Mppt size

[Thisguy585]

I’m doing a 24v system with 1200w (200w pannelsx6)solar array setting up by wills website recommendations and says I can use Epever 40a 150v Mppt but all the other calculators says I should use a bigger Mppt. Panels are 24.3v voc. Is it ok to use 40a 150v Mppt with panels in series. Thank you

 

[circus]

calculators says I should use a bigger Mppt. Panels are 24.3v voc. Is it ok to use 40a 150v Mppt with panels in series

Calculators are right. 1200w/24v=50a

 

[Bud Martin]

6 panels in series, VOC of PV panel is 24.3VDC, so 24.3VDC x 6 = 145.8VDC @25C, but as weather gets colder the VOC will rise so it will be higher than 150V (Typ. you should factor in about 15 ~ 20% higher for cold weather) which will exceed the SCC 150VDC max PV input Voltage.

 

[Thisguy585]

That’s what I’ve been seeing thank you for the confirmation. Any recommendations for a bigger Mppt thanks again

 

[Thisguy585]

That can hold 4awg wires

 

[circus]

Any recommendations for a bigger Mppt.... That can hold 4awg wires

4awg was a tight fit and I don't know if mine is any good. Fine so far. Esmart3 60a

 

[rmaddy]

Consider 3S2P for your panels then something like a 100V/50A SCC would work. This gives you plenty of voltage and it gives you some shade protection.

 

[Thisguy585]

I was think that but would it be enough voltage to charge a 24v battery bank? Wouldn’t equal only 36v(12v x 3) or do u multiply the voc

 

[rmaddy]

It's based on Voc so 3 in series gives you 72.9Voc. That's certainly more than enough for a 24V system. Most MPPT charge controllers need 5V over base voltage to begin charging.

 

[Pappion]

I wouldn't be concerned about harvesting peak watts on the rare occasions everything works as spec.
You don't need the excess, unless your running AC.
1200w / 28v = 42A, 1200 / 25.6v low battery = 46A

4awg may not save you much power. Use an online calculator to compare wire power loss (4 vs 6awg) for your length. Also there are many ways to mate 6awg pigtail to 4awg.

If it is absolute voltage accuracy your after, consider a Victron Smart Shunt voltage sense networked to a Victron Smart Solar controller.

 

[Thisguy585]

If running parallel would a fuse for the panels be necessary?

 

[rmaddy]

Fusing isn't usually needed until you get to 3P or more so at 3S2P there is no need.

 

[Thisguy585]

Got it!! Thanks all you guys have been great and very very helpful!!

 

[Pappion]

Also consider you may lose 4-10W in the wiring from the solar panels (at peak watts).
Also the MPPT might be 96% efficient, which is a 4% loss. or 48W at peak.