Two Panel Wiring Query

[ElliesBoss]

Been meaning to ask you clever folk for a while now. We have two rigid 80W panels on the roof and a roof "gland" box with two connectors. A twin wire come out of connector one and into the first panel. A twin wire then comes out of panel one and goes to panel two. A twin wire then leaves panel two and returns to the second connector. Only two wires arrive at the solar controller. I have one or two ideas how it may have been wired but just wondering if any of you have some suggestions?

 

[andy63]

It sounds like the panels have been wired up using twinned cable ..and in series..
Check the voltage at the connector on the roof..a voltage if mid to high 30 odd volts would confirm that..
Andy.

 

[ElliesBoss]

It sounds like the panels have been wired up using twinned cable ..and in series..
Check the voltage at the connector on the roof..a voltage if mid to high 30 odd volts would confirm that..
Andy.

thanks for the reply. That was one of my thoughts although I'm sure they could have done it with single thicker wires which obviously go from the box to the controller. Couldn't think of any other reason unless wired as a "ring" but couldn't work out why that would be necessary.

 

[Phil 748]

Hi as Andy Says could be wired in series or could be in parallel to reduce the volt drop due size of cables and distance only way to check is at the controller with a multi meter to what voltage there is, I would say around 19v if in parallel or 30v plus if in series

 

[Arty fjr]

I am in a similar situation but have new ones to fit do i go for parallel and keep the volts low with high amps or series and keep the volts high with not so many amps .
The joys of choice .

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[paddymcc]

Most people go for wiring them in parallel so that if one is in shade it doesn't affect the output from the other.

 

[DBK]

Victron recommend wiring in series, it's more efficient but shading has a greater impact I believe. I wired mine in series as the existing cable to the controller was a bit thin and replacing it wasn't easy to do.

 

[autorouter]

I am in a similar situation but have new ones to fit do i go for parallel and keep the volts low with high amps or series and keep the volts high with not so many amps .
The joys of choice .

Check the input voltage limit of the solar controller. Usually it's not a problem because most motorhome setups are wired in parallel. Some of the cheaper controllers, especially PWM types, have quite a low limit. For two panels in series the panel voltages add together.

 

[Off da Grid]

To put it simply the higher the voltage the easier it flows through a thinner cable.
But as said before the caveat of wiring panels in series if one is shaded it will drop the whole array.

 

[Raul]

One more think to add, if you got a mppt controller, it will take advantage of the series connected. If PWM, series connection, would literally throw away half the power.
MPPT = power in power out
PWM = amps in amps out, the rest of the voltage gets wasted, where with the mppt, gets converted in extra amps. As for shade, parallel is best.

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[Off da Grid]

Ditto

 

[ElliesBoss]

Confused at moment. PWM controller fitted. Only 18V going in to PWM. Suggests parallel connection unless one panel is u/s in which case would the other one work if wired in series? Checked Sargant unit and it is set to smart charge and displays battery voltages (14.7V leisure and 13.8V vehicle). Obviously things are charging as Bond has been parked up for about ten days. Might just leave it for quieter times and get an expert to have a butchers. Thanks for all your inputs.

 

[Raul]

If you got a PWM charger than parallel is the correct way of connecting them. I would leave them as they are, unless you got a fault. Max amp from the two 80w panels would be around 9amps when sun is above them.

 

[ElliesBoss]

If you got a PWM charger than parallel is the correct way of connecting them. I would leave them as they are, unless you got a fault. Max amp from the two 80w panels would be around 9amps when sun is above them.

I don't intend changing anything. Just as per my original post I was a bit confused by the wiring on the roof.