Which MPPT device for a 200W 12V panel?

DIY
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1

Hi,

I’m looking at solar panels for our camper. This actually will be the third time I’ve installed solar but it’s been enough time in between each I don’t 100% trust my memory on the details…

I’m considering thin film panels this time (having used rigid mono panels the previous times). I’m looking at 200W 12V panels, these ones:

My basic math says this panel would put out 200W/12V = 16.7A (?). So if one single panel then which charge controller? I’m trying to read the specs on the SmartSolar devices for a max input current but don’t see it. The spec sheets does have a “Rated charge current” which for the 75/10 is 10A, the 75/15 is 15A etc. So would I need to go with the 100/20?

Thanks,
Toby

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As your panel will seldom produce 100%, I’d go for the 75/15..

290$ for a 200w panel is steep, Here in spain i pay 90€ for a 450w panel. 110 for 640.

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Thanks for the speedy reply. So then I should read the ‘15’ part of 75|15 as that being the current input limit? What happens if the panel does produce 100% and exceeds the 15A limit?

(And yeah, those thin panels are stupid expensive.)

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It should be fine as long as you don’t go over voltage. If your panels produce more than 15A the MPPT simply won’t draw more than 15A, so it’s a waste of a larger panel. With a 200W panel the voltage will actually be closer to 17 Volts at Maximum Power (VMP), and that puts it closer to 12A, so the 75/15 is appropriately sized.

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5

I have a similar panel that charges at 12-13amps into the battery 160-175W. When a cloud comes over and leaves it will boost to over 200W and produce just over 15A. It’s not much more to get the 100/20 and it’s the same footprint and has a heatsink. I find the 75/10 I have gets pretty hot I would think the 75/15 would be similar. I am using a 100/30 with this panel it’s what I had left over. I do have a 100/20 and will replace this one and use the 100/30 for a larger array.

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The spec sheets do list the maximum input current limit, look at the row titled “Max PV short circuit current”, this is the max allowed current from the PV panels. Your panel specs are Isc = 10.74A so you are OK with both 75/15 or 100/20 versions.

In terms of the equipment rating the 75/15 means max input voltage = 75V and max output current = 15A.

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You can always check things with the Victron MPPT calculator.

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No, its the output limit, and as the solar voltage is always higher then the battery’s, the current on the solar side is always lower.

As the output side is limited by the mppt, the solar side should never be stressed with a slightly too large panel

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8

OK, great info all, thanks!

So, what if I added another 100W / 12V panel in series, so that I had a 100W / 24V array? The MPPT 100/20 would still be appropriately sized as the Voc looks like 48.8V, correct?

Looking at 2x of these panels so as to get a 24V system:
100W 12V Flexible Monocrystalline Solar Panel | Renogy Solar

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The 75/15 would still be enough, your solar voltage would be high enough to charge 24v battery, but you’ll have only ~5a solar current.

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Ah of course, 100W / 24V =~ 4.2A.

So I guess this means I could go with an even smaller controller, like the 75/10 or the 75/15. That’s correct?

(And there’s only about $2 difference between those two models so I’d just get the 75/15).

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No, you have 200w @ 40v input

200w @ 24v output.

But indeed @24v a 75/10 would work

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OK, got it, thanks!
Is there any downside (besides the upfront $ cost) to use a larger-than-necessary charge controller?
Seeing as I will be running a bit less than 10A I could get away with the 75/10. But if I instead used the 100/20, is there any inefficiency there?

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No, none at all

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Awesome, thanks!
Someone had mentioned preferring the 10/20 for its heatsink, which doesn’t seem like a terrible idea.