Testing Batteries - Manual and Automated

September 2020

Published in Soaring magazine
February 2012 Page 27

(Click on Images to Enlarge)

Each year I like to test my ship's batteries and replace those that do not have enough individual capacity to last 3 hours at a 1A load. But how can the average pilot perform a reasonable "real world" test with easily obtainable equipment?

See the Excel spreadsheets linked below and this Soaring magazine article for an explanation of the testing that I perform and the simple test rig that I use, along with Excel templates for gathering the data and then graphing the results.

There are three versions of the spreadsheet;

  1. Original - This version of the spreadsheet is the original mentioned in the article with a few minor updates. Time must be entered in a "hh:mm" (24 hour) time format.
  2. Beta - This version of the spreadsheet has separate columns in Testing Results & Graph tab for hours and minutes. I think this is easier/faster to use for data entry than having to enter "hh:mm" - that colon really slowed me down. Now I can tab between columns (hours, minutes, voltage) and hit a return between rows. Tell me which you prefer!
  3. Pre-Filled In - This version of the spreadsheet already has at set of times already filled in for you The first 5 minutes are by 1 minute increments starting at 00:00, then 10 minute increments. This requires the use of a stopwatch, rather than just a clock, to take voltage readings are set intervals. It is handy to use an "interval" timer smartphone app* set for 10 mins to tell you when to take the next voltage reading.
*Smartphone App - Get yourself a Smartphone App that does interval countdown timing with an alarm. Those typically used for exercising will have a repeat function. These apps provide a few countdown beeps leading up to the end of each period, and then a different single beep at the exact time to take the next voltage reading, and then automatically starts the countdown again. Slick!

Battery Testing Automated!
       2x16 LCD Display         240x320 TFT Touch Display

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Taking hours to manually collect battery test readings can be BORING! I have now automated testing using an inexpensive Arduino Duemilanove single board computer coupled with a display shield and a few other components. There are two versions of the display used. Initially I used a simple 2 line by 16 character LCD B/W display. Lately I began using a 2.4" 240x320 pixel TFT touch sensitive color display (ILI9341) which allows more room for information, a simple graph, and other niceties.

Also needed is a voltage "divider" made from two resistors (22KΩ and 10KΩ). Lately I added a simple piezo electric buzzer to chirp at each reading and then alarms at the end of the testing to tell you to remove the battery from the load resistor (12Ω). These components were most recently conveniently mounted on an Arduino breadboard shield (see the pictures).

The complete required Arduino hardware and associated parts might cost you $30 on eBay or Amazon.

Pictures - Pictures of the hardware for each display type can be found here.

Arduino Code - My latest Arduino software packages for each display type can be found here. After you open Arduino code packages you will find full build instructions in the comments area near the top of each listing.

Spreadsheets - Spreadsheets for each display type to help parse your data, and to graph the results, can be found here.

Aruduino Software - The Arduino free editing software (required) is available here. NOTE: For the TFT display you will need special drivers available online.

Aruduino Hardware - Can be found on eBay or Amazon. The hardware specifications can be found in the comment fields of the code.