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Manually charging HV/Traction battery

Discussion in 'Generation 1 Prius Discussion' started by erkme73, Jul 17, 2012.

  1. erkme73

    erkme73 New Member

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    First post...

    I don't own a Prius, but my parents own two identical 2002 models (each with 120k miles).

    My mother's car wasn't driven for nearly a month (hip replacement), and when they tried to start it last week, the ready light would blink 3 times - but no cranking.

    After taking it to the dealer, they were quoted $4600 to replace the traction battery and ECU. We did the mandatory research on rebuilt batteries, but with only a vague diagnosis from the dealer, we were not convinced that this was the (only) problem.

    So, my brother and I decided to swap the ECU, then the battery from my father's working Prius to my mother's - thereby proving the issue. Upon removing the 'dead' battery from mother's car, I decided to open the module, and check each battery. We measured anywhere from 3.0 to 6.4V on the individual cells - and 7.0V to 11V on the paired cells. It was clear that the batteries had discharged unevenly. The total charge remaining was about 151V - still above the 40% SOC minimum I'd read about.

    We then bought 5 x 10A chargers from Walmart, and connected each to a pair of modules. Set the charge to rapid (10A) and waited 30 minutes (or until the charger indicated full). After 2 hours, all 19 pair were charged fully - with each reporting 15.7V +/- 0.5V. The total power was about 295V.

    We reassembled the battery, re-installed it, and the car started immediately. We let it sit running, until it cycled off on its own. About 5 min later, the ICE fired again to charge the 12V battery - but it threw a P3006 error code. It showed a PS + MAIN + battery icon on the MFD. Using an OBDII scan tool, we cleared the error, and drove the car for a few miles. The error code did not return during that drive - but did one more time after letting it cycle off/on automatically. After clearing the code a second time, it never repeated again.

    My assumption is that the 300V HV charge was above the 80% SOC and it didn't like that. But after a few cranking cycles, and the tendency for the battery to discharge back to it's rated output, the error no longer repeated.

    The entire process took about 5 hours - and we only did it today. So, I guess we'll know whether this adds any more life to the system.

    My parents were fully prepared to plunk down >$4k to have the dealer do the work. After talking them out of it, it looked like it'd be around $1700 for the rebuilt eBay specials. Little did we know that the cost (at least for now) would turn out to be $0.00.

    My guess is that with regular driving, the different discharge rates of the paired cells will likely not be evident - and it was only due to the month-long dormancy that the delta between the cells grew larger than the allowable 1.2V tolerance.

    It maybe short-lived, but my bro and I sure feel like the little guy won one this time.
     
    #1 erkme73, Jul 17, 2012
    TheDoof, alekska, bwilson4web and 1 other person like this.
  2. joedirte

    joedirte Member

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    If you have to do this again (and you may identify a few bad cells that won't stay at the same voltage as the others) or swap out a few cells... Use a 2A rate if the charger has it. And make sure they don't get too hot when you are charging them, or you can permanently make them lose sealed in goodness. Since they are 6 to 7 Ah cells, you should ideally try for a lower than 1C charge rate. Also if you charge the cells manually again, let it sit for a day or two then level them off again, and shoot for much closer to 0.1V difference. And the voltage may change as they cool off. Also letting it sit will allow you to notice any cells self-discharging too much.

    The cells may also now have a tendency to self-discharge faster than normal. And it might throw uneven codes or low voltage codes if you don't run it daily.

    I'm guessing the 12V battery might be screwed if it is a 2002 and sat for a month.

    The real test will be how far you can drive in golf cart mode (or reverse) before the bars jump. But at the very least it should run with too much ICE and bad mpg, but probably run ok with it trying to keep the cells at 60% even if they now have a higher self-discharge rate.

    Make sure you drive around with FRESH air setting and the fan on med or high to keep the HV battery as happy as possible for awhile.
     
    #2 joedirte, Jul 17, 2012
  3. erkme73

    erkme73 New Member

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    The 12V battery was replaced about 2 years ago. It had run down as well, but maintains about 12.6V in an unpowered state.

    We considered the slower charge rates, and in retrospect, wouldn't have lost anything (other than time) - but none of the chargers, cables, or batteries increased in temperature - at all. Also, most of the terminals has a fair amount of gooey crusty stuff on them.

    Given the battery discharged so unevenly after only a month, I have little doubt the time is nearly up on them. Hopefully with regular daily driving the voltages will remain more even.

    So by having the fan on med/high and fresh air, how does that tickle the HV battery? Is it to help drop the higher voltage? I assume you mean with the A/C off?


    ETA: What's golf-cart mode? Did a search under this sub-forum and couldn't find it.
    ETA2: Never mind... found it...
     
    #3 erkme73, Jul 17, 2012
  4. joedirte

    joedirte Member

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    It might be worth cleaning all the crusty stuff off the terminals if you ever have to take it apart again. It can also account for uneven currents. The HV battery has a fan, but running the blower on fresh (ie. not recirc) will force the air out across the HV battery if the windows are up. Use A/C when it is like 90 degrees out. I am just suggesting heat is the enemy now to an old battery.

    In fact one bad cell will heat up more than others and then heat up the neighbors, there are only 4 thermocouples to detect battery temp, so there could be cases where the ECU thinks the battery is cool but 1/4 of it is too hot. At any rate temps over 100F drastically reduce the cycle lifespan.

    Golf cart mode or whatever you want to call it (EV mode or stealth mode) is when the ICE kicks off and you are running on just the battery. You can read more about S4 mode and all that. Basically when you are under 42 mph and the coolant is warmed up and say you come to a stop at a light for 10 seconds. If you are very very gentle with the gas pedal (like a 1mm sweet spot) when you are at speed (normal acceleration requires the ICE running) you can get it to run just on the HV battery and the ICE kicks off. ie. going 35, tap on the brake to get the ICE to kick off (no A/C) and then lightly as possible apply gas pedal pressure. Too much and the ICE will turn on again. Also on an old battery it may not be a good idea to regen a lot or use the HV battery a lot... ie. you could argue it is better to drive around with A/C on and bad mpg but the HV battery stays at constant 60%
     
    #4 joedirte, Jul 17, 2012
  5. joedirte

    joedirte Member

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    Also it might be worth the $40 to buy some ATF WS or ATF T-IV and cork gasket and change the transaxle oil depending on when they had it done. It is pretty easy to do if you have a socket set and ideally a torque wrench to evenly torque down the drain pan gasket. There are threads on here with pics.
     
    #5 joedirte, Jul 17, 2012
  6. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    Great story erkme73. I love hearing stories like this. I'm gonna make this prediction:

    You will have no more DTC's, the battery will be fine for many miles to come.

    There is no doubt that charging that fast was taking a chance but, it appears you left them in their housing so they didn't expand (I'm guessing). Of course there are alway dangers when messing with the batteries but, it looks like you did your research and were very careful about it (other than the fast charge). What would have been even better (for those reading and contemplating this themselves) is to cycle the batteries through at least 3 charge/discharge cycles individually (very time consuming). It is good to be able to boast about a $0.00 cost to repair.

    Just to satisfy my curiosity, which chargers did you buy? Schumaker Pba chargers?
     
    #6 usnavystgc, Jul 17, 2012
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