split charging

Every split charge system I see is a fire waiting to happen. They're a nightmare

Theres two workable ways, either way keep your fridge on a relay direct from the main battery as it's totally impractical to run from a leisure battery - it'll draw about 10A. I presume it's got gas or mains supply.

Way 1 is "cheap £14 wanky ebay auto sense split charger and loads of thin wire"
This works but is slow to charge so you can't really just run the engine for half an hour every few days and expect to keep your beer cold,
The relay will realistically only handle 15A tops so if you use thick wire there's not enough voltage drop and the fuse blows - These are designed to be used to keep a caravan battery charged when you're driving, with a huge length of wire with enough resistance that you drop about a volt across it and it limits the charge current in practice to 10-15A.

If you fit one to a camper with short thick wires, you'll blow 20A fuses often. So you have to use fairly thin wire (12AWG) to keep the current down.
Fuse as close as practical to both positive terminals with a 20A blade fuse.
No matter what, the relay will probably fail after a while. If you use them at 35A or 40A like they claim to handle, they will melt the casing and weld the relay contacts shut.



Way 2 is to use a "proper" split charge relay and proper wire that will handle everything your alternator will give out.
The leisure battery will charge much faster, you won't blow fuses all the time but you'll need to spend £60 instead of £30. Disadvantage is that the leisure battery will charge at a much greater current so it'll actually slow down charging of the main battery. In practice this isn't an issue unless you flatten both.

Durite make a decent self sensing 140A relay. part no 0-727-33
Use 4AWG wire and a 100A fuse as close as practical to the positive terminal of both batteries.

I seem to have an old school 3rd way.

Bog standard plastic cube relay triggered from the alternator light wire.
This relay then directly connects the batteries.
No fuses.

I just realised the fridge relay (also triggered by alternator light) is also unfused so no fuse at all on the fridge!

So, back to what I should be doing...

The relay you mention looks loads better.
So if I fit a big proper relay and decent wiring (with fuses) I assume my old bedford alternator will keep up ok?

Ill re route the feed to the fridge relay to a fused supply.
Ive been reading a fair bit about the fridge though and people seem to think you should run it from the leisure battery (only when engine running) and taking the power from the engine battery is a hang up from the old days.

All new to me though.

Thanks.
I like these durite things.

Lights are getting replaced as there ropey and LED is the plan.

I'm also in need of sockets as they were all ancient and odd fittings. The sockets I was looking at also have volt meters in. Didnt realise, untill you said, why youd need one though.

You'll probably be OK If you make sure your charging leads and engine earths etc are all good and solid, so that you're getting every bit of that 36A.
That said there's probably a fairly simple upgrade for your alt.

Yeah, a 3 way fridge would be nice but I don't think we'll be on camp sites much so wont use ehu often so gas will do.

I have no problem with your plug

Nice unit, starting to get a bit overkill for a small split charge system powering a couple of lights though.

However, if RR discount gets it sub £40 id gladly use it