Finally, accurate current measurements

Getting to the "truth"

With a borrowed Fluke 600A DC amp meter, I now have accurate current measurements for the charging system.

1. The charger's current reading is within 0.1 amps of what the Fluke reports for current going into the batteries.
2. The charger pulls 10.1A @ 240V or close to 2,450W.  The fan adds another 0.4 amps.
3. The 12V battery charger pulls about 0.5A @ 240V
4. The 12V power supply draws approximately 0.1A but is probably in the noise.

Impact

1. The current monitor (fuel gauge) Arduino is calibrated to the charger.  This should be now less than 5% off.
2. The fuel gauge is set to never exceed 100%, so it should "zero-out to full" near the end of every charge cycle, as long as the cycle runs to completion.  By ignoring the charging efficiency of the LiFePO4 cells, the fuel gauge should hit 100% about 1%-2% before the batteries are full.
3. The charger's efficiency is about 55%-60% based on power-in (240V x 10.1A = 2425W) divided by power-out (~90V x 16A = 1440W; the charger is rated at 1500W).  The charger spec states that charging should take 1.41x the battery capacity / 16A.  Not a surprise this ties out to the 60% efficiency, though it is spec'ed at 85%-95% efficient.  Maybe at the higher voltages it can achieve this.
4. The best news is the overall energy efficiency of the car is coming in where predicted.
1. 4000 KWH of usable capacity (80% of the pack)
2. Today I drove close to 12 miles using 48% of the pack.  This included several hill climbs and normal traffic driving. 
3. This leads to about a 25 mile range with 20% reserve. or 160 KWH/mile.
5. At work, there is CharePoint charger which reports KWH used, so next I'll try to calibrate against that with the data above.  Mostly it is good just to have an accurate fuel gauge