Battery Has Cell That "becomes Weak"

July 31, 2008

I have a 2003 Prius with 105,000 miles, almost all highway miles. 2 weeks ago had Master Warning light come on and after diagnosis, Dealer told me "Bad Cell in Hybrid Battery Pack". Also noted that "HV Battery Pack #5 becomes Weak." I looked at print out of Computer Screen and it showed that Cell #5 had a "Value" of 16.49 where all others had "Values" between 15.97 and 16.10.

My question to the service people at 2 different dealerships was: What happens when one cell out of 19 "becomes Weak"? Does that mean that the Battery is bad; or is going to fail soon; or is going to fail some day in the future; or the cell will continue to weaken? I have driven the car about 800 miles, mostly highway miles" since the first warning light. I have had the warning light come on 3 times since. BUT after a day or two the Master Warning Light goes off and only the check engine light remains on.

Has anyone had a similar problem? Does this mean that the entire battery must be scrapped because of one weakening cell? Can that individual cell be replaced without replacing the entire battery? I have been offered a new battery replacement for $2,630 installed.

August 1, 2008

I have a 2003 Prius with 105,000 miles, almost all highway miles. 2 weeks ago had Master Warning light come on and after diagnosis, Dealer told me "Bad Cell in Hybrid Battery Pack". Also noted that "HV Battery Pack #5 becomes Weak." I looked at print out of Computer Screen and it showed that Cell #5 had a "Value" of 16.49 where all others had "Values" between 15.97 and 16.10.
My question to the service people at 2 different dealerships was: What happens when one cell out of 19 "becomes Weak"? Does that mean that the battery is bad; or is going to fail soon; or is going to fail some day in the future; or the cell will continue to weaken? I have driven the car about 800 miles, mostly highway miles" since the first warning light. I have had the warning light come on 3 times since. BUT after a day or two the Master Warning Light goes off and only the check engine light remains on.
Has anyone had a similar problem? Does this mean that the entire battery must be scrapped because of one weakening cell? Can that individual cell be replaced without replacing the entire battery? I have been offered a new battery replacement for $2,630 installed.

David, I have been in a similar situation, but worse. I had to change the HV Battery for the reason that one cell in my Battery was dead and the car would not start. The computer on board would not allow the operation of the hybrid system because it senses that there is a high difference of voltage within the cells of the Battery, that could(apparentely) cause overheating and perhaps explosion of the battery.

Your battery is at an early stage in that regard so it is still operational.

From my browsing experience on the net i remember noted that in the US you can actualy change the cells individualy rather than the entire battery so I will recommend that you should browse the net for specialists that will do that for you around where you leave. It will be much cheaper, from my understanding, than replacing the battery. By the way, in Ireland that was not an option and the battery is much, much more expensive to replace than what you would pay in the states.

If you have difficulty with getting a specialist i have a e-mail address in the states for one that may be able to help you. Let me know and I will post it to you privately.

Good luck with it.

But coming to think of it, providing that your car is not imported privately from abroad, Toyota should replace your batery under the 8 years warranty for the hybrid system!

August 24, 2008

I have a 2003 Prius with 105,000 miles, almost all highway miles. 2 weeks ago had Master Warning light come on and after diagnosis, Dealer told me "Bad Cell in Hybrid Battery Pack". Also noted that "HV Battery Pack #5 becomes Weak." I looked at print out of Computer Screen and it showed that Cell #5 had a "Value" of 16.49 where all others had "Values" between 15.97 and 16.10.
My question to the service people at 2 different dealerships was: What happens when one cell out of 19 "becomes Weak"? Does that mean that the battery is bad; or is going to fail soon; or is going to fail some day in the future; or the cell will continue to weaken? I have driven the car about 800 miles, mostly highway miles" since the first warning light. I have had the warning light come on 3 times since. BUT after a day or two the Master Warning Light goes off and only the check engine light remains on.
Has anyone had a similar problem? Does this mean that the entire battery must be scrapped because of one weakening cell? Can that individual cell be replaced without replacing the entire battery? I have been offered a new battery replacement for $2,630 installed.

I just found his on e-bay.

Hope it will help...

"Item number: 160255759611"

"TOYOTA PRIUS Battery CELLS HV HYBRID 2001-2003

ALL PRIUS PART IN STOCK AND SHIP DAILY 1-866-984-7377"

Good luck!