Hi

I have a 2006 FEH with ~120,000 miles. It mostly drives fine except I am noticing that it increasingly seems to lose charge over night or within a few days of not being drive. It turns on and drives but with no hybrid assist/very slow acceleration for the first ~15 minutes of driving. The hybrid cooling system also seems to be faulty in that the battery will heat up and not allow the vehicle to kick into hybrid mode or charge. There is a short window (between 15 to 45 minutes of a given drive) when the battery is charged enough and cool enough to allow Hybrid mode.

(A mechanic recently told me that if the battery isn’t charging because it is overheating it might be why it has low SOC the following drive… seems plausible to me)

I have BCM codes P0A81 and POA1F and PCM codes P2521 and P2524 (screenshot attached)

I have never gotten a stop safely event while the vehicle has been warm and running ForScan for the last month or so I haven’t seen the hybrid battery get hotter than 108 even while be driven for hours on end on recent Death Valley road trip

From ForScan I also have seen a large difference in SOC and temperature between the most and least charged battery cells. For example the max charged cell will have 80% SOC while the minimum cell will only have %40 SOC. And once at “operating” temperature cells with have a ~20 degree range from hottest to coolest. Is this normal or does this indicate bad cells ? (screenshot attached to illustrate point)

Other potentially pertinent info: The low voltage battery seems to be fine and AC blows pleasantly cool in the cabin. Both HVTB service harness was replaced and BCM was reprogrammed in 2018 ~40,000 miles ago. Over the 50,000 miles I have owned the car I have gotten reliably between 24 and 27 MPG and haven’t noticed any declines with the recent increase in issues. I wonder if these issues have always been present and are getting worse?

Questions:

• Do I have both a failing hybrid battery and a failing hybrid cooling system or would replacing the hybrid battery fans fix both issues?
• If both parts of the system are failing would replacing the battery include the fans?
  • I might be able to replace the fans myself, but I don’t want to replace the fans, if fans are included with a replacement battery.
• Is it possible only some cells are bad, and I could have the battery reconditions for less than the cost of a full replacement battery?
• Are they any stats or testts I could monitor using ForScan to get a sense of the overall battery health?

Sorry for the long post, I am just trying to wrap my head around the different possibilities and figure out the most efficient and affordable path forward.


P Codes found

What I monitor in ForScan highlighting temp and SOC difference between cells

 

When this happened to me it was due to a broken A/C refrigerant line. Due to the first two codes, it is likely the same issue. I would also run the BCM self-test (which checks the fans) and check the battery compartment air filter as it could also be an issue with one of those.

 

I cleared the codes and the two AC codes have never returned. My AC blows cold so I am not sure what set those codes in the first place.
I did BCM self test and determined the fan on the passenger side didn't turn on, then I replaced both fans myself following these videos:
https://youtu.be/t01s5Y_eloY
(took me maybe 2 hours and ~$330 for parts and tools.)
My car is running much better and more predictably, the only thing now is that POA1F still come back after clearing codes.My guess is that I have a few bad cells and that might be triggering POA1F (ForScan data suggests that I have at least one cell that will not charge above 55% SOC and that this low cell drops quite a bit while sitting. Rebalancing allow doesn't charge this ler ow cell)

I would be interesting in hearing any other thoughts on POA1F now that I have solved the other codes.

 

A bad fan would explain the problem. If this happens again, take a look at the battery evaporator temperature (there's a PID for it). If that overheats in sync with the battery temperature, there's a problem with the refrigerant line going to the battery (this can fail while the passenger compartment A/C still works).