24 volt wind into 12 volt bank??? [RE-wrenches]

graham at solarexpert.com graham at solarexpert.com
Fri Dec 5 10:29:36 PST 2003


Geoff,

Thank god this lady finally has a local qualified PV guy helping her.  I
remember this person well, was sold boxes of parts including two SW's
from a supplier that vanished.  I'm looking forward to NABCEP posting a
list of those who passed the test on their web site because this will
allow for quick referrals to local professionals.  I spent many hours on
the phone with this person trying to understand and help her situation.
Next time someone calls from Ohio I will have them contact you.  I wish
I could help with your question but I don't know much of anything about
wind power devices.

Graham 

-----Original Message-----
From: RE wrenches [mailto:Geoff at Third-Sun.Com] 
Sent: Friday, December 05, 2003 7:35 AM
To: RE-wrenches at topica.com
Subject: 24 volt wind into 12 volt bank??? [RE-wrenches]


OK - here is a good problem to sink your teeth into, and it involves no
trigonometry!

A year ago I was asked to install a wind genny into a poorly designed
and poorly functioning system. (Graham has also helped this customer
with advice). Off grid, one 240 load (well pump) someone sold her a
stacked power panel and set up a 12 volt system!  undersized solar, big
line losses, no design work, no breakers, no metering, no load analysis,
16 T-105 batts... I should have advised her to start over...

She has a huge diesel genny on auto that starts about 6 times a day
(typically when well pump surge brings down voltage) and slams 200 amps
into that small bank!  (oh - terrible corrosion at bank interconnects
and it wasn't cabled from the corners...).  So... I have corrected all
these problems (still need to turn down the charge amperage though, the
voltage climbs quickly and the thing runs for 1/2 hour max).

So... the wind...  In hindsight, perhaps I should have gone for a 12V
unit, but I like the Bergey XL-1  (run one myself, installed plenty) and
the distance to the tower is about 215'.  So - with discussions with
Bergey folks and Solar Converters folks (yes, I speak Canadian) I split
the battery bank into a high low 12/24 bank with a solar converters EQ
12/24-50 set up as an equalizer.

In other words:  the bank is 24 volt, the Bergey feeds the bank, the
inverters and solar are hooked up to the bottom 1/2 of the bank (12
volt). The "battery equalizer" is supposed to balance the two halves of
the bank.

The problem:  repeated blown 25 amp fuse on the Equalizer (it has 25 amp
to the high positive and 50 amp fuse to the 12 v positive).  The Bergey
will put out up to 60 amps into my 24 volt bank (at 29 volts!), so this
may be the culprit, but the batteries should be absorbing the energy and
the EQ (as I understand it) will move power over a long period of time
to "catch up" and keep the banks even.  The other culprit could be the
high 12 volt charging regime, which I think is too high anyway.  (C20 of
1760 ah IS 88 amps).

Solutions....?  Parallel a second equalizer in the same set up?  Step
down inverter charging amps (still have surge loads pulling huge current
though)... OR  rewiring the bank to simple 12 volt and using the EQ
12/24-50 as a "DC auto transformer" stepping the 24 V wind input down to
12. This would also help keep the trimetric more useful, as the split
bank approach does not allow the Tri Met to log wind amps.  Amps is the
reason we didn't do it this way the first time, but I am considering
paralleling a second unit and trying this.

Sorry for the long winded post... I share this as it is a good question,
I need help/input, and maybe this will help future retrofitters avoid
these pitfalls.

Sincerely,

Geoff Greenfield
NABCEP Certified Solar PV Installer TM
GLREA Certified Photovoltaic Systems Integrator/Installer License Number
0211-01

THIRD SUN SOLAR AND WIND POWER
340 West State Street, Unit 25
Athens, OH 45701

Phone (740) 597-3111
Fax   (740) 597-1548

www.third-sun.com

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com
--^----------------------------------------------------------------
This email was sent to: michael.welch at homepower.com

EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9.bWljaGFl
Or send an email to: RE-wrenches-unsubscribe at topica.com

TOPICA - Start your own email discussion group. FREE!
http://www.topica.com/partner/tag02/create/index2.html
--^----------------------------------------------------------------












More information about the RE-wrenches mailing list