Jerry,
No doubt about it lithium battery chemistry is more efficient than
lead-acid battery chemistry. That is a good reason to choose lithium
batteries. However, 98% RTE is wrong. While being charged the terminal
voltage for lithium iron phosphate batteries, in a 48-volt system, is
typically 54.4 volts. While being discharged at light load the terminal
voltage is about 51 volts; it is even lower if being discharged rapidly.
The RTE efficiency cannot be greater than 51/54.4 or 94% and typically
it will be even lower than that. Many battery manufacturers claim over
95% RTE but that is only possible when the battery doesn't go through a
full discharge cycle. There are many sources on the internet that say 98
or 99%, but that is wrong, among us let's get it right.
Kent Osterberg
Blue Mountain Solar
On 3/20/2021 7:01 PM, Jerry Shafer wrote:
Wrenches
So what l got from the question is why when my batteries are at 100%
isn't everything just passing through. Well, your batteries may be the
issue, l stopped using AGM batteries because of what l called spill
over, the batteries are never full and are leaking out as they are
getting full. This can just be loss because of the chemical reaction
and the electrons, even waist heat. AGM might have a RTE of 82% (round
trip efficiency) so some battery storage energy is lost to the cosmos.
Lithium ion phosphate can have a RTE of 98%, lead acid 75% Edison
batterys maybe 60%. So what l am getting at is different batteries
have different losses internally, AGM's are cheaper then some so you
pick your efficiencies and losses, a solution may be to fatten up the
array to compensate for the storage losses. I am sure someone may have
an alternate solution
Jerry
NABCEP PV Inspector
On Fri, Mar 19, 2021, 9:49 AM Christopher Warfel
<cwar...@entech-engineering.com
<mailto:cwar...@entech-engineering.com>> wrote:
I have not been able to find a way to set my customers battery
charging parameters so that the AGM batteries do not consume less
of the pv output to maintain charge. Here is an Optics view of the
situation with a small image embedded. (If you can answer, please
remove image per Mr. Welch's request.
I have the absorb voltage at 54.3 for one hour, the float
voltageat 54, the equalize at 56 (disabled for this battery type).
It seems like this is a lot of energy being used by the batteries,
but I am hoping that some one with more experience in these
settings can weigh in on any changes I should make, or if this is
just how it is. Thank you, Chris
--
Christopher Warfel
ENTECH Engineering, Inc.
PO Box 871, Block Island, RI 02807
401-466-8978
<http://entech-engineering.com>
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