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I've recently added a Junktek bluetooth battery monitor/shunt to the battery in our caravan to keep an eye on the state of the battery. The negative lead now comes from the battery to the shunt and then on to the rest of the power system. As I've just turned a couple of old 80w pv panels into a folding setup to charge a power bank in my wife's summer house, I've realised this would be a handy thing to take when we use the caravan if we want to spend time off-grid or on sites that don't offer electrical hookups.

I can easily add a pair of Anderson power poles wired to the caravan battery via a victron 75/15 charge controller I had in the spares box. That way I can just open the panel on the side of the caravan and plug in the cable from the panels. Usually you'd just wire the controller straight to the battery but as the shunt is inside the caravan, it's easier to just connect it there rather than running extra wires into the battery bay.

What I'm not sure about is whether it makes any difference what side of the shunt it should be wired to so that the shunt/monitor sees the charge going in to the battery. I think it shouldn't make any difference but figured I'd ask here to get a more educated answer.

Also, I'm assuming it's correct to add a fuse into the positive connection between battery and cable. I'm running 30A cable and shouldn't get more than 13A (160w/12v) so 20A fuse. The victron controller has a 20A fuse.

From the pov of the charge controller: it's optmal to keep the resistance between the controller and the battery to a minium for best performance - suggesting connect on the battery side of the shunt. It will still work fine via the shunt, but may charge the battery slightly slower (in theory).

From the pov of the battery monitor: if it is of the coulomb counting type then having charge going into the battery without going through the shunt will presumably throw it off in its calcs, so definitely connect the charge controller to the battery via the shunt. If it's just showing volts and amps then it won't matter, except you won't see the charge going in from the solar.

Thanks very much for the detailed reply, that's really helpful.

This morning I've managed to finally find a diagram showing a charger in the circuit which shows it to be on the load side

Update.

Installed the charge controller and power connectors this afternoon. 3D printed a bulkhead holder for a pair of power pole connectors, one for the solar panel to connect to the controller and another for a regular battery charger so I don’t have to remove the battery to give it the occasional top up and equalisation.

After an afternoon in the sunshine, the Victron controller was doing an equalisation charge and at that point I reset the battery capacity to 110Ah on the shunt software so it should be all set up now.

Of course now I’m looking at lithium battery upgrades

Couldn’t offer any advice on shunts, never seen one, glad it’s all worked out!

Yes, it absolutely matters which side loads and chargers are connected to a shunt.

The only thing that should be on the battery side is the batteries, no loads and no chargers.

The whole point of a shunt is to calculate the SOC, and for it to do that correctly it needs to see all power going into and coming out of the batteries.

Thanks Ronski, that's what I've ended up doing. Now I think about it, it's obvious

here's a few photos of the install