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getyrie avatar image
getyrie asked

Which MPPT Solar Controller

Hi all,

UK resellers not too helpful....hence asking question here. I'm running 2x150w mono flexi panels on my RV in parallel connected to 3x100amp AGM batteries.

the spec of the panels are:

Max Power Voltage per panel - 18.15v

Max Power Current - 8.26amps

Open Circuit Voltage - 21.45v

Max System Voltage - 100v

Short Ciruit Current - 8.68amps


Would I be correct in saying that the 100/20 would suit at a squeeze (300watt panels / 14.2v) = 21amps? Or I could go 100/30 should I want to increase PV panels?


I have a bonus question:-)

I'm currently running a cheap vechline PV controller with these specs:

vechline.png


I'm guessing the Vechline is bottlenecking the whole system?


Your help is much appreciated.

MPPT Controllers
vechline.png (194.5 KiB)
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2 Answers
seb71 avatar image
seb71 answered ·

So that must be a 12V battery.

A 20A MPPT should be enough for 300W PV array.

Make sure you get a SmartSolar, not a BlueSolar MPPT.

Are the two PV panels oriented the same? Any shading issues? If yes on first and no on second question, then you should rewire them in series. You might even need to, because otherwise the PV voltage might be too low (to start charging, the PV voltage must be at least 5V higher than the battery voltage).

If you are thinking about future upgrades, besides getting a MPPT with bigger output current, maybe look into a 150/xx SmartSolar MPPT (smallest is 150/35).

The old charger is a 10A charger, so with a 12V battery you are indeed limited at about 140W from the PV array, no matter how clear the sky is.

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getyrie avatar image getyrie commented ·
Thanks Seb, yep 12v batteries:-)


So regarding orientation you are saying that if they are fitted in the same orientation I might have to rewire to series anyway as my battery voltage (3x12=36v) is a bit close to max voltage of the 2 panels (2x18.15v=36.30v)?

Why would running in series increase the max voltage?

Thanks

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seb71 avatar image seb71 getyrie commented ·

Seems you got the series/parallel backwards.

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If you plan to build a "12V system" (meaning a system which uses a 12V battery bank), then the three 12V 100Ah batteries must be wired in parallel, not in series. You will have a 300Ah 12V big battery (battery bank).

Make sure all three batteries are fully charged individually before you connect them in parallel.

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So regarding orientation you are saying that if they are fitted in the same orientation I might have to rewire to series

It's the other way around: if the panels have the same orientation, then you can wire them in series.

When you wire PV panels in series, you get a so called "string" (of PV modules/panels). The string voltage is the (PV module/panel voltage) x (number of PV modules/panels in a string).

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getyrie avatar image
getyrie answered ·

Thanks Seb

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