'06 completely dead after hybrid battery cell replacement

Hi all,

I recently replaced a battery cell in the hybrid system of my '06 Prius (~ 111 k miles). When I finished the replacement and attempted to start the car, it was completely dead. I assumed the 12v battery had been drained. Everything appeared to be fine after a jump start, but after ~ 2 mins of driving my poor beast went back in to limp mode with all the associated warning lights.

There was some moderate corrosion on the terminals in the hybrid system, so I suspected that was the culprit. After thoroughly cleaning them I decided to double check the voltage of each cell, and discovered a different one was slightly low (7.0 when all others were 7.2 - 7.3). I replaced that one and reinstalled the battery, and again found the car to be completely dead. I haven't tried to jump it yet for fear of the same situation. Any ideas of what is going on here? This isn't the original hybrid battery on the car, as I had that swapped for a refurbished one ~ 1.5 years ago when the hybrid system stopped working. Trying to save some money and do it myself this time.

Thanks!!

P.S. I double checked and the orange key is locked in place and installed correctly

 

I just replaced the one cell without balancing the pack, but all were 7.2 - 7.3, including the replacement cell.

After the initial jump the would car start and drive in limp mode just fine. It only went dead again after I reinstalled the hybrid battery the second time. Should I still replace the 12v? The 12v battery going dead doesn't seem typical for a hybrid battery repair.

 

Thanks for the welcome, and good idea! I assume the cable is to connect to a phone instead of a code reader? I did borrow a friend's code reader before the battery failed initially and got the following codes:

HV ECU:
P3000: Battery control system

HV Battery:
POA80: Replace hybrid battery pack
P3017: Battery pack becomes weak
P3000: Antilock brakes
C1259: HV system regenerative fault
C1310: Fault in HV system/fault in ACTV brake booster solenoid

 

Haven't checked the 12v yet, but I will this evening and report back.

 

-_- of course I meant the 12v going dead in conjunction with the hybrid cell replacement and working fine otherwise, not the battery going dead in general.

Thanks for the information about voltage in the rest of the modules; I hadn't realized that they were low enough to be worried about.

 

Unfortunately all I can provide right now are the codes I posted above, as the car is completely dead.

My main concern is making things worse by jumping the car if there is a problem other than just some bad hybrid cells.

What I was trying to explain was that it did not seem typical that changing a hybrid cell and reinstalling the battery pack would deplete the 12v battery. Not that a battery going dead in general is atypical.

 

12 volt battery is at 2 volts right now. No date code filled out unfortunately, but it's an intimidator 9A51P. I got the car in late 2017 and haven't changed the 12v, so it's at least that old.

I'll just reiterate that the 12v started the car and otherwise worked fine, except on the first connection with a hybrid pack with newly replaced cells. After the initial jump I got the car running several times in limp mode with no problems (except the non-working hybrid pack, of course). I just find myself in need of a jump again and am wondering if the draining the 12v upon first connection with the hybrid pack is a symptom of a larger problem.

 

I do have a battery charger that I charge 12v boat batteries with, but I'll have to check if it's compatible with this one.

Aha, I did not disconnect the 12v during either replacement. The first time I replaced a module it wasn't running for about a week, but now it hasn't been running for about six weeks as I have been out of town. I wasn't driving much; maybe an hour or two per week. I would regularly go several days without driving, and actually the initial issue with the hybrid pack came up after the car sat for three weeks.

I'm out of town again but will check the voltage of the hybrid pack when I return in a few days. I don't have a grid or other charger aside from the one I mentioned above.

Thanks a bunch to you and everyone else for taking the time post your questions and suggestions. I'll update the thread with codes when I'm able to get them.

 

I'm sorry for the lack of updates; I've been out of town yet again. Really hoping to find some time to work on the car in the next couple of days.

Ok, thanks for the guidance.

Looks like the charger is compatible! I'll give it a try and see how it goes.

Bummer about the usage, as I don't expect that to change. My fiancee drives about the same amount as I do, so maybe I can get her to take the car on the days when I don't use it.

 

For anyone still following the thread,I returned home and was able to jump the car. Happy to report that I drove it around for about an hour and had no issues with the hybrid system! The 12v, on the other hand, is shot, as the car will not start without a jump. I'll be putting a new one in tomorrow, hopefully ending this chapter in the saga of repairs!

Thanks for all the advice!