HI Bob,
What are you using 80v battery banks for or which inverters anyway?
Would be great for larger systems.
thanks,
jay
peltz power
On Aug 1, 2008, at 10:18 PM, robert ellison wrote:
When i went to an SEI class at the Trojan factory one of the points
mentioned was that the best way to get the lowest cost per watt
from the battery bank
(T-105's were at the time the lowest) was to cycle them to 80%
discharge then fill them all the way up. Not feasible in an off
grid system at all.
We get more years life by just taking off the top 20 - 25% and
returning it daily.
My battery distributor says that an industrial deep cycle battery
needs to be cycled occasionaly to prevent them developing a
"memory" so to speak.
I recommend to my customers that they occasionally let them run
down to 50 -60% DOD and fill them back up with an EQ charge to stir
up the electrolyte so you can get an accurate reading with a
hydrometer.
Stratification will throw off the gravity readings unless they get
stirred up occasionally.
I have pulled apart batteries that did not get an EQ and found the
bottom of the plates wore out and the top still looking reasonably
good. That is from the acid being a lot stronger at the bottom than
the top and just working on the bottom of the plates in the
battery. This is not a "fun" project and usually results in some
trashed clothes, rubber suit or not.
I have 80 volt battery packs that get cycled to 70-80% DOD daily
for 5 months a year then sit for 7 months with just a couple
freshening charges and last 6 - 7 years till wore out, some of
these are hi acid batteries that are in the specific gravity range
or 1.325 or more when fully charged instead of the usual 1.265
-1.270 that we are used to seeing.
I am not a battery "expert" I just have several big banks that I
maintain and have formed some opinions over the last 15 or so years.
I have also experienced wearing out a set of L-16's by hitting the
end of their cycle life in just over a year. It was way too small a
battery bank and got cycled fully almost daily hitting it's cycle
life limit far sooner than a larger bank would have if treated well.
Good night,
Bob
On Sat, Aug 2, 2008 at 12:01 AM, jay peltz <[EMAIL PROTECTED]> wrote:
Hi Robert,
When you mention cycling batteries, are you saying that batteries
in a offgrid system that are being cycled 15-25% a day should be
cycled even deeper than that?
Thanks,
jay
peltz power
On Aug 1, 2008, at 8:36 PM, robert ellison wrote:
A couple things that I haver noticed in the past, sometimes
batteries like to be cycled, shut off the controllers and run them
down, then charge them up fully and then give them an eq charge
till it comes up the peak voltage and hold it there as it
(sometimes) slowly rises. Any of these thoughts are superseded by
Jamie if he has any thoughts.
Also, if you have not given them an eq in a while it might take
longer than the available solar time has to get them to the top
and hold them there..
Have the controllers settings changed?
Bob
On Fri, Aug 1, 2008 at 10:18 PM, Allan Sindelar
<[EMAIL PROTECTED]> wrote:
Wrenches,
In late 2003 we installed a 24V set of Rolls-Surrette 4-KS-21PS 6V
1104 A/hr batteries in the off-grid system of a long-time client.
The client's system had a democracy array of around 800 watts of
tracked PV. In early 2005 we added 1,280 watts of additional PV,
and the client hasn't run the generator since; the system rarely
drops below 80% and fills to 100% most days in sunny New Mexico.
Batteries are located in a basement, so temperatures stay
relatively constant, although it will vary slightly seasonally.
MX60 controller is temperature compensated, with 29.6 VDC bulk and
31.4 VDC EQ set points.
The problem is that the client reports being unable to achieve
previous EQ voltages, and this inability appears to be a new
development. The system is otherwise performing well. As the
client is sharp and pays close attention to the system's
operation, I'm not ready to blame user ignorance (with one
possible exception; read on). This may be an issue of seasonally
warm temperatures, but I'm not sure this would explain the full
0.4 VDC reduction in voltage. I told him that I would post his
problem to this list, and also request advice from Surrette Battery.
Here is the client's description of the symptoms:
I'm concerned that I am unable to equalize batteries at this
time. Up
until June of this year the Tri-Metric readings during equalizing
indicated
holding voltage at 31.1, with maximum amps gain of around 52.
Three weeks
ago, when set on equalize, the maximum voltage reading was 30.7, with
maximum amps of 46; this was reached around noon, and by around
1:30 pm
voltage/amps began its typical afternoon drop-off. I attempted
equalizing
on two other occasions since then--the last time this past
Saturday, with
clear skies up until mid-afternoon--but having the same results.
So, the
question is: are my batteries beginning their decline? We've had
this set
for 4 1/2 years, so it would seem a bit too early for this, given
that these
batteries are expected to last 7-10 years.
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