The Automobile Storage Battery: Its Care And Repair

by Otto A. Witte

Level of Electrolyte. During charge the electrolyte will expand, and will generally flow out on the covers. This need not be wiped off until the end of the charge. When the electrolyte has cooled after the battery is taken off charge, it must be about 1/2 inch above the plates. While the electrolyte is still warm it will stand higher than this, but it should not be lowered by drawing off some of it, as this will probably cause it to be below the tops of the plates and separators when it cools.

TROUBLES

If all goes well, the charging process will take place as described in the preceding paragraphs. It frequently happens, however, that all does not go well, and troubles arise. Such troubles generally consist of the following:

Specific gravity will not rise to 1.280. This may be due to the plates not taking a full charge, or to water having been used to replace electrolyte which has been spilled. To determine which of these conditions exist, make cadmium test (see page 174) on the positives and negatives, also measure the voltage of each cell. If these tests indicate that the plates are fully charged (cell voltage 2.5 to 2.7, Positive-Cadmium 2.4 volts, Negative-Cadmium minus 0.15 to 0.20 volts), you will know that there is not enough acid in the electrolyte. The thing to do then is to dump out the old electrolyte, refill with 1.300 electrolyte and continue the charge until the specific gravity becomes constant. Some adjustment may then have to be made by drawing off some of the electrolyte with a hydrometer and adding water to lower the gravity, or 1.400 acid to bring it up. Remember that specific gravity readings tell you nothing about the plates, unless it is known that the electrolyte contains the correct proportions of water and acid. The cadmium test is the test which tells you directly whether or not the plates are charged and in charging a battery the aim is to charge the plates, and not merely to bring the specific gravity to 1.280.

If the specific gravity will not rise to 1.280 and cadmium tests show that the plates will not take a full charge, then the battery is, of course, defective in some way. If the battery is an old one, the negatives are probably somewhat granulated, the positives have probably lost much of their active material, resulting in a considerable amount of sediment in the jars, and the separators are worn out, carbonized, or clogged with sediment. Such a battery should not be expected to give as good service as a new one, and the best thing to do if the tests show the battery to be more than half charged, is to put it back on the car, taking care to explain to the owner why his battery will not "come up" and telling him that he will soon need a new battery. Remember that improperly treated separators, or defective separators will cause poor Negative-Cadmium readings to be obtained.

If a fairly new battery will not take a full charge, as indicated by hydrometer readings and cadmium tests, some trouble has developed due to neglect, abuse, or defect in manufacture. If all cells of a fairly new battery fail to take a full charge within 48 hours, the battery has probably been abused by failing to add water regularly, or by allowing battery to remain in an undercharged condition. Such a battery should be kept on the line for several days more, and if it then still will not take a full charge the owner should be told what the condition of the battery is, and advised to have it opened for inspection.

If one cell of a battery fails to take a charge, but the other cells charge satisfactorily, and cadmium tests show that the plates of this cell are not taking a charge, the cell should be opened for inspection. If one cell of a battery charges slowly, cut the other cells out of the line, and charge the low cell in series with the other batteries on the charging line.

If all cells of a battery, whether new or old, will not take even half a charge, as indicated by hydrometer readings (1.200), the battery should be opened for inspection.

If the gravity of a battery on charge begins to rise long before the voltage rises, and if the gravity rises above 1.300, there is too great a proportion of acid in the electrolyte. The remedy is to dump out the electrolyte, refill with pure water and continue the charge at a lower rate than before, until the specific gravity stops rising. Then charge for ten hours longer, dump out the water (which has now become electrolyte by the acid formed by the charging current), refill with about 1.350 electrolyte and continue the charge, balancing the gravity if necessary at the end of the charge.

If a battery becomes very hot while on charge at a rate which is not normally too high for the battery, it indicates that the battery is badly sulphated, or has a partial short-circuit. Gassing generally goes with the high temperature.