2009 not going into gear, several codes

Sorry, but the arrows in the OP's picture looks to be pointing to the battery input studs on the contactors (right side of the pic is the battery case- left side is the cables going to the inverter)

I would think any voltage reading from one of those studs to chassis ground indicates leakage in the HV pack or possibly the battery ecu.

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The silver box in your pic (between the 22 and . 7) is the battery ecu. Towards the "top"of the pic on the ecu is an orange cable with an orange connector. Unplug that connector. If you still have any voltage reading from either battery lead (at the relay studs) to chassis ground then yes, you have to disassemble the pack to replace module(s) as needed.

Then you are opening the whole "replacing a single module with a different capacity" can of worms. Maybe you can talk to the members here and "guesstimate" the condition of your pack and supply a decent replacement. Or you replace the bad one and recondition all your modules (individually with hobby chargers and lots of time, or a grid charger and less time). Or you end up playing "whack a mole". Or you decide to get a new pack.

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Ah, thank you, I was turned around. (I must have been picturing my Gen 3, which is turned around with respect to Gen 2.) Yes, those are the input studs. Sorry, I should have slowed down and looked again.

Seeing the leak voltage at only 22 from one end, 0.7 from the other, at least means the leak impedance is still rather large, compared to the impedance of StephenJ's meter.

If there's only one leak, I guess I would expect it to be within a couple modules of the SMR3 end of the battery. That's if there's only one.

 

The sharpie marks are normal.

Once you remove the busbar assemblies, you can do another voltage check. Put the black lead on the case and using the red lead, touch each terminal on each module. You should see about 0 or a small voltage that quickly dissipates. If it shows something higher (but will still be 8 volts or less) and it hangs around, you've found a problem. Maybe not THE problem, but A problem.

 

The 'short circuit' is somewhere between the terminal where the safety disconnect fastens and the relay where you measured 22 volts.

This 'leak' will have NO measurable effect on overall battery voltage or individual module voltage.

Be very careful if you have the safety disconnect installed. That disconnect (being removed) is what will save your butt if you accidently put yourself in contact with each end of the battery.

 

With the HV disconnect plug fully engaged, you would measure 200+V across the two relay input studs (ie, full HV battery potential). You are trying to locate a high resistance "connection" from somewhere on the HV battery to chassis ground. Understanding all the details of what (can) happen is above my pay grade- that and I've never seen it myself so I just don't know all the details.

That said, the battery ecu has small wires connected to the HV battery to measure block voltage at the orange connector (each block = two modules in series). And the ecu is connected to the low voltage (12V) system as well. And corrosion at the orange connector and the circuit board is not uncommon. So you could have a leak in a battery module (a "connection" to chassis ground through electrolyte) OR damage to the ecu ("connection" between HV and low V circuits or chassis ground through corrosion in the ecu) Unplugging the ecu is quick and can eliminate it as a possibilty.

There have been all kinds of module leaks on the forums- pinholes in the metal side plates, or cracks in the plastic around the bottom mounting holes or around the connection studs). BTW- the busbar corrosion you have is typical and not unusual.

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The leak (or possibly leaks), somewhere in the battery, are not like solid, low-resistance connections. They are probably tracks of leaked electrolyte, contamination, and/or moisture, with some fairly high resistance.

Your voltmeter itself has a certain resistance. When you put your voltmeter into the circuit, you are creating a circuit that has some voltage sources (the leaks) with some resistances, and your meter with its own characteristic impedance, which could be replaced in theory by a "perfect" voltmeter and that resistance in parallel with it. Thévenin's theorem tells you there's a way to simplify that whole mishmash into an equivalent with just one voltage source and one series resistance and your voltmeter's resistance pulling it down, winding up with the 22ish volts you are seeing.

 

^ This.

Other than the weird way we use the words "open" and "closed" in electronics ... when you close a switch, it conducts, and when you open the switch, you open the circuit, meaning it doesn't conduct. Just have to get used to it. The relays are "open" (not conducting) when the car is off, and when the HV ECU completes its safety checklist and decides to start the car, it "closes" them.

Like other relays in the car, they could be tested by taking them out and applying 12 volts on a workbench to the coil terminals and measuring the resistance across the contacts. But it's probably not necessary; I don't hear of them going bad very often, if at all, and it's much more likely the HV ECU has decided not to close them, and will give you codes explaining why.

 

As stated, those relays have "normally open" contacts inside (ie they are open circuit)- the ecu has to energize the relay coils in order to close the contacts and complete the circuits from the HV battery to the inverter. Since your car does have a fault, the ecu is just leaving things turned off as it was programmed to do.

There's really no need to test the relays (you could remove them and test like any other relay if you wanted to). The system is pretty good about setting the appropriate code if there's a fault with one.

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Technically it might be possible to have some sort of weird fault with the wiring or a relay but that's really really unlikely. I would be pulling the HV battery out and do a closer visual inspection. Then pull the busbars and test each module to ground ad needed to locate the offenders.

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StephenJ,

I just pulled codes P0AA6-526 and P0AA6-612 on my 2009 Prius. 73,000 miles on mine. Same DTCs as you had. So I'm researching the Forum as preparation for troubleshooting my Prius.

Did you make any further progress on your vehicle? If so, can you share what you determined, and how you proceeded?

 

Unless you happen to have the OP's car, you might consider looking in the service manual for the code troubleshooting procedure so you can perform tests and determine what's wrong with your car.

The list of possible faults that can cause the INF code 612 is pretty short: HV battery module leak or battery ecu are the most likely. Wiring or relay fault are possible but unlikely.

You could get some safety gloves and a capable HV multimeter, remove the disconnect plug and upper battery case, then start checking the HV system for voltage readings to vehicle chassis ground. Once you get a voltage reading, disconnect things (ecu, busbars, etc) until you isolate the part that still have voltage to chassis ground. Then replace that part.

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I had similar symptoms on my 2002 Prius in 2017. A couple batteries modules had cracked cases and that resulted in leaking electrolyte which shorted to ground. I suspect the battery modules cracked due to freezing at near zero degree temperatures a couple weeks before the malfunctions started.