Has an infra-red thermometer been used on every battery's terminals to check
for resistance? I recall, although this might be my own thoughts, that internal
resistance of each cell can be measured with an ohm meter...Chris Worcester
[email protected] from my Samsung Galaxy s9.
-------- Original message --------From: Jeff Clearwater
<[email protected]> Date: 7/14/21 1:42 PM (GMT-08:00) To:
RE-wrenches <[email protected]> Subject: Re: [RE-wrenches] How
Best to Load Test 2 V Cells Hey Jay,
Yes the Sunny island Master of this Quad SI AC-coupled off-grid system
has been giving automatic Eq and Full charge charges perodically as
appropriate to this 48 V EnergyCell RE2700 pack.
We are getting whole pack volt drops way before we should at 600 well-
maintained cycles. When we do whole pack testing - when the voltage
drops off there are 5 of the 24 cells lagging - their voltage drops
faster than the rest - but they operate well between 50%-100% - all
busbars have been triple checked for corrosion and tourque.
So it looks like they just aged prematurely - so I'm in the process of
collating data from EnnexOS to get exact numbers on how they've been
treated. But even with a few hard cycles they should held up better
than they have. So perhaps a warranty claim - I've gone through charge
settings with SMA etc. I did have the AHrs programmed slightly below
rated AHrs due to confusion of whether the SI uses the 20 hr or 10 hr
rate (in Europe they use 10 but apparently - unbeknowst to me - the US
SI uses the 20 Hr - I swear SMA tech support years ago told me 10
hours) but now they are claiming that might be the culprit - I have a
hard time believing that setting the Ahour rating in the SI to 2100
instead of 2288 as rated would lead to pack failure - but they are
claiming that could have contributed.
Thoughts?
Best,
Jeff
Jay
July
14, 2021 at 1:15 PM
Hi JeffIf it’s
the energy cell xlc from Outback then it shows an eq requirement. If not that
battery, most industrial
quality VRLA I’ve seen have a eq requirement, conditioning charge or
something similar. And the lowering of capacity is
common from experience. QuestionWhat equipment/brand is charging it?JayPeltz
power
Jeff Clearwater July
14, 2021 at 11:32 AM
Thanks Dave - yes I've
done whole pack load testing. The deal with this pack though is that it
is so remote and the expense of "just replace the pack" in terms of
shipping and labor is extreme - (tiny Bahaman island with only regular
small boat access}
And if it was toward the end of the pack's life anyway I'd not mess
around - but with only 600 well documented cylces on a $25K pack - and
with probably half that again in shipping and labor to replace - I'm
needing to carefully document the lagging cells for either a warranty
claim or at least to make good decisions going forward.
It's easy to access the cells as this is an EnergyCell AGM stack with
easily accessible terminals and removable terminal bars.
If we replace we'd go LFP - on the order of 100 KWHrs. So no small
decision for the customer - so worth the testing.
Thanks!
Jeff Clearwater
Village Power Design
www.villagepowerdesign.com
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