HV Battery Cell Replaced, Now What?

You have to determine if the replacement module you put in is actually a good module. Then you have to make sure it's capacity is a good match to the rest of your pack.

What you are doing is a very unreliable repair. There's a lot more to repairing a battery module than just swapping out a module.

If I had to guess, it would be you have more than 1 failed module.......and/or the module you put in is not a good match to the rest of your pack. It also can be the module you put in is also a failing module.

 

8 volts doesn't really mean anything as most modules fail when they start dropping in voltage. you have to read the codes in the car to determine which block has failed and look at those modules

 

You need to read the codes on the car. I'm pretty sure it's the new module that you put in that's not compatible or is a failing module.

I'm not really sure how you can buy a refurbished module that cannot be refurbished

 

welcome! the reason you're saving up the $3500. is because replacing one cell is hit or miss. some get lucky, and think they've beat the system, and some don't.
if you can do all that yourself, why not look around for a new battery closer to $2,000.?

 

Read this entire FAQ (it's very short): Texas Prius Battery Replacement

An autoparts store can read some (but not all) of the codes for free.

 

Get the codes read and it'll save you a lot of time and headache in guesswork

 

understood. not many warranties cover 10 year old products. sorry for your troubles, i wish you all the best!

 

The open circuit voltage (OCV) of a module isn't all that helpful in determining the state of health of an HV battery. Practically useless in fact. It's unfortunate that novices like the OP don't read up on what they should be doing before attempting a repair. Without adequate preparation, a second repair soon after the first is practically inevitable.

Most modules are very close in OCV but act quite differently when a load is applied. Only by testing all 28 modules for voltage drop
over time is it possible to weed out the weak modules and have reasonable success in getting an HV battery to last six months
or more. Balancing the modules is also important since an out of balance battery throws DTCs.

 

Try load testing each module to see which one(s) are causing the issue. A voltage test without load is not a reliable indicator of cell/module health. We make a simple inexpensive load tester, or you can build one for yourself:
Prolong™ Battery Module Load Tester - Hybrid Automotive

 

You need to drive the car around and get live data on each of the battery modules. If you have an android phone then a bluetooth code reader is an easy option to keep a code reader in your car at all times.