Voltage intermittnently going negative in banks 2 and 3

Hi Everybody,

Last fall I picked up this 2007 Prius. I live in the Midwest and I had to buy it in a hurry. Let's be blunt and say I didn't pick the right car and I ended up with a rather rusty prius that is now throwing a red triangle.

Some pertinent details- It looks as though this car sat for a while. As far as the extent of corrosion present, I would say imagine as bad as possible while still barely working. This car has spent it's life in the upper midwest. The red triangle first appeared in May showing a PA080 HV battery failure and the banks voltage off code. The car began throwing a red triangle every day when the temperature went above 80 which for where I live is sweltering.

While watching the voltage live on toyota techstream banks 2 and 3 would dive from voltage being within .01 of all the other cells to being -15 volts or so and then it would go back up.

When I pulled the cover off the battery a very long black wire that is very narrow guage came off with the cover. It was puzzling because it looked like none of the other wires in the battery.

Immediately after this happened I spoke to Eric, he was very helpful in weighing my options. Since then.

• Obtained tech stream on an old laptop
• I have removed the battery and tested individual cells with a multimeter.
• All cells were within .1 of each other under bench testing conditions.
• Cells tested 7.91 volts or 7.92 volts before
• I cleaned buss bars with vinegar and cleaned posts with steel wool.
• Reinstalled with dielectric grease on all connecting surfaces.
• Ordered used set of bussbars, computer, controller etc for the battery.
• 4 new cells arriving tomorrow.
• Voltage on posts tested at 210 before going back into car.

My plans going forward

1. Remove bussbars and re torque all hardware going into cells.
2. Possibly replace banks 2 and 3 with new cells. (I know this is a bandaid solution.)
3. Possibly replace buss bars and computer.

I installed it back in the car and got the same codes and a P3000 code.

I'm not in a position now to buy a new battery soon. I would like to purchase an additional battery and rebuild it in my spare time, but junkyards are pretty strict about collecting a core and not selling me the cores they get in return, which sucks.

If anybody knows of a salvage yard in from Duluth MN in the North to Peoria IL in the south that would sell me an hv battery for a reasonable price without a core required I would be interested. Or if you have a battery to sell I would also be interested.

My questions as of this point.
Is it possible corrosion reached the computer?
Is it possible to wire two of these batteries in series so that weak cells within one battery won't trigger these red triangles?
What is the torque for the battery posts?
Is this likely a sensor attached to the bus bar issue?
Are there any other likely culprits that cause the intermittent negative voltage other than corrosion?


My skill level:
I am not an EE or a very mechanically minded person, my career areas are natural resources, special education and educational technology. But my father was an auto mechanics teacher and I have built my own computers and RC car style battery packs for competitive robotics I'm good with terms and theory, not the best at applying it though. I do most of my own car maintenance and can get by asking my brother and friends for help. None of them really know hybrid batteries though. I have all the tools I need and 6 RC car chargers to drain/charge cells if I need to and a laptop running Techstream.

Any advice would be greatly appreciated.

 

The wires looked rough and the sensor fitting that bolts on top of the buss bar was very corroded.

I spoke to Eric about the battery costs. He was really helpful in explaining the whole situation, unfortunately he is about 5 hours away from me so while he is the closest person I don't think I can afford to buy a battery pack from him right now.

The bolts on the modules were torqued to approximately 35 ft lbs. Which is probably too much.

 

I think I figured out the problem. It looks like a whole pin completely corroded off. I think I am just going to order a new battery computer. I don't think jamming a pin in there and doing a dubious solder job or redoing all the connections is a repair that will hold well for any length of time.

Thanks everybody for the help. Despite this being a kind of ongoing frustrating process I am glad that I learned some of the ins and outs of this battery.

 

I have a used harness for that side, it's not new and it shows some corrosion, but it looks way better overall. I ordered a package from ebay that basically had all the wiring and relays and such. It came from New Jersey so I think it's a medium level of corrosion and stress.

I'm also possibly just buying a parts car tonight too.

I appreciate you letting me know that. I read in other threads the corrosion ran all the way down to the line to the computer and made the computer fail.