Battery module compatibility

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by macman7500, Mar 15, 2025.

  1. macman7500

    macman7500 New Member

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    Hello, I want to know if I can mix 3rd gen and 2nd gen Prius modules to refurbish the battery? I already replaced around 10 modules from possibly a 3rd gen into my 2nd gen, but I'm having some problems with the red triangle and p0aa6 code. Are they compatible?

    Just want to make sure because the seller of the modules said they are but on the forums say otherwise.
     
  2. JC91006

    JC91006 Senior Member

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    The modules are compatible. However used 3rd gen batteries are usually significantly worse off than 2nd gen modules. 3rd gen cars are really hard on the batteries making the used modules from their cars practically useless, unless you can obtain some really low mileage examples.

    Also P0AA6 errors are not specifically a battery issue. Did you have this code before you replaced the 10 modules?

    It also very unusual to have a battery with 10 failed modules, unless the battery you're fixing has already been fixed before by a rebuilding company (not original). These rebuilders are horrible and will mix all kinds of bad modules from different generations together, and that would be the only time I can think where you need to possibly replace 10 modules to make it work again.
     
  3. macman7500

    macman7500 New Member

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    I cycled all the modules more than 3 times from 2 different 2nd gen battery packs to see which ones were the best and had to order at least 10 more online that were used condition that were likely from a 3rd gen but not sure. The packs I have were basically cores and not great condition.

    I'm trying to get at least 5000 mah discharge capacity and 7500 mah charge when I cycle the modules. I did all that but I still have problems and going to have to bring out the battery for a 3rd time. On the dr. Prius app it looks like the blocks are not balanced and discharges and charges fast even though I balanced the modules for 24 hours prior to install.

    My research indicates the p0aa6 is likely from a module shorting out to the battery case and the frame of the car. I didn't have this code before.

    That's good info about how 3rd gen modules are almost useless and I would have to somewhat agree.
     
  4. MAX2

    MAX2 Senior Member

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    It is possible that one of the modules has a damaged case and is causing a current leak.
    You can check with a voltmeter between the module terminals and the module case and its attachment point at the bottom, there should be no voltage.
    Modules from Gen3 can be used when the donor had a low mileage and got into an accident, and the battery is in good condition. The modules themselves are getting better in new generations, manufacturers are improving their characteristics. But engineers are also trying to squeeze as much out of them as possible.
     
  5. macman7500

    macman7500 New Member

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    I disassembled and checked all the modules and around 6 were leaking voltage on the bottom mounting bolt. Some were 1 volt or more. And others were between 0.05 and 0.03 volts. 0.03v not a big deal but I figured the module is going bad and going to leak more voltage later so better to replace some of them. The rest were 0.00 volts.

    Do you think it's a good idea to put tape on the bottom mounting bolts of the modules that have 0.03 volts to isolate them from the case and keep using them longer?

    That's interesting how the 3rd gen and later cars use more energy from the hybrid pack, essentially shortening the lifespan but at the same time the chemistry is getting better. The 2nd gen is conservative with its energy usage.
     
    #5 macman7500, Mar 18, 2025
    Last edited: Mar 18, 2025
  6. MAX2

    MAX2 Senior Member

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    If there is a leak, it doesn't matter 1V or 0.001V. This module should not be in the battery.
    The thing is that in series-connected modules, the constant voltage reaches more than 200V. This voltage will go to the case, which will make the battery unsafe to use. Therefore, the battery ECU will show an error and stop working.
    No insulation will help here, the voltage and current values are too high.
     
  7. Hayslayer

    Hayslayer Member

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    I'm pretty sure the standard black electrical tape from a reputable manufacturer is rated for 600v. I have an HV battery in my car right now that has one module with a double tape layer under the mounting ferrule (no fastener installed) to insulate it from the case. Been in for about a year and a half. I wouldn't recommend doing it for more than a few modules, since you don't want to lose mounting integrity, but it's working just fine for me clearing that P0AA6 where I had about 5 volts on the ferrule. It's not a difficult job if you have a reasonable understanding of how electrical systems work.
     
  8. MAX2

    MAX2 Senior Member

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    It is only attached by two neighbors, there is no own fastening. The pressure inside the module when heated can squeeze it out like an accordion.

    I believe that it is acceptable as a temporary measure in the absence of good modules.
     
  9. macman7500

    macman7500 New Member

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    Is it bad that I didn't put over half of the mounting bolts on the bottom of the modules? The problem is the case is slightly bent and the holes don't line up. Need to figure out a fix.
     
  10. MAX2

    MAX2 Senior Member

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    Fasteners are required.
    BULGED BATTERY MODULES? NEVER SEEN THAT BEFORE | PriusChat
     
  11. Hayslayer

    Hayslayer Member

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    The modules are interlocked together by the keys on the sides. There is no squeezing out like an accordion of one module that doesn't have a fastener. Gen 1 modules had two fasteners per module. Gen 2 reduced that to one fastener per module. Skipping one fastener means you have three consecutive modules with no support on that one side. Still not enough to cause a problem. I would be wary of skipping two consecutive fasteners on the same side, but even that is unlikely to allow enough bowing to cause a catastrophic failure.
    Most instances of the modules bursting out of the clamp frame is when few to no fasteners are installed.

    The base of the battery is relatively light sheet metal and can usually be flexed to align the holes. A lot of times, the holes don't line up because the modules were not aligned perfectly straight or not properly clamped prior to installing onto the base. Do not tighten any bottom fasteners until all are at least started by a few threads. I always assemble batteries with it sitting vertical. Install the 10mm hex nut loosely on each clamp to hold the base in place, loosely install the fasteners on one side of the base, then install the other side. This allows maneuvering the base as needed to align holes. Then tighten to 48 inch-pounds.

    As to having installed only half the fasteners, it wouldn't be the first time I've run across a used/previously rebuilt battery like that. I wouldn't be comfortable with it.

    The clamping system is just like an empty aluminum drink can. You can put a lot of weight on an empty can, but once you bend the side of it, the can will immediately collapse. The clamping system on the modules can withstand an incredible amount of force, as long as it's maintained straight. That's one function of the base and the fasteners, keeping the modules straight. If the modules expand, and start to bow upward, it will lead to immediate catastrophic failure. They'll bend the metal tubes, the clamp will fail. Cats and dogs play together and all the end of the world stuff happens. The most important fasteners are the ones in the center, because that's where a bow or droop will start to form in any unsupported material, especially something trying to expand, like a warm battery pack.. The fasteners become less important as they get closer to the outer clamping plates.