P0AA6 explanation

I use the Autel AP200. Take a look at post #37 in this thread Gen2 OBD2 app review, and also this thread
Autel Maxi AP200 - go buy this . The INF codes are in the freeze frame data for the P0AA6 code. The INF code will narrow down the area of the car that is having the problem. The Autel AP200 costs about $60 to $70 on Amazon.
Autel MaxiAP AP200 OBD2 Scanner Bluetooth Wireless OBDII Auto Diagnostic Tool with Full System Diagnostic

Base on the pictures of the battery, I would guess that the high voltage leakage is in the battery area. The INF codes would confirm that.

 

I’m currently experiencing low insulation resistance in the hv battery pack. I have taken all the modules out and tested each one and finding most with varying resistance from 500 megohms down to < 5 meg. I have tried cleaning and sanding the plastic surfaces and that initially appeared to be the fix but later on when I started assembling the pack the low insulation resistance returns. The batteries perform satisfactorily in terms of capacity and appear to have normal SOC characteristics but have low insulation resistance thus setting off P0AA6 on each trip. I checked all of my spare modules that are the same age and they exhibit similar symptoms. I have checked all of the wires, relays, and battery Ecu, all normal. I am guessing that the modules I have all have leaked some electrolyte which has left conductive paths on the module exterior.

 

So, what you are looking for is any module that has some continuity to chassis ground (ie, the battery mounting housing - frame).

What I do is to have all the modules bolted together to the frame. Then use my multimeter to check for any voltage (millivolts) between each battery terminal to the mounting frame.

If the pack is fully assembled and I have a "bad" voltage reading (more than 0.00mV), then I remove a busbar in the middle of the pack and recheck. I keep dividing and rechecking until I have narrowed it down to the individual faulty module(s).

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Thanks for your reply

I have multiple modules that have some conductivity from the output terminal to the module exterior using my Fluke insulation resistance meter with the 500v setting. The resistance varies from a couple megohms to the maximum 550 meg ohms that the Fluke displays. I have attempted cleaning the exteriors with little success. What does help is to lightly sand the plastic housing. I suspect that over the years KOH electrolyte has seeped out from the terminals and left a conductive residue on the module exterior, especially in the area underneath the terminals down to the base surface. The modules function satisfactorily capacity wise. Currently the combined parallel insulation resistance of the modules is around 3 meg ohms which is high enough to not trigger a fault . I’m going to try doing some light sanding to the module exteriors- plastic section to remove the leakage paths, otherwise I may go ahead and replace all of them (they are 20 years old)

 

removal of busbars shouldn't be necessary. The isolation fault location is the short to the case and will be the zero reference for a voltage reading. Connect black lead of multimeter to the case and just take voltage readings, where the polarity reverses on the meter reading is where the short is located. Based on the voltage reading at that point, you can determine which module and even which cell in the module is faulted to the threaded insert.

 

You may be looking at it incorrectly. The isolation fault isn't from internal electrolyte to the plastic case, it's to the metal threaded insert on the bottom of the module. If there's a ton of seeping electrolyte, it could be from that, but normally internal microcracks where the insert was pressed into the module eventually allow electrolyte to make contact with the metal insert and therefore electrical continuity with the case. Ive seen this cured just by finding the right module, removing the fastener loosening the adjacent ones to allow a slight "pry it up" gap and slipping a piece of Scotch Super 44 between that metal insert and the case for insulation and leaving that fastener off.