Gen II Prius Individual Battery Module Replacement

It is interesting to note that the actual capacity of these batteries can and does even after extensive use exceed the original specification of 6500 mAh.

John (Britprius)

 

Great thread on rebuilding the Prius battery! I've got similar issues (P3011) with my Higlander battery so I need a little advice on adapting the knowledge in here for use with my 9.6V batteries used on the Highlander. I have 2 Hitec X4 chargers on order which should allow me to go through the battery in a decent amount of time (hopefully all testing done in under a week). Will need to source batteries from salavage vehicles since these batteries are alot harder to find than their 7.2V cousins.

Here's what I was looking to use for settings:
2 amp Charge
1.0 amp Discharge to 8V (1.0V per cell, 8 cells per 9.6v battery)
7250 mAhr (I assumed battery capacity was the same, just different voltage)
dsch<chg 3 cycles
What voltage would you enter for charging on the X4? (nominal 9.6V? other?)


Any tips or advice on the above from the OP or those more knowledgable than I would be most appreciated.

 

Hey, I'm very glad someone led me to this site. Thanks sideways, you have completed what I'm starting. Tons of valuable info here. My question is do you have any torque values for the reassembly of the battery pack? I can't seem to find anything for the screws at the bottom of the batteries or the 8 clamp bolts. This is my 1st time to work on a hybrid, and some of the info I've printed says that the torque values are pretty important. I've found some for the housing hardware, I guess I can correlate that to stuff that's the same size. Any suggestions???? Also,
does the computer count the modules from the left to right? No one I've asked can tell me. When I had the codes checked, it said cell 11 was weak. But my 2 modules with low voltage were the 8th and 12th from the LH side. And I thought I was buying a spare when I bought 2 modules! I was about to put everything back in the car until I finished reading your posts. Now I will definitely balance all 28 mods.

 

The modules are counted from the terminal (high voltage ECU) end of the battery. The module nearest the ECU being (1) the furthest away being (28).

John (Britprius)

 

Thanks. Any idea where to find the torque values? Just snug them up good and evenly?

 

The upper battery carrier torque: 5.5 N*m 49 in*lb
The upper battery cover 8 N*m 71 in*lb
Battery Assembly 19 N*m 168 in*lb
Frame wires 5.6 N*m 50 in*lb
No. 6 Battery carrier panel 7.5 N*m 66 in*lb
Remaining brackets 28 N*m 248 in*lb

I would not think these are all that critical. As for the frame wires and cell interconnects: firm, but not so tight as to strip the threads.

 

Thanks a million! I didn't see what was so critical, just wanted to be careful since I've never worked on a hybrid before. I talked to 2 dealerships and no one could (or would) give me that info. After reading these posts, I feel pretty confident about fixing our car now. The local dealership wanted $4800 to repair our car. I won't mind letting them know it can be done for much less.

 

Thanks for the excellent write-up.


My O5 hv battery gave me the big red triangle at 157K miles. I started another thread on the subject as I did not balance modules- simply replaced the bad one. Around 9k miles on battery since without issue. This includes a couple of thousand miles of grueling mountain driving. From reading up on the issue it has become abundantly clear that either I am very lucky or the next failure is lurking.


Just purchased a used 09 complete HV pack today off ebay for less than 1k including shipping, claimed to have 27K miles on it. Seller does not want my old pack so I will keep it. Plan is install the new one in my car and properly rebalance the 05 pack and keep it as a spare. May seem like overkill however there are three aging prii in the family and a replacement pack will likely come in handy. For piece of mind If for nothing else. Two O5s and a 07. All with over 130K miles. All three live in the hot south. I suspect that ambient heat/sun has a lot to do with pack failures. I intend to keep my shaded and as cool as practicable.


Will use your write-up as a guide.

 

Hello,
I recently rebalanced a 2005 Prius battery pack using a 7215 mAh limit and ended up with a CEL that said the battery had abnormally high voltage. After driving the car for about 25 miles, I removed the pack and checked the voltage. It read 230.16 V.

230.16 V / 28 = 8.22 v

Prior to Installing this pack, I balanced the modules by wiring them up in series for 6 hrs. (as recommended). After balancing the voltage I checked the individual voltage of each module and each module was at 7.88 V.

7.88 V x (28) = 220.64 V, so what the crap?? I don't know how I get abnormally high voltage.

Now that I have removed the overcharged pack, I am going to go ahead and cycle each module 2x and stop at 6500 mAh to see if that fixes this abnormally high voltage. Hopefully I didn't overcharge and permanently damage the 28 modules on accident.
Did anyone else have any similar issues?

BTW: I used a Hitec H4 to balance each module.
settings were:
Charge 5.0 amp
Discharge 0.8 amp
7215 mAh (used this number because the charger only allows charging by percentage. 6500 x 111%)
Discharge > Charge X3 cycles
Also, delta peak settings were turned off. Should I turn delta peak on? would it benefit me even if Im not using a temp probe?

Any advice would be appreciated!
Dante

 

Dante,

The Delta-Peak system is there to prevent over charging. You used the safety limit to cut off your charging and ran the risk of overheating your modules since the charging continued at 5 amps as the modules approached full charge. Did you record your discharge data for each module on the three discharges?

JeffD

 

Jeff,

Thank you for your reply. Yes I recorded the discharge data in an excel workbook. By the 3rd cycle most of the modules discharged between 4900 mAh and 5200 mAh, and then charged back up to 7215 mAh. I assumed this was a good thing.
Does the delta peak system monitor series resistance to keep the module from overcharging or does it only monitor it by the temperature? I don't really understand it.

Dante

 

Here is a discussion of Delta-Peak from "Backlash" an RC hobbyist group member:

Peak Charging For Idiots - All things electric... - Tamiyaclub.com Forums

"For the Delta Peak Voltage setting, its probably easier if I give you a basic explanation of what it is.. When a NiCd or NiMh battery reaches full charge, the voltage hits a maximum (PEAK) value, and then "changes" (DELTA meaning change) and the voltage starts to drop or reduce as the battery starts to go into overcharge.. So this setting refers to the point at which the Batteries Voltage reaches its PEAK, and then Changes (DELTA) and starts to drop...

What a "Delta Peak" charger does is monitor the batteries voltage, and when it senses the Change in Peak voltage, the charger turns off with the battery being fully charged.. With your charger, you can adjust the point at which the charger registers the change, so as to remove the possibility of having a pack false peak, and also ensure that the pack is fully charged.. The greater value you set the Delta Peak setting at, the more your charger will overcharge your battery..

Most NiMh packs don't like to be overcharged at all, so I generally use a setting of between 3 - 6mV per cell (8mV/cell maximum for my older packs)."

We are trying to slightly overcharge our modules on each cycle. This allows the cells in each module (there are 6 in series) that have a lower SOC to catch up with those with a higher SOC (which dissipate the excess energy as heat) thereby "balancing" the module.

JeffD

 

Want to thank the OP for this thread...
I have seen random owners/posters Gen 2 create a threads begging for help HV "dying" "what" do I do kinda thing
and clearly these posters are in a dire place.
I have also read on wiki and a moderator post that stated you can get a salvage pack from local for around $500 dollars or there about. Sadly this does not bear out. Reinvolt/dorman,hybrid battery depot, prius rebuilders,prius hybridbattery, batteryboy all of these with the exception of Autobeyours are /where the secondary market is currently.
I am very skeptical of the cells, modules, and HV packs listed on ebay for the following issues. ......oem mfg date/age, past history, pricing, reliability , workmanship, and warranty...

 

I'm hoping the balance gurus will give me some insight here. I'm still waiting on the data from the last 5 batteries I re-cycled in hopes of increasing the capacities. But I have some confusing data from some of them. First I need to explain how my balancing process began. Secondly, I want to make sure I understand the principle of bringing the capacities back up to where they need to be and know which mods to ditch. It is the discharge capacity I'm wanting to be at or near 6500, right? What is acceptable?

I was unable to figure out how to set the 3 hitec x4 chargers to automatic mode so I ran the 1st cycle manually. I started with the 1st 12 odd # batteries. I set it at .7A dis/5A ch and set the timer for 240 min. Little did I know it would take 3 times that long to discharge. And I couldn't reset the timer without stopping the cycle and starting over. So I changed it to 480 min and restarted, only to find out that it took even more time. The next day I was able to get them in auto mode thanks to a quick phone call to customer service, and I set my timer to 660 min. I then ran 2 cycles on auto and got good results for most of them. Some were noticably lower in the discharge capacity even though they all charged to 7250. Next I did the last 2 odd ones and all the even ones. Then I tried another cycle on all of the ones below 5500mAh. Most of them decreased or only slightly increased. I figured it was because the batteries had sat over a day or two while I was charging the other mods. So I picked out the lowest 12 and ran 2 cycles at .7A dis/3A ch with 660 min timer. Four of them did get a low voltage shutoff on the 2nd cycle since my wife didn't plug the batt charger up while I was at work. So I added 2 more. This is where it went crazy. I think I lost a cell in 4 of them but I don't know what happened. Here's the data on 7 of them:
# Dis/Ch Dis/Ch Dis/Ch Dis/Ch Dis/Ch Dis/Ch
7 4551/7251 5456/7250 4443/7250 5037/0105 0125/7250
8 1651/7250 4385/7250 4958/7250 4489/7250 4939/0101 0119/7250
10 1631/6852 4536/7229 5217/7251 4781/7251 5062/0126 0145/7250
11 batt full msg 3492/6756 3667/7250 5042/7250 4776/0101 0122/7250
19 4782/7250 5157/7251 4868/7251 5058/7250 5581/0106 0138/0096
26 3268/7250 4849/7250 6008/0016 0133/7250 6045/7250
28 2531/7250 5515/7251 5898/0077 0160/7250 5965/7250

I know that #s 26 and 28 got the LV shutoff during the 2nd charge. But what happened to #s 8,10,11, and 19 on the last 2 cycles? It was after I changed the charge rate to 3A but there were no interruptions in the cycles either from the safety timer or the low voltage shutoff. I believe I lost a cell. I checked the voltage of # 19 and it was only 7.15 compared to about 8.25 on the ones I only charged at 5A. Can't remember for sure but I think those 4 all measured about 7.15V. I'll be home Monday to get the data on the other 5 and I can doublecheck these 4. On the other mods, the capacities ranged from 5217/7251 to 6025/7250. I can post those values if needed.

QUESTIONS:
What caused the values to decrease, some slightly and then some unbelievably?
What is the acceptable variance between mods and what is an acceptable capacity?
Do I keep trying to raise the lower ones up or ditch them?
Also I tried to ohm the batt terminal but had no luck so I set a 1A discharge and checked the voltage. It was basically the same as without the load.
What should the resistance be of a good cell?
Do I need to use a headlight to load test? If so, what should the voltage be?

I believe I'll wait for some answers before I go any farther. Thanks a million for sharing the knowledge!!!

 

Hey Grease,
First off I am far from a guru. I am about 3/4 done with my first balance. So take this for what it is worth.

These little chargers are great but they are a bit confusing to operate.

The good news is that it is unlikely that you have destroyed these modules.

It is a little hard for me to follow the total sequence. No insult intended but it sure looks like operator error . This operator had done a plenty of them. Sort of looks like several of them did not get recharged. I intentionally discharged a module to 6v a second time after it was discharged and had sat for a while. Got between 100 and 200 mahr before it stopped the second time. Sort of agrees with your data. Also 7.15 V does not indicate a failed cell. It looks like a discharged module. My experience has been that after dc down to 6v the module rebounds to about what you are seeing. It would be somewhere in mid 6 range with a failed cell- each cell has a nominal voltage of 1.2 so that is roughly how far it would be below a full normal voltage. You should wait for someone smarter to weigh in but this is my suggestion. Set your charger to stop at 6v per module on dc, set dc amp rate at 0.8 amp. They seem to be limited to about .8 automatically even if you set them higher. I have been using a 720 min time limit. So if you have in fact reversed a cell the module is toast and you will not damage it farther no matter what you do. Treat them like there are good modules that are discharged. Recharge them to either 7250 or to the high neg dv limit whichever occurs first and them dc them and check your numbers again. You may want to do a little mini charge to be sure that the setup is good before proceeding with a full charge.

As far a measuring resistance, I think you need about a 10 amp load to see much. I have not done it yet.

According to my mini VCI, normal module pair resistance is around .025 ohm- so half of that

What is the acceptable variance between mods and what is an acceptable capacity?
I really don't know but the closer the better. One thing to do is to match modules in pairs to get fairly even pair capacities. This helps with the prius battery management system since it looks at pairs vs individual modules. As far as overall capacity it doesn't matter much. Not within any realistic values you will see.
Good luck.

 

Thanks Ed. I just got your reply but that's just what I did when I got home Monday morning. I picked the 5 that had the crazy readings and started 2 more cycles at .7A dc and 3A charge. 4 of them did just fine, getting the discharge cap up to 6200mAh on one of them. Other 3 were 6100, 6000, and 5500. The 5th cell just did 2 more cycles of the same thing. Coincidentally it was the mod the the computer diagnosed as becoming weak when I had the codes checked at the dealership. It was NOT one of the two that I replaced for having 6.25 volts. However, it was NEXT TO one that I replaced. The partner to the other one I replaced is one of the 4 mentioned above that improved to at least 5500 mAh. I will ditch the mod that wouldn't behave and replace it with a gen 3 mod if I can find one. I think I'll work on some of the mods that are around 5500 and see if I can get them up around the 6000 - 6200 mark for discharge capacity.
Thanks again. I'll probably post all the final results when I put them on a spreadsheet.

 

Hey Grease

Glad to be of almost assistance. Looks like you sorted it all out on your own. You may want to check around before proceeding with mixing gen 2 and 3 modules. I don't know for sure but I recall that 3s are a little longer which may make fitting the bus bars a trick. Be a step onto and off the module which might make the adjacent module fit up screwy. Also there is an issue with mixing aged cells with much fresher ones. The fresher one may end up causing a delta V alarm. The ECU looks at high to low module pairs V. I think the setpoint is 0.3 V. The idea is to keep age and capacity as close as practicable. If the capacities stay fairly close the car will be happy with the battery longer.

 

after reading this thread, I guess my pack is not balanced. I rebuilt my gen one with gen 2 packs, 28 were from a 2006, other 10 unsure. I have removed pack twice for testing. last weekend after 300 miles pulled pack and the 28 were 8.2 volt range, the other 10 were in 7.8 range. I guess this is enough to throw p3006, battery levels unusually different ? I even bench load tested it with 2 95 watt 120 volt flood light in series and the lowest the 10 dropped was 7.5 This has not been a good project car to resale!! ha, I have 2 lipo chargers i used to charge, I didn't cycle all of them. back to the work bench! runs and drives ok 38 mpg? I red some where that connecting the pack in parrell would balance it ? is this a bad idea? Would Toyota shop be able to read moor into this, or would my obd2 tell me what bank is bad if any?

 

Hey Bernie,
I replaced a failed module without balancing. Now I am balancing. Connecting the pack in parallel will not balance the individual modules. What it does is levelize the voltage between the modules. Having all near the same voltage is needed but it is not to be confused with balancing. It is the final step after balancing. You need to have them at near the same voltages before connecting in II. The higher V modules charge the lower ones so if there is a large difference in V the modules may have excessive current while they are levelizing. In theory at least. I have not done it but the number that I have seen is .05 or less difference before ll connection. You get this by selectively discharging the high ones and or by charging the lower ones. After ll connection for a few hours to a day voltages should be dead on.

The ones at 8.2 V are maybe being overcharged by the prius. They may actually be the weaker modules . Then again they may have been installed at a higher voltage and have not had time to adjust. If module capacities are reasonably close they should self adjust over time by virtue of the fact that charging efficiency is lower at higher SOC. But this also means more heat. Probably not a good plan for the long term health of the pack. On some of the modules the first two letters of the serial numbers is the year of manufacture. Hard to see but they are there.

I don't know about using a lipo charger on a Nimh module. Does not seem like a good idea. I bought a thunder t6 for around $85. Other than having useless directions I am happy with it. It will do 4 modules at a time. Will charge most any type of battery out there but it uses a different scheme for different types. It requires a 12 v power supply. A car battery hooked up to a charger works but requires baby sitting to keep from over charging or depleting the battery. Some folks use a doctored computer power supply.

You could try levelizing and seeing if it works out. I would balance all the modules. But everybody has different circumstances.

Good luck