Part 68 (2/2)

It will generally be found that when a battery is sulphated, it is operating in very low specific gravity, or, in other words, the charges have not been carried far enough to drive all the acid out of the plates.

A battery that is not receiving quite enough charge may not as a whole become ”sulphated,” but several cells might become considerably weaker than the others and become ”sulphated,” causing trouble in these particular cells. Such cells will not bubble freely, or possibly not at all, when the other cells are bubbling freely. Therefore, a few questions to the user will generally help in locating the low cells.

Cells that are in trouble, or which soon will be, can very easily be picked out by making a few tests on the battery. Therefore, on all inspections, regardless of the age of a battery, it is suggested that the following tests be made: Take a specific gravity reading of all cells and note if there are any cells much lower than the others. Amy cells having a specific gravity of 30 points lower than the average will generally be found to be in trouble, unless these cells happen to be low from having had spillage in s.h.i.+pment, replaced with water.

(This condition, however, should not exist in future installations if the spillage is properly taken care of, as has been explained on page 482.)

Voltage Readings

After taking a specific gravity reading, a voltage reading of each cell should be taken. Voltage readings taken on open circuit are of no value, so while taking these readings the battery should be on discharge, having at least a discharge of 15 amperes. A good way to get this discharge is to hold the starting switch in and set mixing valve lever at lean point or wide open.

A low or defective cell will show a voltage reading .10 to .20 volts lower than the other cells on discharge, while a reversed cell will show a reading in the reversed direction when on discharge, especially on heavy discharge.

The voltage readings are a sure check if taken in connection with the specific gravity. When you have low specific gravity and low voltage on the same cells, it is a sure indication of low cells. These cells should be inspected for the probable cause of their being low.

Shorting of the lugs at bottom of plates and moss bridging across at bottom of the elements, or possibly a split separator, will generally be the main trouble.

When any of these conditions exist, it is best to take the low cells back to your shop for repairs.

When there is absolutely no indication why the cells are low, they can be cut out of the battery on discharge and put in on charge, until they come up.

The following is a good example of readings taken on a battery with a 10-ampere discharge and having four low cells, 4, 8, 11 and 16. The battery had been giving poor service, due to insufficient charging:

Cell No. Specific Gravity Volts 1 1.200 1.98 2 1.180 1.95 3 1.205 1.98 4 1.150 1.75 5 1.190 1.95 6 1.195 1.98 7 1.200 1.98 8 1.130 1.70 9 1.200 1.95 10 1.205 1.98 11 1.100 1.40 12 1.190 1.95 13 1.180 1.95 14 1.195 1.98 15 1.190 1.95 16 0.000 zero or reversal

The main thing to consider in checking voltage readings is the variation from the average. The average voltage readings will vary, depending on the state of charge of the battery when the readings are taken.

REPAIRS

To repair, the following equipment is necessary:

1. Portable lead burning outfit.

2. A suitable blow torch.

3. Standard sealing nut wrench.

4. File (shoemaker's rasp).

5. Pair of pliers.

6. Putty knife.

7. Pair of tin snips.

8. Wooden blocks to support elements while being worked upon.

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