[RE-wrenches] C-40 question

[Larry Crutcher, Starlight Solar Power Systems]

Allan, 

12 100 watt modules are more likely to be about 60-70 amps. With all the losses involved in a poorly designed DIY system (like most of them), I would expect to see more than 25% power loss. Perhaps that is why the controller lasted.

There is no current limiter in the C series controllers. 

Great advice about upping to 24 volt. I can only imagine how many strings of batteries they must have at 12 volts. Egads!

Larry Crutcher
Starlight Solar Power Systems


On Oct 24, 2012, at 2:45 PM, Allan Sindelar wrote:

Wrenches,
Sometimes I encounter a situation that I have never encountered, simply because it's so far beyond normal limits that I would never try it to find out what would happen. Here's one.

A did-it-myself customer called me for batteries for his system. I learned he has a 12V system, with twelve 100 watt PV modules and a Xantrex C-40 controller. He has been using this for five years.

Twelve 100W modules is around 80-90 amps - double or more the C-40's capacity. Assuming that what he told was accurate, why is the C-40 still working? Is it current-limited internally?

By the way, since he had a 7,000 watt (yeah, right) 12V inverter from a truck stop, I encouraged him to buy a 24V inverter and rewire everything to 24V; then his C-40 would (just) work.

Thanks, Allan
-- 
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com



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