Another Gen II Rebalancing Thread

I've been lurking for a while. Mostly I joined the forum because I wanted to do some mods to my Prius. It's a 2005 with 210,000ish miles. Unfortunately I've only owned the car for about 10,000 miles and only 4 months before the HV battery went out (codes for two pair out of voltage). I have the full history of the car and know the previous owner, so I know the car has been maintained. I also knew going into buying the car that it was a gamble with an 8 year old battery.

So far, I've removed and disassembled the battery. I've found quite a bit of corrosion (looking for suggestions to clean up the bus bars). The battery module terminals all looked good after removing the nuts, so I bought 4 DC6 Supermate Chargers and went to town.

From a quick voltage check, I found 6 modules that were low, but decided to try rebalancing everything because of the corrosion. For rebalancing, I setup up the chargers for 7250 mah, 5 D/C cycles, and no safety timer. I left Delta V at default and charged at 5 amps and discharged at 0.7 amps (set on 1, but only did 0.7). Below are the results.

Discharge Charge

	Column 1
0	[tr][th] [th]#1 [th]#2 [th]#3 [th]#4 [th]#5 [th]#1 [th]#2 [th]#3 [th]#4 [th]#5
1	[tr][td]1. [td]3321 [td]5771 [td]5928 [td]5846 [td]6198 [td]6751 [td]6750 [td]6751 [td]7250 [td]7250
2	[tr][td]2. [td]3657 [td]5988 [td]6176 [td]6288 [td]6240 [td]7250 [td]7250 [td]7250 [td]7250 [td]7250
3	[tr][td]3. [td]2334 [td]5085 [td]5406 [td]5920 [td]6044 [td]6936 [td]7160 [td]7251 [td]7250 [td]7250
4	[tr][td]4. [td]3162 [td]5831 [td]6091 [td]6122 [td]6241 [td]7250 [td]7250 [td]7250 [td]7250 [td]7250
5	[tr][td]5. [td]2812 [td]5547 [td]5824 [td]6064 [td]6070 [td]7251 [td]7251 [td]7250 [td]7250 [td]7251
6	[tr][td]6. [td]2963 [td]5652 [td]5885 [td]6040 [td]6139 [td]7251 [td]7251 [td]7250 [td]7251 [td]7251
7	[tr][td]7. [td]2331 [td]4840 [td]5260 [td]5393 [td]5579 [td]7250 [td]7250 [td]7250 [td]7250 [td]7251
8	[tr][td]8. [td]2662 [td]5164 [td]5420 [td]5467 [td]5615 [td]7250 [td]7250 [td]7251 [td]7250 [td]7250
9	[tr][td]9. [td]1383 [td]4593 [td]4393 [td]5034 [td]5191 [td]6189 [td]6816 [td]6910 [td]7055 [td]7175**
10	[tr][td]10. [td]365 [td]1399 [td]1336 [td]1317 [td]1297 [td]3201 [td]3532 [td]3382 [td]3261 [td]3104*
11	[tr][td]11. [td]1985 [td]4775 [td]5055 [td]5114 [td]5225 [td]7015 [td]7250 [td]7250 [td]7250 [td]7251
12	[tr][td]12. [td]1 [td]1465 [td]1495 [td]1400 [td]1329 [td]3257 [td]3235 [td]3404 [td]3286 [td]3418*
13	[tr][td]13. [td]1269 [td]4051 [td]4319 [td]4855 [td]5029 [td]5573 [td]6838 [td]7077 [td]7251 [td]7250
14	[tr][td]14. [td]2 [td]1214 [td]1273 [td]1335 [td]1349 [td]2909 [td]3039 [td]3296 [td]3531 [td]3403*
15	[tr][td]15. [td]11 [td]1276 [td]1122 [td]980 [td]878 [td]2738 [td]3059 [td]3069 [td]2834 [td]3074*
16	[tr][td]16. [td]1848 [td]4661 [td]5208 [td]5290 [td]5511 [td]7050 [td]7251 [td]7250 [td]7250 [td]7250
17	[tr][td]17. [td]1 [td]816 [td]734 [td]612 [td]563 [td]2500 [td]2436 [td]2205 [td]2196 [td]2040*
18	[tr][td]18. [td]2106 [td]4720 [td]5066 [td]5462 [td]5586 [td]7069 [td]7250 [td]7250 [td]7250 [td]7250
19	[tr][td]19. [td]2088 [td]4289 [td]4849 [td]5220 [td]5350 [td]7037 [td]7191 [td]7251 [td]7250 [td]7250
20	[tr][td]20. [td]2984 [td]5326 [td]5625 [td]5486 [td]5823 [td]7250 [td]7250 [td]7250 [td]7250 [td]7251
21	[tr][td]21. [td]1878 [td]4573 [td]5133 [td]5256 [td]5545 [td]6948 [td]7250 [td]7250 [td]7250 [td]7250
22	[tr][td]22. [td]980 [td]4050 [td]4239 [td]4577 [td]4969 [td]5844 [td]6696 [td]6834 [td]6961 [td]7067**
23	[tr][td]23. [td]1 [td]396 [td]336 [td]306 [td]263 [td]2620 [td]1869 [td]1752 [td]1744 [td]1751*
24	[tr][td]24. [td]2309 [td]4806 [td]5207 [td]5079 [td]5479 [td]7250 [td]7251 [td]7250 [td]7250 [td]7250
25	[tr][td]25. [td]2725 [td]5242 [td]5625 [td]5722 [td]5845 [td]7250 [td]7250 [td]7250 [td]7251 [td]7251
26	[tr][td]26. [td]2093 [td]4510 [td]4645 [td]5133 [td]5495 [td]6564 [td]6655 [td]6905 [td]7251 [td]7250
27	[tr][td]27. [td]3039 [td]5218 [td]5516 [td]5530 [td]5836 [td]7250 [td]7250 [td]7251 [td]7251 [td]7250
28	[tr][td]28. [td]3067 [td]5495 [td]5728 [td]5564 [td]5893 [td]7250 [td]7250 [td]7250 [td]7250 [td]7250

* These 6 are definitely bad (and were the ones that tested low voltage originally)
** I'd say these 2 might be bad (looking for second opinions)

Could the rebalancing gurus chime in and give their recommendation? I'm under the impression that the modules are 6500 mah each, but none ever reached a 6500 mah discharge.

How does one measure series resistance? What recommendation is there for pairing up modules?

Currently, I'm a little short on funds, but should be purchasing used modules in the next couple weeks. I will rebalance those and post the results at that time.

Thanks for the help!

-Mushatsu

 

Bump

 

Thanks John. I went ahead and ordered 6 replacement modules. I'm a bit tight on money, and I know that I have to replace those. I also wanted to get a jump on rebalancing them. At 2.5 days a module, I'll still need the majority of a week to balance. Once done, I'll repost numbers on all 8 modules; including the 2 with the 6th cycle.

 

Yes, that's 5 discharges followed by 5 charges. Undecided on 5 because I have a fairly old battery that didn't get much TLC. It seems that I made the right decision, as many of the modules balanced out after 3 cycles. Unfortunately, the formatting was lost when I posted.

 

Actually, I've had a chance to order and receive modules. I'm currently mobile, so I'll report the results later. Both of the original modules balanced out and 5 of the 6 new modules did. Now I'm waiting on another module to arrive to finish things up.

 

Since the formatting didn't work out last time... Let's try this way.

Discharge #6
9. 4201
22. 3360

Charge #6
9. 7250
22. 7250

Here are the numbers for the 'new' modules

Discharge #1-#5
29. 3460 5313 5555 5562 5671
30. 3656 5274 5585 5511 5694
31. 3836 5077 5441 5426 5578
32. 3969 5281 5554 5292 5562
33. 3446 5194 5445 5454 5557
34. 427 820 882 889 914

Charge #1-#5
29. 7251 7250 7250 7251 7250
30. 7251 7251 7250 7251 7250
31. 7250 7251 7251 7250 7250
32. 7250 7250 7250 7250 7250
33. 7251 7250 7251 7250 7250
34. 2811 2565 2688 3005 3019

Obviously, #34 is bad. I contacted the seller and he sent me a new one no questions asked. He didn't even want the old one back. It looks like I'll be in business as soon as I get the last one.

 

(cgates30) I've decided to keep 9 and 22 and move them to positions 27 and 28. That way they will be the limiting pair in the set. Being on the outer edge should limit their thermal load and make them easy to replace in the future. There is also a temp sensor on the bottom of that pair, so I can easily watch their temp.

(marcs_carhole) I am the second owner of this car. The first owner had it in Flordia for 3 years and Texas for 4. I've had the car for almost a year now (though it hasn't been driven much in 6 months). The car has been exposed to lots of moist environments due to the previous owners (an my) love of scuba diving. As for the original codes, they were for Block 6 and Block 7 (corresponding to modules 11 & 12 and modules 13 & 14). It could be that there is a max number of codes set, but I doubt that as it wouldn't make sense from a diagnostic point of view. It could be that the remaining blocks were on the limit or hadn't persisted long enough to trip the code. Also, when these codes were read, the computer had been reset a number of times due to disconnection of the 12V battery. So the code might not have tripped yet. Another thing is that the car had to be driven over the 6 month time frame a few times. This may have caused more modules to fail.

 

Time for another update!

The latest module also looks kind of weak. I went 7 D/C cycles because of this. It seems to be about it's peak, so I'm just going to try it and match the pairs up as best as possible.

Discharge 1-7
35. 5037 5236 5210 5231 5218 5013 5262

Charge 1-7
35. 7010 7194 7150 7156 7178 7178 7151

If I can't find my ammeter to check the resistance of the modules under load, I'm just going to discharge them to a voltage and wire them in parallel overnight. I plan on restacking the pack tomorrow and installing the pack Thursday (I'm not welcome in the kitchen while my wife is cooking anyway). I should be able to put a 100 mile test drive on it Friday. And the ultimate test will come at the end of December where I have a 2200 mile trip planned.

 

Success!!! The Prius lives!!!

Restacked and voltage balanced the battery pack the night before last. Yesterday being Thanksgiving, all I did was hook everything back up that evening. This afternoon, I put the battery pack back in the car and bolted in all the supports, ducts, and the 12V battery. I left out the interior pieces just in case something happened.

Started it up and it ran! I'm really excited that this worked! Plus, I averaged 50 mpg on the way home from where I was storing the car (about 30 miles).

I'll post an update after about 500 miles (a week or so) and again just before and after my late December trip.

 

Sorry that I didn't post after 1000 miles. Things got a bit crazy before going on my trip. I've put about 3500 miles on the rebuilt pack without any problems. The interior has been put back and I had a pretty good trip. Overall, I averaged about 45 mpg going 70 mph. My best tank was 50 mpg at 70 mph and my worst was 35 mpg at 65 mph. I was driving into a 30+ mph head wind and up hill most of the tank. Overall a success.

@cgates I wouldn't worry too much about a few hundred mah. My pack was built up with ones from 4900 to 6100. Just pair them up as best as possible. As for longevity, it will reduce the life, but I can't say by how much. The higher the mah, usually the longer the life. We'll see what happens in the next year or so.