[RE-wrenches] Sunpower off grid?

[Ray Walters]

Greetings fellow Wrenches;

I have a customer that just purchased some Sunpower E20 -435 modules 
somehow from Ebay, and wants me to design a backup power system for him.
This system would be battery based and not be grid tied.  SO the 
question is: has Sunpower put to rest the positive grounding issue with 
these modules?
I would want to either use a negative ground system or go ungrounded, as 
the charge controllers and battery based inverter do not play well with 
a positive grounded system.
My idea is that I could run these modules at lower voltage, either all 
in parallel (85.6 Voc) or 2 in series (191 Voc) with Midnite Classic 
controllers, and that the whole surface polarization issue will be 
minimized at these lower voltages.
I know this came up before, and Sunpower basically said they would 
revoke their warranty for any battery based systems, (which is why I'm 
no longer a Sunpower dealer.... :)
Don't the newer Sunpower modules no longer need positive ground, and if 
so, which models is this true for?  In this case, the warranty is 
already suspect, so that's not an issue.  It just has to work safely.

Thanks in advance for your help,

-- 
R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760