Batteries – Don’t Get Burned

Corrosion of your battery terminals can cause real problems in flight, and even on the ground. If your aircraft is equipped with an electrical system, it’s likely you have a battery on board and unless you are a pilot of a jet or high-performance twin, most of those batteries will be the lead-acid type. These batteries (as their name suggests) generate electricity as a result of the reaction between the lead and the acid.

Cause: Corrosion will usually occur as a result of acid leaks, which can seep out of the cell caps during high angle of attack takeoffs, or even during moderate to severe turbulence. When the acid seeps out, it weeps across the top of the cell — and will usually find its way to the battery connectors.

Effect: Once acid reaches the connector, it begins to corrode the connector. The corrosion will actually form in the joint between the battery terminal and the connector to your airplane. This forms a layer of insulation on your power circuit that can make it seem as if your battery is dead.


  • If you can see wet stuff on the top of the battery, get the battery serviced promptly. Why: Acid has another ability – that to form a connection between your battery and ground. If the acid makes a connection, your battery will slowly drain to aircraft ground, leaving you with no power when you want to go fly.
  • If you see anything white or green coming from your battery terminals, corrosion has set in. Have your A&P clean the terminals up, and clean the top of the battery while they are at it.
  • Black connectors, or connectors with heat damage. This is a clear indication that corrosion has formed directly between the battery terminal and the connector, leading to a nearly invisible insulator. The discoloration is the result of heat damaged caused to the terminal by the current draw.

WORST CASE: Corrosion can drop the voltage on the battery, and even cause the terminal to overheat so much that it burns right off the top of the battery!

Inside Information: Acid leaks can also form a connection between your battery and your airframe, causing increased corrosion. The combination of a little acid and high humidity can result in severe and expensive corrosion damage to parts of your airplane.

BOTTOM LINE: Keeping an eye on the outside of your battery will help keep what is inside functioning properly. While aircraft batteries are simple and easy to maintain, making sure your battery is in top condition will help you to avoid any “shocking” problems while in flight.