What gauge/type of cable from Victron controller to battery

[VXman]

As thread title really - What gauge/type of cable should I use from Victron controller to the battery? the stuff I have is really difficult to get it it fit/sit in the cable screw sockets within the Victron. The cable feels to big and doesn't secure properly. It was cable supplied by the original fitter when I had a NDS controller.

 

[peterc10]

One of the things I didn't like when I installed a Victron solar controller is that the small screw sockets. I could only get a 4mm2 cable in. OK if you have a short run from the panel, but you will get voltage drop if the run is long. Previously I fitted a Votronic and they were much better.

 

[PeterCarole29]

Can not run the cables into a bus bar just before the controller messy and more expense but purhaps the compromise

 

[RogerIvy]

You didn’t mention which controller you have.

 

[autorouter]

According to the datasheet, the terminals will take 6mm2 wire. Maybe a bootlace ferrule on the end would make it easier to get the strands bunched together enough to fit.

When sizing the cable, you obviously want to keep the voltage drop to a minimum, and also to avoid heating the cable, so that power generated by the panels isn't wasted. However another factor is that the voltage drop means the MPPT is working on inaccurate battery voltage measurements if it has to rely on the power wires for battery voltage measurement. That's one reason why extra-thick wire is used, to get a more accurate battery voltage

It is common to use another method to get accurate battery voltage to the MPPT. One method is to use a pair of thin voltage sense wires, which may be easy to wire in while you are running the power wires. Alternatively Victron do a 'Smart Battery Sense' module that sticks on to the side of the battery, and sends battery voltage and temperature data via Bluetooth. That's even easier than running sense wires, provided the MPPT has Bluetooth.

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[Lenny HB]

One of the things I didn't like when I installed a Victron solar controller is that the small screw sockets. I could only get a 4mm2 cable in. OK if you have a short run from the panel, but you will get voltage drop if the run is long. Previously I fitted a Votronic and they were much better.

I used 10mm sq when I did Tam's I just crimped bootlace ferrals on the cables.

 

[Lenny HB]

As thread title really - What gauge/type of cable should I use from Victron controller to the battery? the stuff I have is really difficult to get it it fit/sit in the cable screw sockets within the Victron. The cable feels to big and doesn't secure properly. It was cable supplied by the original fitter when I had a NDS controller.

How long is the cable run and what is the max current, can't answer without that info.

 

[VXman]

How long is the cable run and what is the max current, can't answer without that info.

Probably less than a metre.

Current? - controller 20 amps. Biggest draw possible is 1500 watts from my inverter.

 

[VXman]

You didn’t mention which controller you have.

I said Victron in the title but specifically it is the Victron smart MTTP 100/20

 

[Lenny HB]

Probably less than a metre.

Current? - controller 20 amps. Biggest draw possible is 1500 watts from my inverter.

I thought you wanted cable size from solar controller to battery?
For that 4mm sq more than enough.

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[VXman]

According to the datasheet, the terminals will take 6mm2 wire. Maybe a bootlace ferrule on the end would make it easier to get the strands bunched together enough to fit.

I think this is perhaps the way forward

I thought you wanted cable size from solar controller to battery?
For that 4mm sq more than enough.

Sorry - yes I wasn't sure what you meant by the question so over answered.

The present cable is more than big enough and I don't really want to change it but getting the end into the small connectors on the controller is a pain. I think I'll give some bootlace ferrules a try.

 

[RogerIvy]

I said Victron in the title but specifically it is the Victron smart MTTP 100/20

Assuming a 2m cable then 4mm is fine for 20A
If your cable has higher temperature rating (75deg instead of 60deg) then even 2.5 would work - but 70deg is pretty warm to the touch!

Edit:
Just to add, the 100/20 can take a 6mm cable.