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Chris (aka-Moose)
Chris (aka-Moose), Auto Technician
Category: Toyota
Satisfied Customers: 947
Experience:  16 years of experience
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I just did a rebuild of my 2005 prius gen2 HV battery,

Customer Question

I just did a rebuild of my 2005 prius gen2 HV battery, reinstalled it and am having some other new problem getting the computer to acknowledge the HV battery and activate it.

I own a 2005 Prius with a Gen 2 HV battery pack. I got the codes from the dealer for a weak battery, Chose to try and rebuild it myself. Ordered 3 replacement cells off ebay, removed the battery, replaced bad cells (3), and returned battery to car only to find just as many error lights as before and the prius will not operate or engage drivetrain. Need help to figure out what to do next.

Detailed background:

Out of the blue upon starting, I got the red triangle, check engine, and ! light. Had no driving issues that I could detect. Drove home. Took to dealer next day - while driving the 1-2 miles to dealer noticed performance lag and hesitation and when I arrived at dealer and stopped I noticed the intake cooling fan for battery continuing to run (never heard it before). Dealer checked codes and got:

P0A80 - hybrid battery pack

P3013 Battery block 3 weak

P3014 Battery block 4 weak

Was quoted $3500 for a replacement battery. After spending a few days on-line and watching you tube, I realized this was an easy (so I thought) repair I could do in my workshop. I removed the HV battery and used multimeter to test each of the 28 cells. 2 of them registered 6.40v. All the rest were in a respectable 7.5-7.7 range. I order 3 replacement cells claiming to be holding 7.5v or better. The bad cells were #21 and maybe #25 as counted from the inverter so It was no big deal to remove the end cap slide off the last 8 cells and put the good ones in place. I chose to position the 7.5v cells at the very end as I heard that grouping like voltage together might be a good idea (not sure, but figured it might not matter). No problems reconnecting and reinstalling HV pack. Started car and instead of success I got even more warning lights (added ABS and the rear traction light as well as an orange indicator on the console screen and the note that the A/C was no off - it had not been on and now the AC button is not a pressable option). The car would not shift into gear.

I pulled the battery out again to see what was wrong. Retested every cell and found a 3rd bad cell reading at 6.4v. Good thing a bought an extra off ebay! I pulled it out and replaced it with a 7.5v cell. Re-installed into the car - same result. Pulled it out again and figured I needed to do some battery conditioning. I went through each cell and used a 12v 1.5amp charger to boost each cell. Some boosted fine, up to 7.80v others did not move much beyond the original 7.55v. This only took matter of a minute for each cell (I saw some people on-line doing it for 5 minutes each cell. My charger would cut off after not much more than a minute). Re-installed battery and still same results.

I have since rescanned for new error codes and got none.

I have recharged the 12V aux battery and it is holding above 12V. I monitored that battery with a multimeter as I tried to start the car and I see the voltage drop a little below 12V but it does not spike up to 13-14V like it should when the inverter kicks on.

I don't hear the three or four clicks I normally hear which I believe are supposed to be the relays engaging the HV battery. MY dashboard display warning lights stay on. I do get a air conditioner off message on the MFD and a red error icon. When I try to engage the transmission the display flickers and resets to neutral and the vehicle does not engage into drive.


Submitted: 2 years ago.
Category: Toyota