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Mick and Wrenches,
I faced a similar question with a new bank just a couple of weeks ago. In my case I asked my distributor, and his response is below. He makes some interesting points, including a very different end amps than the factory's. We have received very good service from this distributor, in case any Wrenches are looking for a Concorde distributor. Allan
Allan Sindelar
On 7/8/2012 9:40 AM, Larry Crutcher, Starlight Solar Power Systems
wrote:[email protected] 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 Allan: I’ve
had this conversation with several engineers and the
responses are variable – so I will present what I believe to
be true. - The
aircraft battery side of Concorde says that a fully charged
battery is one that reduces its current draw to under a
nominal 0.5% of the 20/24 hour rating. - The
RV/Marine & Solar guys insist that 2% to 5% is also a
realistic number. - The
factory only quotes numbers for new batteries – I have not
been able to get concrete numbers for “less than new”
batteries. - It
is my opinion that the “right” number is very low with new
batteries and climbs with battery age. My
choice would be to program a 2.5% to 3% current draw using
a temperature compensated charger. When
looking at real world conditions that you and I encounter
daily: 1) Off
grid PV systems most often do not have enough available
hours to be concerned with excess absorption/acceptance
hours. Even “occasional use on weekends” type systems are
limited to “x” number of hours of solar input. (It gets dark
for several hours every night – no matter what!) In reality,
BY FAR more systems suffer from chronic undercharging than
excess time in absorption mode! 2) Grid
tied battery backed systems, along with wind and hydro
turbine systems can be a different animal because of the
potential for “unlimited hours” of full power input for
charging. THIS is when the current draw being used as a
charge level indicator is most often needed, but........ 3) Undercharging
is still by FAR the most common cause of premature battery
failure. I have seen several battery banks survive the abuse
of constant 24/7 charging at full absorption levels for five
to six years, but I have yet to see one battery bank survive
chronic undercharging for five years. These batteries used
in RV/Marine/Industrial applications often see constant
alternator-regulator outputs of 14.2v for 12 to 16 hours per
day continuously. No, they don’t last as long as we want to
see for our needs, but they often make it 5-7 years under
really harsh conditions coupled with no float time. Re-stating
my view in simple terms: - A
battery bank is fully charged when the current draw drops
to 2.5 amps per hundred amps of battery bank capacity.
Time to reach this point is almost irrelevant because of
the variables. - BUT......a
programmed time limit can be a VERY good thing in case of
battery system or cabling faults which present a false
load to the charging system – resulting in runaway
charging! - The
best time limit is dependent upon individual project
parameters, but a good starting point is 25%-50% more time
than the calculated charging time for a depleted battery
bank. Hoping
this makes sense! Allan,
always feel free to send a note to Concorde to get their
input! As I said above, I can’t avoid seeing things through
the filter of my experience. That doesn’t always jive with
the manual. Best, Marc
Kurth Centex
Batteries, LLC 704
W Highway 71 - Suite B100 Bastrop,
TX 78602 Ph
512 308-9002 Fax
877 254-2702 From:
Allan Sindelar [mailto:[email protected]] Marc, Hello Mick, |
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