Monitoring-Diagnoses-Repair of the IMA battery pack

[JimIsbell]

[Mod Insert, The merge is complete. Copied from JimIsbell's post, 5th below ]

Originally Posted by JimIsbell

As per a suggestion from Mike I am starting a new thread for this discussion and the other posts on PHEV thread will be moved here. This started on PHEV ....because it had to do with external charging of the battery pack, then segued into monitoring of the individual sub packs.....because I modified mine so that could be done. Now because of the utility of the monitoring it has further moved toward the Monitoring-Diagnoses-Repair of the IMA battery pack. So that's what this will be titled.

[end]


Bad news on the "new" battery. Apparently it has a dead sub pack. Yesterday I noticed that sub pack #11 was 1 volt below the others. During all the testing, this had never happened. But I had left it uncharged over the holidays after a complete discharge 14 days ago. All the sub packs showed 7.54 volts at that time (they recovered to that level in 30 seconds from 5.9 volts at the end of the discharge cycle) ...including #11.! So when I saw the low one I charged it alone with 300 ma for 12 hours and brought it up to 7.2 volts then started charging the whole string for about another 3 hours before installing it in the car. The low sub pack had come up to 7.7V as did all the others. It looked good but I was a bit worried because that sub pack had never indicated any problems and it stored a full charge of 5.5Ah just like all the rest. Apparently, I had reason to worry.

After the installation, I took it for a drive. Almost immediately I got a positive RECAL and it moved all the way to 19 bars on the SOC. I was really grinning. Then at about 8 miles, 12 minutes, into the test drive the IMA light came on (first one I have ever seen) and the SOC stepped down to zero bars. This happened just as I started a heavy assist as I accelerated from a stop sign.

On arriving home I checked all the sub pack voltages...I can do this now with the external monitoring barrier strip I installed. and found that #11 sub pack was at 6.4 volts and the others were at 7.7 volts. It looks like the battery that I thought was in perfect shape had a hidden problem, a cell that goes south when under heavy load. It never showed up during the three charge and discharge cycles I used because the load was never over 3 amps, but apparently 50 amps caused one cell to reverse polarity. At least that is what it looks like.

I went back an looked at the discharge curves of the cells and I do note a a slightly odd ending to that sub pack just at the end when it drops to 5.9Volts. The curve is oddly different from the others, a different slope.

Tomorrow will be cold (dropping to 41F tonight) so it will have to wait, With the IMA disabled, but on Tuesday I will put the best sub pack from my Civic battery into #11.

At least I now have my feet wet on a round trip battery replacement. It took me just 3.2 hours on this first one but I am sure I can do it in 1.5 hours the second time because I know where I am going and wont be running back and forth to the tool box and the manual for every step. Maybe less on this one as I can just pull the pack and balance it on the back of the car while I swap out the one sub pack. I wont have to swap out all the modules and the fan and ducting this time.

[retepsnikrep]

Jim you have shown the usefulness of your subpack monitor/access strip already

You now know the weak pack and can go straight to it

That weak pack would not have been easy to locate if it held up under test charging etc.

Well done.

Peter

[IamIan]

Agreed, being able to identify and pull out the one single bad 6 cell subpack is a good thing... means you can still reuse the other 114 cells... my kind of combination of cost effective & earth friendly

Do you have any plans of further testing or reconditioning of the bad 6 cell subpack?

[JimIsbell]

Originally Posted by IamIan

Agreed, being able to identify and pull out the one single bad 6 cell subpack is a good thing... means you can still reuse the other 114 cells... my kind of combination of cost effective & earth friendly

Do you have any plans of further testing or reconditioning of the bad 6 cell subpack?

I would like to see if the single cell can be "repaired" in a way similar to the sub-pack repair that we do on the whole pack. Try to individually charge it first, then the entire sub pack. BUT...I dont have much faith that it will work because that sub pack came up to the full 5.5Ah charge the others did so that cell was probably responding properly at the 2 amp level.

I now have to start looking for 2 or 3 more sub packs, as I am now one sup pack short of a full three packs so I need some to repair.

That might be a good phrase to describe a EVer that is loosing his marbles, "He's just a few sub packs short of a full battery!"

[Mike Dabrowski 2000]

Jim,
If you can identify the bad cell, you could try the Capacitor discharge method of fixing a leaky or shorted cell.
A 2000-5000Uf cap charged to 50-100V discharged right through the bad cell will disintegrate and nickle whiskers that are the likely cause of the high self discharge.

[JimIsbell]

As per a suggestion from Mike I am starting a new thread for this discussion and the other posts on PHEV thread will be moved here. This started on PHEV ....because it had to do with external charging of the battery pack, then segued into monitoring of the individual sub packs.....because I modified mine so that could be done. Now because of the utility of the monitoring it has further moved toward the Monitoring-Diagnoses-Repair of the IMA battery pack. So that's what this will be titled.

My experience last night with the IMA light coming on 12 minutes after installing the "refurbished" battery has opened a whole new ball game. As noted earlier, when the IMA light came on I drove home and immediately checked the voltage on all 20 sub packs and found #11 to be over a volt LOW. This I thought indicated a faulty sub pack.

Maybe...maybe not....

Last night when I quit I hooked up the external charger (PHEV stuff) and let it run for 14 hours at 200 ma on the whole pack. #11 was at 6.8v and the rest were at 7.7v. This morning I came out and #11 was at 8.5v (High) and the rest were at 8.2v....now figure that out!!! I pulled the plugs then replugged them on the BCM to reset the IMA light and went on a 15 mile drive. It immediately stepped up from 1 bar to 19 bars on the SOC within the first minute. It then stayed between 16 and 19 bars. Its working fine right now. On returning I measured the sub packs again and after that 15 mile drive #11 is at 8.06 and the others are at 7.99. #11 is still HIGHER!!! I am going to wait and see what happens before swapping out #11. I plan on riding this horse until it drops!!!

[Hybrid-Battery-Repair]

Originally Posted by JimIsbell

Bad news on the "new" battery. Apparently it has a dead sub pack. Yesterday I noticed that sub pack #11 was 1 volt below the others. During all the testing, this had never happened. But I had left it uncharged over the holidays after a complete discharge 14 days ago. All the sub packs showed 7.54 volts at that time (they recovered to that level in 30 seconds from 5.9 volts at the end of the discharge cycle) ...including #11.! So when I saw the low one I charged it alone with 300 ma for 12 hours and brought it up to 7.2 volts then started charging the whole string for about another 3 hours before installing it in the car. The low sub pack had come up to 7.7V as did all the others. It looked good but I was a bit worried because that sub pack had never indicated any problems and it stored a full charge of 5.5Ah just like all the rest. Apparently, I had reason to worry.

Jim,

This is why I recommended letting it sit for a week after fully charging all the sticks. I had three bad ones (well, two bad and one half-bad). Your bad stick is shorting internally and self discharging far faster than the rest of the pack. Interestingly, my two bad ones were in the center of the second row just like yours. I'm not sure if it is coincidence, a heat problem or because they are in the middle of the battery series.

It's too late now, but I would like to have known if your number 12 (you count top down) was performing below par before your charge/discharge cycles. It is the stick adjacent to the bad one.

[Hybrid-Battery-Repair]

Originally Posted by JimIsbell

I would like to see if the single cell can be "repaired" in a way similar to the sub-pack repair that we do on the whole pack. Try to individually charge it first, then the entire sub pack. BUT...I dont have much faith that it will work because that sub pack came up to the full 5.5Ah charge the others did so that cell was probably responding properly at the 2 amp level.

I now have to start looking for 2 or 3 more sub packs, as I am now one sup pack short of a full three packs so I need some to repair.

Jim,

There is an Instructable (http://www.instructables.com/id/Bring_D ... k_To_Life/) on using a disposable camera (the flash) as a high-discharge source to jump-start dead batteries. This might be a way to try out Mike's theory of blasting out the internal shorts.

If you need one or two sticks, let me know. I'm selling them as part of my IMA battery rebuild business and it doesn't make sense for you to buy an entire pack just to get a couple good sticks. I have the charge graphs on each stick.

No matter what you do, I still recommend that you charge the pack up and let it sit for a week and then test that each subpack has the same voltage.

[Hybrid-Battery-Repair]

Originally Posted by JimIsbell

As per a suggestion from Mike I am starting a new thread for this discussion and the other posts on PHEV thread will be moved here. This started on PHEV ....because it had to do with external charging of the battery pack, then segued into monitoring of the individual sub packs.....because I modified mine so that could be done. Now because of the utility of the monitoring it has further moved toward the Monitoring-Diagnoses-Repair of the IMA battery pack. So that's what this will be titled.

My experience last night with the IMA light coming on 12 minutes after installing the "refurbished" battery has opened a whole new ball game. As noted earlier, when the IMA light came on I drove home and immediately checked the voltage on all 20 sub packs and found #11 to be over a volt LOW. This I thought indicated a faulty sub pack.

Maybe...maybe not....

Last night when I quit I hooked up the external charger (PHEV stuff) and let it run for 14 hours at 200 ma on the whole pack. #11 was at 6.8v and the rest were at 7.7v. This morning I came out and #11 was at 8.5v (High) and the rest were at 8.2v....now figure that out!!! I pulled the plugs then replugged them on the BCM to reset the IMA light and went on a 15 mile drive. It immediately stepped up from 1 bar to 19 bars on the SOC within the first minute. It then stayed between 16 and 19 bars. Its working fine right now. On returning I measured the sub packs again and after that 15 mile drive #11 is at 8.06 and the others are at 7.99. #11 is still HIGHER!!! I am going to wait and see what happens before swapping out #11. I plan on riding this horse until it drops!!!

I really wish you had a way to test Ah capacity instead of just voltage. I'd love to see what is going on with that stick. I'm not sure that it is performing properly. I'm also not sure that having it in-circuit is not influencing the results you are seeing.

[JimIsbell]

I DO, test Ah on each stick.

I use a CBA-II and do a three cycle discharge recharge cycle on all of the sub packs. In this case, every one of the sticks...INCLUDING this one....stored and regurgitated 5.5Ah. I have NOT dont an AH test on it since the test in the car. But if it persists, I will try again before I replace it.