Cell Module health and rehabilitation

Holy Mackeral, this is a lot of questions. I'll do my best.


For a 2006 Prius showing red triangle and P0A80 code. 126K on the battery.

I aquired an OBDII bluetooth reader and the Prius Doctor smartphone app. After some careful driving I think I've
narrowed down the offending module by watching both the total battery voltage graphs and the indivdual block voltage
readings as the car pulls under load and then breaks down hills and to stops. With this I think I've narrowed it down
to block 7.

After running the car backwards up a hill to deplete the battery voltage to the low state, I then measured the voltages
of the two modules in block 7 to identify the one offending module, and I think it is this one here - it shows 1.5 volts
under the readings of all the other battery modules in the pack. It also happens to be the only module with a lower
voltage than the others, and the sum total of it's voltage with it's paired sister matches the block total shown by the
Prius Doctor app.

I've used my Turnigy Reaktor rebalance charger on it 3 times to find that it will not accept more than about 1500-1600 mAh
charges or top a voltage of about 6 1/2 volts.

Yes, a 6.3 volt module is NO GOOD. Don't even try to restore it. It will just bite you later.

From my donor battery, I've identified 4 modules as possible replacement candidates. I've put each through several cycles
of discharge and recharge treatments.
My charger settings were:
- NiMH battery
- dschrg-chrg 3 cycle: manual amp settings
- dischrg at 2A down to 6.3V
- chrg at 4A (no option to select an upper voltage here, either in the automatic or the manual mode)
- delta V sensitivity: default for NiMH mode
- with an upper capacity stop limit of 7200mAh.

I don't see any significant problems here.


My 1st choice had the highest residual voltage of the entire pack as it came from the salvage yard, measured under load.
Problem was, although it looked good through the cycling process, it hit the upper capacity stop limit which I had
initially set at 7800mAh. So I lowered it to 7200mAh for all my following treatments after that. Problem continues,
however, because every treatment , with only one exception out of 30 treatments, on all of my candidate modules, have
hit that upper capacity stop limit before being able to continue the cycles automatically....regardless of the
automatic or manual setting of the cycling mode. No settings that I pick seem to avoid this.... any ideas????
(I chose 7200mAh for fear of overcharging - Valid? Ending voltages always seem to be up in the 9.05V range
before shut-down.)

This is not a problem. You're not completely understanding how the charging cycle works. The charge cycle is looking for delta V. Sometimes, the chargers may have a hard time actually detecting it, so there are safety setpoints that can be used to prevent overcharging. Your capacity stop of 7200 (or 7800) merely stops the charge once the charger calculates it has pushed that amount of energy TO the module. The modules do not charge at 100% efficiency. Probably lucky if it hits 80%. So...7800 out of the charger could actually be only ~6200 absorbed by the battery. The rest is gone due to inefficiency losses. This is no big deal. If it hits the capacity cutoff, thats not necessarily a bad thing. Typically it just means it's not max charged yet. Of course, the inefficiency works in a similar way on the discharge cycle.

As a result, I have to perform three sets of separate 1 cycle discharge-recharge treatments at a time. These seem to work,
and my intake/discharge capacities seem to increase over time. All 4 candidates have raised up from hundreds, or around
1500mAh levels, to now routinely accepting the capacity stop limit of 7200mAh and then discharging around 5500 to 6500mAh
levels, consistently for each module. All battery modules have remained cool to the touch throughout all treatments.

Great. The higher the discharge number, the better the capacity of the module. Typically....other things like self discharge can alter this.

My Questions are these -
1) My initial favorite (candidate 2B) showed good recovery numbers, however exhibited a little bit of swelling of the
casing sides, despite being clamped between two other batterys with 2x4s and a C-clamp. This swelling amounted to about
the thickness of two pennies on a side. All the time the module remained cool to the touch, my charger unit remained cool,
and the swelling had dissapeared by the following day. It now looks perfectly normal..... Is this module any good, can I
still use this one? If a battery swells, does that mean it is ruined?

Does this mean you unclamped them immediately after the charging cycle? This could be a bad thing, as it hasn't allowed time for internal pressure to reduce. I typically wait at least 24 hours before I unclamp anything. Charge em up, unclamp it, and watch the expansion/swelling go crazy...not the best thing to do.

2) My LEAST favorite (candidate 1A) showed the best recovery numbers. I had initially dismissed this one because it was one
of 2 in the donor pack that was completely flat (voltage = 0) when it came home from the salvage yard. I was just
experimenting with it, but it showed such great recovery numbers I'm now wondering if it is one I can try using. It
climbed up very rapidly from an initial discharge/charge cycling of

d0049/c7258, d5009/c6727, d5049/c6689, Vfinals= 8.37Vo, 8.31Vcl

to lately showing

d4614/c7035, d5274/c6863, d5322/c6870, with final resting voltages of 8.56V(open) & 8.53V(closed).

Incidentally, this is the only battery module that successfully completed
all three DSCHR/CHRG cycles automatically without hitting the upper capacity stop limits.
....Can this be a viable candidate?

Anything can be a candidate, but I would be wary of self discharge issues in the near future for that module.

3) My Turnigy Reaktor has an Internal Resistance Measuring function. Problem is, whenever I use it,
it gives different numbers than the Open/Closed circuit voltage resistance calculations on the battery modules.
The Turnigy always gives me I.R. readings in the 40s to 60s and even 70s mOhm ranges, and it does this for all the
modules I test, in either battery pack, and regardless of being rested, or fresh off a discharge/charge cycle.
Can ALL my modules really be That BAD?

Whereas, when I use the (Vo-Vcl)/(current) flow method, I keep comming up with I.R.s more in the 15 to 23 mOhm range.

Any suggestions on which estimates I should use?

My recommendation is to cycle a few modules, pick one that shows around 5000 capacity and use it. You don't want a super high cap module to be installed in a battery where the other 27 modules are probably averaging around 4000-4500. You want to be fairly close. The goal is consistency between the 28 modules.



Thx[/QUOTE]