Old lead acid batteries can be tricky to repair. Often, the cells inside the battery are cracked and corroded, making it difficult to get a good connection. The first step is to clean the battery terminals and connections with a wire brush. Next, you’ll need to test the cells to see if they are holding a charge. If not, you’ll need to replace the cells. Finally, you’ll need to reconnect the battery terminals and test the battery to make sure it is working properly.