Gen II Prius Individual Battery Module Replacement

P0A9E is an open on a temperature sensor I believe, I would make sure your plugged in good to the Battery ECU. That's the smaller white connector on the side of the module that faces forward. If that's good then there is a problem with the temperature sensor harness underneath the modules themselves.

The modules can equalize with use if their SOC is not to far apart when you put them together. If they are to far apart trouble codes will be set before they can equalize. Self discharge will not balance them, sorry.

Matt

 

Balancing is at the cell level. It is important that all 6 cells in a module be at the same State of Charge (SOC) to both maximize module capacity (determined by the weakest cell) and to reduce the possibitity that a cell will be reversed as the HV battery is discharged (destroys that cell).

Equalizing is getting all of the modules (monitored in pairs by the battery ECU) to the same voltage. If module pair voltages differ by more than 0.3 volts, the ECU will code.

There are no stupid questions

Besides equalizing and balancing you also need to load test each module and check the self discharge rate. Any module differing from the others in these tests should not be used in a rebuild. The in-car reconditioning package will do a good job of balancing and equalization of a battery that starts in a reasonable condition (no reversed cells where th module voltage drops by 1.2 volts).

JeffD

 

OK, so somebody said no stupid questions, so I'm going to shoot:

I'm really new to the Techstream software. How do I look at the live battery data? Is there a screen or menu item that I'm supposed to go to. I can run the health check and when it showed a DTC for the battery pack, I could click on it and see the voltages of the 14 blocks. But that was probably a snapshot in time. The health check message says that it doesn't show live data. Does it have anything to do with the version I'm using?

When I cleared the codes, there weren't any DTCs and I didn't know how to get to data.

When driving my car, I got 2 code-free days again, and it tripped on the 3rd day again. There almost seemed to be two stages of limp mode. One where the warning light first came on, and the hybrid battery provided some assistance. Then the second stage, where the hybrid battery didn't work at all, and it was all gas engine. Can I do the forced charge and discharge in this state?

 

Deleted.

 

You were really close. After running the health check click on HV battery on the left side. Then click on data list. The first time usually errors out. on the second try it will work.


Brad

 

How is possible to charge a module so that all six cells are at the same SOC when the weakest cell will become full (100% SOC) sooner than the others in the module? Is this accomplished by deliberately overcharging the weak cell until the other five reach their respective fully charged states?

How long can this balanced condition be expected to last? It seems to me that the weakest cell will still discharge faster from 100% than the more robust cells and then the module no longer has balanced SOC. Are you saying that the weakest cell regains nearly the same capacity as the others by deliberately overcharging it?

In my experience, overcharging the weak cell(s) in a marginal module (capacity of less than 3.5 amp-hours) only results in increasing the module temperature causing it to expand between its adjacent modules in the compressed pack. I have tried charging at a much lower rate (0.2A) but still don't see any significant change in actual improved capacity during discharging and the module still experiences thermal expansion. I did allow the module to charge to 6.5 amp-hours capacity before stopping the charge at the 0.2A charge rate.

When I tried charging at a higher current (2A), the expansion occurred sooner and was more severe which I decided was not a good thing so I stopped charging at 4 amp-hours capacity then on my marginal modules. Strong modules (>5.5 amp-hour capacity) can be fully charged with minimal thermal expansion at the 2 amp rate.

Consequently, I have not seen the discharge time from fully charged to 6.0V increase much after overcharging even though other people have seem to have had great success with it. I have been using a halogen bulb to discharge the modules at what seems to be a 16 amp load.

Don't get me wrong, I am not disputing what others have achieved. I'm merely admitting I haven't been able to accomplish this (yet).

 

Yes, but only at a very low charging current to avoid over heating the weaker cell

If the weak cell has a faster self discharge rate, the module is bad. Since the module capacity is limited by the capacity of the weakest cell, balancing will improve module capacity. The real measurement of capacity is overstated by discharging at a low rate as the capacity is defined at a discharge rate of 6.5 amps (the rated capacity).

I charged at 1 amp and successfully increased module capacity. I did make certain that the module was clamped to prevent bulging and supplied cooling air to limit over heating. None of my modules were lower tha 4 amp hours (measured at a low discharge rate) when I started.

Charging weak modules at a higher rate will cause heating problems as you note.

You are assuming that the total amp-hours put into the module equals the state of charge. The final SOC is equal to the initial SOC plus a percentage of the added energy in the charging cycle which gets very inefficient as the SOC gets above 90% of module capacity. Your charger should detect "Delta V" to determine when to stop.

This is a learning process, keep the faith.

JeffD

 

Thanks for responding and answering in full, Jeff. Greatly appreciated.

As to your comment shown above, I wasn't providing enough detail apparently. I'm not referring to self discharge - which is a big problem on its own. What I meant was when the cells of a module discharge under load - say 10A - wouldn't the weakest cell discharge more rapidly under the load than the stronger ones? That's what causes the weakest cell in an overall weak module to experience polarity reversal and cell failure. How does the weak cell recover much of its capacity by doing the overcharge?

No need to answer this, Jeff. I've read it has something to do with the crystal structure or size of the NimH material that is rejuvenated by the overcharge (or standard charge if that's all it needs). I find it hard to believe that a 2 amp-hour capacity cell can be coaxed back to 5 amp-hours by this miracle treatment. But I've been wrong before - too many times to count.

But I infer from your comments that some <4 amp-hour modules with weak cells are too far gone to rejuvenate no matter what you do.

 

It deserves an answer. The "weaker" cell doesn't discharge faster, it starts at a lower SOC. Balancing builds up the SOC of the weaker cell(s) in the module

Hey that's how we learn

Yes, Either the anode/cathode material or the electrolyte are too degraded. Most of the degradation comes from too much heat. I live in a moderate climate which accounts for much of my success in restoring my modules.

JeffD

 

Jeff,
The only way this model makes any sense is that the "weaker" cell has the same capacity as the other five. Through use the weak cell has simply dropped to a lower state of charge. With a controlled over charge the higher SOC cells hit full first and start producing heat and gas. While the stronger (higher SOC) cells burn off excess charge the weak and lower SOC cell continues to charge until it reaches 100% SOC. Then you have six balanced cells at 100% SOC with the same capacity.

This is not the model I have confirmed through cell level testing. What I have observed is that the "weaker" cell will have significantly less capacity than the other five. A typical spread is five cells at 5000 mAh and one at 3000 mAh. I have measured a Gen I module that had one dead cell and 5 that still had 6000 mAh capacity. With this model the weak cell is the first to hit 100% SOC while under charge. The weak cell will also discharge to a lower SOC faster than the stronger cells. In the car the weak cell goes through ever increasing SOC swings. This is what kills cells and modules. This is what jadziasman was describing.

Cycling modules can remove voltage depression. This is how capacity gains are achieved.

Brad

 

Thanks, I forgot to clip the first of the 3 module sensors (sensor A) to bottom of module 1.


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Ok, information and explanation much appreciated, Jeff!

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There is one way to put the pack together correctly.
Many, many ways to do it incorrectly.

 

.08 dB

Thanks. I guess I won't pay any more attention to that, then. I haven't gotten into Tech Scan or Torque very far but I'll be wondering if there's a setting that will allow me to lower the temperature at which the battery fan will start.

 

That's a temp sensor code, not a battery voltage issue.......might be an easy fix if you go back in and have a look.

 

Brad, "attention to details" is not your strongest point. Some people with lack of attention should never attend to work on HV Batteries as they can overlook something and kill themselves. We need you alive as otherwise the life would be dull without your comments...
..
1) You CAN NOT test on the individual cell level NP1 NP2 Prius Modules. They are sealed. That is only possible with cylinder type Panasonic modules - e.g. in the very first Prius (1997-1999). Please do not spread nonsense.
2) You have no clue of how my Analysers work, hence please do not make wrong assumptions about things you do not know about. It is in black and white in plain English on my site. My Battery Analyser is not a Discharger, it Controls the connected external Load and that Load can be almost ANY Load you choose - from milli-amps to 100 Amps. There is even one custom-made sample with 100 amps connectors. I have published screenshots with 20 - 40 amps currents before. Most recently was testing Deep Cycle batteries @25-27 Amps with my Analyser and results have been published here: Toyota Hybrid Battery Experts | Facebook.
Another thing: Prius C, for example rates battery in the User Manual as 6.5AH @ C/3 - that is about 2 Amps Load.
So it is up to you to choose whether you discharge at 20 amps or at 2 amps.
Digital measurements means some sort of a sampling rate.
The higher your discharge current the less accurate results you would have.
It is important for results to be comparable.
That last important bit is what is non-existent with any method where "one module at a time" is tested as in with any RC Toy Chargers, even 4-channel ones.
Play safe and pay attention to details, mate. Silly comments on the net do not kill, High Voltage does....

 

Kiwi, read Matthew 7:4 and 7:5 before writing another post like this one.

 

You can if you cut the top off the module. Perhaps that is what Brad did.

 

Kiwi,

This is a good example of your arrogance. Rather than asking how I test at the cell level you state the it is simple not possible because the modules are sealed. Seals can be broken.



Here is a shot of the weakest cell dropping out at 20 amp load. The third cell dropped out while the other five are still going strong.

I choose 20 amps. A 2 amp load test is meaningless.

This is a major safety issue with your system. You are doing far too much work at high voltage. For no good reason. Testing at the individual module level is far safer.

Brad

 

How long do I need to wait after driving the car to open the battery pack?

I've always waited overnight or around 5 hours or more but I'm in a hurry this time I need to know how long I need to wait before the battery modules cool so they don't swell up.

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