just to be safe for the inverter negative.

So the Orion XS negative & solar & mains charger negatives all go to the busbar. I’m using 16mm cable for the three chargers.

What I’m struggling a bit with is do I connect a new 90mm negative to the chassis to complete the circuit of the same gauge cable as the LB positive or a 16mm to match the Orion XS negative or just rely on the existing thin AT connection behind the sargent psu to the chassis share the Leisure battery negative earth to the chassis with the vehicle battery? My previous Orion was an isolated version which I felt was easier & ensured the vehicle and leisure battery negatives were taken care of rather than relying on the thin AT wire. Hope this makes sense.