- 1). Wearing mechanic's gloves and safety goggles, brush any loose corrosion from the battery's terminals.
- 2). Brush on a coating of baking soda and water paste, and let it sit for 15 minutes. Then wipe the battery post clean with a rag. Dispose of this rag in such a way that pets and/or children can't be exposed to it.
- 3). Turn the "Load" control on the carbon pile load tester completely counterclockwise to the "off" position. It's dangerous to connect the tester while a load is dialed in because sparking will result, which may cause the battery to explode. Lead acid batteries produce hydrogen gas, which is highly flammable and explosive.
- 4). Connect the tester to the battery. Connect the black, negative (--), lead to the negative battery post and the red, positive (+), lead to the positive battery post. The battery posts are labeled, but they are also distinguishable by their diameter. The positive (+) post is larger in diameter than the negative (--) post.
- 5). Rock the cable clamps back and forth on the posts to verify that they are making good electrical contact with the lead posts.
- 6). Hold this load for, but no longer than, 15 seconds. A prolonged load will cause the battery to overheat. Overheating can damage the battery by warping its plates.
- 7). Note the reading on the voltmeter at the end of the 15-second load. The numbers can be confusing for a beginner, but the meter is also color-coded. If the needle is in the "Green" on the battery test scale, the battery is good. The battery is good even if the needle is also in the "Red" on the battery's "State of Charge" scale. The battery is good but it does need to be charged.
- 8). Turn the "Load" control to the "off" position and remove the test cables.