HV Battery problem

OP, I completely apologize that your thread has been hijacked. I sincerely hope that the advice I gave will help you with your problem. Out of respect for you and Danny and others on this forum, I will no longer allow myself to be sucked in
Sorry that you had to deal with that.

 

First of all my apologies to usnavystgc who was obviously offended by some of my posts even though there was never any intention to offend him/her or anyone else. I believe both usnavystgc and I were trying our best to help the OP. It just so happens that we disagree on what the best action for the OP to take is.

Now let's go back to the OP's HV battery issue and I will try to give a detailed argument for everyone to take a look and see if it makes sense or not.

First some history of the thread that points to the central issue:

The OP was capable of opening up the battery but initially did not find a problem:
OP:I tore it down and just finished that. All of the cells measured 7.88 to 7.92 all the way down.
Read more: HV Battery problem | PriusChat

Later the OP did find a bad cell:
OP:We checked the batteries and only 1 cell that is out. All the rest measured the same at 8.10. The bad one was at 6.86 & dropping.
Read more: HV Battery problem | Page 2 | PriusChat

OP replaced bad cell:
OP:I was lucky to find a replacement in town! We put it back together and boom. Done.
Read more: HV Battery problem | Page 2 | PriusChat

Still HV battery problems. Replacement cell was not at the same voltage as the rest when installed. OP asked whether the cells would balance by themselves:
OP:it threw P3016 & P3017. ....
One note, the new battery was charged up to 8.2v when I picked it up from the local guy. The others were at 7.88 to 7.92v by the time we got home to put the new one in.
What do you guys think of letting it sit for a day so that they all even out?
Read more: HV Battery problem | Page 2 | PriusChat

I said the cells won't balance by themselves and need manual balancing:
me:I don't think they would even out by themselves. Try discharge the new module to the same voltage as the others with a light bulb.
Read more: HV Battery problem | Page 2 | PriusChat

usnavystgc suggested discharging/charging procedure:
usnavystgc: Drive the car on a flat surface below 42mph and hold in EV mode for as long as possible (trying to run the HV battery down as low as possible) The idea is to get it into the purple bars. Run it until the ECU's automatically fire up the ICE to begin recharging the battery (this doesn't have to be done while driving, you could also do it by simply turning it on and letting it sit. The main focus is to drain the hv battery as low as the ECU's will let you). Then, drive it to a long downhill stretch and coast down the hill in drive (attempting to get the battery to 8 bars). ...
The idea behind this is to attempt to balance the pack using the cars charging system. I might even do this 2 or 3 times.
Read more: HV Battery problem | Page 2 | PriusChat

I disagreed on the discharging/charging procedure and reiterated on the need of balancing:
me:I have to disagree. Assuming all the modules in the pack are in good health, and the problem is that one of the module is too full or too empty as compared with other modules, then going through deep discharging/charging cycles as usnavystgc suggested won't help, since the modules are connected in series in the pack, and in the worst case it will hurt, risking overcharging a module that's too full or over-draining a module that's too empty. The only correct way to balance the modules is to open up the casing to access individual modules and charge up the module that's too empty or discharge the module that's too full.
Read more: HV Battery problem | Page 2 | PriusChat

usnavystgc disagreed and suggested the cells will self-balance over time:
usnavystgc:I was totally expecting this type of response and its just so overbearingly false I have to respond to it.
For one, how will what I suggest take any module through a deep discharging/charging cycle? The ECU will not allow it to go below 40% nor will it allow it to go above 80%. Since the module in question is presumably overcharged, It could possibly take one module above 80% (but this is a very remote possibility). Even if it takes one module above 80%, the fact that the modules are in series will cause the excess charge to spread throughout the battery over time.
There is not even a possibility that what I suggest will risk "overcharging a module that's too full or over-draining a module that's too empty. If there is, I would like to know what that scenario is.
And to say that the only way to correct it is to do what you say ("open up the casing to access individual modules and charge up the module that's too empty or discharge the module that's too full) is very presumptive.
It always amazes me that when I try to offer a suggestion to someone to help them, someone has to come in and shoot it down right away. And its usually someone that hasn't completely thought things through (as I believe the case to be here).
You can disagree all you want but at least offer a logical argument for your disagreement (with at least some basis in fact).
Read more: HV Battery problem | Page 2 | PriusChat

After some more back and forth, I suggested we go back to the same basic science - it's the same science no matter one is inside or outside of the Navy - the Navy training material is quite good, and I was hoping it will be familiar and easy to read for usnavystgc's convenience.
me:I hope to write a reply in more detail soon. In the mean time I dug up the attached Navy training material that should help our US Navy STGC and other interested members refresh his/her memory on how DC electricity and batteries work.
Read more: HV Battery problem | Page 2 | PriusChat

For some reason usnavystgc was offended. My apologies again.
usnavystgc:Content removed out of respect for others


Now the argument:

It should be apparent by now to the interested reader that the disagreement hinges on the effect of the discharging/charging procedure and whether the cells can self-balance. usnavystgc thought the procedure is beneficial and the cells can self-balance. I think just the opposite.

I tried to put myself in the shoes of the OP and usnavystgc to think of reasons why they would think that the cells can self-balance. (Remember the OP was asking:"What do you guys think of letting it sit for a day so that they all even out?" and usnavystgc wrote:"the fact that the modules are in series will cause the excess charge to spread throughout the battery over time".) I came up with two possible misunderstandings:

Confusing batteries with charged bodies:
Common phrases such as "charging up a battery", "this battery does not hold a charge" etc. may mislead people into thinking that a battery stores net charge just like a charged body. Then the obvious (wrong) conclusion from this (wrong) idea is spelled out in the training material: "When a difference in potential exists between two charged bodies that are connected by a conductor, electrons will flow along the conductor. ..., until the two charges are equalized and the potential difference no longer exists. " (page 1-26) (I said there will be a quiz. ) Thus the wrong conclusion that the battery cells can self-balance, or "even out" in OP's words.

In reality, a battery does not store net charge - in fact a battery is always charge neutral. What a battery stores is chemical energy, and it converts the chemical energy into electrical energy during discharging. (page 2-2 of training material) The chemical reaction dictates that there are always the same number of electrons entering one electrode and leaving the other, thus no net charge is stored in the battery, only chemical energy.

Confusing parallel circuits with serial ones:
If the cells were connected in parallel, i.e. positive to positive, negative to negative, then there will be current flowing from the positive side of a cell with higher voltage to the positive side of another cell with lower voltage (and same value of return current on the negative sides), until all cells are at the same voltage, thus self-balanced.

In reality the cells in our Prius HV battery is connected in series, thus no possibility of self-balancing.

I hope I made a good argument that the cells in our Prius HV battery pack can not self-balance.

On the effect of the discharging/charging procedure:
Now let's look at the other issue of disagreement: the discharging/charging procedure. We recall that the OP had one fully charged replacement cell installed in a pack with all other cells partially discharged. In general there is a risk of overcharging that replacement cell by charging up the battery pack to the max (allowed by Prius computer; ~ 80% SOC). usnavystgc actually agreed with such risk but dismissed it as "a very remote possibility". I suppose some people are more risk tolerant than others. If it was my car I won't risk it.

We can also try to estimate how big the risk is. We will need more data and research to precisely calculate OP's specific case. Nevertheless we can do a ball park estimate. Assuming the replacement module was at 80% (since it was just charged up by the seller according to the OP) and the rest of the 27 modules were at 60% (standard level that Prius computer aims to achieve). Then the pack SOC is
(60% * 27 + 80%) / 28 = 60.7%
Now if the OP follows the charging procedure to 8 bars, then the pack SOC will be at 80%. That's an increase of pack SOC of 19.3% (from 60.7% to 80%). So at this point the replacement module will be at
80% + 19.3% = 99.3%
Now one could argue that 99.3% is not 100% yet so there is no overcharging. However remember that this is just a ball park estimate and I would argue that 99% is too close to 100% to be deemed "almost risk-free".

I hope I have demonstrated that the discharging/charging procedure is risky and does not help the HV battery issue. Since the OP appears to be competent in doing individual module voltage measurement and module replacement, I would maintain my original suggestion to balance the cells by discharging the replacement module to the same level as the rest of the modules.

PS. Just found this thread
Gen II Prius Individual Battery Module Replacement | PriusChat
that has more in-depth discussion on module replacement. If OP's issue can not be solved by just matching the module voltages then info from that thread will help. Good luck!

 

In the above discussion, 2009 Prius is again attempting to make himself look good by making others look bad. If he were to actually read all of what I said and not leave out the part of my post that he doesn't like or is not convenient, he would have noticed that I said "I would give this about a 10% chance of helping you.

2009 Prius, I find your apology half hearted and I stand by what I said in my pmail. If you can't understand why your post (that was clearly meant to belittle me) was offensive, I can't help you. What you're basically saying in your apology is, I'm sorry that usnavystgc was offended but that's his problem because I didn't do anything wrong.

 

One of your modules may have a higher series resistance from the others so that it drops to a lower voltage when you accelerate. The ECU will alarm when one module pair differs from the others by about 0.3 volts or more. A fully charged module sits at just below 8 volts and a fully discharged one is just above 6 volts.

You can measure series resistance by putting a known current load momentarily and checking the voltage drop with a digital voltmeter. Divide the voltage drop by the current to get the series resistance.

JeffD

 

If the resting no-load voltage differs by 0.2 V as you posted then yes the replaced module is very likely deemed bad by the battery ECU.

 

Did you charge the "replacement module" to the same voltage as the rest of the modules in your battery before fitting? This is the very leased requirement to have even a chance of the battery working.

John (Britprius)

 

Cash only! Did U have to pay sales tax?

 

I got the dreaded triangle of death today, and the dealer confirmed the battery has failed. I have 127K, 27K past the 8 year 100K warranty. Oregon is a "Ca. Emissions State", which extends the warranty to 10 years/150K, but since Oregon adopted this in 2008, my 07 falls under the old warranty. Cost:$2900.
I have a case started with Toyota, hopefully they can cover some or all. Otherwise, I must pay $3000+ as the small battery is also bad.

 

A salvage battery from a totaled Prius can be had for $1000, If you are mechanically inclined and have at least one strong friend, you could install it your self.


04 Prius battery in Batteries & Cables | eBay

 

Yes, there are options beyond just giving in to the dealer. Research rebuilt batteries also, and you may find some more economical choices. At least change the 12V yourself, it's easy, and you'll save some there as well.

 

What do you guys think caused his battery to fail so early? A 2007 w/ 127k????? I have an 01 (with inferior batteries), with 127k, an 05 w/ 150k and had an 06 w/ 117k all on original battery. Oregon doesn't seem like a place that would be extraordinarily hard on a battery.

Are you certain the dealer is right on the diagnosis? What are the codes that lead to that diagnosis???

 

I didn't get the code, but am relying on the dealer's diagnosis. From my symptoms, I suspect one cell failed, causing the warning. The small battery is also bad, so the cost for both is $3300. I have a case with Toyota active, hopefully they will offer some assistance. I also told Toyota I felt the battery failed very prematurely and they should back it up, as, per their comments, it should last "the life of the vehicle". I am still waiting for the call.it seems to me that if Oregon adapted the Ca Emissions Standards in 2008, Toyota should honor the 150K warranty, even on my 07.

 

Update! My perseverance with Toyota Corporate paid off: Toyota picked up 80% of the hybrid battery cost!
I still had to pay for the failed small battery, after 6 years, that is ok. Instead of $3300, it was $800.
Thank you Toyota!

 

Cool!