Whats wrong with this procedure? The HV battery is connected in series , the ECU reads in banks of 2

Phillip,

You are doing a "rapid" charging of your modules. When I reconditioned my 2004 battery modules (6 years ago), I only had one hobby charger so the procedure took over a month to do the 27 good modules (the 28th had a bad cell - hence the need for a "new" battery.) All of my reconditioned (balanced) modules were used by 6 individuals to successfully get their batteries functioning again.

It is the overcharging at a very low current that actually balances the 6 cells in a Prius module. The lower SOC cells catch up while the Stronger SOC cells dissipate the excess energy as heat.

JeffD

 

Yes, the bypass resistor allow limited current flow for sevseral reasons. The "soft start" prevents a surge that would happen when the inverter powers on and the capacitors charge up- so no arcing and pitting of the contactor (relay) points. It also lets the HV ecu test the HV circuits.

Imagine what might happen if there was a short and the high amp contactors closed, the contacts might weld shut then you would have to depend on the HV fuse to open the circuit.

If you look at my signature, that is a oscilloscope capture of a curent probe for the HV battery during a hard accel then decel. Momentary peaks were about 150 amps discharge and 80 amps charge.

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The Prius only permits high charge/ discharge current so long as the SOC stays within 40-80%. When you are "reconditioning" the modules everyone reccomends very low current. I used about 1.5 amps. The idea is to gently exceed the normal boundaries of operation, each time increasing the limits. More current means more heat- that can be especially bad at the extremes of capacity.

So first I went down to 7.0V and charged to 6500mAh. Then 6.5V and 7000mAh. Third was 6.0V and 7500mAh. However several modules still had low capacity as measured during the discharge cycle. Just overcharging ("top" balancing) had limited results.

They improved as I did more cycles, going lower to 5.0V then 4.0V. I had a fan blowing through the (outlet) duct into the bottom of the assebled pack for the 1 month plus that the entire procedure took.

After cycling you want to perform a load test. Measure voltage then apply a fixed load (minimum of 5A but more is better- up to say 20A) for exactly 2 minutes and record voltage again right before removing the load. Look for even voltage drops from each module.
I replaced the initially failed module (had a shorted cell that was 1V lower than the others under load). Also 3 three others had high self discharge or weak load test results.

When I put the pack back together all modules had 5500 to 6200mAh capacity.

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Phillip,

The root cause of the problems with your Prius is the engine is not running. This caused the battery problems which you made worse with your attempts to recondition the battery. This thread contains another example of a PC member chasing phantom battery problems caused by engine failure. Petrol Engine not Running | PriusChat

At this point your goal for the battery should be getting it back to a point of not throwing codes with a consistent SOC across 28 modules. The three to four deep discharges done have already extracted most of the benefit and harm possible. The weak modules got hammered by your parallel setup. Slow deep discharges and charges are great for reconditioning modules but you are past that point.

The one Integy charger you have is a real beast at discharging. It is far superior to any timed light bulb load test. Use It's power to measure the capacity of each module.

1. Discharge at 20 amps to 6.3 volts. This will bring each module to the same starting point.
2. Charge at 6 amps to 4500 mAh. An automatic shut off timer would help. 4500 mAh is a safe amount for a 6 amp rate.
3. Discharge at 20 amps to 6.3 volts. Record this capacity number. A consistent time between charge and discharge is necessary.
Replace modules with poor results.
4. Charge at 6 amps to 4500 mAh.
5. Reassemble the battery.

 

BOB WILSON HAD A ... er ... Bob Wilson had an interesting idea making a foil-and-plastic sandwich on one side of his clamp: effectively a capacitor, whose capacitance would increase with the pressure, and could be monitored electrically to detect if module pressure was going up.

 

Happen to have any OBD2 codes (DTCs) worth sharing?

 

The batteries need a kick in the butt. Get the Dr. Prius app and compatible OBDII adapter ie tonwon wifi. use the battery test life function.
Basically: park brake on, foot on the brake hard, put car in DRIVE and floor it until the battery is fully charged (1-2 minutes). This hard charges the battery, causes the plates to swell and expose fresh surface area. That will either rejuve the pack or expose the faulty blade...
save you months of #### around. Make sure the orange battery ECU connector is clean and some contact cleaner to prevent corrosion/fire.

 

Hate to be a party pooper, but in-car charging in this way will not do this. As the battery ECU keeps the car operating in the 40% - 80% band of SoC, it will not do any rejuvenation of significance. While you are correct in that the battery needs a kick in the butt, this will not do it.

It may do this, but only if the hybrid vehicle battery was about to fail anyway.