Trying to decide on wiring in parallel or series ?

unioncreek

New Member
Joined
Sep 23, 2021
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First post here. I'm going to install 2 solar panels to charge deep cycle batteries to power a 12 volt well pump when so we have access to water when our power goes out. I'm trying to decide whether to wire the system in parallel or in series. The distance from the panels to the charge controller will be short, less than 10 feet. I have the following panels, charge controller and batteries. Can I hook my system up in either parallel or series and if so, is one better than the other?

Thanks,
Bob

Panels: https://www.amazon.com/dp/B07L7ZGGV...abc_ZWWCY0W9AJSZV3Y3DXK7?_encoding=UTF8&psc=1

Charge Controller: https://www.amazon.com/dp/B08NQTW94...abc_6TAT1Q1M9FQX78KMM9KM?_encoding=UTF8&psc=1

Inverter: https://www.amazon.com/dp/B00T564EI...abc_D5NM2H4F97Y1HW4EJ1WM?_encoding=UTF8&psc=1

Battery Info: Interstate marine/RV deep cycle battery. Provides power and endurance over the long haul. Cranking amps: 750. Cold cranking amps: 600. 12 volt.
 

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fafrd

Photon Sorcerer
Joined
Aug 11, 2020
Messages
2,242
First post here. I'm going to install 2 solar panels to charge deep cycle batteries to power a 12 volt well pump when so we have access to water when our power goes out. I'm trying to decide whether to wire the system in parallel or in series. The distance from the panels to the charge controller will be short, less than 10 feet. I have the following panels, charge controller and batteries. Can I hook my system up in either parallel or series and if so, is one better than the other?

Thanks,
Bob

Panels: https://www.amazon.com/dp/B07L7ZGGV...abc_ZWWCY0W9AJSZV3Y3DXK7?_encoding=UTF8&psc=1

Charge Controller: https://www.amazon.com/dp/B08NQTW94...abc_6TAT1Q1M9FQX78KMM9KM?_encoding=UTF8&psc=1

Inverter: https://www.amazon.com/dp/B00T564EI...abc_D5NM2H4F97Y1HW4EJ1WM?_encoding=UTF8&psc=1

Battery Info: Interstate marine/RV deep cycle battery. Provides power and endurance over the long haul. Cranking amps: 750. Cold cranking amps: 600. 12 volt.
For a 12V battery with those panels, you can go either way.

Parallel will result in higher cabling losses (or the need for thicker / slightly more expensive wires).

Series may result in lower charge efficiency when charging a 12v battery from a higher string voltage (check SCC manual),

In the end, it really all boils down to efficiency and cost.

And for your small system, it’s unlikely to make much difference either way…
 

unioncreek

New Member
Joined
Sep 23, 2021
Messages
3
Texas-Mark/fafrd,

Thanks for the quick reply. I just needed someone else to double check me so I could get it right. I've learned a lot from the forum already.

Bob
 

The New JC777

Solar Enthusiast
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Sep 17, 2020
Messages
131
Your PWM controller requires you to wire the panels in parallel with your 12 volt battery . I didn't read any specs that said this controller would step down the voltage from a series wired (24 volt) panel array to 12 volt.
 

fafrd

Photon Sorcerer
Joined
Aug 11, 2020
Messages
2,242
Your PWM controller requires you to wire the panels in parallel with your 12 volt battery . I didn't read any specs that said this controller would step down the voltage from a series wired (24 volt) panel array to 12 volt.
Missed that (didn’t review the SCC).

If it’s PWM, then yes, 12V battery should be charged with those two panels in parallel.
 

unioncreek

New Member
Joined
Sep 23, 2021
Messages
3
OK, I understand what you saying about the step down. I had thought about if it would be able to charge two 12 volt batteries if I wired everything in series. I have plenty of #10 wire that wiring in parallel will be OK.


Bob
 

fafrd

Photon Sorcerer
Joined
Aug 11, 2020
Messages
2,242
That is your best option and gets a big thumbs up from me.
You guys are confusing me.

I thought the OP meant he was considering charging both 12V batteries in a 2-battery series string (meaning a 24V battery).

If they will be used as 12V batteries and not as a 12V battery, that is a very bad idea.

And if he is charging 2 12V batteries in parallel with a PWM SCC, using his two panels in parallel is the way to go (may not even work with panels in series and will almost ccertainly be far less efficient even if it does).
 

The New JC777

Solar Enthusiast
Joined
Sep 17, 2020
Messages
131
I had thought about if it would be able to charge two 12 volt batteries if I wired everything in series
I was responding the last 6 words from the OPs reply. "if I wired everything in series"
24 volt array, 24 volt PWM SCC, 24 volt battery, 24 volt inverter. He just doubled the capacity of the system by adding 1 12 volt battery.
 
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