How To Load Test Your Car Battery

December 7, 2012 by Pat - Comments - 2 min read

Just for good measure, let’s get this out of the way up front:

  • The information within this article is to be considered educational only. Do not try this at home. Do not attempt anything you read in this post. Consult with professionals. Be smart and be safe. I’m not responsible for any damage to person or property for the information contained in this article.

Recently I’ve been plagued with a dead car battery. We found out that there was a high draw on the battery when the car was off. Normally car batteries are supposed to have less than 50mA (milliamps) draw on it when the car is off. My car had 350mA draw, which was killing it in a matter of a couple of days.

So I wanted to put up a post on how to determine your cars draw in case you need to do this yourself.

  1. We won’t be working on the red/hot side of the battery. Do not touch the red battery terminal. 
  2. You’ll need to put your probes on your multimeter onto the Amperage terminals. Turn it on to the DC Amps settings.
  3. Remove the NEGATIVE (black) cable from your battery.
  4. Put the positive (red) multimeter lead on the black battery cable clamp.
  5. Place the negative (black) multimeter lead on your battery terminal post.
  6. Read the multimeter for the amperage.
  7. I found that my car had an initial load of about 3 amps when I first connected it, then after about 10 seconds it dropped down to a steady 23mA.

I hope this post helps you out! Here are some pictures for reference

Share this post:

About Pat

I'm an I.T. systems engineer by day and in my spare time I code. I've made WordPress websites and plugins, weewx extensions and static html sites using Jekyll. I'm a technologist at heart and I enjoy tinkering on many different technology projects. Here on my site you will find some of the projects I've worked on, and other random bits of knowledge that I hope help someone along the way.

mentions