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

Hi Guys, I'm working on reconditioning my Gen 1 HV battery and I can't get the last 5 silver bolts off so that I can get to the cells, any help or advice to get them out would be greatly appreciated!

 

Hi there, do you happen to know why all of the modules on my battery showing 10.5 volts?
Also, any insight on best way to recharge these modules.

Thank you

Ed

 

Where do you buy the gen 1 cells to swap out, ebay?

i have seen people online selling or talking about buying a grid charger and charging their hybrid traction battery to full capacity and then discharging it to minimum to exercise the memory and get the cells back to great health. Are those chargers and procedure worth doing? Does it really make a difference? If so what charger and discharger do you recommend?

 

A small editorial notice about the terminology that is consistent with the terminology used in the repair manual, just to avoid misunderstanding or confusion.

Techstream will show blocks which are pairs of modules. A module is a sealed unit that contains six cells.

A Gen 1 has 19 blocks, 38 modules, or 228 cells.

 

I have read through the problems you are having to keep the engine running. Why do you now suspect the battery that you just replaced? Are you getting battery codes? Do you know how to do a forced charge and discharge test on the battery?

99% of original Gen 1 battery modules are now junk. I suspect the used battery you just bought was a factory replacement at some point. The battery modules have a date code. You can read this date code on a few of the modules by pulling the fan tube off the battery. The first two digits are the day, the third digit is the month with X,Y, and Z used for Oct, Nov, and Dec, the fourth digit is the year starting with A for 1999 and continuing from there. A serial number starting with 135L means the module was made May 13, 2010.

Tracking down a P3191 engine failed to start code can be a bear. First to check is the MAF sensor. Be sure to clean the wires buried deep inside the top recess. A funky fuel pump can make the car seem possessed. The hybrid battery is NOT causing the engine no start problem.

I am local to you and rebuild Prius batteries for a living. Feel free to call for help. My number is at the bottom of my post.

Brad

 

oddly enough the replacement battery i purchased is a original with one red/white sticker on top but appears to be working extremely well i have a bad battery laying in my garage checking at 60V i wanted to rebuild that one and get it back up to perfect health.

Also i do not know how to discharge or recharge a hybrid battery. I have been looking at the chargers online but look very expensive so i was trying to figure out cheaper options.

 

Thank you for the valuable information. Super extensive.

 

Strawbrad, do you have an estimate for what the 'life' of a Prius Gen I NiMH module night be? Clearly if the case breaks or leaks occur around the terminal, that's a failure, but do the modules themselves actually have a finite number of charge/discharge cycles?
I have in the back of my mind that NiMH batteries can be charged/discharged almost an infinite number of times between 20% and 80%, which is where the Toyota battery control algorithm keeps the modules during normal operation.
That many of them have in fact lived for over 20 years is pretty remarkable.
The reason I'm asking is that in looking over my experience with the Gen1 HV packs, when Techstream reports a "low battery module", it's been about 50:50 between a poor-performing module (leak, swelling, etc) and problems with the sense wires/connectors to the battery control computer. Buildup of corrosion on the pins.
So for those interested in refurbishing their marginal Gen1 battery pack, besides the modules themselves, my advice is to plan to not only check out the sense wires and the connection to the battery control computer.
I recently had to fix a bad battery "module" by cleaning up the appropriate pins in the hybrid battery control computer module voltage sense input connector (the orange one). The module voltage was fine; what the computer sensed was incorrect due to a voltage drop at the sense input connector pin.
Some interesting reading from history (the thread started in 2015):
The battery fires at ECU sense connector thread | PriusChat