2007 Toyota Camry Hybrid. 144K miles. Presumably lived it's whole life in AZ, but I don't know that for certain.

This is the 3rd Camry pack I've evaluated. The other two exhibited very similar results.

P0A80 error code. No other codes.

Battery minimum rating when new: 6500mAh

As-removed module voltages after 7 days sitting:As-removed module capacity in mAh after 7 days sitting:Post reconditioned capacity in mAh:Of note is the very high standard deviation. Multiple modules have extremely low capacity.

Generally acceptable threshold of battery life: 80% rated capacity.

# of modules at > 80% rated capacity: 5
# of modules at > 70% rated capacity: 20
# of modules recommended for replacement (<4500mAh capacity): 14

In short, for any chance of a long term repair, 14 modules should be replaced.

Of note is that ALL modules show "good" voltage based on the public's understanding of how these modules fail. Which would you replace?

Even with a range of seemingly good voltages, the actual capacity of these modules varies dramatically demonstrating that voltage is a non-indicator of module health. it is only confirmation of bad health, i.e., low voltage guarantees bad, but "good" voltage does not confirm good health.

Behind the scenes, with what I can see from other characteristics during test, a very large number of these modules exhibit internal imbalance where one or more cells is extremely weak while 4-5 cells are very strong.

Of key importance is the 7 day sit. This allowed the voltages to settle and for self-discharge, if present, to contribute to the discrepancy. Had these voltages been checked shortly after the pack was pulled, there would have been far less spread.

I have an informal rule of .05V... anything below 0.05V from the highest voltage module should be replaced, i.e., in this case, 7.64 to 7.69 were "good" modules. Had this been observed in this case, 15 of the modules would have been replaced instead of the recommended 14. Lowering this to even 7.63V would have included two modules of < 50% capacity.

This is a perfect example of my whack-a-mole scenario... simple module replacement is a game of whack-a-mole. If the typical owner repair of just replacing failed modules was done, it would continue until the 14 modules were replaced... assuming the owner could even identify the bad modules, which isn't possible in this case based on voltage.

The attached chart shows all the data.

INIT=as-removed capacity (left axis)
DCH3=fully reconditioned capacity (left axis)
V_I=7 day as-removed voltage (right axis)

The chart has been shaded to indicate anticipated longevity of repairs ASSUMING all modules have been fully reconditioned.

Green should be a multi-year repair
Yellow should be a ~1 year repair
Orange should be a < 1 year repair
Red is a non-repair. A code will return in days/weeks.

As you can see, MANY fall into the yellow zone, with only a few in the green.

 

OK, so, questions:

1. What's your preferred method for measuring capacity?
2. How do you recondition the modules?
3. For modules that can't be reconditioned, how do you get known good replacements?

 

1) 1C charge to -dV, 20 minute wait, 20A discharge to 6V.
2) A combination/derivation of the typical methods you can read about online.
3) Not possible as stated. I have never encountered a "known good" source. I buy a salvage yard pack, test and recondition them.

IMHO, reconditioning or rebuilding a Camry pack is a losing proposition here in AZ. The only solution I regard as viable is a new pack. My experience with Dorman and Cardone as replacements does not suggest they are a good value.

 

If you rebuild the battery with modules that average 70% capacity and have a very tight standard deviation in capacity and internal resistance , under ideal conditions how long would you estimate the battery to last? For example a battery pack with 90% capacity and a SD of 3% , is it possible for a battery pack with 70% capacity and a SD of .5% to outlive the 90% or is the capacity difference too great? I'm totally new to this , but I was wondering if there is an equation that would take in capacity% , SD% and any other metrics that I'm surely forgetting in order to calculate longevity under ideal conditions?