Allan,
MPPT technology is for harvesting the most power possible from any
voltage being produced above the battery voltage, not the difference
between Voc and Vmp. Because of this, nearly every battery charging
system will benefit from MPPT chargers. The climate does not matter
for properly designed systems. In a hot climate (like Yuma ;) ) you
want a much higher operating voltage from the PV panels. There will
still be a big advantage from MPPT. There are very few situations
where I would recommend a non-MPPT controller anymore.
Concerning Blue Sky charge controller failures, I have sold and
installed over 1000 BSE products at our retail store over the years
and they have the LOWEST failure of any controllers we have sold. And,
the customer service is second to no one else. I understand and agree
with your opinion to have serviceable equipment in remote locations.
The most reliable equipment should be considered first. I also believe
that a project like the one Walt is dealing with should have included
spare equipment as part of sale, and, of course, it should have been
designed right.
I had a Phocos MPPT 100/20 in a test setup for 10 months when it
failed. I can't even begin to talk about Outback problems unless I
take my comments to the RE-bitching list. The BSE 3048 would be a good
replacement controller because it has the same footprint as the SB50
and will handle the high Voc.
Kindest Regards,
Larry Crutcher
Starlight Solar
(928) 941-1660
Renewable Energy Products, Service and Installation
Mailing Address (NO SHIPPING):
11881 S Fortuna Rd.
#210
Yuma, AZ 85367
Shipping and retail store (NO MAIL):
2998 Shari Ave
Yuma, AZ 85365
On Jun 30, 2009, at 12:01 PM, Allan Sindelar wrote:
Walt,
I would also offer that in a hot climate, MPPT in general is only
useful in a case where odd cell counts take the Vmp away from 24V
nominal specs. That is, MPPT was originally developed to harvest the
voltage headroom between Voc and Vmp, which was greatest in cold
ambient temperatures. There is little benefit to MPPT in a tropical
climate, unless it’s being used (incorrectly in this case) to adapt
a particular module with odd cell count.
Walt, I would suggest that you consider pursuing replacing the
Sharps with any 12Vnom or 24Vnom module commonly in use there, and
then either keep the SB50 because it’s already there, or replace it
with the most reliable non-MPPT PWM controller you can bring in or
find in country. This maximizes the likelihood that the system can
be kept in operation even if the SB50s fail (and experience says
that some will in time) and the locals can’t get service or
replacement product. It seems to me that the SB50 is an
unnecessarily complex component for this application, and a standard
PWM replacement controller will match poorly and inefficiently to
the Sharps.
FYI, I called Earthwalk and spoke with “Joey” there. I copied him on
Rick’s email, and got a read response. So Earthwalk is aware of this
situation, although Joey was a computer tech, not one of the “solar
experts”. If they have integrity, they’ll contact you and start
making arrangements to get this resolved. Perhaps they can wire you
the funds to purchase compatible modules locally?
I have copied Joey on this message as well.
Allan Sindelar
al...@positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
EE98J Journeyman Electrician
Positive Energy, Inc.
3201 Calle Marie
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
