Need help hacking a 2002 Prius THS

Discussion in 'Generation 1 Prius Discussion' started by Persanity, Apr 28, 2012.

  1. Persanity

    Persanity New Member

    Joined:
    Apr 28, 2012
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    Watertown,Connecticut
    Vehicle:
    2002 Prius
    Model:
    N/A
    Hello,

    I just acquired a 2002 Prius for free that was left sitting for 9 month.

    I would like to try to get this car running in a unique way.

    More on that later.

    This is what I know of the car.

    It was being driven daily for a few years and it died one day.

    Dealership said it was the battery but they drove it away I guess.

    A week after it died at the house and they did an oil change on it but I was told the wrong oil was used, Have not had a chance to check yet.

    I got a simple code scanner from advance auto and pulled code P3030.

    I took apart the battery and all the terminal nuts, bolts, and battery connector plates are pretty corroded.

    The orange connector for the current sensors that connects to the battery ECU apparently did one of 2 things and probably both,

    1. High voltage vaporized 2 of the individual terminals on the battery ecu side of the connector and some of the plastic on the wire side of the plug.

    2. it caught fire momentarily after it vaporized the 2 terminal prongs

    I did open up the battery ECU and everything appears to fine on the inside. I have no way of knowing if it is good though. I just can't see any visible damage or scoring marks on the individual board components.

    Before I replace the ECU I am going to try wiring the individual current sensing leads directly to the ECU board.

    Now I only know simple auto repair stuff and simple house electronic repairs but did build a simple electric motorcycle once so I have a good grasp on the technology in general just not the Prius.

    Here is where it should hopefully get interesting.

    I have seen threads about people not wanting to use the battery pack but those threads never got anywhere.

    I need help understanding exactly what communication is going on between all these parts so I can trick the car into thinking the battery is always full and then not ever wanting to use the battery beyond starting the car.

    I understand the Prius engine has no torque at low speed and by itself is not a good choice to move the car.

    I would like to always use the power generated by the generator to drive the car and use a very small battery or capacitor pack only to provide the power to start the ICE.

    It is my understanding the car already has a mode where it does this just not till its over 34mph.

    So the task becomes to get it to always operate that way regardless of speed.

    As far as tricking the battery ECU,

    Can a "device" be made that plugs into the battery ECU that gives the readings its looking for?

    I was thinking of use capacitors to provide the voltage/amperage the ECU is looking for so it always says "Hi! I am fine" to the rest of the system.

    Can capacitors be used to a mock battery pack?

    If anybody can point me in the right direction for GEN 1 resources I'd appreciate it.

    Understanding how everything talks together would help alot.

    Thank you,
    Aaron.
     
  2. seilerts

    seilerts Battery Curmudgeon

    Joined:
    Mar 7, 2010
    3,325
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    Santa Fe, NM
    Vehicle:
    2005 Prius
    Model:
    N/A
    Search here for 'Frankenstein'. It has all the info that you need to fix your battery. Anything else would take way more time and money than it is worth. Thing with capacitors is, how do you get them charged in the first place? They will only hold a charge for a minute or two. Now, one interesting thing is that many, many people have rebuilt their packs using two Gen II packs, but it is not clear that all of those old Gen 1 modules are actually bad. It is even possible that all of your battery modules are good, and that you just need to clean things up. For example, you have not posted anything about the terminal voltage on all 38 modules. If you were to find that they were all e.g. 7.3V - 7.4V even after sitting for a year, then that is a good battery. If you find that you have some at 6.1 and others at 7.3V, then you have a problem.
     
  3. Persanity

    Persanity New Member

    Joined:
    Apr 28, 2012
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    Watertown,Connecticut
    Vehicle:
    2002 Prius
    Model:
    N/A
    the 2 end cells(the one all the way to the left and the one all the way to the right) were 6.5v the next 3 or 4 batteries going towards the middle were 1.2v the middle 30 or so are 0v.

    I was thinking of getting a 7.2v NiMH charger for RC packs and trying to charge the individual cells and seeing which held a charge and which won't.

    With the capacitors for starting the car I would use the standard protocol to charge them like they were the batteries.

    I.E. Use enough capacitor "packs" to make a mock battery.

    The capacitors would discharge faster and charge faster then the batteries.

    My thinking is this,

    If the computer still used them like it uses batteries wouldn't it try to keep them in a 60-80% SOC at all times?

    Then the SOC would just be different cause the power density of the capacitors would be far less then the real battery pack, right?

    I don't know enough about how the THS does what it does at this point to know if this would work.
     
  4. Persanity

    Persanity New Member

    Joined:
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    Watertown,Connecticut
    Vehicle:
    2002 Prius
    Model:
    N/A
    Let me ask another question, The newer Pri have a boost converter to get the 200v pack to 500 or 650 volts. Can I use something similar here?

    Lets say I end up with 5 or 10 good cells from the pack, Can I boost the voltage to what the computer expects for voltage?

    For right now I just need the car to think the battery is saying it is OK so I can check the status of the rest of the car.

    Ultimately the entire drive train is coming out of the car as the car itself can not be registered or insured for use on the road.

    Does anybody know a good 7.2v NiMH battery charger for testing used cells?

    I am looking at the MRC superbrain 989 but would love a cheaper option.
     
  5. seilerts

    seilerts Battery Curmudgeon

    Joined:
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    Santa Fe, NM
    Vehicle:
    2005 Prius
    Model:
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    Supermate DC6 is the cheapest viable option for a charger. Modules must be held under compression when charging, even if all you have is a C clamp and two pieces of wood.

    If you have 0V in modules, then they are most likely bad. The fact that the middle ones are all zero while the end ones show some life means that the battery has suffered chronic overheating. However, like I was saying, it may be possible to get old Gen 1 modules really cheap, because many people have upgraded to Gen II, even though they may have only had 1 or 2 bad modules. The modules don't have to be perfect. They just need to hold 3-4 amp hours at >7.2V -- that will buy you at least a few months.

    The battery ECU monitors the string in 19 groups of 2 modules (12 cells). It is a voltage divider, which means that it will expect to see 15V at the first pair, 30V at the second, 48v at the third, ..., 285V at the 19th pair. If it detects one pair being low, then it will divert charge from elsewhere in the pack to bring the laggards back up.

    So, you must either match the battery topology, or spoof/replace the battery ECU. People have been able to replace the Gen II battery ECU. This opens the door to using e.g. a custom Lithium pack or other novel replacements. However, Gen II utilizes CAN Bus to connect the battery ECU with the HV ECU. Gen I has a different protocol for sure, some kind of serial bus. I don't know if anyone has ever been able to replace it. You would need to determine the protocol and monitor the traffic in a working car in order to figure out how to replace it. So try to dig up some old Gen 1 modules in case you can't get most of yours to hold a charge.

    You also face an uphill battle with the gas engine. It is possible that you already have a few stuck open valves since it has sat so long. Go out and give the crank three full turns right now.
     
  6. Persanity

    Persanity New Member

    Joined:
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    Watertown,Connecticut
    Vehicle:
    2002 Prius
    Model:
    N/A
    I can not get to the car til Monday, long story on that, but I will try then.

    Right now I am just toying with ideas because the car was free and can't be used as a car.

    If I hooked the transaxle to a different engine, one with a normal starter, how would the hybrid system respond if the generator just started providing power?

    I know the transaxle and inverter have been used in pure EV projects but I think they are all Gen II parts.

    I want to try to reuse as much of the original system as possible but I know that won't be possible in alot of cases.

    Lets say I can source really cheap 7.2v RC packs but they are only 1 or 2amp hour each pack, Would that be good enough to start the car(assuming the original engine in perfect condition)?

    Also, if the Prius cells are dead from sever overheating, could the rehydration trick discussed elsewhere on this site be used to try and fix them?

    There isn't really a budget for this project btw.
     
  7. Mr Camouflage

    Mr Camouflage New Member

    Joined:
    Aug 27, 2011
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    Perth Australia
    Vehicle:
    2001 Prius
    Model:
    II
    That is exactly what happened with my Prius, except only one of the terminals melted (cell closest to the computer), as it arced to the casing and melted a hole in that. Although most of my cells were still good.

    Dash showed the Red triangle, but the engine would still start.

    I have replaced the 2 end cells as a pair with 2 second hand cells from ebay, and bought new parts to replace the damaged/melted/burnt parts (bus bar, vent tubes, thermo loom etc). Put it all back together and so far so good. Car is still unregistered, but i have taken it on small trips around the suburb to test it out. It gets inspected this friday, and will hopefully be back on the road then.

    Good luck with your project. I'd start with trying to get some cheap gen 1 cells and rebuilding the battery pack, rather than what you have planned.