Gen II Prius Individual Battery Module Replacement

I have been reading this thread since I joined. I bought my used Gen2 Prius in April of this year. It showed a hybrid battery failure two days later. I parked it and didn't remove the battery until later. I acquired a HiTech X4 AC model and started charging the modules. I started with the ones which showed the least Voltage on a Fluke 189. I use a more relaxed schedule than most of the thread posters here. I go through one cycle at a time, so the cool down time is sometimes just a minutes (however long it takes me to reset the the charger after it beeps) to hours. I try to take accurate observations and record them. I do some things differently from anyone on this thread. I attribute this to stubbornness and having other vehicles to use.

**After some confusion on my part, I now number the modules similarly to the way the Prius computer does. I pair them up so the the first pair is labled "1" and "1'" (one and one prime). This pair is at the end opposite the computer (ECM or ECU?) and number one is at the very end. This means that the pair nearest the ECU is 14 and 14' and the one nearest the ECU is fourteen prime.

Why am I telling you thread-readers this? Because I am uploading a spreadsheet with a lot of data using my labels. It uses color, so be forewarned.

Before I bought it, a previous owner had already had someone "repair" the hybrid battery. Perhaps more than once. The evidence is in the non-consecutive module production numbers but also there were red marker spots on the positive ends of the modules and a Voltage reading was marked on a module which was weak. What threw the computer codes was the one module which tested at 6.57 Volts before charging when all the other modules were at least 7.65 Volts and most were 7.69 to 7.70 Volts. This was after the car had been sitting for at least a couple weeks. 6.57 Volts seems an obvious cell failure; also the module heated up more than any of the others. I measured 106F on the top surface using an infra-red thermometer.

I haven't load tested yet. I also remember reading that a scan tool will give the Prius computer's measurement of the internal resistance of each module. My main source of leakage data right now is the loss in voltage over the weeks measured by my Fluke multimeter.

This spreadsheet is very wide. You will see why: I have put some modules through 15 or more cycles. There is a guide to the colors at the bottom. The format I am uploading is from Libre Office calc converted to an Excel suffix. Sorry, it is read only. The hidden columns are previous multi-meter data and mostly blank load testing data. Voltage readings were taken after the discharge-charge cycle and immediately before the next discharge-charge cycle. The Voltage reading is the highest voltage among several briefly displayed as the module began to adjust to the discharge cycle. In every case the Voltage dropped within less than a second.

Ambient temperature in my garage varied as indicated. We are in The South; it has been warm and humid did not drop into the low seventies (Fahrenheit) until yesterday. Charging is ongoing and will continue. I will try to repost when all is done.

 

I see that the thermocouple for detecting battery ambient temperature is near where the cooling air is blown through the battery. I speculate that if I reverse that support and put the thermocouple at the warmer end of the battery that the cooling blower will run more often and longer and keep my battery cooler. Has anyone tried this? I also think, because heat rises, moving the thermocouple to the bottom of the battery where the warm air is exiting will not work even if it causes the blower to run longer because it will make the battery get much hotter before the blower will kick in. Any opinions?

 

It seems you have an issue with out of balance block capacity. It's clear to me that the actual capacities of the 14 blocks in your pack are all over the place which is causing the weak block codes to appear. The P3011 to P3024 DTCs are triggered by the battery ECU when the block voltage (pair of modules) of a particular block under load decreases too much from a set point that only Toyota knows. Some say that a voltage difference of 0.3V between blocks is enough to set a DTC but I'm pretty sure it's much more than that - closer to 1V.

Actual capacity of a module can be estimated by the charge curve (voltage/time). The voltage of a fully charged module will not continue to increase even when it is provided additional charge - that energy is converted into heat which causes the module to bulge from heat expansion. So, a specific module has reached its total possible capacity when the module voltage levels off at the end of the voltage/time curve (however, multiple discharge/charge cycles often allow recovery of lost capacity but not always - see below). These curves vary quite a bit among the 28 modules in an unbalanced battery pack.

Your load test with a the 100 amp tester from Harbor Freight is not a precise enough way to measure the actual capacity of each module so that it will be possible for you to pair the modules so that the entire 14 block battery pack capacity is balanced as good as it can be. What you need to do is run at least one discharge/charge cycle on each module to find out what their actual capacities are and then pair the modules into blocks of equal capacity (or as close as you can make them). This means, for example, if you have modules ranging in actual capacity from 3.5 amp hours to 6.5 amp hours you would pair up the strongest and weakest first and continue pairing them until you reach the modules at the midpoint of the range. In this example, the average for all 14 blocks would be as close to 5 amp hours capacity as you could get them. This method will buy some time - how much time depends on when the weakest cell in the weakest module gives up the ghost and causes yet another module to bite the dust. It could be days or months later. This method typically does not buy much time - 6 months at most generally.

What the above method does is save some time and money. This method does not try to recover lost capacity; it just sorts the modules by capacity. Trying to recover the maximum capacity on all 28 modules requires multiple chargers or a grid charger, which entails an investment of $300 or more any way you slice it. Using the quick and dirty method I described above, a successful repair could be achieved with a $50 investment for a single channel charger/discharger. This does not include the cost of replacing failed modules - obviously.

The ideal method is to discharge/charge the modules until they're all at 6 amp hours capacity or above. This might not be possible with an HV battery that's more than 10 years old with >200K miles on it. Capacity decreases over time and it generally is not possible to recover capacity on all 28 modules as ryousideways just demonstrated in his last couple of posts during his second issue with a failed module.

It's also a good idea to move the modules that were in the center of the pack to the outer edges and vice versa. The modules in the center of the pack tend to fail first and continue to do so if they remain there.

These tips might help solve your whack-a-mole problem.

 

I doubt that it would make much of a difference moving the intake air temperature sensor from the passenger end of the case to the driver side - if that's what you're referring to - for U.S. left side driver vehicles that is.

When the Prius is shut off, parked, and left for several hours, the temperature of the pack will (or should be) about the same - top to bottom and left to right. Turning the Prius on and driving it when the battery pack is hot (above 100°F) will engage the blower, which in turn, will introduce cooler air to the top of the pack. This air subsequently travels through the gaps between the modules from top to bottom and exits the battery pack at the bottom. Consequently the air temperature at the top of the battery from left to right will not vary significantly with the blower running or not - in my opinion.

 

I'm encouraged that there's possibly light at the end of the tunnel because I was almost ready to throw in the towel. What gives me hope is that I already have bought the grid charger. On the other hand I thought I was balancing the pack by using the fill and balance instructions from the grid charger.

What I don't know Is how to measure the capacity of individual modules? And does the pairing of strong and weak modules help in increasing the capacity of weak modules?

You'll have to excuse me because my technical knowledge is limited but what are my next steps?

 

Get a Reaktor 300W. It can charge and discharge at a 20 amp rate. This is 20 or more times faster than most other hobby chargers. Just one can run through a pack in a reasonable amount of time.

Absolutely not.

The pack is one big series string. The same current flows through each module. One module can not help out another. The battery pack just like a chain is only as strong as it's weakest link.

Techstream, and the car monitor module voltages in pairs. Pairing strong and weak modules is an attempt to trick the computer. The computer only sees the total voltage of the module pairs. Paring strong and weak is really not effective at tricking the computer.

Codes P3011 to P3024 are tripped when one pair under load drops to 1.2 volts below the rest. This is always caused by the weakest cell (not module) dropping to zero volts. Paring modules in any fashion can not overcome one single cell dropping 1.2 volts below the others.

Use Techstream to look at live battery data while performing a charge and discharge test. Weak module voltage will swing wider under charge and discharge. To force charge set the parking brake, put the car in drive and hold both the brake and gas down. The car will just sit still and charge the battery. To discharge use reverse. Give the car enough gas to create a load on the battery but not so much as to cause the gas engine to turn on. Running the AC on max cold can add to the load.

Brad

 

That's what the grid charger does. It charges all 28 modules at once which will equalize the capacities as best as can be achieved. As I mentioned before, the actual capacities will still vary among the 28 but the variation will be considerably lower since some of the lost capacity in the weaker modules will be (or should be anyway) recovered with the grid charger (or discharge/chargers like the Reaktor 300W).

As strawbrad noted, the 168 cells (six in each module) are connected in series. The battery fails (P0A80) when just one of these cells fails. So, a grid charger should not be considered the holy grail since there still can be weak cells in a fully balanced pack. A brand new pack from Toyota is the only way to be 100% certain you won't get stranded somewhere in BFE with a failed or weak HV battery.

 

I second this. Also, when you put a strong and weak module in a block together it removes the computers ability to protect the weaker module. Your car will run fine but you will be beating the crap out of the weak cells and one will fail in a short time. If you pair the weaker modules together the computer can do a better job of limiting current and keeping them safe. You may suffer some battery performance but your rebuild will last much longer which is what you want.

Matt

 

Care to elaborate how the "computer" keeps them safe when you pair weak ones? Please explain.

 

Let's say I go the route of paring modules together, if the car reads the modules in pairs, how can I tell the individual capacities of the two modules in a block?

 

You won't be able to do that - the battery ECU is capable of reading only the 14 block voltages - not individual module voltages. The torque app for android or techstream can provide you with this live data.

I monitor the block voltages with the torque app when I'm driving and can clearly see the app with my smartphone - sometimes it's too sunny to view the app.

 

Pairing the weakest modules together will give the computer a true picture of the voltage swings. It will then calculate a higher delta SOC. Hopefully with this info the system will dial back the current in and out of the battery.

 

Brad got to it before me. Another thing to consider, when you sort best to worst you'll always end up with your weakest block right on top of a temperature sensor. This means that the BCM gets a true indication of the hottest section of the battery and will run the fan more to protect that part. Heat kills batteries, heat is a function of current and resistance. You can't fix resistance so control the current and heat and your pack will last much longer.

 

I put 11 modules from gen 3 manufacturered in 2014 with 18 old ones manufacturered in 2005 and was was going to get 18 more newer ones this month, but last night while driving home the state of charge kept getting lower and lower and I started to smell burnt Electronics and car got super sluggish now I don't know what to do I might have destroyed some of the cells or something I have no idea what happened.

No lights flashing or anything.

Posted via the PriusChat mobile app.

 

Sorry to hear that g. Burnt electronics and super sluggish but no red triangle of death (yet)?

Time to remove the battery and do triage on it. If you're lucky maybe just the 2005 modules are toast.
You were going to toss them anyway.

 

Yeah, no lights... how will I know what's toast and what's not, will it be obvious?


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I think it will be obvious. Two likely spots are the orange plug into the ECU and the other would be loose bus bars connections.

The battery fires at ECU sense connector thread | PriusChat

Battery Fire | PriusChat

Brad

 

If one cell (in a 6-cell module) drops to zero - I clearly see it with my Battery Analyser(s). Those modules are not considered as "weak" they are dead / faulty and must not be used.
People should not be confused about pairing modules a) with different capacity and b) pairing with those "dead" modules.
I can observe the difference in behaviour of those discharged simultaneously on the module level. While a) could be helpful b) is complete waste of time and must not be attempted.

Loss of capacity in the module (6 cells) caused by aging is fine as long as all 6 cells had degraded similarly; loss of capacity when one cell in 6-cell module is "dead" renders that module useless - even if you read something like 3AH DSCH out of it with your RC chargers.
I am capturing those at a glance and discard those from further use. Pairing aged but still good modules with different capacity (if you do not have a choice to compile a pack from similar capacities) could reduce delta V on pairs and make better pack provided you have not used those "dead" modules.

 

Kiwi,

I cut you a lot of slack because it is obvious that English is not your first language. That's no excuse for truncating a quote out of context.
Here is my original statement which I stand by.

We all know that 6.XX volt modules are dead. What I have tested and confirmed is that 5 of the cells will be still be near 1.2 volts and the sixth cell makes up the .XX. Put that module under load and the weak cell drops to zero and trips the code. Before the module goes to a 6.XX state the car will still run without setting codes. When the weak cell can no longer take it's ever increasing abuse it drops off the cliff, the code is tripped, and then you have a 6.XX volt module.

Cells within a module do not degrade similarly. One cell always degrades faster than the others. I have tested this many times at the cell level. Modules die one cell at a time!

My "RC toy chargers" can discharge at a 20 amp rate. That is 3 1/3 times the rate your Battery Analyser discharges at. At a 20 amp rate to a 6 volt termination the "toy" charger is measuring the capacity of the weakest cell in the module. Again, I have tested and confirmed this with data graphing and by directly monitoring the voltage of each cell. At a 20 amp discharge rate 5 cells simply can not hold at 6 volts without the help of the sixth cell. Once the weakest cell begins its rapid decline at the end of it's discharge curve the module will hit 6 volts and the capacity of the weakest cell in a module has been measured. This does not tell you how much is left in the other cells or how well the module is balanced. There are other ways to determine that.

Pairing weak and strong modules could reduce delta V between pairs for awhile. This is nothing more than an attempt to hide the weak modules from the computer. That is not a better pack. It's a pack that will die sooner. The weak modules will get hit harder because you have hidden them from the computer.

No one has enough modules to build a perfectly matched pack. Put the strongest modules you have in the center where the heat is high and life is hard. Let the weaker modules have a little easier time at the ends. That's a better pack that will last longer.

Brad

 

Popping P0A9E code now.

If blocks are not equally balanced, won't they pretty much self discharge to equal resting voltages eventually if no power applied for like a week?

Or won't they equalize each other out eventually?

Probably stupid questions, but I've asked them nevertheless.

Anyway, I didn't mess with balancing voltages cause my fingers are all blistered and eaten up from the gloves and I couldn't take it anymore, so I just put it back in unbalanced and will buy a HA Prolong reconditioning package next month when I get more money.

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