Which controller would you choose?

[tmartin000 (Tom)]

My understanding is wattage is more desirable over amperage from the panels…Knowing there can be a sunny side, and a shaded side. So I was thinking two strings of three, port-string and starboard side-string…

So…

The batteries are the LiTime 24V 280Ah LiFePO4 Lithium RV
There will be two in parallel.

6 Rich Solar 250 panels…
44.7 VOC
7.08A ISC

Essentially 3S 2P
Totals…

134.1 VOC
7.08a ISC

What would you choose… use 2 seperate Victron 150/30 controllers?

Sorry for the extra wide view…it messes with depth perception…

[Ludo]

3s2p

14a in total

You’ll have shading , so I’d take 2 controller’s, also to have some degree of redundancy.

The 150v iis ok, the amperage is dependent of your battery voltage

[RaySun]

A critical datum is missing: battery voltage.
Assuming 12V nominal,
250W x 6 = 1500W
1500W / 12V = 125A maximum charge current.
Two 50A charge controllers will split the current delivery duty effectively.
That would be 3 panels in parallel on each controller.

[Ludo]

Yes but at 48v two150/30 will work

[lxonline (LX)]

@tmartin000

The batteries are the LiTime 24V 280Ah LiFePO4 Lithium RV
There will be two in parallel.

The batteries are parrallel not series and they are 25v.

But yes 2 x 150/30s would work.
@tmartin000
You can confirm using the MPPT calculator.

[lxonline (LX)]

Batteries are 25v

[Ludo]

Sorry, too early for mme making sense

[tmartin000 (Tom)]

I’m confused…I cannot figure out temp coefficient for current and voltage?

I’m trying the Victon app…

[owenb79 (Owen Buttigieg)]

This should be it change the min temp to what you need. data sheet is on the website.

VOC + ((1-min temp - NMOT) x (Temp Coeff VOC% x VOC/100))
Say - 20degC min temp
44.7 + ((1-20 - 45) x (-0.29 x 44.7/100) = 52.99VOC

[water_rat (klim8skeptic)]

I have never seen NMOT used as the basis for working out panel Voc at low temps.

Usually I would use the Temp C/O of Voc and multiply by deviation from STC.

Ie, Temp dev of -45c x -0.0029 = 0.1305
13% increase of STC Voc of 44.v = 50.53v.

[lxonline (LX)]

Pity the database doesn’t have the 250W built in.
The co efficient will be on their datasheet as owenb79 showed.

[tmartin000 (Tom)]

I AM LOST!!! -------- Someone please do this for me.

I will Apple Pay for $40!

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Well, every solar calculator that is designed for Victron solar chargers says If I want 3P2S I cannot use the 150/60…

CRAP!
It always says to use Victron SmartSolar MPPT 250|60. The temps that cause the voltage increases and decreases have the voltage too high for the 150/60.

Solar Charge Controller Calculator

MPPT Calculator - Victron Energy

Both say the exact same thing!

—it looks like below:

Important Numbers:

• Solar Array Wattage: 1500W
• Temperature Compensated Array Voltage: 168V
• Controller Output Amperage: 52A
• Array Short Circuit Amperage: 14.16A
• Max Series Fuse Rating: 20A

[RaySun]

I’ve been installing solar panels since before those on-line calculators existed. Never had a problem figuring out the specs on the back of a cocktail napkin (even a used one.) The calculators, to me, are a P.I.T.A.

Battery: 25V nominal
Array: 1500W nominal
Max charge current: 1500W / 25V = 60A

No array puts out max charge current enough to worry about peak current, so 50A charge controller would be more than enough.

Panel V(oc) at STC: 44.7V
Array V(oc) 2S x 3P: 89.4V
Max V(oc): Nowhere near 150V unless the panels are in outer space.

A single SmartSolar 150/45 or 150/60 (either will run barely above ambient temperature) will do the job just fine.

Oh bartender! Put my scotch on Tom’s tab.

[RaySun]

My alternate suggestion is to split the panels onto two arrays: 3P each.

The 44.7V(oc) and 21A(sc) maximums would easily be handled by a pair of controllers.

I’d suggest the SmartSolar 100/30. Not because 100V max is needed, but because this is the first model that gets out of the “toy” small controller class and is built around a real heat sink and high-power parts. They will run forever in this application.

The two array, purely parallel wiring will be the most tolerant to shading.

[lxonline (LX)]

@tmartin000 either configuration is acceptable down to -15°C.

3s (will need 2 MPPTs)
150/35

Summary

100/20 (will need 3 MPPTs)

Summary

@tmartin000

If I want 3P2S I cannot use the 150/60…

You could depends on how cold it gets by where they will operate (3s 2p). A 150/70 would be better.

Summary

I have run calculations at -15°C

The online calculators usually recommend something where there is no power clipping.

[RaySun]

The original array configuration proposal: 3S2P looks to be the simplest wiring plan on paper, but is probematic in two ways.
3S will be most susceptible to shading.
3S will require stepping up to (a far more expensive) 250V charge controller.

[tmartin000 (Tom)]

Thank you everyone! I learned a TON…

It seems that my confusion was in USING the app’s…and the temp stuff. I called Rich Solar and am expecting a tech to call and I will tell him we NEED the real spec sheet listed (like the other ones on the site)

RAYSUN- You nailed it! I was serious about Venmo/or Apple Pay.
3 panels in parallel, 2 separate strings going straight into the controllers!
100/50 x2. (added head room)

PM me and I will get back with you!

ps…I may run those 2 strings into a box up top and send down to 8ga pairs each to the controllers…I hate line loss over a long distance…

Tom

[owenb79 (Owen Buttigieg)]

It would help if I posted the link sorry.

Vmax = Voc + ((TLow - TStc) x (VocCoef x Voc/100))

Solar Inverter String Design Calculations