MPPT Sizing Suggestions for 40v / 380w panels

[naah_naah]

Hello,

I've got 3 panels used recently:

Nominal power 380w
Isc 10.50a
Voc 45v
Vmpp 37v

I've also got another panel, 310w/32v/10a

I'm interested in building a pretty simple 12v or 24v system off it to run a 1000w inverter for running a 115v deep freezer pulling about 125w on average.

I'm interested in the Victron MPPT charge controllers, but it seems their calculator often overestimates my needs. I don't mind if I overshoot what a MPPT can take power wise. I live on the north side of mountain with darker winters.

If ran these 4 panels in series, could I get away with something like a Victron 100/50?

It's my understanding if I'm peaking W over the nominal PV power it isn't an issue, and my current in series should be under 60A. Or am I off base on any of my suggestions above, e.g. I should not run all 4 of these in series, etc.

 

[sunshine_eggo]

If ran these 4 panels in series, could I get away with something like a Victron 100/50?

4S of those panels on would be nearly 200Voc. Would kill a 100/50.
2S2P is still too close.

380W * 3 / battery voltage = amps

= 95A @ 12V
= 47.5A @ 24V

Once you've selected system voltage/amps, then you determine configuration. Since your panels are 24V, putting 3 in series on a 150V controller is a no-no. Too close to the limit. You'd have to bump up to a 250V unit, and the cost goes up.

The 100/50 is a very popular and cost effective unit. 3P array on that controller would work for 24V.

If 12V, probably makes sense to put 2P on a 100/50 and 1 panel on a 100/30. You'll lose a little on the 2P array, but not much when looking at the total kWh/day. Given your seemingly poor conditions, you may not lose anything.

I'm interested in building a pretty simple 12v or 24v system off it to run a 1000w inverter for running a 115v deep freezer pulling about 125w on average.

That's hopefully not the case. 125W * 24H = 3kWh/day. That's probably 50% more than typical. Have you used something like a kill-a-watt meter to measure actual usage?

I'm interested in the Victron MPPT charge controllers, but it seems their calculator often overestimates my needs. I don't mind if I overshoot what a MPPT can take power wise. I live on the north side of mountain with darker winters.

This is a grave concern. It's very possible that solar may not even be an option.

 

[naah_naah]

4S of those panels on would be nearly 200Voc. Would kill a 100/50.
2S2P is still too close.

380W * 3 / battery voltage = amps

= 95A @ 12V
= 47.5A @ 24V

Once you've selected system voltage/amps, then you determine configuration. Since your panels are 24V, putting 3 in series on a 150V controller is a no-no. Too close to the limit. You'd have to bump up to a 250V unit, and the cost goes up.

The 100/50 is a very popular and cost effective unit. 3P array on that controller would work for 24V.

If 12V, probably makes sense to put 2P on a 100/50 and 1 panel on a 100/30. You'll lose a little on the 2P array, but not much when looking at the total kWh/day. Given your seemingly poor conditions, you may not lose anything.



That's hopefully not the case. 125W * 24H = 3kWh/day. That's probably 50% more than typical. Have you used something like a kill-a-watt meter to measure actual usage?



This is a grave concern. It's very possible that solar may not even be an option.

Thanks for the detailed response. Definitely open to just utilizing 2 panels, or something less. 125w on the freezer is an estimate, I can run a kill-a-watt on it and see.

tbh this is a bit of a pet project without much of a use case. I've enjoyed building my smaller 200w 12v self-contained setup and wouldn't mind just building something else a bit of a larger scale.
tbh this is a bit of a pet project without much

'north side of mountain' = ~full sun from 9:30AM to 7PM early June, or the full sun 10AM to 3PM in December.

 

[naah_naah]

My suggestion for 'series' is only based on just trying to avoid having to purchase a bunch low-gauge wire to finish a build out.

 

[naah_naah]

Roughly, the motivation and design prompt here is:

"how do I best utilize these free panels in a way that makes some cost-efficent / low-cost use of them to build out a self contained multi-purpose system."

 

[sunshine_eggo]

My suggestion for 'series' is only based on just trying to avoid having to purchase a bunch low-gauge wire to finish a build out.

Understood, but you can't sacrifice vital equipment for thinner wire.

Roughly, the motivation and design prompt here is:

"how do I best utilize these free panels in a way that makes some cost-efficent / low-cost use of them to build out a self contained multi-purpose system."

Use link #1 to PVWatts in my signature to determine your max available solar for your location by month. The leftmost column of the output will give hours. Multiply your array wattage by your available hours, and that's your average kWh/day.

You may need to reduce that due to terrain. You can output hourly data and see where you will miss out on what PVWatts thinks you should get.

 

[pollenface]

I'd opt for 24v to double your SCC value

Victron 75/15 for the 310w panel (little price difference between 10a & 15a models)

Victron 100/30 or 100/50 for the 3x 380watters (in parallel)

Add a battery sense module to synchronise the controllers.