Converting to lithium - wiring sense check

[meza]

Hey all,

I'm switching my leisure setup to lithium. I've got the main components ready - 2000W Renogy inverter, 30Amp DC-DC charger, and a 200Ah LiFePo4 battery.

I'm looking for feedback and tips on the wiring and fuse sizing on the diagram please - I look at the complexity and cost of this and it makes a power-station look SO much simpler! But hey we don't do this because it's easy, right?

Thanks in advance.

 

[TallPaul_S]

I would probably match your chassis ground cable from the battery to the same 50mm² as your main positive cable.

Also you might want to just run battery negative with 50mm² to chassis ground, then use a separate chassis ground for the negative bus bar. This would also give you more freedom over the placement.

Also, up your fridge wiring to 4mm² (unless it's already wired in) as they tend to be sensitive to voltage drops. Generally, 4mm² is the minimum for short runs.

 

[meza]

Thanks for the quick feedback Paul.

So I understand why I'd want a larger ground, can you help me understand why?

I was assuming the main usage for the ground was the return current from the alternator supply to the DC charger (30A, fused at 40A), as all the other 12v consumers are going back to the battery negative rather than via the chassis.

How would you get a ground point in the van for a big 50mm2 lug? My install is going in a kitchen cupboard around the front area of the rear O/S wheel arch. I found what seems to be a threaded hole on the front of the wheel arch - maybe previously a lashing point. Could that be a good point? Scrape off some paint and use a toothed washer?

Fridge - was already wired in to the van with 2.5mm² (flex). But I may have a spare conductor I could double up with for effective 5mm². I'll take a look. And if not it wouldn't be too big a job to run another wire down while everything is in bits.

 

[meza]

From someone else's photo, the circled point is what I was thinking for the ground

 

[TallPaul_S]

Yes that's true, sorry - you'd want a bigger negative to chassis ground if you had just the battery negative going to ground then a separate busbar to ground as the battery to chassis would be the return path for everything (except the inverter).

Which is how you'd have if if you had a shunt.

As it is, it's just your DC-DC, 12v devices, and solar that will be connected to the bus bar via the 16mm² cable.

What length is your fridge cable run? Definitely worth checking the manual to make sure you have a sufficient cable size whilst you can get too the wiring.

Another thing - I think the manual (if I'm reading there right one) for that DC-DC recommends a 45-60a fuse between starter and DC-DC. And if you have a smart alternator you'll need the ignition signal wire too.