Here is a step-by-step tutorial on how to fix a car battery:

1. Clean the battery. Wearing protective clothing, gloves, and goggles, mix a 2:1 mixture of baking soda and water, then either pour the solution over the terminals or use a toothbrush to apply it. You’ll see a chemical reaction, but this is normal.

2. Check the battery reading.

3. Empty the battery.

4. Clean the battery cells.

5. Replace the electrolytes.

6. Charge the battery.