How to wire four panels for 24 volt battery?

[camperw/AC]

Four 200 watt solar panels- pairs of two panels wired in series then those pairs wired parallel?

thank you

 

[camperw/AC]

What if there was a fifth panel?

 

[Mattb4]

Depends of the Voc and Vmp. Plus the SCC's max Voc. It could be that your SCC can handle the 4 panels in series. Likely you need 2 in series minimum though to have enough voltage to charge a 24vDC nom. battery.

 

[camperw/AC]

Voc; 21.8v
Vmp18.6v
I haven't shopped for a SCC yet.
Is it better to run the panels all in series?

 

[Mattb4]

If the SCC permits the voltage of 4 in series (~88Voc) there can be an advantage in reduced wire size since your current will be that of 1 panel and also less voltage drop for a longer distance run. Also some MPPT SCC seem to do a better job at a higher PV voltage. Since you list Nebraska as your location though you have to keep in mind that cold weather increases panel Voc and therefore you need to allow for that higher voltage so you do not exceed your SCC max voltage. Exceeding max PV voltage can quickly destroy a SCC.

Some high voltage SCC's need more than 4 panels in series of the specification you list to operate. The one in my 24vDC PowMr AIO does not turn on until 150v is exceeded and needs a minimum of 120v to operate. It has a max Voc of 450vDC. For it I run 8 panels in series of similar ratings as you listed to have ~176Voc.

 

[camperw/AC]

Okay, excellent, thank you.

For the SCC : Victron SmartSolar Charge Controller MaxPP Voc 100V Max output 30A $128
or :Victron SmartSolar Charge Controller Maxpp Voc 150V. Max output. 45A. $218

It's very unlikely that panels will be added. Planning on one or two 100Amh 24V battery.

 

[Mattb4]

Of the 2 SCC's you mention I would probably go with the 150/45. Although you say you will not add any more panels than the 4, you already mentioned possibly five. 5 in series would be 110Voc and be a good amount of leeway to the max 150Voc of the Victron.

4 in series of 88Voc is getting close to the 100Voc with really frigid weather of the Victron 100/30.

 

[camperw/AC]

Excellent, thank you.

 

[camperw/AC]

I can fit five panels on the 6x12 cargo trailer conversion but settled on four b/c I thought they should be deployed in pairs (page 31 of Will's book Mobile Solar Power.)
So now I'm thinking I should use five panels.
Your thoughts on this and anything else.

 

[MisterSandals]

Voc; 21.8v

So now I'm thinking I should use five panels.

1000W / 28V charging = 35.7A

Pretty easy choice: (as previously recommended by Mattb4)

Amazon.com

You'll love the bluetooth.

 

[Mattb4]

I can fit five panels on the 6x12 cargo trailer conversion but settled on four b/c I thought they should be deployed in pairs (page 31 of Will's book Mobile Solar Power.)
So now I'm thinking I should use five panels.
Your thoughts on this and anything else.

For parallel operation obviously you need an even number of panels. In parallel the voltage stays the same but the current adds. Depending on placement of panels and shading issues sometimes parallel operation is better. Also if constrained by a SCC's max voltage an array made up of parallel and series connected panels allows operation that an entirely series setup will not.

For instance 4 same rated panels wired 2S2P gives you twice the Voc and twice the amps. (Watts never change and W=VA). Take the Victron 100/30 but the panels you have are rated 25Voc instead of the 21.8v. 4 in series would put you right at the max Voc of the SCC and with cold weather blowing right on past it. However with 2S2P you are a Voc of 50v so in a good safe place to be.

If you can fit 5 panels the additional wattage would be handy thing.