Gen II Prius Individual Battery Module Replacement

Yes all my modules showed a consistent internal resistance of 0.029 ohms across every bank on the pack (viewed using mini VCI). I bought a standard Sylvania H6054 glass headlight and was thinking I should be able to hook up both the high/low beams at the same time to hopefully draw 120W (55W + 65W). Would increasing the load make it any easier to find a bad module?

 

Just a report back and Jeff was spot on with the voltage drop. I tested one of my spare cells which had a capacity of approximately 6000 mAh and loaded it for exactly 1 minute (used stopwatch) with the high/low beam (120w) headlight setup and saw right around 0.22v drop during that time. I'll try and post a pic of my test setup so others can see what I did. I'm going to pull the packs again this weekend and see if I can find the bad one (this should at least verify if in fact the battery is the issue).

 

Remember that there is also a voltage drop in your test leads. You should connect a DVM directly to the module terminals so that the drop in the load wires does not affect your measurements.

JeffD

 

Ok well I have some good news......
1) I found the problem and
2) It looks like everyone should be doing a load test too when rebuilding their hybrid packs!!!

I've attached a pic of my test setup so people can see what I did and how to build one for testing themselves.

• Headlight (65w high beam, 55w low beam.....you'll use both)
• 16 gauge speaker wire (50ft roll)
• Common wall switch
• Stopwatch (used daughters ipad, googled "stopwatch online" in safari)
• Heavy gauge terminals (yellow)
• Multimeter w/alligator clips (voltage)

Here's the test results on the packs as promised (each was tested with the 120w load for exactly 60 seconds.......start voltage, end voltage, voltage drop):

Pack 1 (passenger side, 12 modules)
10.71v, 10.17, 0.54 <= BAD!!!!!!!
10.73v, 10.49, 0.24
10.72v, 10.48, 0.24
10.72v, 10.48, 0.24
10.71v, 10.47, 0.24
10.71v, 10.47, 0.24
10.79v, 10.54, 0.25
10.76v, 10.52, 0.24
10.78v, 10.54, 0.24
10.75v, 10.51, 0.24
10.77v, 10.54, 0.23
10.74v, 10.51, 0.23

Pack 2 (middle, 6 modules)
10.73v, 10.51, 0.22
10.72v, 10.50, 0.22
10.73v, 10.51, 0.22
10.71v, 10.48, 0.23
10.73v, 10.51, 0.22
10.73v, 10.50, 0.23

Pack 3 (driver's side, 12 modules)
10.71v, 10.48, 0.23
10.73v, 10.51, 0.22
10.69v, 10.46, 0.23
10.71v, 10.49, 0.22
10.68v, 10.45, 0.23
10.72v, 10.49, 0.23
10.68v, 10.45, 0.23
10.72v, 10.49, 0.23
10.69v, 10.46, 0.23
10.72v, 10.50, 0.22
10.69v, 10.47, 0.22
10.73v, 10.51, 0.22

Note: For people finding this later, these are 9.6V (8 cell, 6,500 mAh) Highlander modules so capacities are similar to the Prius, but voltages will be different.

 

It's official, my issue is solved. Interior is back in and I got a chance to clean everything in the process. The car has had this weak module since I bought it (got it with 220k on odometer) so I was never really able to experience what a hybrid was supposed to be like and wow it stays in EV mode for a long time compared to how it operated before. Fuel economy has shot back up too.

Getting the new module in was a bit of a pain on a Highlander because the 3 battery packs inside are held together with rivets. So in order to make them servicable you need to drill out the rivets on one side and replace them with 10-32 machine screws, then tap the end plate with threads to accept the screws. The cross bands also need to be drilled out to allow the screws to pass through. Whatever you do, the rivets are steel so don't use aluminum rivets to put it back together, they are much too weak and may blow apart when the modules are under pressure while charging! I used some heavy pipe clamps to squeeze the pack together in order to get the screws in and used a little blue loctite to keep them from vibrating loose. Other than that just keep everything very well organized and take lots of photos because you'll have a pile of parts to go back in and it's hard to remember where it all went 1-2 weeks later.

Few more tips:

• Get mini VCI so you can monitor your battery in the vehicle both before and after rebuilding
• Make sure to disconnect both the 12v aux battery and remove the orange service plug before touching the hybrid battery
• Get at least 2 quad chargers (Hitec X4 AC plus work great), rebuilding goes alot faster that way
• Only cycle every other module at one time and keep them as cool as possible during the process
• Use good quality leads (chinese stuff is very poor gauge, use 16 ga or better), building your own works best
• Cycle your modules using conservative settings (7000 mAh and 2A charge rate worked best for me)
• Modules with the highest capacity should be moved to the center of the pack (they will even out over time)
• You need to do both load testing and capacity testing to verify all your modules are in good shape
• Take your time and don't rush.....if the car isn't ready when you need it, rent one.

Hopefully my posts will help others looking to rebuild their own packs no matter what hybrid vehicle you drive (Prius, Camry, Highlander, Lexus, etc).

 

Very good job Mtl_hihy.

 

I'd like to say a big thanks to all the folks in the PC community......invaluable resource and a wealth of knowledge for sure.

Couple more funny anecdotes with the car I forgot to mention. I had a neighbor walking the block and happened to pass by while I was initially pulling out the packs for testing. She saw the vacuum at my feet and assumed I was cleaning the car so she mentioned she should be doing the same with her car. I told her that wasn't really what I was doing and she was surprised so she came over to have a look. When she saw what I was really up to she looked in horror like I just ran over her son. I had a similar thing happen when I went to Walmart to look for a headlight to use for load testing and another patron asked if I needed help. After explaining the situation you'd have thought I told the guy I was robbing the place and by the time I left he was calling me MacGuyver. Moral of the story is don't tell people what you're doing and expect them to understand because for the most part this stuff is way over their heads.

 

Anyone know why my Hitec 4x wont automatically start the next cycle? I set it to 3 dsch/chg cycles with a 5 minute waste time but when the alarm goes off at the end of the cycle, I wait the 5 minutes and it does nothing so I have to manually start the next cycle. Dont want to have to babysit this thing. Thanks!

 

When you start the cycle are you holding the start button on the screen where it shows DCHG>CHG 3?

Also did you go into "user set program" and set these too?
1) waste time = 5 min
2) safety timer = off
3) capacity cutoff = on and 7000 mah (set to 4500 on the 4th cycle to be ready for balancing)

 

Ok that was my mistake, not starting the cycle in the chg/dchg screen. My numbers are not looking good tho. It must be hitting delta at low mah numbers in the 3000 to 4000 range on the charge cycle. I adjusted the delta sensitivity up to 12mv and brought the charge amps down to 1 from 3. Hope this helps. Would it be a bad idea to set the delta at 20mv? My cells dont seem to be getting hot or anything.

 

Basically, I wont be getting much balancing going on at these numbers. Or are my cells that far out of balance? Any input would be helpful, thanks!

 

If that is a pack from a 2001 then yes your capacities may actually be that low. Don't mess with the deltas, leave them at default (already been tried and got poorer results). It won't help you to begin generating heat in the cells either (leave capacity at 7000 mAh) so I would just keep cycling them to see if they improve. Keep charge current at 2A or less and watch to see if the capacities are improving. If this is a gen 1 pack you may benefit from buying a later gen 2 pack and using those modules to rebuild yours. Hopefully someone more knowledgable than I can comment on the latter as well.

 

Yeah my hope was not to buy modules, but I guess these are shot. Heres my numbers on 4 modules.

 

Oops posted one twice. Anyway this sucks. These modules must be crap. Ill reevaluate this project. What is 3 more cycles gonna do? Guess its not worth my time

 

Good thing you posted those pics.......something doesn't look right here, those numbers are WAY low!

1) 1717>1815>1729
2) 1358>1547>1567
3) 1633>1784>1783
4) 1554>1725>1730

Are you using cheap chinese leads on these? I suspect you may be having the same problem I did when I first did my testing and that is that the gauge on the wire is too small and/or not well connected so it screws up the delta sensing on the charger causing it to stop well short of a full charge. Obviously this is extremely important when your trying to rebuild a hybrid battery pack.

You can see what my setup looked like here:
http://priuschat.com/attachments/img_20140426_174849-jpg.64227/

I strongly suggest taking the time to make your own charger leads (all available from Home Depot):

• Roll of 16 gauge speaker wire CE TECH 50 ft. 16-Gauge Stranded Speaker Wire-Y280730
• Banana plugs GE Banana Plugs (10-Pack)-72999
• Ring terminals Gardner Bender Vinyl-Insulated Ring Terminals (50-Pack)-10-106
• Terminal crimper (don't use a cheap one!) Klein Tools Journeyman Crimping/Cutting Tool-J1005
• Use the OEM 8mm nuts on the batteries to secure the leads' ring terminals to the battery module

Then retest 4 different modules (in case you damaged the last 4 by not starting your cycles on the DCHG>CHG screen) and run those for 3 cycles to see if they do any better. Post up what you find when you do this.

BTW there is an "edit" link under your post on the left if you want to go and remove the double pic on your 2nd cycle above.

 

Just a follow up on mine, fuel economy on the Highlander has gone from around 10-10.5 l/100km (23-24 mpg) up to around 7.2-7.5 l/100km (30-32 mpg).

Edit: My mileage has gone back down a bit since summer requires constant use of the AC but still never get worse than 9.0 l/100km (29 MPG)

 

Danahurling,
I completely agree with MTL_hihy about the test leads. You are only injecting about half of the charge you need to inject into the modules to net a good result. Pls reevaluate what you're doing and try again. You need to inject at least 7000mah into them.

 

I used the leads that came with the charger. So yeah, chinese. Heading to home depot in a bit. Hope thats what is going on.

 

Yeah I knew that with these low numbers I wasnt getting anywhere. Im gonna build some good leads and start over. Gotta get these numbers up sarge!

 

Sounds good and don't forget to reattach your pics again to your post above (looks like they all disappeared now).