everything I see says undercharge. I have run AGM's for the last 8 years on my camper... and now on my cabin (1 year) "with a Morningstar MPPT 60 controller that is set to a 2 hour absorb time
Absorb Voltage is 28.6, Float voltage is 26.6V. Eq Voltage is 31.0 and set to Eq
for 2 hours every 45 days. See my post on July 9 on this thread for more
Equalization details."28.6 is only 14.3VDC per battery, 26.6 is only 13.3 neither is high enough for a AGM solar battery bank I do not care what anybody in the industry says. I have "low end" batteries the entire time. none of the fancy stuff and mine are running fine and dandy 8+ years later by simply keeping the bulk and float charges high enough. even trojan and concorde have both raised their bulk and float voltages over the last 10 years... In some cases drastically. FYI I use the same morningstar controllers as well as a magnum inverter,its not the gear, its the charge cycle.
I can't speak to the AGM's, but I can to the SPRE415's (L-16 REB's). My, pre-smart carbon, REB's are now 7 years old. They have been at a warmish avg of 81 degrees F, cycled between 100% and 65% SOC daily. I basically followed BB's advice in 2007 and hunted down 100% every day if possible. Only 4-5 times a year does bad weather makes this challenging. However, I have been a little more gentle with them in old age. I have cut back absorb a tad (eg. from 2.2 hrs to 1.9hrs), EQ from 1.5 hrs to 1 hr. In other words, my 100% is a less aggressive 100%. There is no science to this, just an instinct. It probably makes little difference. Who knows. I hope your new bank does well. I am hoping to re-battery in early 2020 with a new bank of SPRE415's. We'll see.
"My batteries (and system) can see temperatures from -15F to +95F." Where is this?, Heat shortens battery life significantly. With that range, a temperature sensor hooked to the charge controller would be mandatory. Are the batteries outdoors? That would be quite a temperature range indoors. Can you dig a hole and keep the batteries a couple feet underground? I'd be working on the temperature. You had two expensive battery strings quit at least 50% earlier than expected. We have a number of techies here that get caught up in esoteric theories and may overlook the basic importance of keeping batteries and electronics cool if possible. By the way, cooling and heating cycles will break electronic "solder type" connections over time. You want a stable environment. That is why electronics in motorhomes and campers like to quit before expected. Plus the bouncy/bouncy roads of course. Marc K feels that equalizing should not be needed for the first 5 years. Another item to consider.
Thanks for your input. You are correct and I appreciate it.
My Cabin is in Adirondack Park in Northern New York. The
Adirondacks is a harsh environment. We see LOTS of rain and LOTS of cloudy days
through out the year. Our winter snow often piles up to over 5 feet. The temps
in the Adirondacks range from +95F down to -15F. There are some weeks that
never see the sun.
The batteries are in a vented battery box that is in a shed.
The shed is not heated or cooled but also has plenty of ventilation and is in a
shady spot. The shed and battery box help to shield the batteries a little from
temp extremes. Since the batteries are in a battery box, their temps might
range from +85F to +10F but the electronics which are hanging on the shed wall see
close to the outside temps plus or minus a few degrees. I agree with you that electronics
should be kept in a stable environment, but I don’t have that choice.
I don’t think putting the batteries into a hole in the
ground would be very practical. The frost line goes pretty deep, and once the
snow starts to fall, you’d have to shovel 5 feet of snow to find them. Also wonder how would the gasses be vented?
I can see that many people on here have a high opinion of
Marc K when it comes to AGM batteries and I’m sure he knows his stuff. If I was
going to use AGM’s again, I’d ask him some more specific and follow his advice.
But I’m done with AGM’s and have switched
to Flooded batteries.
I’ve set up my Morningstar MPPT Controller to do daily 2
hour absorb and a 3 hour equalize every 30 days on the flooded batteries. I’m
following Trojan’s user manual. I’ll
monitor that for a little while and adjust these settings if needed.
The nice thing about going to flooded batteries is that I
can now verify the water levels and measure SG. This will allow me to make
adjustments to my charging as needed. The bad thing about going to flooded batteries
is that I will NOW HAVE TO monitor water levels and measure SG. (It’s a double
I loved the “maintenance freedom” of AGM’s but but you pay
the price for that freedom. AGM’s are a guessing game. Even the manufacturer
doesn’t know if or how often to equalize (as demonstrated by the 3 user manual
revisions that I detailed earlier in this thread.). You also can’t add water if
they start to dry out.
Ralph Day said:
The equation for the absorb time FLA batteries need (from Surrette):0.42 x (20 hour C rate for your batteries) / amps you can deliverFor my S550 Surrette L16's: (.42 x 428ah) / 30a = 5.9 hours2 hour absorbs just don't cut it for most of us.
3 hrs EQ seems a bit harsh. I'd extend the daily absorb a bit instead, and only EQ if cells are not holding their SG.
Nothing like beating a dead horse here. The batteries were replaced and he spent a lot of time coming up with a new charging regimen. I know everybody has good intentions but it confuses when so many opinions are proffered. He is going with battery mfr recommendations and that is maybe hard to second guess. Though I think we will all agree that a Battery Temperature Sensor needs to be hooked up with a battery temp swing of -15F to 95F.
Huh - I have not heard of employing two temp sensors. We all know how the CC sensor works. I wonder how the inverter sensor works.
Dave Angelini said:
One of the problems I see with sensors all the time is the person who installed the sensor did not finish the job by calibrating the battery spec to the electronics. The second is the sensor is installed and the default temp was not updated to the bts. Pretty basic power system configuration.
The fact that many manufacturers have changed their mind so many times gives some pause for reflection........
2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.
The fact that many manufacturers have changed their mind so many times gives some pause for reflection. It would be of some interest if a clear battery case was possible.