Trying to get my head around Victron kit #2 : string voltage and power limit calcs for Victron charge controllers

Talk Electrician Forum

Help Support Talk Electrician Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

bladerunnerpv

Well-known member
Joined
Sep 1, 2022
Messages
328
Reaction score
73
Location
Hertfordshire
From comparing victron 250/85, 250/100, 450/100, my conclusion it that the 250/100 will handle the most PV panels [Edit...] in parallel and input power, the 450/100 will handle more panels as a single string but less input PV power than the 250/100

Have I got it right ? Please could someone cast an eye over the method for calculating string voltage and powers for different victron charge controllers please and let me know if I've made any howlers?

Thanks for taking a look

[Edit: I know there's an MPPT calculator on the victron site but you can't select one product and try different panel combinations on it !]


Panels 405W Qcell
https://midsummerwholesale.co.uk/pd...m-g11-series-390-410-30t-2022-06-rev02-en.pdf
I think:-
The 250/85 will take 6 panels in a string, or 2x5 in parallel, or 5panels into MPPT1 and 5panels into MPPT2

The 250/100 will take 6 panels in a string, or 2x6 in parallel, or 6panels into MPPT1 and 6panels into MPPT2, as it will cope with more PV power than the /85 model

The 450/100 will take 10 panels in a string, or 5panels into MPPT1 and 5panels into MPPT2,
It cannot be used for two strings in parallel due to PVmax of 18Amps
The Voc max is limited by the battery float voltage [Edit: to 8 x float voltage, which means it can be less than 450V]

String voltage at -10degC example calc, using STC of 25degC
e.g. Voc + Voc*((-0.27/100)*(-10-25))
e.g. 37.18 + 37.18*((-0.27/100)*(-10-25)) = 37.18+3.51 =40.69V

For the power limit then the panel's Pmpp and it's variation vs temperature is what to watch ?
Power at -10degC example calc
e.g. Pmpp + Pmpp*((-0.34/100)*(-10-25))
e.g. 405 + 405*((-0.34/100)*(-10-25)) = 405+48.195 =453.2W

Victron 250/85:-
[Edit...]
A) MPPT 250/85, 3x MPPT trackers
PV max power 4900W, Vmax 250V
70A max PV short circuit current, 30A per MPPT
https://www.victronenergy.com/uploa...oller-MPPT-250-70-up-to-250-100-VE.Can-EN.pdf

1684017888147.png

Victron 250/100:-
[Edit...]
B) MPPT 250/100, 3x MPPT trackers
PV max power 5800W, Vmax 250V,
70A max PV short circuit current, 30A per MPPT
https://www.victronenergy.com/uploa...oller-MPPT-250-70-up-to-250-100-VE.Can-EN.pdf

1684018186862.png


Victron 450/100:-

[Edit...]
C) RS MPPT 450/100, 2xMPPT trackers
PV max power 5000W, Vmax 450V, 30A per MPPT
https://www.victronenergy.com/solar-charge-controllers/smartsolar-mppt-rs-450-tr
https://www.victronenergy.com/upload/documents/Datasheet-SmartSolar-MPPT-RS-EN-.pdf

1684018745469.png
 
Last edited:
Top