[globe]

The dude at jaycar sold me this.

https://www.jaycar.co.nz/6-gauge-figure ... e/p/WH3067

To wire this

https://www.jaycar.co.nz/125a-dual-batt ... r/p/MB3687

to the vans battery and the the lesuire battery. Looking at it a bit harder it looks under rated, am I right? (90A wire 125A VSR)

[Nut17]

This is a pretty handy chart to calculate the wire size required.

https://www.wirebarn.com/Wire-Calculator-_ep_41.html

Remember you must include the full length of both positive and negative cables to calculate voltage drop. The 6g 90 amp rated wire may do the job over half a metre, but will suffer severe voltage drop over 10 metres with 90 amps passing through.

[globe]

Nice thanks, that’s super handy

[globe]

This is a pretty handy chart to calculate the wire size required.

https://www.wirebarn.com/Wire-Calculator-_ep_41.html

Remember you must include the full length of both positive and negative cables to calculate voltage drop. The 6g 90 amp rated wire may do the job over half a metre, but will suffer severe voltage drop over 10 metres with 90 amps passing through.

So would one base the cable requirements on the VSR rating or the battery (leisure),cheers

[Nut17]

You will need to fit an auto reset fuse between the tug battery and the VSR. I have used a pair of these in parallel https://www.jaycar.co.nz/chassis-mount- ... c/p/SF4106 to limit current to 100 amps in previous installations.
This will limit the maximum current that can pass through and enable you to decide on the wire size required. If this is a caravan installation, the length of cable used will severely drop the voltage by the time it gets to your leisure battery, although it will put some charge in, you really need to use a DC - DC charger to make the exercise worthwhile. Something like this https://www.jaycar.co.nz/dual-input-20a ... medium=web would provide a proper multi stage charge to your leisure battery at 20 amps.

[globe]

Cheers, it’s just a weekender and I’ve popped some door on the roof along with having a battery tender to top it up as I’m parked up at home so yeah dcdc would be great but at this stage I believe it’s overkill for my needs tbh hence the VSR route. Should do enough to run a few lights and a couple of USB chargers hopefully

[Neddy]

A VSR based dual AGM battery system will easily outperform a 20A DC/DC charger - and cost a lot less. With all solar power disconnected, our 12v VSR setup can on occasion show charge rates of over 40 Amps. One hours motoring would generally add about 30 Amphours to our House battery.

I would strongly advise you NOT to get that JayCar VSR. I think you will find that it isn't "dual sensing". The very low price is a clue. Sooner or later you will want to add a bit of solar power to your rig. A dual-sensing VSR will utilise that solar power to keep both House battery AND your Starter battery fully charged. It also has the effect of increasing your House battery capacity. Expect to pay about $140 for a good quality BEP DVSR.

Neville.

[96coaster]

As far as I can see in the Jaycar add, there is no mention of “dual sensing “ it is described as as “dual battery isolater”, although the wording “Ensure you can always get your dual-battery vehicle started.“, is a bit misleading.

This could imply that charge from house to starter batteries “may be available.