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Custom Enginer PHEV (8kWh)

Discussion in 'Prius PHEV Plug-In Modifications' started by krousdb, Aug 29, 2009.

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  1. krousdb

    krousdb NX-74205

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    Today, on the way back from the beach, I picked up my car and drove it home. I used up what was left in my Aux pack and only got 70 MPG on the way home. The 15 MPH headwind and heavy rain didn't help much. That bought my tank down to 90.2 MPG at 640 miles or so.

    I decided to install the second charger which arrived on Friday. Everything had to come apart because I have the chargers under the battery carrier. Before removing the batteries, I cyced through all of the cell voltages. I knew that I had 3 weak cells because earlier in the week, I saw them down at 2.4-2.5V before charging. Today they were 1.3, 1.5 and 1.7V. Just my luck, each was in a different pack. So I spent most of this evening replacing the bad cells with some spares that Jack sent me. Then I tested the new charger. Now I am letting the cells balance in the rebuilt packs before putting them on charge. So tomorrow, and possibly the rest of the week, I will be non-PHEV.
     
    #81 krousdb, Sep 7, 2009
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  2. Flying White Dutchman

    Flying White Dutchman Senior Member

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    so you simple get new cell under waranty..

    3 bad cells is a lot.
     
    #82 Flying White Dutchman, Sep 8, 2009
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  3. krousdb

    krousdb NX-74205

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    3 out of 64 is a lot if you assume that they were bad to begin with. For a few days I only had 4 balancers. I could have damaged them myself.

    The main problem is that I am pushing the pack too hard, I'm guessing 90% DoD. When you have cells that are not perfectly in balance, you can easily discharge a few too far. When I am back up and running, I will be running one converter until I am able to plug in at work. Then back to two converters. If I can't keep to less than 70% DoD, I will consider adding 2kWh more.
     
    #83 krousdb, Sep 8, 2009
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  4. miscrms

    miscrms Plug Envious Member

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    I'm not sure the Voltage change overnight is a cause for concern in of itself. I would guess this is mostly the difference between the resting voltage of the pack and the "active" voltage. For example, 100% SOC of a lead acid battery is ~12.5V and yet the system voltage when the car is running and the alternator is on is usually ~13.5V. When the car turns off the battery voltage will initially be high, and then settle back to its ~12.5V resting 100% SOC value. I believe that the NimH modules exhibit a similar effect, resulting in the discrepancy between these two graphics:

    Typical observed voltages during operation:
    [​IMG]
    http://www.eaa-phev.org/wiki/Image:Index.54.jpg

    Resting pack Voltage vs. SOC and Temperature
    [​IMG]
    Prius PHEV TechInfo - EAA-PHEV

    Based on these curves, it seems like a typical voltage during operation at 60% SOC is going to be in the 225-230V range, while the normal resting voltage at 60% SOC at 20 deg C is ~205V. Note that there is also significantly lower Voltage at a give SOC for a cold pack vs. room temp, and a hot pack should be even higher.

    For your error condition, it seems like you must have triggered SOC drift (recalibration). This would generally require that the battery pack voltage at least temporarily goes above 242V. When this happens the controller throws out its coulomb counting SOC value and revises SOC upward very quickly. Please try and capture the error code if this happens again. I believe this is another thing the CAN-View does well if the Scan Gauge doesn't. This has been one of the concerns with this method from the start, it certainly seems to work most of the time but some questions remain in my mind about whether it is robust across a wide variety of operating conditions (temperatures, SOCs, loads etc). One possible difference in this case is battery temperature. When the battery is cold, I believe it has a higher internal resistance than when hot. Normally the controller would reduce CCL to keep this from being an issue. Since the Enginer pack doesn't know about CCL, and just sees what it thinks is a very low pack (based on its low voltage) it starts pumping current in. Since the pack may not actually be as low as the converter thinks it is, and its resistance may be high (causing more delta V for the same current) That would account for the voltage climbing very quickly and causing SOC drift and potentially your error condition. If thats true, we may start seeing a lot more issues with these kits once the weather starts getting cooler. Maybe its not a problem when running only one converter, or maybe this isn't it at all, but its definitely something that needs to be looked into and understood.

    Rob
     
    #84 miscrms, Sep 8, 2009
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  5. krousdb

    krousdb NX-74205

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    Back up and running tonight. Beginning tomorrow morning, I will be running one converter. 8 kWh should get me to work and back without much problem.
     
    #85 krousdb, Sep 8, 2009
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  6. krousdb

    krousdb NX-74205

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    9/09/09 Morning Commute

    One Converter only!

    Driving Conditions
    Dry roads.
    Ambient Temp = 64F
    Winds = 4 MPH tail wind
    Windows Closed
    Fan set to level 1, no AC.

    Route
    12.0 Miles suburban at 25-45 MPH
    52.0 Miles in the Interstate, CC set to 55MPH
    3.6 Miles suburban at 45 MPH

    Results
    Trip ScanGauge MPG = 80.6
    Trip MFD MPG = N/A ***     See note
    Current Tank = 61.6 Miles
    Tank ScanGauge MPG = 82.0
    Tank MFD MPG = 81.8

    Analysis
    Very similar to yesterday's morning commute with no PHEV, 65.5 MPG

    PHEV Performance
    80.6/65.5 = 23.0% Improvement using one converter only.

    Notes:
    *** Filled up the tank 6 miles into the drive, MFD ended at 81.8 MPG for 61 miles and does not reflect the cold start this morning.
     
    #86 krousdb, Sep 9, 2009
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  7. kiettyyyy

    kiettyyyy Plug-In Supply Engineer

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    Are you running just one converter to be on the safe side?
     
    #87 kiettyyyy, Sep 9, 2009
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  8. krousdb

    krousdb NX-74205

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    No,
    I am running one converter because I cannot plug in at work yet. I don't have enough capacity for the whole commute using two converters, so I am using one.
     
    #88 krousdb, Sep 9, 2009
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  9. krousdb

    krousdb NX-74205

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    #89 krousdb, Sep 11, 2009
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  10. ericbecky

    ericbecky Hybrid Battery Hero

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    Edit: Question deleted. - (figured out answer to my question)
     
    #90 ericbecky, Sep 11, 2009
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  11. Flying White Dutchman

    Flying White Dutchman Senior Member

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    what was the question and the answer? haha
    share it with us
     
    #91 Flying White Dutchman, Sep 11, 2009
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  12. ericbecky

    ericbecky Hybrid Battery Hero

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    I was wondering if there was another way to see the info. Some people who would want to see it may be banned or or not able to otherwise access the site Dan linked to.

    The solution: If you are banned from a site, sometimes you can use an anonymous web service to access said site.
     
    #92 ericbecky, Sep 11, 2009
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  13. Flying White Dutchman

    Flying White Dutchman Senior Member

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    so in other words you are banned on that site haha.
    what did you do....
     
    #93 Flying White Dutchman, Sep 11, 2009
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  14. ericbecky

    ericbecky Hybrid Battery Hero

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    <redirects thread back on topic>
    Dan,
    I look forward to seeing your results. Thanks for posting them.
     
    #94 ericbecky, Sep 11, 2009
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  15. krousdb

    krousdb NX-74205

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    Finally I had a chance to go on some errands. This was on mostly rural roads, speeds ranging from 35-50MPH. I made two stops and then back home. 30 Miles total with two converters, 128MPG which included a cold start.

    During this trip I was in EV below 40 MPH about 1/4 of the time. The remaining time, above 40MPH I was loping along at 1200 RPM. I noticed something interesting. On three occasions, then the SOC got down to 70%, the MG sent a heavy charge, around 30A, into the battery until the SOC got up to 75%. Then switched back to current flow out of the battery. No matter how I tried to back off the throttle, the instantaneous dropped to 50MPG during that charge cycle.

    Anyway, no DTC's or MIL's. All is good.
     
    #95 krousdb, Sep 12, 2009
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  16. Dan.

    Dan. MPG Centurion

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    Yep, I see that too without the kit. I tried to start up a thread on heretical mode over at CMPG but it didn't really get anywhere.

    I classify it as three different states. For need of a buzz phrase, "Heretical Charge", "Heretical Assist" and "Heretical Balance". Super Highway Mode (SHM) is a special case of Heretical Balance.

    The Heretical Charge is really interesting. If you cruise at about 1200 RPM at about 40mph you'll end up charging the heck out of your pack. Kinda freaky since It won't break out of the cycle till charge gets real high. I did find that over 70% soc, WS would allow a lot of power from the pack.

    Anyway if you can manage to hold throttle steady on the highway you will get the same "lock" condition on the flip side. You will get into a heretical assist that will pull a constant 10A (possibly more at higher SOC) while your loafing around at 1200 RPM. It's enough power to hold up speed at 60 mph although I haven't tested 70 mph or 80 mph.

    I'll see if I can't pull out my notes and try to put something together after all.

    11011011
     
    #96 Dan., Sep 12, 2009
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  17. krousdb

    krousdb NX-74205

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    Cool! So the current injection isn't causing this to happen. I didn't notice before because I hadn't been monitoring BTA and BTV previously.
     
    #97 krousdb, Sep 12, 2009
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  18. krousdb

    krousdb NX-74205

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    Ran a few more errands tonight, ended up at 175MPG at the end of the trip. The total for today was 56 miles at 148 MPG.
     
    #98 krousdb, Sep 12, 2009
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  19. krousdb

    krousdb NX-74205

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    Drove about 50 miles today with the family on board. Church, lunch, movies and back home. With 4 passengers and 300 lb of PHEV, we were close to the max weight limit. So about 5 minutes into the drive, I get into the crazy charging mode that I spoke of before, exept this time, it didn't stop at 75%. When I hit 77% SoC, a code flew and got the christmas tree lights. Before clearing the code, I noted that it was "P0000".

    My search found several hits on P000. So I guess it's not even a real code? If anyone knows what it is, please let me know.

    Anyway, after clearing and rebooting, the SoC showed 59%, exactly what happened the last time. My guess is that all that crazy high MPG driving yesterday had something to do with this. Maybe we shouldn't be concerned so much on how much current can be tolerated at any given time, but rather the total current mismatch over a given period of time. I have driven a thousand commute miles, about 2/3 of them with 2 converters running and no DTC. The two times I get a code have been either right after grid charging the OEM pack or after a few long drives with a high percentage of EV. Back to work tomorrow so lets see if I stay code free on my commute.

    Anyway, after the code, we proceeded to point A 15 miles away, stayed for an hour and proceeded to point B 5 miles away, stayed for an hour, proceeded to point C 20 miles away, stayed for 2 hours and back home, 10 miles away, 50 miles total. The whole time I had no access to EV mode, perhaps a result of the code and the fact that it was warm and I parked in the sun each time. We had A/C on for the 20 miles between point B and C. Total trip, 50 miles, 92.1 MPG. Not bad for not having EV mode and AC use.
     
    #99 krousdb, Sep 13, 2009
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  20. krousdb

    krousdb NX-74205

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    I couldn't help myself. Last night, before plugging in for the nightly recharge, I decided to go for an all EV mode drive. The OEM battery had cooled sufficiently to allow EV mode. So off I went, both converters injecting about 18A onto the DC bus. I stayed on gently rolling rural roads, speed limit 35-45. No one was out last night so driving around at 30MPH didn't cause any road rage. So I managed to go 8.7 miles before a low cell alarm went off (the pack was largely depleted when I started so I was happy to get that far). The trip average was 23 MPH, much of it at 30-33 but dropping down to 20 going up the hills. The OEM pack SoC did drop from 72 to 60% during the drive. Overall I was pleasantly surprised at the ability of the two converters to keep up with the demand. No codes thrown last night, and none thrown on the way to work. I am starting to form a theory on what is causing the P0000 code, but I need some time to prove it out.
     
    #100 krousdb, Sep 14, 2009
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