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Measuring battery internal resistance

 
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nuckolls.bob(at)aeroelect
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PostPosted: Sun Jun 28, 2020 5:42 am    Post subject: Measuring battery internal resistance Reply with quote

At 10:29 PM 6/27/2020, you wrote:
Quote:
--> AeroElectric-List message posted by: Dick Tasker <dick(at)thetaskerfamily.com>

Oops. For your example, the delta current is actually 2.444-1.235=1.209A. So the R=0.015/1.209=12.4 milliohms.

You forgot to subtract the first reading. Other than the simple math error (something I do all the time...) the rest of the explanation is spot on.

Dick Tasker


Good catch! Thank you sir.

BTW . . . I've been playing with my
newly acquired CBA IV battery analyzer
from West Mountain Radio.

I've confirmed suspicions that not
all 18650 cells are what they're 'marked
up' to be.

A few utility cells in the stable
are marked with truing amazing
capacity values like 3800 and 9000 mAh!

While doing cap checks on the cells I'm
noticing some common traits in LiFePO4
cells that contribute to and article/white
paper on system integration of lithium
onto our airplanes.

I do have a couple of cells by Panasonic
that were advertised as 2900 mAh devices.
They are proving to perform as advertised.

Just for grins, I conducted a quick
delta-I resistance check on one of the
cells last night. Snapshot attached.

The CBA IV software has a 'dynamic'
current mode that allows you to change the
load current while the test is running.

Pretty cool . . .

I've got brand new Aerovoltz and Hawker
batteries ordered on which I'll conduct
and record a library of performance curves
for comparison in the white paper.




Bob . . .


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nuckolls.bob(at)aeroelect
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PostPosted: Sun Jun 28, 2020 2:06 pm    Post subject: Measuring battery internal resistance Reply with quote

At 03:58 PM 6/28/2020, you wrote:
Quote:
Thanks Bob and Dick for the details of measuring IR....
I will pursue a simple test setup....
Dave

What are the highest and lowest voltage battery
packs you want to test?



Bob . . .


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