Hi Steve, sorry it took so long to get back to you . I built your grid charger/discharger. I also probed the connections above. I got:

14-6 = 15.8
6-13 = 15.8
13-5 = 15.8
5-4 = 15.8
4-1 ---------
1-7 = 15.8
7-2 = 15.8
2-8 = 15.8
8-3 = 15.6
3-9 = 15.8

I was unable to get a reading at 4-1 no matter how hard I tried and even though I got normal readings at 5-4 and 1-7 easily. What does this mean?

Jen

 

It means I told you wrong (4-1 is not a connection). Sorry.

Should be:

14-6
6-13
13-5
5-4
1-7
7-2
2-8
8-3
3-9
9-10 - you need this one.

Can you measure to 2 decimal places? XX.XX?

Check 9-10 and let me know.

 

I will redo the measurements at 2 decimal places. I got 15.83 for 9-10 and 158.8 for the pack.

Was it possible that I got the uneven stick or weak battery code because I put the battery together not very long before it was put in the vehicle? Should the pack be left to sit with the switch on for a time before putting it in the vehicle?

 

14-6=15.89
6-13=15.92
13-5=15.86
5-4=15.85
1-7=15.88
7-2=15.90
2-8=15.86
8-3=15.82
3-9=15.91
9-10=15.83

pack=158.8

 

Yes if the sticks were empty.

No. The only time the pack should "sit with the switch on" is if it's in the car and waiting for the next drive.

These are the voltages the car measures at all times. If the difference between the Min and Max is 1.2V or greater at rest, then the IMA system is disabled due to the likelihood that there is a bad cell in one of the sticks in that pair.

0.2V is reasonably balanced. Smaller is better, but this should be fine.

What can happen is that under the 100A peak loads the car induces, one of those 10 voltages goes way out compared to the others, this can also cause a code.

What happened with the pack swap?

 

He said he had no problem with the known good battery but his answer could have been motivated at this point since he was also get the code for the BCM and might have wanted to go with that and return the battery. Hard to know. I have a 500 amp carbon pile load tester now. I think I will test the sticks with that since these ones were only tested to see how low they would go at 30 seconds. I need to do the 30 sec on 30 sec off test with them. Do you think 80 amps would be too hard on the tester?

 

I'm thinking:

Grid charge to SoC
Let sit 12hrs
Disassemble pack
Test each stick at 80A, 30 secs on 30 secs off, to 6V.
Reassemble pack
Pack discharge as per your instructions in your signature
Grid charge to SoC
Store


Thanks,
Jen

 

The tap voltages you report are great. I see 15.82 to 15.92V. Given the consistency of your test results, I would be surprised if something is wrong with your pack. It's possible something else is messed up that's not stick-related, but I highly doubt it.

Please confirm those voltages are basically as-removed from the car?

I'm not overlooking anything, right? All your testing showed consistent results for each test?

By grid charge to SoC, you mean to 100% SoC? In your case, since it's clearly been charged and in operation, you likely don't need to go 24 hours. I would go until you hit a peak voltage and it stays there for 8 hours... do not exceed 24 hours and keep a fan blowing through the pack.

80A on the tester is nothing. The tester can do 500A @ 12V or 6,000W. You'll only be doing 7.2V nominal @ 80A = 576W or about 10% of the max load.

It's unlikely that the sticks will support 80A for 30 seconds and stay above 6V.

Instead, I propose driving it a little higher at 90A and run the discharge 15 seconds. Record the voltage immediately before the test. At the end of 15 seconds, the voltage should mostly stabilize, i.e., while it may still be falling, it will be falling slowly. Record that voltage. It will almost certainly be under 6V. If it stays above 6V, you have some great sticks.

Whatever you do, don't try to "catch " the voltage in a fall. If it hasn't stabilized as described above in 15 seconds and is still falling fast, that stick is likely bad.
After the discharge, you should check the temp of each cells. If a cell is significantly warmer than the rest, the stick may be bad.

Additionally, a big disadvantage to the carbon pile tester is the difficulty setting a specific load. It's a great tool, but it's a tough one to master.

I think the tone the unit emits is after 10 seconds at a set load. If that's a more convenient target point for you, that's fine too. Just make it consistent.

If you have already deep discharged these sticks (I know I recommended it before, just don't remember), No need to deep discharge again.

Use your bulb discharger to discharge sticks to 6V. Reassemble pack and then WAIT.

Partially charged sticks can go imbalanced faster. It's best to let the pack sit in the discharged state until it's ready for installation. Grid charge for 4-24hrs before installation. Don't let it sit for weeks again. The car absolutely will not care if it gets a fully charged pack. It may take a couple SoC gauge cycles to stabilize and figure out what the SoC is, but it hurts nothing.

Before you send it off for installation, check and record the taps again. They should be < 0.20V difference.

Steve

 

The voltages I reported were right from the car meaning no charging or discharging was applied. It had been sitting for about week. Yes I meant to say 100% SoC. I had deep discharged the sticks but individually. I was thinking (aquiescing) that the pack deep discharge is better and could be added for extra measure.

Thanks so much
Jen

 

All is well then. Those are great voltages. If you had a self-discharge problem, you would probably see significant variation. Those are tight.

Deep discharging a pack is a shortcut to avoid discharging all the sticks. Stick discharge is better, so you have nothing to gain with a pack discharge.

I truly suspect that you had a customer with other problems, and he didn't want to commit to the pack purchase. Nothing is saying that you have a bad pack.

Steve