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Replacing Original Traction battery with Nexcell LiFePO

Discussion in 'Gen 2 Prius Technical Discussion' started by JasonMRC, Jan 30, 2023.

  1. JasonMRC

    JasonMRC New Member

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    I recently purchased a 2008 Prius with 218k miles. This is my first time owning a Prius or a Hybrid, although I know my way around cars well enough. During the testdrive everything seemed to be running well. A few days later I noticed that the battery seems to drain and charge irregularly. The engine also seems to stay on a lot while driving, which seems odd but I have had the heat on most of the time (it's been in the 30s here in GA) and, again, I have no experience driving Prius.

    I did some intentional testing and found the battery drain from 7/8 bars to 2/8 bars when driving with electric over the course of about two miles. I then ran up higher speed and the engine charged the battery back up to 6/8 within a few minutes.
    I deduced from this that my battery is bad. Is this an accurate assessment?

    According to the dealership maintenance report, the battery has never been replaced, so it is likely the original 15-year-old battery. I purchased the car from a private dealer, who turns out to not have been as forthcoming as one would hope...

    I came across Project Lithium's Nexcell LiFePO replacement battery pack and was intrigued. It seems like a great alternative to standard Ni-Mh replacement batteries, but I am a little leery about shelling out the $2100+. I've seen quite a few good comments about them on these forums, although most that I read were a year or two old. I would love to hear more recent firsthand stories before I make the purchase.

    I've also heard you can send your cores back to Project Lithium for a rebate, or possibly resell them online. Does anyone have any experience with either of those options? How much $$ could I recoup from that?

    Thanks in advance for your help.
     
  2. dolj

    dolj Senior Member

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    Just purely on the basis of this test, I wouldn't say it proved anything one way or the other. The Prius is a gas car with electric assist and is not designed to be used as an EV. It is quite normal for it to go not very far before running right down if forced to use only the electric motors. It will then charge up quite quickly over the course of 3-5 miles.

    That is not to detract from the fact that you have an old (most likely original) battery and your observation quoted below:
    is more telling. Personally, I wouldn't jump to any conclusions until you have driven it a bit more. I would also ensure to drive it regularly as well.

    Having said that I have an older car (2007) with the original battery and it is still running perfectly well for its age.
     
  3. SFO

    SFO Senior Member

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    Welcome to PriusChat!!
    Please tell us more. Were you watching the center screen (MFD) for changes in the HV battery state of charge (SOC)?
    Normal for the engine to run when heating or AC'ing.

    FYI : you're moderated until you've posted 5 times.
     
  4. AzusaPrius

    AzusaPrius Senior Member

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  5. JasonMRC

    JasonMRC New Member

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    Ok, so I ran some more tests and learned a few things. Eager to hear your analysis.

    So first off I've since learned through reading more posts that the 8 pip SOC icon on the MFD actually reflects 40-80% charge, not 0-100% as I initially thought (new-Prius-owner mistake I suspect).

    Some of the battery charge irregularities I mentioned I noticed when cleaning the car the other day. I had it in Ready with only the radio on and the windows down while I cleaned. It was at about 6/8 when I started. After awhile it got to 2/8 and kicked on the engine until it go up to 4/8, when the engine cut off. This repeated three times over the course of my ~2 hours of cleaning. The only thing running was the stereo and whatever base system the car uses when in Ready. This seemed like an awful lot of charge used for a supposedly small drain. I've left the radio on in my regular cars while cleaning for hours before and they were just fine.

    For today's tests I had a Bluetooth OBD2 connected and was monitoring the car via the Torque Pro app while I drove. For the first test, I used my tablet and for the latter tests, I used my phone. I used the tablet for more screen real estate while checking the battery blocks because I wasn't quite sure which gauges/things to monitor, so I used a variety.

    One of the first things I noticed was the SOC depleting as I was sitting in my car - in Ready, engine off, not even the radio on. I timed it and lost 0.5% charge every 65 seconds, or 1% every 2:10 mins. This seemed odd to me, so I made a note and then began driving.

    Screenshot_20230201-131843.png

    These results were after driving around for about 20 minutes. I traveled on mostly level roads with one downhill/uphill. Notably to me are the low ratings on blocks 6, 7, 10, 11, and 13. I recall reading or seeing a video about less than 13.4 volts being an indication of dying cells? I could be remembering wrong.
    I didn't notice then, but looking at the photo I see all three temperature gauges have about an 11 point range and gauge 2 is reading 4 degrees higher than the rest. I thought NI-MHs were finicky about temperature... is this indicative of anything?

    I then switched to my phone with a more condensed display utilizing the readouts that seemed to provide the most useful info. If there is a certain information type that would be helpful please let me know.
    For these tests I had readouts for Blocks 6, 7, 10, and 13 as they seemed the lowest.

    Screenshot_20230201-141048_Torque.jpg

    78% SOC is the highest I reached and is represented by 8/8 pips on the MFD.
    Are these block readings anything of note? Ranging from 13.7-20.1? I don't know what the other blocks were at this point, but these 4 had the largest variation before.

    I then timed how long it took for 0.5 SOC to discharge with no load aside from the radio and found it averaged 1:11 between each 0.5 SOC loss, or 1% lost every 2:22 minutes.

    Screenshot_20230201-141655_Torque.jpg

    I then drove back up/down my hilly 1/2 mile driveway. It mostly uses electric on the drive and regenerates some along the way. Below is the result after I parked at the house.

    Screenshot_20230201-142047_Torque.jpg

    It was at 5/8 pips. I made a few notes and then closed the app and began getting ready to turn off the car when I looked up and saw it show 3/8 pips. The car was in Ready, parked, with the engine off the whole time. Only the stereo was playing. I had already closed out Torque Pro and put my phone away, so I opened it again and got my stopwatch out again and watched as it ticked down.

    Screenshot_20230201-142243_Torque.jpg

    Note the time - 2 minutes later and we've lost 14.5 SOC. I timed the losses as they happened and it was about 4.5 seconds between each 0.5 SOC loss. The engine kicked on at 39.5 and began charging.

    Screenshot_20230201-142422_Torque.jpg

    2 minutes later it had charged back up to 50.5 SOC. After taking pictures and recording these numbers, I turned the car off and ended testing.

    The ambient temperature today was 60 degrees. All driving was done on mostly flat roads. Some was on a highway at 55 MPH using cruise control. The highway driving had the downhill/uphill.

    Thoughts? Analysis? Is this normal?
    If there are more tests I should do please let me know.
     
  6. bisco

    bisco cookie crumbler

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    if you were able to drive 2 miles on the battery alone, that's like brand new
     
  7. dolj

    dolj Senior Member

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    It is not an absolute voltage that is important but the voltages under load i. e. when accelerating (Amps out of the battery) and deceleration (Amps into the battery) relative to each other. Any block that was 1.2 V higher (decelerating) or lower (accelerating) may be suspect.
    You need to see all the blocks. Having blocks in isolation is almost meaningless.

    FWIW, in your tablet image, I don't see any of the blocks with alarming voltages. But, there again, in that image, you are only drawing 1.3 Amps.
    I only see a 4.3 ºF difference and it is normal for the second temp gauge to read higher than the other two. that gauge reads the middle of the pack and it is quite normal for it to be higher there. Have you checked your cooling fan (situated behind the right rear panel above and in front of the 12 V Battery) to see if that has any significant crud bogging it down?

    Other than addressing those specific points I don't see anything that is overly concerning.

    I haven't used it myself but there is another phone app called Hybrid Assistant that can run analytics and give you stats to help determine the health of your hybrid vehicle (HV) battery. If you can get the paid version and run its test (or tests) and there are other members here who can help interpret the results.

    Really though, get over the tunnel vision (new owner syndrome) focused on the HV battery.

    Run three or four tanks of gas with you at the helm and tell us what MPG you get. That would be a better benchmark.

    If anything you are probably affected by a battery with a lower capacity. The only thing you could do about that would be to wake it up a bit with a round of grid charge/discharge cycling. However, at the age of your battery, I don't think investing in the gear would be worthwhile. Seeing if you could borrow or rent might be a better option though.

    At the end of the day if the battery/hybrid vehicle ECUs are happy there is nothing wrong with your battery. When those ECUs see anything that troubles them, they will let you know with relevant codes.
     
    #7 dolj, Feb 1, 2023
    Last edited: Feb 1, 2023
  8. TMR-JWAP

    TMR-JWAP Senior Member

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    You are over complicating the H out of this. The car is smarter than you, and me, and every other swinging D on this forum. Let it do its job. The car is completely happy with the condition of the battery and you're trying to find a problem where one doesn't currently exist.

    If you want to buy a new battery then do it, but you're doing it because you want to, not because you need to.

    as I was sitting in my car - in Ready, engine off, not even the radio on. I timed it and lost 0.5% charge every 65 seconds, or 1% every 2:10 mins. This seemed odd to me, so I made a note and then began driving.

    Looking at your photo the HV battery had a current draw of 1.3 amps and has a rating (when NEW) of 6500 mAH. So one must ask.....how does that relate to your numbers.

    A new battery with a 6500 mAH rating is being drawn down at 1.3 amps so in a perfect world, it should be able to handle that for.....5 hours ish

    Lets assume your 1% every 130 seconds is accurate. 100% would be 13000 seconds....or 3.6 hours.

    But overall, that's a lot of simplification and assumption
     
    #8 TMR-JWAP, Feb 1, 2023
    Last edited: Feb 1, 2023
  9. JasonMRC

    JasonMRC New Member

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    Good to hear. I have no experience with hybrids and don't know what numbers and ranges are good, so thank you for educating me.
    Only visually and it seems clear.
    Glad to know that's the only problem!

    Thank you all for educating me on what's normal for my Prius and for saving me $2k+. It's encouraging to know there are many helpful people here for when I really do have a problem.
     
    bisco likes this.
  10. drone13

    drone13 Active Member

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    @JasonMRC I not sure why no one has recommended the Dr Prius app, but I really think you should consider getting it. There is a free version that gives some very good info, if you are familiar enough with Prius batteries and their characteristics. But the real value comes from spending (about $20) for the in-app purchase that gives you some tests to determine the condition of your HV pack. It will guide you through several very simple steps and calculate a percentage of how your pack is performing compared to a new pack. You don't need to know anything about batteries, but you'll learn a lot. This app has always been regarded as one of the core apps that all Prius drivers with battery questions should have. I know when I purchased my first Prius in 2020 this was highly recommended by users here at PC.

    There is nothing wrong with the Torque app. It is a very comprehensive app with the only drawback being you the user knowing how to interpret the data. It also allows for data collection that can be graphed, charted, and exported to Excel if you wish which can be a huge help with emissions and other problems. So, by all means keep the app since it will serve you well for other purposes at some point I'm sure. But for the uninitiated to Prius batteries (like I was just a couple of years ago), the Dr Prius app was exactly what I needed with my low experience level. The simple tests showed my battery at around 60% of usable life and after repeating the test several times over several days it was very consistent with the results. The real value of this app is you don't need to know anything about how Prius batteries work to get a pretty accurate indication of your battery's health. This puts you in the driver's seat (no pun intended) in regard to if you need or want to change out the pack or you have enough life left in the pack to let it go for a while and maybe re-run the test once in a while to reassess. You will find many Dr Prius data discussions with screenshots on PC if you want to see what it's all about.

    Good Luck!
     
  11. drone13

    drone13 Active Member

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    I'm going to mildly disagree here. When I was new to Prius, I was very concerned over how good my HV pack was and how long I might be able to keep driving on the pack that came with an '07 at 126K miles. I mean I was glued to the MFD watching the battery bars without a clue what I was watching and if it all fell within a reasonable range for a decent battery. I just didn't have a clue. My first Prius was a pretty steep learning curve and a totally alien concept to every ICE vehicle I've owned in the past.

    But you are correct to say that the Prius will let you know when a problem occurs, because it will happily do so. The only problem for me is I'd rather not wait for the Prius to chime in with an RTOD to let me know that a critical problem has occurred if I could know in advance and plan for that. I'm not really disagreeing with you as much as wanting a better way for me to handle a potential problem and take corrective action before it happens. I think this might apply to other users with a new but used Prius.
     
  12. donbright

    donbright Active Member

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    if you have readings from the original it would help to compare to the lifepo.

    anyways the temperature differential is normal, the temperature sensors are at different positions in the battery compartment and get different airflow.

    I have some data collection runs from my 2007 running NIMH battery cells from NewPriusBatteries, here: https://treecricket.com/vehiviz and its normal for the HVBattery temperature sensors to differ by a few degrees. Here is some temperature data from a run i did in August 2020.
    (the website lets you checkmark different sensors to make graphs like this)
    newplot.png

    best of luck to you

    If you have Torque setup properly and set it to save logs, i could actually load some of your data into the website if you want and make graphs like this for your car, it can display voltage, temps, O2 , current, anything Torque can store basically.
     
  13. donbright

    donbright Active Member

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    I'm not sure if i understand which of your screenshots go with what description. Normally the HV battery current is small and positive when idling, then the ICE kicks in and starts charging it so the current goes negative.

    Normal amps with 0 speed , 0 ICE revolutions per minute, should be small and positive. This plot below is a typical ride, just get in, wait a few minutes, start accelerating, the amps go up, the ICE kicks in the amps go negative.

    newplot(2).png

    Here's another run, showing how Regen makes the Battery current go negative (its charging). Red is regen torque, green is HV battery current.

    newplot(3).png
     

    Attached Files:

  14. donbright

    donbright Active Member

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    Another thing is... my SOC doesn't change that much. Like i would have to deliberately try to make it move more than a few percent. Most of my graphs show it around 60, very occasionally about 40

    here is one where it did hit up towards 70. if you zoom in on the website you can see a huge spike in Regen combined with a slowdown in speed, probably going down a hill and braking possibly plaing with the "B" mode on the shifter.

    newplot(5).png
     
  15. ChapmanF

    ChapmanF Senior Member

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    You were on the right track there when you included "whatever base system the car uses when in Ready". That's been reported as around 400 watts minimum, and more depending on what accessories, lights, HVAC, etc. are doing.

    So quite a bit more than you might be thinking just for radio listening.
     
  16. pasadena_commut

    pasadena_commut Senior Member

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    400 watts with just the radio? That is 33A at 12V, so it doesn't sound right for "nothing much going on". A car radio at a reasonable volume is maybe 25W. No lights on. No AC. No motor. No cabin fan? That pretty much only leaves the various computers, and that is a lot of power for running little tiny computers, most of which should only be a few watts. (Remember, these have no graphics, no sound, little memory, and no rotating storage.) That leaves what, charging the 12V battery maybe? 400 watts at ~12V would be 33A, which seems like a possible value if the battery was depleted.
     
  17. dolj

    dolj Senior Member

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    That was not what was said.

    It was more like in addition to the radio the base energy use is something like 400 W.
     
  18. donbright

    donbright Active Member

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    400 watts at 200+ volts is like 2 amps.

    which is not too far off the data i have collected. Torque can measure the current

    The Prius computers were likely made before 2004 so maybe not as energy efficient as modern stuff. The coolant pump might be running intermittently, the MFD might be on, the vacuum fluorescent display for the speedometer takes energy, dome lights and door lights if you have the doors / trunk open, etc etc.
     
  19. JasonMRC

    JasonMRC New Member

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    Wow! Lots more replies. Sorry I didn't reply sooner.

    @drone13 I invested in the Dr. Prius app tests today after reading your post. Here are the results. I ran the battery test first, then the Full diagnostic test after driving for about 20 more minutes.
    LifeTest_2023-02-19_03-03-04.jpg FullDiagnostic_2023-02-19_03-22-29.jpg

    The battery test result says 37% life remaining. According to the app, anything below 40% is poor condition and should be replaced soon.
    I found it odd that the Full diagnostic said the battery was fine. Which is correct? Should I run both again?

    @donbright the pictures I posted previously are mostly in order of description, not as captions. My paragraphs explain something, then I show a picture related to that point, then comment on that picture and/or how my experience progressed from there.
    Those pictures may not be terribly useful, as I didn't know what I was looking for then. I've learned a little more through further testing since then, although I still have much to learn.

    My SOC can fluctuate quite significantly throughout a drive. Last night it was at 4 pips (~50% SOC) when I parked it. Today it was at 3 pips and drained to 1 pip as I began driving down my 0.4mi driveway (it reached 4 pips by the time I reached the road. It then charged back up to 7 pips after 15 minutes of driving when I reached my destination. Throughout the day I ran the above tests and monitored some things with Dr. Prius and Torque. When I got home to the start of my 0.4 mile driveway it was at 8 pips. By the time I reached my house it was at 6 pips, which is standard. As I began to backup I noticed it begin to drain rapidly from about 55%. I left it in reverse while holding the break and it drained to 38.5%. It does this almost every time I return home. I'll be at 6 or 7 pips (55-65% SOC, I don't always have the meter active) and then reach my house and by the time I get done backing up about 15 ft, the engine has to kick on because it is at 2 pips/sub 40%. Sometimes it drains before I even switch to reverse.

    The below pic is taken right after the engine kicked on. Sorry for the low resolution on the two graphs, this was from my phone which has significantly less screenspace than my tablet. In this photo you can see that the SOC had been steadily decreasing over the past few seconds - yet the HV Current shows essentially no draw until it goes into negative when the engine kicked on. I could take a video of this decrease sometime, unless y'all think it is normal.
    Screenshot_20230219-160956_Torque.jpg

    I've "filled" the tank twice since my last post. The first time since then the fuel gauge was reading 7/10 pips and the pump kept cutting off until I repositioned the nozzle and held it, then it finally pumped ~3 gallons and then continued cutting off, so I left it. I had traveled 174 miles and supposedly used 3.068 gallons, equating to an MPG of 56.71. I then ran that tank all the way to 1 flashing pip. I then "filled up" and it cut off after adding 7.284 gallons. I had driven 260 miles, which equates to an MPG of 35.69. These are mathematically calculated MPGs, not the MFD readout - the MFD read about 43 MPG.
    I intend to drive this tank all the way to flashing pip again and see what the result is.

    Thoughts? Analysis? Follow-up tests I should do?
     
  20. drone13

    drone13 Active Member

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    Sounds like your battery is nearing its end. But you now have some warning and a bit more time to make plans for how you want to resolve this whether new, reman, whack-a-mole, or sell the car and get something else. If you take it fairly easy while driving, now that you know the pack is a bit weak, you might get a few months or more use out of the pack to make a decision on how to resolve this. I wouldn't think you'll start getting codes really soon, just don't push the pack too hard.

    The fact you haven't gotten codes yet is good because even in a weakened state your battery is still serviceable for now which is why it wasn't a test failure at this point. Just headed that direction. The life expectancy test is usually pretty accurate, so I would tend to believe it and plan accordingly. I'm glad you did the test. Having a good idea what you're looking at without seeing RTOD or codes is preferrable to surprises.