I finally got my Android tablet to work with Dr. Prius. The secret to making it function was to finger touch the MAC address shown in the app's opening screen image. There is no documentation with Dr. Prius and it's not obvious that touching a random text string on the tablet screen possessing no button border around it is required, but I digress.... Using Dr. Prius I drove around northwest Indianapolis on a 50 degree day with indicated battery temps in the 70 degree range. Some of my trip was at high speed on our beltway. Some of the trip involved high amperage regenerative braking coming to a stop. Amazing how much battery current (>100 amps) that regenerative braking creates. Dr. Prius' important display seems to be the accumulated voltage delta of the battery blocks. Averaged over my 5 mile drive the worst block had a delta of 6.40 volts. The least delta was in an adjacent block at 5.95 volts. As an EE this suggests to me that the battery blocks are fairly well matched. Dr. Prius' indicated series resistance was <20 milliohms across all blocks. Is my conclusion that this battery is OK correct? The battery pack has 150K miles on it. I was motivated to test it because it has been periodically storing P0A0D codes and showing "check hybrid system" messages on the instrument panel.
Since writing the comments above I drove my wife's 2006 (new Toyota battery 40k miles ago) a longer distance:10 miles on our beltway. The accumulated delta voltage on her Prius ranges from 5.04 volts on the highest block to 4.64 volts on the lowest, a difference of 0.4 volts. All the indicated internal resistances are clustered around 23 milliohms. One observation is that the accumulated delta voltage on our 2010 is about 0.4V worse in than her 2006. The explanation is that the 2010 has 100k+ more miles on its battery pack. In the 10 mile drive the central thermistor in the battery pack read 94 degrees F and the two edge sensors were at 87F. The tailgate area of the vehicle's cargo area below the panel should have been 55F.or so after a long outdoor soak on an autumn day in the low 50s. Again, I'm impressed that aggressive driving produces currents above 100 amps when you pull away from a standing stop or upon heavy braking. The total battery pack voltage briefly exceeds 260 volts with regenerative braking. As an aside, the Dr. Prius screen presentation is dominated by bright vertical bar graphs showing the 14 block voltages in real time. I think the voltage difference between the tops and bottoms of these bars is less than 0.1V and the center point is dynamically adjusted around 15 volts. This tight voltage scale on the bars makes them dance in a fashion that prevents their conveying any useful information. I wish there was some way to turn off the dancing voltage bars or reduce tenfold their gain.
