Yet Another Hybrid Battery Replacement

Having just purchased a very high mileage used 2005 Prius for a good deal and putting about 1,000 miles on it before getting the triangle of death, I was faced with the thought of spending $3,500 for a dealer battery replacement or attempt to DIY for about $50. Thankfully #ryousideways just finished on a a great documented write up in a thread here and a must read before you get started as I am just going to summarize my experience with pictures.

My Error Codes:
P0A60 - Voltage difference between battery blocks is higher than standard
P3019 - BATTERY BLOCK 9 BECOMES WEAK

1st Lesson Learned - You can't trust the error code descriptions from any OBD2 reader, except at Toyota. Make sure to check them online against official Toyota repair manual descriptions.
2nd Lesson Learned - Don't assume you battery is bad without first making sure your battery ECU is not bad (P0A1F)
*I will include a documents link at the end of this for items I found helpful

Tools Used -


3rd Lesson Learned - Disconnect the 12v battery before proceeding, or you will find you cause even more error codes when finishing the job
4th Lesson Learned - Remove the G2 Service Plug before proceeding, but also remember when done and re-installing it's not actually in place until you hear the clicking lock when pushed down
5th Lesson Learned - Don't remove the HV battery cover as I did in the picture below before removing from the car, it loses it's rigidity



6th Lesson Learned - Use the sharpie liberally and measure each batteries voltage. Even though the computer error said battery #9 they are measured in pairs and turns out to be #18
7th Lesson Learned - Be very careful with the wire clips, screw threads, and everything in general. Don't believe me read another very useful thread by #YY4U on all the hurdles he had to overcome.



- Note in the two pictures above the color of the replacement "new" battery and #27. Apparently this isn't the 1st swap this car has seen. Also note you have to start at #1 and remove in order to get to #18

Disclaimer: In the picture below I wasn't actually re-balancing #18 while putting the batteries in parallel; I just forgot to take a picture during balancing it, so hooked it up to show for the camera.

Now here is where I am also going to go against what the experts on this forum tell you; I did not re-balance the whole battery pack. Why, well because of time. And where I understand it can breath new life into old batteries and find other bad batteries in the process. I decided to take the chance and choice to deal with that problem when I come to it versus spending the long time or charger investment upfront to "do it right". I am happy to say since the install a month has passed an over 1k miles on the replaced pack. YOUR RESULTS MAY VARY



8th Lesson Learned - I went with the B6AC charger because Amazon had it cheap on prime 2 day shipping and unlike the other charger DC6 I was able to plug this one into the wall socket.

The overall high level steps I followed were:
1. Remove the battery
2. Replace the bad cell with a known good cell
3. Charge the new cell to within +/- .2 v of the rest of the pack
4. Put the whole pack into parallel to level out the voltage
5. Put it all back together

Overall the next step of putting the pack into parallel and taking it back apart was the hardest part of the whole bit; especially when taking it apart. It's like defusing a bomb, minus the boom . Think the kids game Operation.



9th Lesson Learned - There is no need to crisscross the wires when putting the pack into parallel except maybe at one end. I did it because #ryousideways did it this way and this is how urban legends are started.



So after popping it back in the car and buttoning it up, that's about it. All in all it took about 6-8 hours over the course of 2 days. I am not an expert but I am comfortable working on cars and DIY around the home electrical installs. Take precautions, be smart, and by no way use this as a guide on how to, just yet another helpful encouragement to tackle it yourself. Results will vary! Happy to help where I can.

Here are the PDF documents I read up on before starting and found just by surfing the web:
- 2004 Prius Repair Manual RM1075U - Section 21-54
- 2004 Prius Repair Manual RM1075U - Section 21-98
- 2004 Prius Repair Manual RM1075U - DTC P0A80
- 2004 Prius Repair Manual RM1075U - DTC P30xx
- Hybrid Battery Safety
- Installation Notes
- Toyota Hybrid Course
- Toyota Prius Dismantling Manual
- and last go back and read those other two threads before starting yourself

10th Lesson Learned - Since I was paranoid about my rebuild and wanted to watch it like a hawk I downloaded the Torque Android App, installed the Prius custom PIDs, and purchased a cheap bluetooth OBD2 from Amazon so that I can monitor the pack in real time.

 

Yep, cleaned any corrosion at a contact point. Mostly on the outside of the rings.

Britprius - that would make more sense

 

Just wanted to give a quick update, it's been a couple of months and 5, 000+ miles since the hybrid battery cell replacement. Good news, no issues even without rebalancing the whole pack. City avg ranges between 42-45 mpg and hwy performing better at 45-55 mpg.

 

So just checking back in with a status update it's been about 3 years and 45k miles since this swap without rebalancing and knock on NiMH still going strong.

Car is currently at 230k on the odometer.

 

I think the biggest thing I attribute it to would be luck; it's been awhile since (3 years) since I read all the original reasons to rebalance but if I am remembering correctly the biggest gain of rebalancing is to...

1) breath new life into your existing pack
2) find early detection of other cells that are not yet failing but will be failing soon (hence my luck part)

I am sure now that I am being boastful about luck; it will bite me in the arse soon