Drake,
Magnum's approach does not use disconnecting the AC output from
the GT inverter as a fail-safe method of preventing battery
overcharge. Rather, the Magnum documents I have use a DC diversion
controller and diversion load for this purpose. Their method
circumvents your problem. Would it work for you?
I forwarded your post to supp...@magnumenergy.com. I'll forward
any response to the list.
Allan
Allan Sindelar
al...@positiveenergysolar.com
NABCEP Certified Photovoltaic
Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
On 3/7/2013 3:00 PM, Drake wrote:
Hello Wrenches,
I had an unexpected glitch in AC coupling a Magnum 4024 PAE
inverter. The system utilizes AGM batteries, which (according to
Concorde tech support) have a very strict upper voltage limit.
The relay used to stop the current input from the direct grid tie
inverter, when battery voltage is high, is controlled by a
Morningstar
Relay Driver. The relay driver is set to shut off the charge at
28.8 volts.
The charger on the Magnum is set to charge the batteries to 28.6
volts.
The plan was to be able to charge batteries from the Magnum
without
tripping the AC connection between the grid tie inverter to the
grid. The Magnum should charge to 28.6 volts, 0.2 volts below the
relay driver's programmed trigger point.
There is one catch to using this approach. The Magnum inverter has
a
remote temperature sensor in the battery bank. The relay driver is
not
temperature corrected. Therefore, when the batteries are cold, the
charging voltage goes up in the Magnum. This higher voltage trips
the relay controlled by the driver, and disconnects the grid tie
inverter
from the grid.
I've played with the voltage set points, but the charge voltage on
the
Magnum would be too low for good battery maintenance. If these
were
liquid electrolyte batteries, I'd crank up the voltage on the
relay
driver. Since they are AGM batteries, it doesn't seem like a good
idea to do that.
The work around for this at present is to;
- Charge batteries at night in the winter
- No problem is expected in the summer
The batteries are in an insulated box in a shed connected to the
house. The inside of the battery box has a screened hole that is
supposed
to allow heated air into the box. This vent doesn't keep the
batteries warm enough to prevent the problem.
Is there a temperature sensitive, voltage controlled relay or
diver
available? Has anyone used a temperature bulb with the relay
driver
in a way that could solve this problem? Has anyone else come up
against
this issue, and if so, what was your solution?
Thanks,
Drake
Drake Chamberlin
Athens Electric LLC
OH License 44810
CO License 3773
NABCEP Certified Solar PV Installer
740-448-7328
http://athens-electric.com/
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