How to Repair Cells in a Marine Battery
- 1). Put on goggles and wear protective gloves. Sulfuric acid is dangerous. It burns clothes, skin and will blind you if it gets in your eyes. Open the battery compartment on your vessel.
- 2). Remove the cell caps located on top of the battery. The caps have slots, so insert a large flat-head screwdriver into the slot and turn counterclockwise then remove them using your fingers. Place the caps to one side.
- 3). Check the electrolyte level. Each cell has two markers; minimum and maximum. If electrolyte is within the two markers, the cell can still retain a charge but needs topping up. If the electrolyte is below the minimum level, the lead plates are drying out and no chemical reaction is taking place so the cell can't charge. The lower the level the worse the condition of the cell.
- 4). Pour distilled water into each cell so that it reaches the maximum marker. You must use distilled water as it is pure and doesn't contain impurities which impede the flow of electrons and corrode the plates.
- 5). Replace the caps on each cell using the screwdriver. Close the battery cover.
- 6). Turn on your marine vessel's engine. You need to charge the battery for some time so the distilled water changes to acid. At this point the cells start to charge and the repair process begins. The longer you can keep your battery charging the better.
Source...