How to Properly Clean Battery Contacts

So, you just found some long-lost electronic device and discovered a nasty mess inside the battery compartment? We’ve all been there. Or maybe your car battery’s terminals are in serious need of a cleaning? This blog and video will walk through the process of cleaning the contacts so your stuff works like new again.

Let’s start with some information. When alkalines leak, the solution is commonly referred to as “battery acid”; however, the substance leaking is actually not an acid at all, but a strong base known as potassium hydroxide. As the cells discharge they produce hydrogen gas. This gas eventually causes enough pressure to create an aperture to escape from, allowing carbon dioxide to enter the battery and mix with the potassium substance to create the crystalized leakage that you see.

To clean leakage from an alkaline battery, you will need:

  • Safety glasses (recommended but not required)
  • Lemon juice (or another acid such as vinegar)
  • Toothbrush or similar
  • Paper towels (barely dampened)
  • Rubber gloves (recommended but not required)
  • Dielectric grease (optional)

First, put on safety glasses and rubber gloves, then open the compartment to remove and properly dispose of the old batteries. Next, brush off any of the loose corrosion. Then put a small amount of lemon juice onto the contact and brush it around. Due to the leakage being a base solution, the acidity of the lemon juice will help to neutralize it. Repeat the last step until all of the leakage is removed. Now you can wipe it off with the slightly dampened paper towel. Please note that too much water can actually create more of an issue and oxidize the contacts, so use sparingly. If contacts are heavily rusted or damaged, you may want to use an abrasive such as sandpaper to clean to the base metal. Because many battery contacts are nickel plated, if the corrosion has eaten through this plating the contacts may be susceptible to rusting in the future. You can use dielectric (silicone) grease to protect these contacts or replace them altogether, see this link for our selection of replacements.

Alright, now let’s talk about automotive lead-acid batteries. These need to be cleaned a little differently because the residue from these is actually acidic.

To clean acid from a car battery, you will need:

  • Baking soda
  • Spray bottle (optional)
  • Water
  • Rubber gloves
  • Paper towels
  • Car terminal brush
  • Dielectric grease (optional)

First, put on your rubber gloves and safety glasses. The acid in these batteries is very corrosive. It can eat holes through clothing and is capable of causing injury, so be cautious. Start by removing the battery cables and brushing off any loose corrosion. To neutralize the acid, you need to add a baking soda paste to the terminals. Either coat the terminals in baking soda, then spritz water on them or mix the paste beforehand and apply it to the terminals. Let it sit and bubble for a while to neutralize the corrosion, then wipe the terminals clean with a paper towel. Use the brush to clean them a little more, then wipe them off with a paper towel again to remove any extra residue. Once they are clean, you can add a light coat of dielectric grease to all the mating surfaces and terminals to help prevent further oxidation and corrosion. Clean the terminals on the end of the wires with the same steps and reconnect to the battery.

About this author

Image of Ashley Awalt

Ashley Awalt is a Technical Content Developer that has been with Digi-Key Electronics since 2011. She earned her Associate of Applied Science degree in Electronics Technology & Automated Systems from Northland Community & Technical College through the Digi-Key scholarship program. Her current role is to assist in creating unique technical projects, documenting the process and ultimately participating in the production of video media coverage for the projects. In her spare time, Ashley likes to – oh, wait, is there such a thing as spare time when you’re a mom?

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