Charge controller sizing - replace FM80's

Stiffmeister

Solar Enthusiast
Joined
Nov 4, 2019
Messages
86
I have had 3/4 Outback FlexMax 80's die on me. My original intention was to oversize the number of panels so I could max out the 80 amps. Original configuration was 12x300w panels. I increased the panels to 18 per charge controller and panels are 300-370watts (3 per string, 6 strings). The FM80's did a decent job topping out at 80 amps.

If money was no object, can I go with the Victron 150/100 VE.can and eek out a few more amps? I am aiming for a total of 72 panels (currently 53) using two MNPV12's (purchased), two Outback inverters sharing the same battery bank. The upstairs and the downstairs of the house are on two separate main breaker boxes (Mexican contractors really love their circuit breakers I guess).
 

sunshine_eggo

Happy Breffast!
Joined
Oct 26, 2021
Messages
3,552
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USA
If you're using 72 cell panels with a Voc of ~47V, you may be hitting the 150Voc limit. This will damage them.

Assuming 48V, you appear to be substantially over-paneled. Driving any MPPT at its maximum current for extended periods is not the best formula for longevity. I'm the proud owner of a 250/100 VE.can, and I wouldn't dream of subjecting it to those levels. Victron recommends over-paneling by no more than 30% though they indicate that staying within PV input limits is the ultimate rule.

Using your stated 150/100 as an example, this has PV input limit of 70A. Due to the 150Voc limit, a Vmp of 100 is about as high as you can expect (2S 60 cell panels). 100Vmp * 70A = 7000W on a controller rated to yield 5800W - about a 20% over-panel.

IMHO, you should stop murdering your MPPTs.
 

Stiffmeister

Solar Enthusiast
Joined
Nov 4, 2019
Messages
86
The Voc is fine with three Silfab's in series per string.

Two charge controllers were used, one works.
One charge controller went pop when I forgot to shutoff circuit breakers...nice arc.
One charge controller got went during the last hurricane.

Don't rate an item for 80 amps if it can't handle 80 amps. I could never hit 80 amps with the STC or NOTC because my panels are mounted flat due to high winds even with 18 panels per charge controller.

The temperature varies from 60's to 90's year round in Cabo.
 
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