Victron MPPT Selection for new RV install

[liamlunchtray]

I'm doing a new RV install and I know just enough to be dangerous.


(Qty 10) JA Solar JAM72D30-545/MB Panels - Bifacial 545w
Voc 49.75V
Vmp 41.8v
Isc 13.93A
Imp 13.04A

48v System feeding 2 48/3000's in parallel

I ran it through the Victron wizard and its recommending:

SmartSolar MPPT 150/85 Tr VE.Can​

MPPT max. input voltage150V
PV min. voltage at 140°F70V
PV max. voltage at 14°F109V
MPPT max. output current85A
PV min. current at 140°F85A
** Power limiting @ high temp.
PV max. current at 14°F85A
* Power limiting @ low temp.
PV Power Ratio: 111%

This would be with the panets wired as 5 strings of 2


Thoughts? I love the idea of only needing 1 controller, but is this really the best way to skin this cat?

Thanks
Liam

 

[sunshine_eggo]

Big RV?

2S5P would work.

They recommend up to 30% over-paneling, so sometimes their recommendations are a little on the light side.

Array power / battery voltage = current

5450 / 48 = 113A

alternatively,

5450 / 55.2 (more realistic "average" charge voltage) = 98.73A

Given that these are bifacial and have the potential to output rated and higher in some conditions (even though that's unlikely on an RV roof), I'd be looking at the 150/100 to avoid clipping especially given there's not a lot of difference in cost. That's what I'd do.

Lastly, you can check out the datasheets for each MPPT, and it will tell you the maximum power output for each battery voltage.

 

[liamlunchtray]

Big RV?

2S5P would work.

They recommend up to 30% over-paneling, so sometimes their recommendations are a little on the light side.

Array power / battery voltage = current

5450 / 48 = 113A

alternatively,

5450 / 55.2 (more realistic "average" charge voltage) = 98.73A

Given that these are bifacial and have the potential to output rated and higher in some conditions (even though that's unlikely on an RV roof), I'd be looking at the 150/100 to avoid clipping especially given there's not a lot of difference in cost. That's what I'd do.

Lastly, you can check out the datasheets for each MPPT, and it will tell you the maximum power output for each battery voltage.

Thanks for the sanity check!

Its a 40' Diesel pusher, so pretty decent size. I was actually debating 650w panels instead, but they're just a hair too big physically. 600w don't seem to be readily available in smaller quantities at the moment, so 545w it is. For the past month we've been running it plugged in to our previous Class C which is 2420W/7.6kwh/Multiplus3000 and aside from tripped breakers when I accidentally turn on two high draw things at once it has worked pretty well.

The rig has a very bright white coating on the roof and the rack will be 12" over that with a tilt setup, so with any luck I'll get at least some some benefit from the bifacial.

 

[MisterSandals]

Isc 13.93A

2S5P would work.

5x 13.93A = 69.65A Yow!

You would need a combiner box, likely up top (before combining in parallel anyway) because the panel connectors re rated for 30A max. From combiner box you'd need to run AWG 1 to 4 to your SCC depending on the wire and length of run.

I'd seriously look at getting a big honking SCC that would accept 5S2P to simplify wiring. A great SCC is a great investment.
Ouch thats expensive! But would be a helluva system...

https://www.amazon.com/Victron-SmartSolar-MPPT-RS-Controller/dp/B08NSMYVBJ/

 

[sunshine_eggo]

5x 13.93A = 69.65A Yow!

You would need a combiner box, likely up top (before combining in parallel anyway) because the panel connectors re rated for 30A max. From combiner box you'd need to run AWG 1 to 4 to your SCC depending on the wire and length of run.

I'd seriously look at getting a big honking SCC that would accept 5S2P to simplify wiring. A great SCC is a great investment.
Ouch thats expensive! But would be a helluva system...

https://www.amazon.com/Victron-SmartSolar-MPPT-RS-Controller/dp/B08NSMYVBJ/

Good catch. I didn't run the numbers. The 150/100 does have a PV input current limit of 70A, so it's just under that. A 150/85 would NOT work.

5S2P would be simpler, but the only Victron product that could support that is the 450/100, and that's a little too rapey on the wallet.

 

[Brucey]

5x 13.93A = 69.65A Yow!

You would need a combiner box, likely up top (before combining in parallel anyway) because the panel connectors re rated for 30A max. From combiner box you'd need to run AWG 1 to 4 to your SCC depending on the wire and length of run.

I'd seriously look at getting a big honking SCC that would accept 5S2P to simplify wiring. A great SCC is a great investment.
Ouch thats expensive! But would be a helluva system...

https://www.amazon.com/Victron-SmartSolar-MPPT-RS-Controller/dp/B08NSMYVBJ/

You gotta watch with the 450s, they are designed for big series strings and limited to 18A effective with reverse polarity to 20A Can overpanel beyond that. Think of the 450/100 as two 450V 18A trackers. Also with their active cooling you need a fair bit of clearance especially above the unit if the magic smoke is released.

If you are paralleling strings they aren't the best choice, stick with a 150 or 250 model.

 

[sunshine_eggo]

You gotta watch with the 450s, they are designed for big series strings and limited to 18A effective with reverse polarity to 20A Can overpanel beyond that. Think of the 450/100 as two 450V 18A trackers.

If you are paralleling strings they aren't the best choice, stock with a 150 or 250 model.

Wouldn't 2X 5S strings, one per tracker, work great?

 

[Brucey]

Wouldn't 2X 5S strings, one per tracker, work great?

It would but I worry about these in more difficult environmental conditions what with the stopping of production until January 2025 while they redesign them to avoid issues with condensation and salty marine air etc.

 

[sunshine_eggo]

It would but I worry about these in more difficult environmental conditions what with the stopping of production until January 2025 while they redesign them to avoid issues with condensation and salty marine air etc.

BAH! I forgot about that.

So the best option on the smartsolars is a 3S3P array on a 250/100, which loses a panel. Still fairly high current, so a breaker box is needed UNLESS legit 50A MC4 parallel connectors are used.

 

[liamlunchtray]

Well this isn't fun at all. Glad I asked.
I was assuming I would need a combiner box up top but I hadnt even checked what the AWG requirement would be running down to the controller. The run would probably be 15-20' once everything was tidied up.
Am I understanding correctly that the 150/100 would work for 2S5P but I would have to run 2AWG from a combiner box up top down to the controller?

I had bounced around the idea of 3S3P with the 650W panels. They would fit but it would complicate my mounting somewhat.

 

[sunshine_eggo]

Well this isn't fun at all. Glad I asked.
I was assuming I would need a combiner box up top but I hadnt even checked what the AWG requirement would be running down to the controller. The run would probably be 15-20' once everything was tidied up.
Am I understanding correctly that the 150/100 would work for 2S5P but I would have to run 2AWG from a combiner box up top down to the controller?

2awg would do it, but it might not be needed. This UL cable:

6 Gauge (6 AWG) Battery Cable with Ends OFC Copper Flexible Stranded UL MTW/THW/SGT

www.batterycablesusa.com

is good to 120A, but you'd want to check your voltage drop.