question

manjo avatar image
manjo asked

Solar panels 12v vs 24v for a 12v system using victron mppt 250/100.

Hello, I am converting my sprinter into a camper van, I have 4x 12v 100ah battleborn batteries in parallel for a 12v system, and victron 250/100 MPPT. I would like to use 3x 320W Monocrystalline Solar Panel ( like Renogy RNG-320D-H )

When read spec sheet https://www.renogy.com/content/RNG-320D-H/320D-H-Datasheet.pdf it says these are Renogy 320 Watt 24 Volt panels, does it mean that it can work only with 24v batteries? I thought the MPPT should handle the voltages from the panels. If I understand it correctly even if I had a "12v" panel I would need 2 in series to drive power to the batteries. Why is Renogy referring to it as 24v panel?


Thanks

Manoj Iyer

battery chargingSolar Panelmppt charging
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5 Answers
wkirby avatar image
wkirby answered ·

The 12V or 24V panel Voltage rating usually refers to the system Voltage if a PWM controller is employed.

You will be using an MPPT controller, so like you thought, the MPPT will do the power conversion for you. Those panels will work well for you on a 12V battery system.
You'll even have the flexibility to wire the panels all in series or all in parallel. Parallel would probably be better for dealing with shading issues.

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michelg avatar image
michelg answered ·

Hi Manjo ! You won't have any problem using the mentionned solar panels, as they go through the MPPT and this one will do the conversion automatically for your setup.

Chose the correct setup either by using the VictronConnect app for the MPPT, or by using the wheel selector on the MPPT itself so it will use the expected parameters for the batteries.

Using a parallel setup for the PVs is the way to go for your setup, as it will provide more power to the MPPT as in serial (in serial if there is shading on one panel you lose a lot of power).

Michel

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manjo avatar image
manjo answered ·

Thanks for setting me straight, I think I can confidently fit 4 panels on the roof. I am leaning towards 2 series and 2 parallel to keep the currents low and deal with the shading issues y'all mentioned. But running them all in parallel would be 35v 40amps, I don't think 10awg would handle that. What gauge wires do y'all recommend for a parallel connection? I guess I would need a 6 or even 4awg? And go.through a 50amp fuse.

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bonie-wanda avatar image
bonie-wanda answered ·

Hi.

Please note that Victron MPPTs will only start to charge if the pv input voltage is >= system voltage + 5v. So for your 12v system you should configure your pv array to always meet that criteria.

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michelg avatar image
michelg answered ·

Hi Manjo, run two cables, one per array (In my setup I do use 6mm2 twice, which can handle 32A without any problem) so one cable per array will only carry around 20Ap in the best conditions, but as the arrays will be fixed on a camper van, they will never provide such power for long periods.

I'll suggest also to connect breakers before the MPPT input, so you can disable the arrays easily if needed, and also a breaker after the MPPT, so you can disable the battery bank or inverter.

Michel

BTW: DC breakers !! The AC breakers are not adapted for DC !

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