Solar installation with aluminum wire

[uncle_bob]

Originally Posted by Alumineer

600 watts at 12V is 50 A. Your 35 foot run of 10 gauge cable would have 0.035 ohms resistance. So you would lose about 1.5 volts. That is quite a bit and you are right to do something about it... but 1/0 is pretty far to the other side of the problem.
Going to 6 gauge would likely be sufficient to reduce your losses to a negligible level without breaking the bank.
A second possible approach is to wire pairs of panels in series, if your controller allows it. This reduces your cable loss by a factor of four.
Or you could wire each panel direct to a bus bar using 10 gauge and minimize the amount of large cable you need.

Hi

Ummmm ...... errrr .... the converter goes at the battery. The down run is at the solar panel voltage and not at 12V.

If you do have 600W and number 10, you put the panels in series. That gets you around 36V into the converter. The not a big deal in that case.

Bob

[Alumineer]

Originally Posted by uncle_bob

Hi

Ummmm ...... errrr .... the converter goes at the battery. The down run is at the solar panel voltage and not at 12V.

If you do have 600W and number 10, you put the panels in series. That gets you around 36V into the converter. The not a big deal in that case.

Bob

I used worst case numbers for the input voltage... I suppose that it should make sense to use the max-power voltage for a panel and in that case you can reduce the current to about 33 amps at 18 volts.

As to the second part... that depends on the controller, and on whether you want to incur the potential loss in one panel’s output due to shading of the other panel with which it is in series. That all depends on where you camp.

I’m contemplating the same problem for wiring 4 x 100 watt panels on our ‘74 Trade Wind project. The panels will be slanted so as to not stick out from the roof profile too much, and that means the panels are unlikely to see equal sun at any time. One potential (ultimate) solution is to drive each panel into a 10 amp rated MPPT charger. But that will have the highest wiring cost for perhaps only a small gain in overall performance compared to a full parallel or series-parallel setup.

[uncle_bob]

Originally Posted by Alumineer

I used worst case numbers for the input voltage... I suppose that it should make sense to use the max-power voltage for a panel and in that case you can reduce the current to about 33 amps at 18 volts.

As to the second part... that depends on the controller, and on whether you want to incur the potential loss in one panel’s output due to shading of the other panel with which it is in series. That all depends on where you camp.

I’m contemplating the same problem for wiring 4 x 100 watt panels on our ‘74 Trade Wind project. The panels will be slanted so as to not stick out from the roof profile too much, and that means the panels are unlikely to see equal sun at any time. One potential (ultimate) solution is to drive each panel into a 10 amp rated MPPT charger. But that will have the highest wiring cost for perhaps only a small gain in overall performance compared to a full parallel or series-parallel setup.

Hi

If you are going to 600W, (or even 400W) you are not going to be using the stock converter. Even if it would handle the power (which it will not) it's efficiency is not that great. A Victron MPPT (or something similar) is what most people go to. The Victron's are quite happy with higher voltage inputs.

*All* solar panels are series setups. The base cell simply does not put out much voltage. You have to put them in series in the panel to get a useful output. The idea that this (rather than a poor controller choice) creates a shading issue is way overblown.

Running each panel on its own controller works *only* if the controllers can be networked together. That's a rare thing in an RV solar setup. Indeed it is not impossible to do. Several of us have all the hardware to get that done in our rigs.

Bob