The Battery Block Delta chart shows maximum, average and minimum value of the battery blocks.
Note that blocks at maximum (or minimum) values at any given instant may not be always the same blocks.
Delta is shown on the right side scale: this is the difference between maximum and minimum values.
Worn out batteries have larger deltas.
The Battery Temperature Chart shows HV temperature over time.
Battery is split in 3 sections, each one having a termal sensor.
Tipically, the second section has the highest temperature, being surrounded by the other 2.
The chart also highlights 3 notable thresholds:
35C: the HV fan starts spinning
42C: EV mode is not available any more due to high temperature
Here are 2 Prius of the same age, with comparable mileage:
Prius 3, 2009, 140.000 km, good battery
The first one has a perfectly fit battery.
The Battery Block Delta chart shows how all blocks values are close to each others:
Max Delta is 0.39
Average Delta is 0.10
Prius 3, 2009, 183.000 km, failed battery
The Battery Block Delta charts shows that max and min values are much more divergent.
Max Delta is 2.79
Average Delta is 0.34, three times as much as the other battery.
By comparison, let's look at a brand new Auris, that uses the same battery model as the Prius 3:
Auris, 2015, 1.000 km, good battery
Max Delta is 1.0, but we can see from the chart that this is due to isolated spikes, probably associated to engine ignitions or others sudden current surge events
Average Delta is 0.10, just as the other good battery.
Here's an older car:
Prius 2, 2005, 270.000 km, good battery
Max Delta is 1.08
Average Delta is 0.15, a little worse than the brand new battery
We arranged to capture a Torque log to see if we could find the faulty element of the battery.
We drove to stress the battery a bit, by driving using EV traction alone, forcing charges by ICE and by brakings.
The car behaved erraticaly: the EV mode was refused even with a full battery and ICE won't stop, even standing still in P and with no HV charge in progress.
We suspected a temperature issue in the HV, so while parked we checked them up:
There was an unusually large difference between the 3 values, and while the fan was running apparently fine, TB3 was holding steady. Even with the car parked and no significant currents from the battery, temperature didn't decrease.
We powered off the car with a final SOC value of 54.1
When we powered it on again after a minute, SOC jumped instantly to 72.9.
We drove in EV trying to deplete the battery and then, suddenly, SOC went down from 62 to 24 in 15 seconds, causing ICE to start charging the battery.
That condition seems to have triggered the error, that showed up on the multifunction display:
The Current Flow chart shows the sudden SOC drop:
The Battery Block chart gives an immediate evidence that something is working out of specs:
The HV Fitness sheet shows how Block 4 has the worst lowest voltage of all, the highest bias and standard deviation from battery average value.