[RE-wrenches] Sunpower modules

[Brian Teitelbaum]

Drake,

Just to add to Allan's excellent post, most of the Arco's made before about 1985 had less than 36 cells. Some were 35-cell, most were 33-cell, but there were also 32 and 30-cell units.

You might want to look into rewiring the modules in higher voltage series strings to get more "oomph" out of the MPPT controller, and reduce transmission losses. However, be aware that many of those old Arco modules had a sticker on them that said something like "do not operate above 50VDC"

I still have 12 Arco, 33-cell, model 16-2000 modules (16Vmp/2A) on my off-grid house, wired in pairs for 24V and going through an ancient Trace C-30A relay controller (not even PWM!). I've contemplated wiring them for 36V and using MPPT, and I may someday, but they have been working so well as is that I haven't bothered. Even on hot days I often see 27.5V and 11-12A charging my 24V battery bank, which I think is damn good performance from a set of 27-year-old modules.

Brian Teitelbaum
AEE Solar



-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Allan Sindelar
Sent: Friday, March 20, 2009 8:32 AM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] Sunpower modules

Drake,
The key to your question may be in the "old Arco units". Most Arcos (all
predate 1990, when Siemens bought Arco) are 36 cell, but both Arco and
Solarex made some 33-cell, 32-cell, and even 30-cell "self-regulating"
modules in those years. With fewer cells, the MPPT was too low to benefit
much from Boost technology.

I have one customer with Arco M52L "Tri-Lams" and another with 32-cell
Solarexes. In both cases I had recommended upgrade to MPPT, but when I saw
what modules they had, I told them not to go ahead with the upgrade, as it
wouldn't be cost-effective.

Allan Sindelar
allan(at)positiveenergysolar.com
NABCEP Certified Solar PV Installer
Positive Energy, Inc.
3201 Calle Marie
Santa Fe NM 87507
505 424-1112
www.positiveenergysolar.com

Please consider the environment before printing this e-mail.

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Chamberlin

At 09:46 AM 3/20/2009, you wrote:
>The CTI-90, rated at 5.15 amps, will reach 7 amps here in Yuma with
>the Blue Sky 3024i.

Do you use the Blue Sky metering, or have you checked the MPPT output
with independent metering?  I retrofitted a 12 V Blue Sky charger on
an old cabin system. The CC had no on-board metering.  My measured
result showed almost the same output and input on a cool, sunny
day.  The modules were ancient Arco units, but I still expected some
improvement.

Drake Chamberlin