Friday, April 20, 2018


For four and a half years I've been operating without any battery instrumentation.  Professionally I work in the field of battery charge estimation, algorithms that decide whether to light 1 LED or 5 LEDs.  My cousin recently gave me a ride in his Tesla Model S and pointed out the irony to my lack of battery charge gauging.  I simply make sure I don't drive more than 40~50 miles on a charge.

When in a pinch I have read the voltage of a single cell with a voltmeter to get an idea, when fully relaxed these voltages are directly related to state of charge.

I've run out of charge only 2 times so far.  One time because I forgot to charge the night before.  And the other time is still a bit of a mystery.  I thought it was perhaps due to running the air conditioning over lunch break but that would not account for how much charge I lacked to get home.  Both times I simply called AAA and was done.

There is a communication port on my battery management system and I've used it for diagnosis using a laptop and to log data using an iPhone.  The iPhone was really too small to be practical and was abandoned.  My family recently upgraded from an old iPad to a Kindle Fire and I've adopted the iPad with cracked screen to up my game.

As a security feature it hides nicely under the passenger seat.  With this I can monitor and log voltages, temperatures, and current.  The app I'm using is called Get Console and is basically a HyperTerminal for iPhones.  I hope to do some more data collection and efficiency calcs soon!


  1. A broken iPad seems like a fine dashboard. You don't want a theft magnet.

  2. hey chris:
    any chance you still have the CAD for the bellhousing adapter?
    looking to machine one up for a pending conversion
    many thanks
    graynak at gmail dot com