Gen II Prius Individual Battery Module Replacement

Okay guys new user here been a long time browser on the forums, I have an interesting one for you. I have a 2005 Prius that originally through that p0a80 code and I remove the battery pack and found one cell at 6.8 volts while the others were reading 8.06. Replaced that cell last year. The voltage on that replacement cell was very close to the voltage on the other cells. All went well until last week when I got the p0a80 code again. This time I noticed through my torque app that cell block 7 was over charging by . 5 volts. I with my quick thinking tried to discharge at cell with a 12-volt lamp to the cell voltage of the other cells. Believe it or not it work for 3 days as I've been monitoring the voltages and once again I got the code. Looks as if when I put the car under a load as in e brake on and pointing up the hill and giving it some gas I can watch cell block 7 voltage drop off by about a volt almost where the other cell blocks stay consistent with each other. When that cell is not under load it goes back to where it belongs with the others. If I remove the battery in test each individual cell with a voltmeter they're all reading relatively consistent but I have read that a bad battery can show good under Idol state but bad under load. My question is I noticed that this cell can also read over-voltage by almost half a volt in an idle state with the car off and the battery out of the car. Does this sound like a bad battery cell? The reason I ask is because after resetting the P code the car will not move past two bars and I'm getting no regenerative braking and it's just limps along unless I remove the battery and reinstall it or disconnect the battery voltage computer

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I should also note that this car only has 130k on it. My other 2005 Prius has 250 k and never had a battery problem

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No, the module is not necessarily bad, just different enough from the others in your pack that it does not play well together with them. You probably need to source another module that matches your other modules more closely. As you are learning this is not an easy task.

Once you have found and installed a module that is a closer match, you should do multiple balance charge/discharge cycles to ensure the modules are balanced.

 

Yes I understand that. It does sound like a lot of fun however does this explain what the overcharging or the over voltage is on block 7 when I individually test each battery module. For example each battery module will be reading roughly 7.9 volts where one battery in block 7 is reading 8.3 volts. What's up with the overcharging on that individual battery cell? , and is this enough to throw the current balancing computer off to where it will completely shut down the battery and go into limp mode? Also there has been a few occasions where the car has not thrown the red triangle or engine light however the battery will not charge past two bars and I have no Regen braking

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Firstly a word on terminology so that we all can understand what is meant;
The battery is constructed with 28 modules. Each module is made of 6 cells. therefore the battery consists of 168 cells. Toyota groups each pair of modules into blocks, so there are 14 blocks. It is not useful to talk of cells as it is not possible to R&R at cell level, given the modules are a sealed unit.

Yes.

It really depends on what is happening under load and discharge the battery while the battery is working in the car, but yes, one module going out of spec is all it takes to put the car in limp mode.

What scan tool are you using to read the codes? Because if the car is behaving this way, I would expect to see codes.

 

Thanks for the reply I'm using the torque app with the Prius add in. I'm constantly monitoring high-voltage block 1 through 14 and of course each block consists of two modules. The one module I replaced last year is the one that is now reading High. I know this sounds crazy but I drained that modules resting voltage with a 12-volt light until I saw the voltage in line with the other modules. Once back in the car I'm noticing that particular block dropping voltage lower than the other modules

Sorry about the confusion when I spoke of cells I was speaking of a battery module.

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What I'm noticing is that under light acceleration that particular block goes about .3 volts higher then the other blocks however under heavy acceleration or with the E-brake on pointing up a hill I notice that particular block can drop all the way as low as one volt below the other cells

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That is a sign that the module is no good.
Often a high resistance problem.
Sometimes even shorted out.

Once in a while it can be mistorqued nuts.
Or bad/broken/corroded voltage sensing wires.

 

Well I acted on my suspicions on one module on block 7 that was reading a resting voltage of 7.5 volts while all the others reading 7.9 to 8.0v. So far under load block 7 is now staying up with the others after the model replacement. Looks like my problem is solved as for now.

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Have completed a reconditioning charge with my Gen2 pack over the last couple of weeks with my toy charger .

Settings based on the Tommy Johnson video settings .. each module cycled 3 times unless it stopped by a capacity cut off of 7500mah . Auto cycle set to 3.0A and discharge to 6.3v with 5 mins waiting .

This is the 3rd time completed with the Junkyard pack that came in my 07 , have been playing Whack-A-Mole for a few years now with 21 bad cells in my core bin. Going through the pack with each module doing a charge cycle seems to spread out the replace the HV pack code being thrown to about 6 monthes . If I could buy a new battery without having to deal with the core charge and dealer it would be worth it . Or having a spare pack in the bench to have waiting or to populate with the dead cells for a dealer core would be ideal too .Car has 204k miles on it so this process is just delaying a major purchase like a batt or a newer car '

Another observation is the last time I did this made 2 cables with 28 clips and discharged all the modules to the lowest voltage of the standing modules and hooked up the modules in parallel ..not to charge but to all equalize .Caught some flak here when I posted that previously ..but for 3 weeks driving the car was awesome ! Just seemed to roll easier felt much snappier overall ...then things settle back to the aged modules not working together as well .

Shout out to EricBecky for some kick *ss cells .. and all the guys that have participated in the forum and keep sharing their hard won experience. In that vein will post my charger used and my latest discharges, charges and difference deltas in case anyone is interested.

My next module to go will be #16 I think . Middle of the pack and not nearly as strong as the others . My failed cell this time #21 showed a year ago a sub 4000mah final charge , but 6 monthes ago recharge it demonstrated a much stronger final charge .

Kenny

 

I bought an 06 hybrid battery from a junkyard ... all cells at the time were 7.5 however when i put it in my car it wouldnt even reguster a purple bar ... how can i get some "juice" in it or charge it?

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That happened to me once.. Orange safety plug was not inserted & seated correctly

Kenny

 

Double checked it and same plug worked in my original battery ... just wanna find out how i can charge a secondary hybrid

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If I were stuck on the side of the road with no other options and I had my car and some wire I would do basically do it like a jump start.. Except wayyyyyyyyyyy more dangerous. Way more.

Put on high voltage safety protection
Remove safety plugs.
Measure to be sure no high voltage is present.
Positive to positive.
Negative to negative.
Insert safety plugs as the final step.

As I said, there would be some risk to this procedure and I would be wearing high voltage safety gloves. Cheap insurance to diminish the chances of killing yourself.

But if you are at home there are safer ways to do it.

All you need is a high voltage charger.
Buy a consumer grade one from someplace like Hybrid Automotive.
Buy a commercially available power supply and modify it for use.
Build one yourself from appropriate parts.

The choice is a personal one based on things like skill level, times, and finances.

 

The major problem I see with what you did was twofold......

1) To do it the way you wanted you should have grid charged the battery pack with the new cell in there first
Prolong® Value Reconditioning Package – Hybrid Automotive

2) You need to go and load test all the modules to make sure they play nice with each other
Prolong® Battery Module Load Tester – Hybrid Automotive

When you do this I'll bet you'll see exactly why module 7 doesn't work with the rest and it will help you test others to find ones that does. Once you do this you can then use the deep discharge/charge method with your HA charger setup to help bring back some of the lost capacity which should result in better MPG overall.

 

--------------- after having replaced the 12v with the proper glass mat unit, the MFD seemed to fail -- seemed to not come on in cold weather... and the little trick to turn ignittion off of holding the button and then pushing it twice -- not a problem when its warm / hot out ---
-- the 14 sense tabs on the pack harness are sure not built with much mass ... understandbly the whole car is trying to save mass to get higher mpg .. but how are you supposed to achieve 300k miles with all the ups and downs that go along with that without the typical corrosions that occurr with batteries -- and where does water come from to replenish water vapor the modules may exhaust ...

 

@chronon, this thread is a HV battery discussion. Please stop hijacking and desist from 12 V battery discussion. Start your own thread to discuss your issues.

 

I mention the HV sense tabs on the hybrid battery so ... it has relevance...

 

Perhaps stick to relevant discussion then. Discuss your other issues in, either, your own or other relevant threads.