William,
Sounds like the Trojan rep
#1 Doesn't know off-grid equipment if they are giving you a different voltage
for absorption than the bulk voltage setting.
#2 Says that "Absorb Time needs to be increased, maybe from 3 hours up to 4 or
5 hours" - that is unrealistic for day to day off-grid PV charging. Sounds like
Trojan is covering their butt by telling you to do unrealistic stuff.
And "1.270 to 1.280 for SG" is really high and only obtainable
if Trojan is loading their new cells with electrolyte that strong (not what
they have usually been doing).
I vary the settings I program for off-grid systems (and often recommend
changing settings for winter vs non-winter pv charging). Typically 29.6/59.2
Bulk-Absorb, 27.2/54.4 Float and 31/62 EQ as a starting point for wet cells.
The biggest determinants of success as I see it are: A) high enough Charge Rate
of PV to rated storage of batteries. B) regular logging of SG readings, all
cells. C) good back-up generator/charger set up and the knowledge of when and
how to use it.
BTW for those newer to wet cell Lead Acid batteries, manufacturer's can tweak
the performance of their deep cycle batteries by varying the strength of the
electrolyte - 1.265 has been typical for true deep cycle storage batteries for
many years.
If you want a battery to have more amp hours of storage and perform well in
initial testing then you could increase the strength of the electrolyte to
1.275 or so. BUT these cells will not last as long (all else being equal)
because the increased acidity will degrade the plates quicker. I have some
German made Hoppecke LA cells in my barn/shop system that were intentionally
made with weak electrolyte to enhance the lifetime of the cells. They are 1.240
SG electrolyte. These batteries are 19 years old now and have never given me a
peep of trouble. I expect them to last for many more years.
Back in the late 80's and early 90's there was an electric car
rally/race here in New England (American Tour de Sol) where the early winners
gained a competitive advantage by removing about 1/3rd of the electrolyte from
their L-16 or T-105 batteries and replaced it with straight sulfuric acid. I
don't remember what the SG of this new "Race Mix" was but the racers who did
this performance enhancement would typically outperform the field enough to be
the top finishers. After a couple of years the word got out and judges spot
checked initial SG's to level the playing field. The racers would correct the
SG in the batteries after the race and they would sell the batteries at a great
discount into the off-grid market.
Some of you will remember that Trojan several years ago was selling their new
off-grid Industrial batteries with a lower SG mix of about 1.25 as I remember.
Good intentions for a long lived battery. BUT the market had trouble dealing
with the low SG and Trojan decided they were spending too much time educating
dealers and consumers on this issue, so they changed to a higher SG after the
first couple of years.
If Trojan has gone to a stronger electrolyte now, I think that
this is not a good sign and it will lead to their batteries failing sooner.
Dave
(semi-retired and not minding it, at all)
David Palumbo
Independent Power LLC
462 Solar Way Drive
Hyde Park, VT 05655
802-371-8678 cell
802-888-4917 home
From: RE-wrenches [mailto:[email protected]] On Behalf
Of William Miller
Sent: Monday, January 18, 2016 9:43 PM
To: RE-wrenches
Subject: [RE-wrenches] Trojan L-16 charge settings
Colleagues:
I have an off-grid customer for whom I replaced a set of 8 Trojan L-16s as well
as upgrading her inverter and charge controller. Right after the job, we found
several batteries with low specific gravity. We spoke with the local
distributor and received two replacement batteries.
The system continues to perform poorly. The customer EQs every 30 days to 60
plus volts for 3 hours. They try to get a full bulk and absorption charge in
every day but this time of year may not. The specific gravity readings continue
to diverge and generally go lower.
We contacted the distributor who told us they have had problems with Trojan
batteries since the company was sold about two years ago. We were told they
had a brand X battery that tested better than the Trojans. We agreed to try
the Brand X but then were told that we had not charged the Trojans adequately.
Below are the settings recommended directly by Trojan
These settings are significantly higher than any I have used before. Also, I
don’t recall it being possible to set different bulk and absorption voltages
with any of the equipment I use. I use Trace, Outback, Schneider default
settings of 57.6 bulk, 54.4 float and reprogram to 60.5 for equalization.
I am curious about what charge settings you find successful for flooded
lead-acid batteries and what any of you might think about the recommended
settings as seen below. Do you feel it is practical to achieve these settings
in an off-grid scenario? Would these high settings cause excessive water
consumption?
Thanks in advance.
William Miller
Gradient Cap_mini
Lic 773985
millersolar.com <http://www.millersolar.com/>
805-438-5600
I looked at the spreadsheet and the SG. readings across each battery are
uniform which tells be that it is highly unlikely that anything is wrong with
the batteries except for being under-charged. Take a look at our User’s Guide
on the Trojan website on page 19 ( Recommended Charge Profile) or FLA
batteries.
The Bulk stage should be @ 59.3V, Absorb @ 58.8V, Float @ 54V and Equalization
@ 64.8V. When the User notices drops in the SG such as in this document, an EQ
charge should be performed in order to get the batteries back up to full charge
(full charge SG being in the range of 1.270 to 1.280. When performing the EQ,
the user should take SG reading for a “pilot” battery every 30 minutes until
the voltages reach that range. Termination should happen when SG reaches full
charge range or if battery temperature reaches 112 degrees F, which-ever comes
first. SG readings can be taken during EQ, but you have to make sure that you
bump the tiny gas bubbles off the Hydrometer float to prevent erroneous
readings.
Seeing the SG readings decreasing after each month is an indication that maybe
the Absorb Time needs to be increased, maybe from 3 hours up to 4 or 5 hours.
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