Summary : Pretty Good Condition. Maybe Mild Climate Related? Just tested our 150k mile 2011's HV battery (original). Condition is pretty good. I wonder how much it has to do with our mild climate (Seattle) and car is nearly always garage parked (stay at home mom's car, not work transportation vehicle potentially parking outdoors all day) Mostly shorter around town hilly trips. A couple of longer interstate drives. Most of the failures I read about seems usually from hot climates. Test Setup Test is starting with 50%+ SOC. Car in reverse. Foot on brake and accelarator to discharge the battery with electric motor trying to reverse while monitoring max/min battery module voltage until battery gets low and engine comes on to charge (In my case, engine didn't come on the entire 5min recording window which is another sign of good health) This is a basic test applying a load (electric motor drawing constant power to reverse) and watching the the max differences in battery module's discharge rate. I followed mostly this post link to Arts Automotive Post Recorded Parameters I did min and max module voltage, min and max module #, battery SOC Test Start ( Data @ ~45s on graph ) Test End ( Data @ ~300s on graph ) Detailed Summary SOC didn't drop much. Was wondering if I was apply a load. Car pushed against the brakes as soon as I depressed the accelerator and battery is clearly discharging so must be working This was my 3rd successive test run (more on this later) max/min module voltage gap was < 0.1V at start and < 0.2v at the end total discharge time 4 1/2 min Interesting Info I did 3 tests. First test has higher SOC (wife just came home and charge bar on center info panel was like 2-3 from full). Between each test I let the engine run to charge battery until it stopped (about middle of the SOC bar on center info panel) Each cycle, the min/max voltage gap during discharge got smaller and start to end SOC drop also seemed smaller. Above graph was on the 3rd run. Center of the pack modules exhibits more wear than the outer edges. Same as everyone's observation and obviously due to less cooling in center. The pattern is as follows At low SOC, center modules voltage is lower than outer. A classic inverted bell curve as someone said. When discharging, center module voltage drop faster than the outer When charging, center module seems to rise faster than the outer Next Step Generally speaking, I guess nothing and probably another 50-100k miles more service life. However, if I rotate the inner modules to outer and outer to inward. Perhaps can increase longevity as the current weaker inner weaker modules would be living much cooler. Its a lot of work but maybe push first module failure out 50k miles? No one really knows of course.
