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Old 03-07-2016, 02:06 PM   #1
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Opelika , Alabama
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Solar - to 12V or 24V or more?

I'm looking at putting eight 100W panels on my roof. I'm wondering what voltage I should wire to the controller and if there's any benefit to upping my battery pack voltage to 24V or 36V? I must admit, 12V simple enough for me. I've attached a sketch that I've come up with that includes several questions.
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Old 03-07-2016, 05:31 PM   #2
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800 watts of solar might be overkill for two 12 volt batteries.

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Old 03-08-2016, 11:30 AM   #3
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Opelika , Alabama
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Thanks for the tip. Maybe I'll go with four 12v batteries. It's a 34' trailer. Anyway, how should I approach considering 12v, 24v, 36v, and 48v solar charging?
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Old 03-08-2016, 07:09 PM   #4
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You need a solar charge controller that has the capability to accept the higher voltage array but will still be able to step down the array input voltage to properly charge a 12VDC battery bank.

As to your 24, 36 or 48 VDC battery bank, how many RV components have you found that will operate on these higher voltages? Any guesses on the answers??

If you are talking about 2, 3 or 4 batteries @ 12VDC connected in parallel rather than series, then you will have a pretty large usable battery reserve.

You need to do a bit more research into your topic. 😄

Lew Farber
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Old 03-08-2016, 08:29 PM   #5
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Since you've decided to install 800 W, the Tristar 45 MPPT is a good choice. If you were targeting 400 W I'd suggest you look at BlueSky's 3024 MPPT since you can add an optional remote to obtain battery monitoring capabilities. Whatever solution you choose, I highly recommend that you install a battery monitor so you aways know how much battery capacity you have consumed.

Assuming you continue with the 800 W, you have two choices: create four groups with each group consisting of two panels in series, or create two groups with each group consisting of four panels in series. The former configuration will need to pass 5.29 A * 4 = 21.2 A, while the latter configuration will need to pass 5.29 A * 2 = 10.6 A. You cannot put all eight panels in parallel with this controller.

As Lew said, you do not have any systems on-board that can benefit from creating a 24 V or higher battery bank. Stick to 12 V so that all your systems will be compatible.

Typically your solar controller is wired directly to the battery bank. This way the system can always charge your batteries.
Al, K6IV
2015 30' Classic, "Chez Nu"
2014 RAM 2500 w/Cummins Diesel
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Old 03-09-2016, 11:14 AM   #6
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What happened to the poster with the 48 volt Chevy Volt LI battery?
That looked like a good way to D it.

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