Wiring Solar Panels In Parallel

Submitted: Wednesday, Mar 13, 2013 at 16:56
ThreadID: 101069 Views:2614 Replies:2 FollowUps:12
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I have purchased two mono 190w solar panels.The wires coming off them have alligator clips. My caravan has two 12v S.L.A. batteries in the boot of the van wired in parallel.
How can I join the two lots of cable from both panels together so as to attach them to the batteries and have the two panels charge together? Regards G.T.





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Reply By: Cravenhaven - Wednesday, Mar 13, 2013 at 17:17

Wednesday, Mar 13, 2013 at 17:17
Basically just connect the 2 panels in parallel and connect them to the batteries. Of course make sure you have all the polarities correct.
But to do things properly
If the panels have built-in regulators then no problem.

If the panels dont have regulators then
1. you should ensure the panels have blocking diodes so that one panel wont force charge through the other.
2. You should connect the 2 panels to a regulator that is preferably mounted close to the batteries.
AnswerID: 506711

Follow Up By: Member - G.T. - Wednesday, Mar 13, 2013 at 18:00

Wednesday, Mar 13, 2013 at 18:00
The panels have MPPT regulators, mounted behind the panels. Then they have 5 metres of cable terminating in alligator clips. So I can`t get the regulators close to the batteries. How do I get the 4 wires down to one pair of +ve & -ve connections to go on to the batteries?
Regards G.T.
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Follow Up By: Member - daz (SA) - Wednesday, Mar 13, 2013 at 18:36

Wednesday, Mar 13, 2013 at 18:36
Hi GT are you looking at a permanently fixing the panels to the roof of the van, & then feeding the power to the batteries.??
Daz
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FollowupID: 783768

Follow Up By: Cravenhaven - Wednesday, Mar 13, 2013 at 18:57

Wednesday, Mar 13, 2013 at 18:57
You can just cut the alligator clips off then join the wires red to red and black to black then connect them to the battery, red to positive and black to negative.
It is probably better to run the 2 sets of wires down to the battery so that the regulators both 'see' the same voltage, but if you use just one cable and it is sufficiently thick then it probably wont matter hugely.
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FollowupID: 783771

Follow Up By: Member - G.T. - Thursday, Mar 14, 2013 at 09:56

Thursday, Mar 14, 2013 at 09:56
Daz , the panels will be free standing. Most of the time I will be wanting to charge the two van batteries with both panels at once.
Occasionally I may want to have one panel charge the A.G.M. fridge battery in my vehicle , so as to avoid idling the motor in the vehicle, whilst having the other one charging the van batteries , at a much lower input.


Cravenhaven, this was my thought also. Could I piggy back - ie clip one set of alligator clips onto the 2nd set that is already clipped onto the batteries? Alternatively , I could buy a pair of larger alligator clips and wire both panels together into the larger clips. Doing it this way will mean that I can`t split the two panels , one for the van, one for my A.G.M. fridge battery.

Another thing that concerns me is that I may get a spark off the clips when disconnecting from the batteries, possibly in the presence of hydrogen.
Do I point the panels away from the sun prior to connecting & disconnecting?
Regards G.T.
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FollowupID: 783833

Follow Up By: Member - daz (SA) - Thursday, Mar 14, 2013 at 10:20

Thursday, Mar 14, 2013 at 10:20
Hi GT Now this may seem over simplistic.
Why not hook one set of alligator clips to one battery & one to the other.The leads should be connected to the solar panels lastly & disconnected from the panels first. That way the leads are not live when connecting to the battery. When taking any leads off a battery, it should always be positive first off & the same when connecting to, positive on first.
Daz
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FollowupID: 783835

Follow Up By: Member - daz (SA) - Thursday, Mar 14, 2013 at 13:19

Thursday, Mar 14, 2013 at 13:19
Sorry GT

Got that around the wrong way It should be when connecting leads to a battery, positive on first & the reverse when disconnecting. Positive off last. This way I believe, eliminates the spark.
Daz
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FollowupID: 783859

Reply By: Rangiephil - Wednesday, Mar 13, 2013 at 20:07

Wednesday, Mar 13, 2013 at 20:07
I would connect the two panels in series , take the MPPT regulators off the panels, buy some quality 8B&S twin core lead and connect to the batteries via the MPPT regulator near the batteries , assuming one of the regulators has enough amp capacity for 2 panels.

A Good MPPT regulator will sense that the batteries are 12 volt and swap volts in for extra current at 14.5 or whatever. You have to always connect the MPPT to the battery before the panels so that it knows that the batteries are 12 volt, so you need connectors.
Regards Philip A
AnswerID: 506730

Follow Up By: Member - J&R - Wednesday, Mar 13, 2013 at 20:45

Wednesday, Mar 13, 2013 at 20:45
So you are suggesting he spend a bleep load of money when a few cuts and crimps/solder would do the trick?

Nice one.
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FollowupID: 783781

Follow Up By: Racey - Thursday, Mar 14, 2013 at 06:13

Thursday, Mar 14, 2013 at 06:13
Rangiephi,l why would you connect the panels in series????????
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Follow Up By: Member - John and Val - Thursday, Mar 14, 2013 at 09:36

Thursday, Mar 14, 2013 at 09:36
Phil,

Most cheap MPPT regulators won't stand the higher voltage from the series connection. I'd also be pretty doubtful that any cheap regulator supplied attached to the panel is actually MPPT.

Discarding the on-panel regulators and connecting the panels in series is a good way to minimise losses IF you can fit a suitable regulator close to the battery. I wouldn't risk it in this case without having a bit more detail.

Cheers

John
J and V
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FollowupID: 783831

Follow Up By: Member - Frank P (NSW) - Thursday, Mar 14, 2013 at 15:53

Thursday, Mar 14, 2013 at 15:53
Racey

"Rangiephi,l why would you connect the panels in series????????"

The ideal situation is to have the regulator close to the battery with short leads and any long leads between the panels and the regulator.

Depending how long the leads are and their gauge you can get significant losses.

By connecting the panels in series you inrease the voltage and reduce the current in the leads for the same power, reducing the losses.

But the way the OP says he wants to use the panels and with regulators already on the back of the panels, putting them in series is not appropriate.

Cheers

FrankP

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Follow Up By: Member - G.T. - Thursday, Mar 14, 2013 at 16:31

Thursday, Mar 14, 2013 at 16:31
I am collecting the caravan on the 25th March from the sales people.
I will consult with the Auto Elec who is wiring my vehicle, so that I can charge whilst driving. He may be the best to advise me when I show him a panel and the lead that come with it. Thanks to all of you that have replied. Regards G.T.
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FollowupID: 783880

Follow Up By: chris g8 - Friday, Mar 29, 2013 at 21:46

Friday, Mar 29, 2013 at 21:46
hi there
if you connect both panels in series you will have a 24 volt system
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