If the specific gravity readings are all above 1.200, or if the gravity reading of one cell is 50 points (such as the difference between 1.200 and 1.250, which is 50 "points") lower or higher than the others (no matter what the actual gravity readings may be), make the 15 seconds high rate discharge test on the battery. See page 266. If this test indicates that the internal condition of the battery is bad, the battery should be removed from the car and opened for inspection. If the test indicates that the internal condition of the battery is good, the specific gravity of the electrolyte needs adjusting. The difference in specific gravity readings in the cells is due to one of the following, causes:
(a) Water added to the cell or cells which have low gravity to replace electrolyte which had been spilled or lost in some other manner.
(b) Electrolyte added to the cell or cells which have high gravity to replace the water which naturally evaporates from the electrolyte.
(c) Trouble inside the cell or cells which have low gravity. The high rate discharge test will show whether there is any internal trouble.
If any cell shows a gravity above 1.300, remove the battery, dump out all the electrolyte, fill battery with distilled water and put the battery on charge.
If the gravity of one or more cells is 50 points less than the others, water has been used to replace electrolyte which has been spilled or lost in some other manner, or else one or more jars are cracked. A battery with one or more cracked jars usually has the bottom parts of its wooden case rotted by the electrolyte which leaks from the jar. If you are not certain whether the battery has one or more cracked jars, see that the electrolyte covers the plates in all the cells one-half inch or so, and then let the battery stand. If the electrolyte sinks below the tops of the plates in one or more cells within twenty-four hours, those cells have leaky jars and the battery must be opened, and new jars put in.
If the low gravity is not caused by leaky jars, give the battery a bench charge and adjust the level of the electrolyte.
2. If you found electrolyte to be below tops of plates in all the cells, the battery has been neglected, or there mail be leaky jars. Add distilled water until the electrolyte covers the plates to a depth of about one-half inch.
(a) If it requires only a small amount of water to bring up the level of the electrolyte, remove the battery and give it a bench charge. See page 198. Only a brief charge may be necessary. Ask the driver when water was added last. If more than 1 month has passed since the last filling, the upper parts of the plates may be sulphated, and the battery should be charged at a low rate.
(b) If it requires a considerable amount of water to bring up the level of the electrolyte, and the bottom of the wooden battery case shows no signs of being rotted, the battery has been neglected and has been dry for a long time, and the plates are mostly likely badly damaged. Open the battery for inspection.