Yes good thought Chris -I doubt if there is an IR tester anywhere on the
island - but when I go I will for sure look at that - thanks for that.
How would one measure battery resistance with voltage present? I guess
with a known voltage applied and current held constant one could
calculate? but then how do you know you are measuring resistance vs
storing energy? I don't think that's possible - others?
jc
Chris Worcester <mailto:[email protected]>
July 14, 2021 at 2:14 PM
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]
530-448-9692
Sent 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
Jeff Clearwater <mailto:[email protected]>
July 14, 2021 at 1:42 PM
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
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Pay optional member dues here: http://re-wrenches.org
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