Hi Jay,
Thanks for that info on AGM behavior. I've advocated for years that
charge controller temp sensors should also be used to sense over temp
and shut down or reduce charge current. Midnite added this feature to
their Classic charge controllers. Its a bit hard to find, but you can
set the temp to shut off at the battery manufacturer's highest
recommended temperature. Besides catastrophic melt downs, high temps
can greatly reduce a battery's cycle life.
Ray Walters
Remote Solar
303 505-8760
On 11/29/18 6:57 PM, jay wrote:
Hi All,
My 2 cents.
I’ve recently had to do some research for someone who had 16 Full
River 400/6v melt down. ( 48v bank, 2-3 yrs old). Both banks, all 16
melted.
In talking with a battery company expert, what I was given is the
following: AGM if not charged correctly, especially if they are
allowed to sulfate ( under charge), and then charged heavily during
hot conditions can melt down. When flooded get sulfated they won’t
accept a large charge, current is low. AGM appear to have the
opposite reaction which is that they create high resistance but accept
current creating lots of heat. They can’t vent the heat ( no caps
and if there isn’t enough room around them they can’t expel the heat
either. In a sense if they can melt together, they are too close
together ) and if there is external heat to contribute then once they
get to 40-50C internal they can melt down. I mentioned in a previous
post that Full River has an EQ type cycle for batteries that are
showing lowered capacity which is a form of sulfation and this EQ is
to try and prevent this exact situation.
As to MK, I don’t use them as they have very low cycle life. Those MK
8D AGM are around 700 cycles to 50%, vs Full River or Rolls AGM at
around 1300 cycles to 50%.
VRLA are a pretty tricky compared to flooded.
jay
peltz power
On Nov 29, 2018, at 8:33 AM, Starlight Solar Power Systems
<[email protected] <mailto:[email protected]>> wrote:
Let me confirm what William has shared about Deka/MK 8D AGM
batteries; they have a very high failure rate. We saw over 40% fail
within 2-3 years of installation. Deka would not own up to the
problem and offered no compensation.
Fullriver has been the finest AGM we have ever sold. All DC models
are excellent. We especially like the 2 volt L-16’s for high capacity
systems. We had one failure, and I know of one other, where L16
batteries went into thermal runaway. The cases welded together. After
fully testing the power system that we designed and installed, we
found no problem. Fullriver would not offer any help or replacement.
Our installations are 100% battery based. When I do see failures I
have many other identical power systems to compare with (in the
thousands, we do 5-8 per week) and this helps me make sound
judgements about our findings.
Larry Crutcher
*3 year old Deka 8D*
<Deka 8D AGM failure_ (2).jpeg>
*1.5 year old Fullriver L-16*
<IMG_0629 (1).jpeg>
On Nov 28, 2018, at 11:43 PM, William Miller <[email protected]
<mailto:[email protected]>> wrote:
Allan:
We have had poor luck with the 8D AGM batteries (MK/Deka). Many of
them have had short life spans along with swelling, heating and even
exploding. Your point about the inefficient footprint is right on.
I have minimal experience with Full River. I have seen a set fail,
but heck, anyone can do that in a hurry.
When footprint is an issue, we have gone to racked AGMs, like the
Deka Unigy. Now to get higher voltages might require custom racking,
but the cells come in lots of sizes and shapes, physically and in
capacity. It may be worth checking into the size of a 400 AH Unigy
cell and see how they rack up. I don’t have but a smattering of
drawings for the models we have purchased, but my cursory look
indicates you won’t save on volume or dollars, but you may gain a
smaller footprint with some Unigy racks in series.
William
<image002.jpg>
Lic 773985
millersolar.com <http://www.millersolar.com/>
805-438-5600
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