[RE-wrenches] Positive-ground question re Sunpower

jay peltz jay at asis.com
Sat Nov 20 16:29:46 PST 2010


Hi Allan,

I have seen the white paper from Sunpower, ( but don't have a copy) that shows the losses as the voltage rises if using neg ground.

But from memory, if using at low voltages such as two in series there should be minimal if any "loss" of watts.
If you could use them as singles, for say a 12v system then there is no loss.

Jay

Peltz power


On Nov 19, 2010, at 7:07 AM, Allan Sindelar wrote:

> Wrenches:
> This has been addressed before in a slightly different context, so a short answer is enough. Can a Sunpower module be used successfully in a negative-grounded low-voltage system?
> 
> The situation: Mark in our Taos office sent me the following: "We have an old time friend and customer. [John] and his wife used to help us on various installations years ago. They're both retired now and living on fixed limited income. About two months ago, we sold them a replacement battery bank of golf carts. They have a  small off grid system with a few hundred watts of PV. Recently, [John's wife] was put on an oxygen machine for a heart condition. The machine consumes somewhere around 800 Watt-hours per day. Their system can't keep up now without running the generator most every day. I was wondering about a couple blem/cosmetic damaged panels that PosE has at their shop in Santa Fe. I'm not sure yet whether the best solution would be to upgrade their existing system, or perhaps a separate system for the O2 machine. Either way, if there is a way to help them with the equipment, then I'd be happy to donate my time to help [John] do an upgrade. If there is some way we can help them out, it would be a good thing. They're just a couple of really good people who've helped a lot of others out in their lifetime. Now they're the ones in need, and I'm just trying to find a way to help them."
> 
> We have two Sunpower 215s with cosmetic damage that can't be sold. I think that one or both can be used here, but are just somewhat less efficient if negative grounded. 
> 
> What's the straight scoop here, please?
> Thanks,
> Allan
> 
> Allan at positiveenergysolar.com
> NABCEP Certified Photovoltaic Installer
> EE98J Journeyman Electrician
> Positive Energy, Inc.
> 3201 Calle Marie
> Santa Fe, New Mexico 87507
> 505 424-1
> 

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