I mean I was hoping to test them all at once and do 2 teardown and rebuild operations.
The reason for this is the little tabs on the sticks which the screws hold onto do not look like they will handle much beyond minimal manipulation. Hopefully I am wrong, but they look like one of those pieces of metal which when bent for a third time decides it would rather be in two pieces instead of one.


I did spend all morning reading the kingking / sucre post on IC (bragging about and asking Eli and HA to test them...and then the far less than spectacular results)
While not helpful for this project, it was entertaining.


So when I'm done and have one decent pack and one not so decent... do I list the remaining parts on ebay and explain accurately their condition or?

 

The PTC strip terminals are absurdly flexible and ductile. Very hard to break if you exercise minimal caution.

I would keep any additional good sticks in reserve.

 

well I'm glad that I'm wrong then.

proceeding.

 

ok, so unloaded resting ideally is within .05v
is there a rule for loaded voltages?

in B pack I have 3 known fault sticks (between 7.36 and 7.54 resting but between 4.6 and 4.8v loaded)
and 2 more probably bad sticks, 5.8 and falling fast along with 5.95 and falling faster than the ones which stated above 6v.

5 sticks between 6.3 and 6.33v
6 sticks between 6.2 and 6.27
4 sticks between 6.03 and 6.23

the bad sticks it's like a whole cell was like "well screw this!"

I am aware that now since I stopped grid charge a month ago almost I need to recondition pack a and wait a month. Meh. Getting lazy over here.

 

loaded is a little more flexible, but for truly healthy and well matched cells, it will be less than 0.1V. More can be acceptable at higher currents.

I assume this is with the 100A/12V load tester putting about 60A on each stick? If so, than there's some wiggle room on loaded voltage.

Note that in your grouping, you have a .03V spread, a .07V spread and a 0.20V spread, and overlaps with the 6 stick group for some reason. It is far more useful to report the 15 voltages than 3 arbitrary ranges and represent them graphically:



I concur with your assessment of the other 5 sticks - they are likely junk. You should look at the individual cell voltages - you will likely notice significant deviations within a stick.

Of the ones that stayed above 6.0V, it's worth checking the resting voltages of the individual cells and compare them to those in the 6.3-6.33 group. If you notice they are all the same but lower - probably fine. If you notice that the voltage spread of the cells in the lower voltage sticks is lower than that in the higher voltage sticks, that's another sign of trouble. This is one occasion where voltages to three decimal places are acceptable. .001V is influential in this case.

Given your numbers, I suspect a 6.13-6.33 range would define healthy sticks.

Note also that low voltage can be a function of IR. If your lower voltage sticks bounce back to comparable resting voltages with the "stronger" sticks, they may be fine - just on the weak side.

Packs can perform acceptably even with sticks that are weaker or higher resistance - the key is to ensure that there are no CELLS within a stick that are significantly weaker - as that will take a pack out quickly.

 

[deleted but it wont die]

 

FYI, my numbering scheme for these is as follows:

From the right side (without all the components), where the empty slot is I numbered 0. The colorful graph shows how I numbered.

Wow, if not for the 6.2 under the 5.82 I would say obviously this thing wasn't cooled well enough!


Now I'm very curious to load test the one in the car...after I rehab it from it sitting. Looks like I got 10 here above 6.2V

 

The tester doesn't appear to have a way to switch between 100amp load and 60amp load. 60amps just because of the voltage? Yes these are voltages after 10 seconds of load with that load tester. Couldn't recall if you said 10 or 15 seconds but figured A. it won't do any more to weed out crap from maybe not crap and B. the tester said 10 seconds max (which may be for the batteries its expected to be on...or because the tester itself can cook if loaded too long)

Can you explain the quote a little more please?
It sounds like you are saying that more balanced cells inside the stick are a little more important than a higher performing stick, just want to be sure I'm understanding.

 

yes - about 60A @ 7.2V nominal is what you get with a 100A/12V tester

10 or 15 seconds doesn't matter a lot as long as you're consistent across both paths.

I'm saying that when you start to consider sticks at the lower end for installation, you need to confirm that their lower performance is not due to imbalance within the stick, i.e., excessive SD of one cell.

Since all this stuff is comparative vs. absolute, checking the cells in the strongest stick helps you define your "standard". If the lower performing sticks show the same level cell deviation, they are probably okay to use.

I find the graphical depiction very useful. Even at a glance you can see the 3 stick out like a sore thumb. By narrowing the vertical axis to a minimum of 3 or 4V, other sticks start to look like outliers. Those are the ones that need a little more scrutiny.

3, 5, 13, 17 and 18 likely require some scrutiny. If their intrastick cells have no more voltage deviations than the strongest sticks, they are likely suitable for use. This can be delayed until after you've reassembled and grid-charged the pack as intrastick imbalance after a couple of weeks of driving is going to be more telling than after a 7 day rest and load test.

I think it's fairly safe to say that 9, 11 and 12 were what took this pack out of service.

Reassemble, grid charge and swap it out with pack A. Repeat everything you did to pack B on pack A. In the end, you may have enough good sticks that you don't have to worry about intrastick cell measurements.

 

It sucks, I think 9 has the catastrophic fail warning strip on it so that will be fun...

Agreed. I am also optimistic that I have enough good sticks to not go crazy scrutinizing.

do you happen to know what the torque spec for any of these bolts?