Gen II Prius Individual Battery Module Replacement

Battery cells

Posted via the PriusChat mobile app.

 

When you replaced the bad cell originally did you balance? Or did you just replace and it worked for a year? I just bought a used 04 and about to change cell. Thanks for your time.

 

Alright guys...I've been checking out this forum for a while now but decided to make an account to get some opinions on the HV battery I'm working on. This is my fiancees car and she called me a couple days ago saying she ran out of gas...after putting a couple gallons in and realizing nothing would turn on I realized that was not the problem. She got the red triangle on the dash and the "there is a problem with the transmission "p" lock mechanism. park your car on a flat surface and fully apply the parking break" message on the screen, which I see a lot of people were saying is one of the symptoms of a bad battery.

I got the pack out and tested the voltages on each individual module with and without a load (12V, 35W auxiliary light). The results are as follows:



At this point I am thinking I have 5 bad modules to replace (4, 10, 12, 20, 23). This seems to be a lot more than I have seen in other posts, is this just a result of me waiting longer than I should have to replace the modules?

There also seems to be a few other modules that are a little lower than the rest (in the 7.3-7.38 range), should these also be replaced or will these even out more after the modules are balanced? I am not as worried about those ones because they seemed to maintain a steady voltage with the load, whereas the 5 bad modules were steadily dropping the entire time the light was on.

Thanks in advance for any feedback!

 

You really need to do a full top balance of each module before doing this test. This means charging at a very low rate (350 mA) until the voltage stops climbing and then continue the charge for another 4-6 hours. The is best achieved (time wise) with a grid charger charging all modules at once, but can also be done with at home RC car/drone hobby charger.

Once you have the battery fully charged, repeat the above discharge under load test. In your spreadsheet, you need to add an additional column that is the difference between start and end voltage. You are looking for modules with a greater difference than its peers.

Those modules (4, 10, 12, 20, 23) are not necessarily bad, but after the above test it will be obvious if any of them show as bad.

You also don't detail your discharge methodology, but the assumption is that the load is applied for 120 secs. What ever you are doing need to be consistently applied in all tests.

Another test that is useful is ascertaining the self discharge of each module which can be done by measuring the voltage of each module, leaving the battery to sit for 7 days (or longer) and then measuring again the voltage of each module. Again, you need to then calculate the difference between starting and ending voltages. You are looking for modules with a greater difference than its peers.

Modules that have a greater difference from its peers in the above tests are candidates for replacement.

In selecting replacement modules you need to find modules that are of a similar capacity and charge/discharge in a similar way to the ones that are existing.

Most people's biggest mistake doing this is not taking the time to do the job correctly and try and cut corners. They end up taking more time, together with frustration and inconvenience at having to "go back in" and do it again. Take you time to do everything well and double check everything. Even so, there are no guarantees with the "whack-a-mole" solution. Good luck.

hope this helps.

 

My Battery by Bobasaurus posted Jun 18, 2017 at 9:07 PM

I am very thankful for all the information on this thread. I have one bad module. It would seem it has a completely dead cell in the module.

It is from my Red 2007 with 128000 miles. I am just going to swap out the one bad module with a used one and go for it. If that does not work then I will have to invest in a charger system and recondition the PACK.

My White 2007 with 189000 miles has never had a issue with the battery and has always shown a better MPG than the red one. They are both salvage cars, both purchased in late 2013.

Thanks again for all the great information. I will let you know how everything works out.

Bobby

 

Bobby,
Thanks for committing to letting us know how everything works out. It'd be even better if you could report back a couple times a year to keep us in the loop.

 

I seem to recall that being a typical error message caused by a weak 12V battery, so you might want to double check your 12V battery too.

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With no balancing whatsoever, there is a relatively large probability that the replacement module will have a different state of charge, leading to an imbalance problem. You can increase your chances considerably by charging or discharging the replacement module to match the other module voltages.

If the replacement module voltage is too high you can easily discharge it with a lightbulb. If it is too low, you can charge it with an inexpensive hobby charger.

 

Couple of problems here.....

1) A 35w load is not nearly enough, minimum of 55w/65w high/low beams on together (120w)
2) Time for each test must be exactly the same (minimum of 2 minutes each, down to the second)
3) You need to calculate voltage change, this is what actually tells you if the module can keep up or not.
4) Charge all the batteries up (RC charger, very low current) and run the test again to get useable results

 

Thank you guys for the feedback! Redid some stuff and wondering if I could get a little feedback again.

I did a top balance on each module (@ 375mA) and got each one up to about 7.7V. The charger I used does not have any bells or whistles so I was worried it might overcharge the modules and pulled them off after they were around 7.7V. The next day I re-measured the voltages right before I did my voltage change test.

I must have misread this, didn't realize you said to do high and lows together (oops). I ended up using a 55w low beam for my voltage change test and tested each one for 120 seconds and tested the voltage for each one immediately afterwards. The modules that I suspected were bad appear to need replacing based on what I found, and it looks like I may need to replace one more as well.



So obviously modules 4, 10, 12, 20, & 23 are in need of replacements. I am wondering if module 13 should also be replaced as the voltage drop is outside of the range of the "good" modules (0.25-0.36). What do you guys think?

 

Thanks again for any feedback!

 

Much better data this time around! The ones you highlighted are definitely bad but in addition it also looks like #13 is NG and #16 and #19 are also borderline. If you are going through the expense and trouble of doing this work I would replace those modules too. Make sure to source good modules (talk with Ericbecky) and load test them too (same as you did with the others) prior to install to ensure they will match well with the ones in your pack already (ie delta V after 120 seconds should be around 0.25-0.32 volts). Ones with less voltage drop during load testing should be moved to the middle of the pack and ones with more voltage drop towards the ends since heat build-up is worst in the center of the battery pack. Over time the voltage drops should even out and provide you with a battery that lasts longer before needing another rebuild.

 

Hi everyone

 

I see talk about load testing and slow charge and discharge i bought a cell online and i lt wasnt the same volts as the other 27 and i havent had any issues since march. Im going to retest all my cells in another week and see where im at.

Posted via the PriusChat mobile app.

 

I did balance the voltage on the new cells with a headlight bulb. The new cells were 0.15v higher than my pack average. All my good cells lost 0.11v over a 1 week span.

I have put 50 miles on the pack with the 2 new cells. I am hoping for the best.

My bad module is below.

IMG_0129 by Bobasaurus posted Jun 24, 2017 at 10:56 PM

 

Okay back again...I got the modules replaced and every module was charged/discharged to get them at near equal voltage. Popped the entire thing back in and hit the power button...nothing.

Had no idea what the deal was so I looked around a bit on here and decided to check the 12v battery. Turns out the thing had drained and I had a 6v battery

Ended up replacing that with a new one and got it all hooked back up. Hit the power button again and it actually starts and drives! However, I still have the red triangle on the dash and now I have a red car with an exclamation in the upper left corner of my screen. I have no idea what would cause that and it makes me nervous to drive it like that. Any thoughts?



Random question too, I did not completely reassemble the back in case I had to take out the battery again. I also left the metal covering that goes over the entire battery pack off because I just did. No particular reason why. I noticed that after a minute or so of the car being on, the fans seem to really kick into overdrive and I was just curious if that was normal? I never noticed it before but of course there was a lot of stuff on top that would've blocked some of the noise.

 

IMG_1381 by austin.hughey posted Jun 30, 2017 at 1:04 AM

IMG_1380 by austin.hughey posted Jun 30, 2017 at 1:04 AM

 

OK, first off, you need to put the top cover on otherwise the battery cannot cool itself, and that is why the fan went into overdrive.

Did you check what codes were there when you powered up? If so what were they? After making a note of them, you can clear them and see what, if any, codes come back.

If you have cleared any codes and they immediately came back, what were the codes?

 

^^^^^ This

Those lights mean that you need to check for codes, then clear them and verify which codes come back after clearing. Post up what you find and we can help you solve them but you definitely need to have the battery together, should always be in the case when driven on the road.

 

Got it, I'll probably be looking at buying a scanner then. From what I've seen, the mini vci ones are the best bet. Any idea of a brick and mortar store that might have them so I don't have to wait until Monday to get it from amazon? I've checked all over the place and no one seems to have them.

Thanks again guys

 

This is not something I can do with a normal OBD-II scanner is it? I already have one of those