1. Attachments are working again! Check out this thread for more details and to report any other bugs.

HV Battery discharge question.

Discussion in 'Generation 1 Prius Discussion' started by adric22, Mar 24, 2010.

  1. adric22

    adric22 Ev and Hybrid Enthusiast

    Joined:
    Apr 6, 2009
    642
    144
    2
    Location:
    Fort Worth, TX
    Vehicle:
    2018 Chevy Volt
    Model:
    Plug-in Advanced
    This is probably something Bwilson4web can answer.. :)

    Before my question - a little background. As I've mentioned before, since my Enginer kit really doesn't provide quite enough watts for a constant EV mode, I have been looking for ways to better utilize it. I've been wanting a way to shut off the engine but be able to restart it when needed without stopping the car and turning the key off.

    However, something occurred to me today. Since my daily round-trip is about 8 miles currently and I know that I can pretty much make it to work without the engine starting, provided that the engine is already warmed up before I leave the house. Perhaps my best bet is to simply disable the engine in the morning and drive my Prius to work on electric only, then drive home with the gas engine enabled. During the warm-up period on the way home it should be able to restore the state-of-charge to the stock battery. Doing at least half of my daily commute on EV would at least cut my gas usage in half.

    BUT - the one thing that still scares me about driving my 1st Gen prius on EV is that I'm told there are no provisions to keep my from draining the HV battery into dangerous levels of depletion. I know the Prius has a SOC indicator on the screen, but how accurate is that? Honestly I've only seen it drop one bar the entire time I've had the car and that was just for a minute or two, and that was without the enginer kit. Otherwise it stays showing fully charged.

    So the BIG question is this: When running the car in EV, with the enginer kit going, would I still be able to see the SOC drop on the screen so that if it got too low I would be able to pull over and restart the engine? I am pretty sure 4 miles is safe anyway based on previous tests, but I'd like to have something I could monitor just to be sure.
     
    #1 adric22, Mar 24, 2010
  2. linuxpenguin

    linuxpenguin Active Member

    Joined:
    Mar 6, 2007
    352
    182
    4
    Vehicle:
    2005 Prius
    Hi Adric,

    Well, you already know my stance on the safety hazards of disabling the engine. The Gen1 doesn't have as much oomph as the Gen2 and the Gen2 really doesn't have enough power to drive in this sort of "limp" mode safely. Clearly the Gen1 wasn't designed to operate in that mode for extended periods of time, but that's really your call. Don't tell CARB, they may eat you for clearing emissions data =P.

    Strictly from a longevity perspective on your battery--yes, it will put additional strain on your OEM traction battery that was not intended and no the Gen1 doesn't have quite as good safety on the discharge side as the Gen2 / Gen3 do.

    The MFD SOC bar has hysteresis on all Toyota hybrids so it will not be exact in it's displaying. It can take some time (10+ seconds) to adjust to the actual SOC and while this may not seem like much time it could damage the battery.

    Personally I wouldn't tempt fate by trying this on the Gen1 given it's past issues with premature deaths of OEM batteries...

    Remember, battery longevity decreases with larger DOD%. Toyota smartly only uses a small swath of the battery under normal conditions so the battery lasts longer--continual use of this forced EV mode would undoubtedly increase the DOD% (not the maximum DOD%, the average DOD%).

    Andrew
     
    #2 linuxpenguin, Mar 24, 2010
  3. adric22

    adric22 Ev and Hybrid Enthusiast

    Joined:
    Apr 6, 2009
    642
    144
    2
    Location:
    Fort Worth, TX
    Vehicle:
    2018 Chevy Volt
    Model:
    Plug-in Advanced
    Well, I've tried it and I think the car has plenty of Oomph. In fact, it has way more oomph than the converted EV I used to drive everyday.

    I'm not sure I totally agree with this either. As stated before, with the enginer kit and when the engine is warmed up I can actually make the trip from my house to work without the engine ever coming on, even without any modifications to prevent the engine from coming on. Which means the computer believes the battery is still within the correct SOC not to damage it.

    I'm not neccessarily looking for anyone to endorse me and guarantee no problems will arise. I mostly just wanted to make sure I'd have a somewhat realistic idea of the SOC in case something goes wrong. For example, if the Enginer kit stopped working for some reason, the car would continue to drive but the SOC would start dropping very fast without the kit to replenish it. As long as I could rely on the SOC graph on the screen, I'd be able to do something before damage occurs.
     
    #3 adric22, Mar 24, 2010
  4. bwilson4web

    bwilson4web BMW i3 and Model 3

    Joined:
    Nov 25, 2005
    27,375
    15,513
    0
    Location:
    Huntsville AL
    Vehicle:
    2018 Tesla Model 3
    Model:
    Prime Plus
    I have a Graham scanner coming off of equipment rental next week. When it gets back to Huntsville, I'll reprogram it for battery monitoring and rent it out, $25/mo. If you're interested, send me a PM with your address and I'll reply with the instrument deposit amount and account. After a month or so, you'll have the information and know how well it works out.

    I'm also testing a Sears scanner but at $250 (I got a $50 discount), it had better stand up and whistle Dixie. Alternatively, the Autoenginuity at ~$500 has a very good reputation.

    Anyway, let me know and we'll go from there.

    Bob Wilson
     
    #4 bwilson4web, Mar 24, 2010
  5. linuxpenguin

    linuxpenguin Active Member

    Joined:
    Mar 6, 2007
    352
    182
    4
    Vehicle:
    2005 Prius
    Correct. While you won't get my endorsement (not that you asked) it's your car--if you feel comfortable driving it in that condition, hey that's your call. I mean you no harm / hostility by any means.

    My original comments still stand though--the Gen1 does not have as sophisticated discharge protection as later models and you are subjecting the battery to increased stress (though this is true of the system approach in general and not so much true to your ICE kill method--I was assuming more aggressive acceleration in ICE-kill). All it takes is potentially one slip of the mind to do permanent damage to your battery pack (like talking on the phone and forgetting about it for example). But again, it's your car.

    The SOC graph does have hysteresis. Bob is correct that if you want instantaneous SOC information you'd need something like a ScanGauge system.

    If your foot is light enough to drive 4 miles w/o the gasoline engine coming on at all--why not just do that? It seems like the safer thing to do here...

    Anyway, just my 2 cents. Feel free to ignore me :).

    Andrew
     
    #5 linuxpenguin, Mar 24, 2010
  6. adric22

    adric22 Ev and Hybrid Enthusiast

    Joined:
    Apr 6, 2009
    642
    144
    2
    Location:
    Fort Worth, TX
    Vehicle:
    2018 Chevy Volt
    Model:
    Plug-in Advanced
    That is what I would prefer to do, actually. Unfortunately, the Prius insists on starting the engine and running it for approx. 5 minutes before I would be able to do this. usually by the time the engine has warmed up, I'm pulling into the parking lot at work. So unless I let the engine idle in the garage for 5 minutes before I leave work (which would waste tons of gas) then the next best thing is to find a way to keep the engine from coming on at all.
     
    #6 adric22, Mar 24, 2010
  7. linuxpenguin

    linuxpenguin Active Member

    Joined:
    Mar 6, 2007
    352
    182
    4
    Vehicle:
    2005 Prius
    Mmm, fair enough :). I would recommend you get a Scangauge then since it doesn't require having a laptop in the car with you to read data and can be mounted to the dash in a relatively care-free manner. I'm not 100% it's compatible with the 2001 Prius--you may want to see if anyone has the PIDs for SOC on the Gen1 Prius.

    Alternatively if Bob has something better / cheaper you may want to go with that.

    Good luck!
    Andrew
     
    #7 linuxpenguin, Mar 24, 2010
  8. orange4boy

    orange4boy Member

    Joined:
    Oct 20, 2009
    231
    43
    15
    Location:
    Vancouver BC
    Vehicle:
    2003 Prius
    Model:
    N/A
    On another forum, I describe how I installed a 1500 watt coolant circulation tank heater which warms up my Prius to 70˚C in less than an hour. When I start the car it runs for about 20 seconds then shuts off so I'm in stage 4 before I leave my driveway without the fuel hungry warm up. It's been good for ~25% better FE on my short commute.

    If you are handy, It's another option.

    It's in the transaxle preheat thread linked below:
     
    #8 orange4boy, Mar 28, 2010
(You must log in or sign up to post here.)