Interesting the earlier EH5 are 60g per cell heavier than the EHW5..
If only running the tests for a month or two, currently the ambient temp range appears to be withing the Lithium sweet spot. 80 - 90 degrees F. ?I no longer have any evidence that suggests these cells are brand new.
It turns out the amp-hour change over time is strongly correlated to time-of-day:
View attachment 98041
If we change the X axis to time-of-day and then overlay these first two days:
View attachment 98042
We can see that the capacity does in fact vary by time-of-day... almost certainly due to daily outdoor temperature:
View attachment 98043
View attachment 98045
Note: This test setup is located in the shade, and does not receive ANY direct sunlight throughout the entire day.
So basically the ambient cell temperature impacts cell capacity substantially more than I expected: nearly 2 Ah of the 47 Ah rating (~4% of total capacity).
FYI: I went ahead and verified the test equipment itself isn't causing this uncertainty: Based on the Lambda Gen specifications, the current measurement error is less than 0.3 Ah (out of 2.0 Ah)... so based on the datasheet at least 1.7 Ah of this error is from the cell under test (not the test equipment). One way to verify the measurement equipment isn't at fault is to connect an additional temperature-controlled current sensor at various times throughout the day, and then make sure the charge current isn't changing as a function of temperature. I'll do this a few times tonight and tomorrow to verify the charge current is a constant 75 amps.
A grinder will solve that problem...Yes, you have a good eye, CMAX terminals are reported to be 1/8" longer then G3 ehw5 terminals. Is that long enough to create issues?
It's easier to shorten the terminals then lengthen.
From the jag35 ad
"G3 cells in 18s configuration.
3.6V 5Ah lithium cells, comparable to CMAX cells, with the G3 terminals being ~1/8" shorter."
Based on my testing just now, if the CMAX terminals are less than 0.320" taller than EHW5 terminals, then they will fit in the OEM battery enclosure.Yes, you have a good eye, CMAX terminals are reported to be 1/8" longer then G3 ehw5 terminals. Is that long enough to create issues?
OH NO. That does sound like Murphy's law though...Last night it rained hard enough that muddy water bounced off the ground into the lowest power supply (GEN 20-165). I had only thought to protect the supplies from water coming from above... I certainly didn't think water would bounce up nearly three feet vertically and four feet horizontally into the electronics.
The mud deposited itself on the serial communication PCB, which corrupted the data sent to the downstream power supplies.
This caused the tester to discharge the EHW5 cell under test all the way down to 0.000 volts. Therefore, collecting additional data from this specific cell has limited usefulness. Fortunately, we were able to log QTY297 complete cycles on that cell prior to this event, so we can use that data as a compare on future runs. I haven't fully analyzed this data yet, but will soon.
Fortunately, the 47 Ah FoMoCo cell under test was not affected.
Right now I'm repairing the serial communication PCB... assuming that's successful, I'll resume testing later tonight.