Solar Cable size??? (1 Viewer)

[tezza-alli]

I'm upgrading the solar on the Carthago and fitting an Enerdrive DC2DC+ with MPPT built in. This unit can give upto 50amps rate of charge.

I've built two 280Ah lithiums with the latest JK BMS's and they are working wonders for our electricity bill. Thats with only 2x100w panels on the roof + the 160W free standing.

I bought the Enerdrive from Australia, the reviews were good so I thought give it a go.
The MPPT on the unit works better with grid type panels of 43Voc and can give a maximum of 47Amps with upto 800watts of solar. So I've bought a couple of 405watt panels one for the motorhome roof and another to go on the trailer roof for when we have it with us and when we haven't I've got a 160watt free standing panel!

I've had a look at cable calculators and they recommend 14AWG for the approx. 5 meter run on the motorhome, (I'm not doing it like Carthago and running to the front of the motorhome via all cupboards and up and under the floors etc to a charge controller and then all the way back to the garage where the batteries are!!!

So I was originally going with 10AWG 6.00mm2 but now thinking 12AWG 4.00mm2 will be ok.
I don't plan to add any other panels to this circuit and the two circuits I will have i.e., the trailer and the motorhome will be two separate runs to the controller or be connected to a heavier cable before the controller. Please see attached details of panels and controller/charger.#
I might move the 2 x 100w panels and have an additional charge controller.

What do you guys think?
Many thanks in advance for your help.
Terry & Allison

 

[Tombola]

4mm will "do" as it can go to about 55 amp
But I'd probably go 6mm for the difference in cost

 

[autorouter]

4mm will "do" as it can go to about 55 amp
But I'd probably go 6mm for the difference in cost

I'd agree with that. To put some figures on it, the amps at max power for one panel is 13A, so 26A though 4mm2 gives a voltage drop of about 4%, and for 6mm2 it's 2.6%. The target is below 4%, but some people work to 3%. That's using the voltage at maximum power which is 31V.

There is a view that in full sun when it is belting out maximum power, you are not bothered about a 4% drop. When the sun is lower and the amps is less, the voltage drop is also lower. Also if you are mounting them flat on the roof, ie not tilted, then you probably will never get more than 80% of the rated power anyway.

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