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mths avatar image

SmartSolar 75/15 and 60W panel

I was going to purchase a Victron SmartSolar MPPT 75/15 for my 60W (3,6 A) panel, but the retailer says the panel is too weak for this controller and that the combination won’t work together. He says the panel should be 80W or 100W. Is this true?

MPPT - Solar Charge Controller
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6 Answers
Justin Cook - Bay Marine Supply USA avatar image
Justin Cook - Bay Marine Supply USA answered ·

@mths, yes, your retailer is correct. If you're trying to charge a 12v nominal battery (so, resting voltage about 12.8v) then you need a panel with a VOC of 20-22v because the MPPT requires vbatt + 5v to turn on and start charging - ie, if your battery is at 12.6v, the MPPT needs a minimum of 17.6v from the panel to start charging. Your 60w/3.6A panel is likely only going to put out around 16.6v, so the MPPT simply won't turn on.

I'd recommend either using a PWM controller instead of an MPPT or, preferably, getting a 100w panel.

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Hi Justin, same here: Would like to buy a smart 75/15. I have a 60w panel, voc 21.0v, vmp 17.5v). Do you think my panel is not enough for this particular smart 75/15 controller? Thanks

Hi @JulGallant, what kind of battery are you trying to charge?

julgallant avatar image julgallant Justin Cook - Bay Marine Supply USA ♦ ·

Hi Justin, an Optima Yellow Top 55A

mths avatar image
mths answered ·

I used my 80W Sunwind Gotland panel + MPPT 75/15 last summer without any issues whatsoever. I’m super happy with that combo.

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dazey77 answered ·

I run a 40w panel with a 75/15 and it works just fine. Its a travel system with 2x20w array that folds and is light and suitable for putting in a carry on bag. Its 2 x 20w 23v panels in series but I tried them in parallel too and that worked as well (but a lot closer to the +5v issue). I used the 75/15 (over a smaller/lighter PWM) as it lets me see consumption and production data.

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johannes-neumeier avatar image
johannes-neumeier answered ·

Just to add some experience based value to what Justin said above, I've tried the 75/15 with a 54W panel and it did charge some when the batteries were very depleted, but seemed to not charge at all or only charge very sporadically after a bit. It's a real shame the manufacturer does not advertise this more clearly.

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mths answered ·

I decided to get a 80W panel instead of 60W (same manufacturer) and it’s working seamlessly. According to the Victron app I’m getting 75W and 5.8 Amps. No need for 100W. I’m pretty sure 60W would have worked, too.

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mths answered ·

Thank you Justin. Accordings to specs, the Voc of that 60W panel is 22.3 volts though.

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