Runaway charging event?

Wow I have never seen this on our 03. It usually is between 55 and 62max soc depending on what terrain it just drove (downhill or level), of course a long up hill will set it back to 50 but will get back up to 58 pretty fast. I have seen in a couple threads the soc will go up and down wildly and that usually is not good. Have you checked you 12V battery condition lately? I know that can cause some pretty weird symptoms, maybe even resetting the system by removing the 12V neg for ten minutes will help. If it does eventually throw a dtc, you need to leave the 12v on to retain the codes. Do you have any way to accurately read dtc"s? If they do arise?

 

I think you saw battery conditioning.
I can't find any other confirmation, just this.

-mort

 

Over in "Prius Technical Stuff" there have been random postings about an elusive, 'charge balancing' cycle that is built into our cars. The car will 'peak charge' the battery to bring all of the modules to an even state. Then when it is over, it will bring the SOC back to the the normal 60% level.

The theory is that by 'peak charging' the pack, the stronger modules will clamp at the higher level and the unbalanced, less charged modules will approach the peak charge. Then as the car sits and self-discharges and/or operates, all of the modules will return to an equal state-of-charge. A couple of weeks ago, I think I read where the TechStream can also command a charge balance cycle.

Based upon my studies and weakness of the NHW11 module seals, I'm not really happy with this approach due to the risk of high internal pressures and heat. Charging is exothermic but when the NiMH battery reaches peak charge, it begins generating gas, another source of pressure in addition to the heat. If the seals were not blown before, this sounds like a receipt for blowing them out of the best modules and getting a P3009, electrolyte leak. I'll have more to share about this in another thread.

If you have min-max module voltages from before, it would be interesting to see if there was a reduction.

Thanks,
Bob Wilson

 

I'd be curious to know what logic decides when to initiate an action like this. With fuel cells we take care to keep temperature and load changes gradual, until we find that the cells are obviously suffering from shorting, contact loss, electrolyte migration or whatever. At that point the way we fix the problem is often to do exactly what we try to avoid with an otherwise healthy stack; free cooling, fuel starving, or slamming load on or off. It's surprising how often these things work to extend the life of the stack.

My guess is that this is a somewhat last ditch effort to straighten things out, rather than a mainenance routine.