How to Change the HV Battery CELL / Module/s on Gen 1 Prius

I wanted to thank the community by posting this tutorial on how to change out a suspect cell/s throwing a CEL: P1636, P3000 and/or P3006 aka ECU Malfunction ( OBD2s) and/or Uneven Charging (TIS)

First of all, I want to acknowledge members Patrick, Bob and S Keith, your combined experience and kindness encouraged me to be brave and tackle this task head on, failure is not an option

Here is the link to my very first post of my Mother in Law's G1 02 woes :-( Gen 1 2002 CEL OBDII Code P1636 HV ECU Malfunction | PriusChat. Did not want to write all the drama here, just a How to...

#1 Rule, BE SAFE and take your time. Better to take extra precautions as not to injure yourself or worse.

DEADLY VOLTAGE IS PRESENT UNTIL ALL THE BUS BARS ARE REMOVED FROM ONE SIDE OF THE BATTERY. WHILE REMOVING THE BUS BARS YOU ARE WORKING WITH LIVE DEADLY VOLTAGE. (Thank you Strawbrad)

Safety First:
1. Use your emergency/parking brakes and/or wheel chocks
2. Roll the windows down just in case you accidentally lock the doors
3. Disconnect NEGATIVE side of the battery then the Positive side, remove and place on a good trickle charger

4. Remove the HV Battery ORANGE FUSE


Access to HV Battery:
5. Remove all items from trunk, liners, spare wheel and jack ( it sucks when you lose a bolt/screw under it ) Side liners can be tucked away

6. Remove the rear bench seat ( lift front up then out, remember the orientation of the seat belt buckles ), unbolt 14MM bolt for the center lap/shoulder belt/buckle and back support ( lift up off the 3 hook retainers )
7. Most of the bolts/a few nuts are 10 or 12MM sockets, There are a ton of these so be prepared.
8. Back to the trunk, disconnect 5 electrical connectors,

Unbolt the bolts for both sides of the cooling fan for the HV battery. I suggest keeping these fasteners in the trunk area so you will not have left overs or run out on install. Remove 2 12MM bolts on each side of the HV Battery
9. Back to the rear passenger area. Continue to remove the upper HV Battery cooling tube, held by 2 10MM bolts and a plastic clip ( It will be allot easier to install the cooling hoses with it off and installed last. Start on the right side or farthest from the driver. When you get to the driver side, STOP and locate the black plate with and ORANGE plug.

For safety, put on your rubber clad gloves or linesman gloves. There should be no charge here but you never know. Remove the 3 nuts and carefully pop the plug open with a pick tool. These two thick orange wires are held by 2 special bolts. BEFORE REMOVAL, PUT YOUR DIGITAL VOLT METER TO DISCHARGE THE CAPACITOR AT THE INVERTOR, BE SAFE Keep a close eye on the orientation of the thin metal lining placed under the wires, you want to make sure it goes back the same way.

Now you can access the last 12MM bolt to remove the HV battery. I tapped it, just to be safe :-P
10. Disconnect rubber vent tube,
11. You need a helper here, the HV battery is around 170-175 pounds so unless you are really really strong, it will be pretty tough to do this by yourself.
12. Use GLOVES, the edges are super sharp, when you grab the ends makes sure you are not grabbing on the wiring harness. Lift up about 2 inches and out. CAUTION, it is heavier than you might think.



Work Table Prep or Cart Prep:
13. Prior to removing the HV Battery, get your work area ready.
14. Remember you need to gain access to the bottom edges to remove all 78 8MM screw/bolts if your plan is to re-organize the blocks. I elected to put stronger batteries towards the center and weaker ones on the ends so they can cool better. I used 4x4" block to support the HV battery and I was able to easily rotate as needed. I saw a fella on youtube that used a plastic cart on casters to accomplish the same thing.
15. You will be using 8 & 10 MM sockets and a pick tool to flip the locking tabs on the bus bars once you get the cover off.

HV Battery Cover Removal:
16. CAUTION, DO NOT close the circuit between + & - on the batteries. DO NOT LET A TOOL TOUCH Both leads on the batteries or you will get some nice fireworks :-o Put your LINESMAN gloves on for extra safety,
17. Remove the remaining cover bolts, just for fun Toyota decided to put one size 27 Torx bolt.

18. Carefully remove the cover, remember edges are sharp.
19. Remove the white plastic cover on the HV ECU.


HV Battery Dismantle:
20. Remove Bus Bar's exterior black covers, here is where the pick tool comes in handy
21. I like to always remove Negative side first then Positive side on dismantle and the reverse on install. CHOOSE A SIDE AND REMOVE THE REAR OR FRONT BUS BARS. BE EXTRA CAREFUL THESE LEADS ARE HOT SO USE YOUR GLOVES AND A TOOL WITH PROPER INSULATION. IF NEED BE PUT A RUBBER SLEEVE ON THE END OF YOUR 10mm SOCKET. DO WHAT YOU NEED TO DO TO BE SAFE!
22. At the HV ECU, Disconnect the two Negative connections, 1 bolt 1 nut, follow that wire back to the last cell, it is connected the Negative side, disconnect it then disconnect the positive connection bolt at the HV ECU. DO THIS IF YOU ARE PLANNING TO REPLACE THE BUS BAR WITH SENSORS

23. Go to the other side to the center black cover, disconnect the Negative side then Positive side.

24. This may be not necessary, but better safe then sorry , continue to remove all Negative side nuts.
25. Remove all Positive side connections on the battery cells.
26. Using a plastic panel ( don not use a screw driver! ) remover, pry the bus from the cells, more likely than not they will have what appears to be sealant or electro-lite residue making it very difficult to separate the bus bars from the cells. Just be careful and pry away at it until they all have separated.
27. On install, I highly recommend using a new bus bar with sensors to help your repair last a bit longer, if not, take a brass wire wheel to the copper plates, safe solvent to clean the corrosion to clean them. A compromised sensor will give you false readings.

The rear bus bars can be cleaned and reused.

28. Even though you have totally dismantled the HV Battery, take care to keep from making contact with both leads at the same time when handling the cells in groups. Individually they are harmless.
29. Remove the Battery Rubber vents from top of the cells, no need to remove them from the side bracket, just put it off to the side. I used some di-electric grease for an easier install.


30. Remove temperature sensors, take note of which cells they are on for install. Again the pick tool is great here to help with the disconnection from the plastic tabs.
31. Remove side retaining plate, top and lower retaining bolts.
32. Gaining access to the bottom, remove all 78 8MM hold down bolts/screws ( I would recommend a 12V hand driver or you will get a work out )

34. Now we are ready to remove the cells in pairs or if you feel brave, remove in groups. I did groups of 6, keeping the original BLOCK sets intact. The plan was to only replace those suspect cells and re-organize the blocks.

Installation is in REVERSE order, sorry :-(
Note: I used a torque wrench at 48inch pound on the battery cell leads and all electrical connections except the 12v Battery.

For extra measure I also placed some di-electric grease at areas where I saw green patina before I cleaned it.

For the Immobilizer Reset:
Turn ignition to ON ( Not Start ) and leave it there while you do something else. I placed a Vise Grip on the trunk light switch to save the 12v Battery and I placed a trickle charger while waiting for the reset to be complete.

20-30 minute later, VROOM ( did oil change, cleaned air filter, fixed passenger door lock and cleaned, sealed head lights and aimed the head lights properly, Hewh, I am tired )

CAVEAT! You are doing this at your own risk, I nor this forum are responsible for any damage that may arise from this tutorial. It is for information purposes only. I am a DIYer, so if you are at all skeptical, DO NOT DO IT, hire a real HV mechanic and save 4 hours of your life.

Please forgive me in advance, I just finished this task and writing this up on pure memory

Break a Leg!

Jim

 

Here is the latest TIS report:



The difference in the highest and lowest block is only 0.36 volts WOOHOO!

 

I must be tired.

Yes, I agree I hate install in reverse order.

I forgot to mention they way I aligned it was to install the cells in groups of 6, place 2 screws/bolts in place and moved to the next group. This really help keep the cells in place and compressed them as well. It really made putting on the side plate easy. I read and saw how people had issues lining things up but this incremental approach worked well for me.

Thanks again Brother Steve, Yes. I will do a load test but I was just too tired and really wanted to take care of the other maintenance issues for my MIL. Man she is so happy. I am just glad I can do this for her. Some arsehole wrench wanted $100 to change light bulbs, what a POS.

BTW, prior to swap the difference was 1.24 volts difference in High and Low

 

Me too, a cold one first

 

Oh My, my very first Sticky. Geez on the Porsche forum after10K of posting 50+ tutorials, never had a sticky. I want to thank you gentlemen, this sticky belongs to all of us

Dr Bob, Yes, I will will do a Load and Charge reading to see if there are any gremlins.

Brother Steve, Oh no, I did not get the charger in time, it is still in route and MIL really needed the car to work for work. I think I can pull the battery within an hour now. So much easier the second time around.

Leve, WOW, you a crazy man, I love it, Next time I will do the same. This way I don't have to fight my step son to get out of bed to help me.

 

Update:

Had MIL come back so I can do the Forced Discharge and Charge.

Happy to report the Voltage Difference from HIGH to LOW has decreased even more. down to 0.10 volts on Forced Charge SOC to 72%


Will post static report in 90 minutes:

0.19 volts variance Static, Not bad

 

Oh Thank You Master Brad!

This is exactly what I was looking for, contribution from more experienced members like you to chime in and assist us amateur DIYers. I sincerely appreciate you taking the time to point us all in the CORRECT and SAFE direction. I searched, read and watched countless videos. I was pretty disappointed in what I found as a "guide".

I totally concur, the Orange plug from the Invertor could have a definite charge from the capacitor. On my very first removal/tear down. I did put a DVM on the two posts to insure there was no residual charge. In fact, this part was scaring the poop out of me. I WILL INSERT YOUR STEPS.

LEADs, Here Here, Yes, I too had a mishap. Moron me used a brass wire brush to clean the residue on the nut removed leads, uhhhh. NO! I was so lucky the handle was made of wood. But I got a nice size arc and worried I damaged the cell. Nope just carbon residue from the spark. Glad to know about the rear thick orange wires are insignificant, I was just being methodical in my tear down procedures

Again thank you for your contribution!

Jim

 

Update:

I am happy to report MIL's Prius is Happy and Healthy

 

Update:

Well, Block 15, threw a CEL "battery too weak", checked TIS, confirmed plus P3006 of course, the block went down to 11.1 volts and charged high as 20.2 volts, swapped the older cell ( cold voltage alone was 6.03 volts vs 8.11 of the NOS ) out right away to insure it will not swell due to overcharging observed on TIS

3 hours, She is all well now. Man I am really fast on tear down and assembly :-P.

Happy and Healthy New Years everyone.

( Haven't been around lately, rebuilding my 911's engine with 316K miles on it )