The Automobile Storage Battery Part 66

(a) Measure specific gravity of each cell. If any cell is badly discharged it is probably short-circuited, or contains impurities and had better be opened for inspection.

(b) Turn on all the lamps and measure the voltage of each cell. If any cell shows a voltage much less than 1.8 it is short-circuited or contains impurities, and should be opened for inspection.

(c) Examine the connections between cells for looseness or corrosion; and examine the connections between the battery and the generator, going over cables, switches, rheostats, etc. Make sure that you have a complete and closed charging circuit between the generator and the battery.

(d) If cutout is used on the switchboard, see that its contact points are smooth and clean, and that they work freely.

(e) Run the generator to see if it builds up a voltage which is sufficient to charge the battery, about 42 volts for a 16 cell battery.

If the generator is not working properly, examine it according to directions on page 451. Check up the field circuit of the generator to be sure that it is closed. A circuit-tester made of a buzzer and several dry cells, or a low voltage lamp and dry cells, or a hand magneto is convenient for use in testing circuits. Test armature windings and field coils for grounds.

By the foregoing methods you should be able to determine what is to be done. The following rules should also help:

Cleaning and renewal of electrolyte is necessary when:

(a) Sediment has risen to within one-half inch of the bottom of the plates.

(b) Much foreign material is floating in the electrolyte, or electrolyte is of a deep brown color.

Replacement of parts is necessary when

(a) Separators are cracked or warped. See page 346 for Separator troubles.

(b) Plates are defective. See rules on pages 339 to 346.

PREST-O-LITE FARM LIGHTING BATTERIES

[Fig. 300 Element from Prest-O-Light farm light cell]

The Prest-O-Lite battery which is designed for use in connection with farm lighting plants is known as the FPL type. Cells of 7, 9, 11, 13 and 15 plates are made, the number of plates being indicated by putting the figure in front of the type letters. A seven plate cell is thus designated as a 7 FPL cell, which has an 80 ampere hour capacity at the 8 hour continuous discharge rate.

The FPL cell, the construction of which is shown in Figs. 295, 300, 301, 302 and 303, has a sealed gla.s.s jar with a lead antimony cover.

The cover construction is shown in detail in Figs. 301 and 302.

Insulation between the posts and cover is provided by a hard rubber bus.h.i.+ng, a hard rubber washer, and a soft rubber washer. The bus.h.i.+ng is shaped like a "T" with a hole drilled in the stem. The stem of the bus.h.i.+ng fits down into the post hole in the cover, the f.l.a.n.g.e at the top testing on the raised portion of the cover around the post hole.

The post has a shoulder a little less than halfway up from its lower end. Upon this shoulder is placed the hard rubber washer, and upon the hard rubber washer is placed the soft rubber washer. This a.s.sembly is fastened to the cover by the "peening" process used in Prest-O-Lite automobile batteries as described on page 386. This forces the soft rubber washer tightly against the cover so as to make a leak proof joint-between the bus.h.i.+ng and cover. The ring of lead formed around the posts by the peening process supports the posts, plates, and separators, which therefore are suspended from the cell cover. The plate straps extend horizontally across the tops of the plates, and thus also act as "hold-downs" for the separators. The separators are held up by two rectangular rubber bridges which fit Mito slotted extension lugs cast into the lower corners of the outside negative plates. An outside negative having these extension lugs is shown in Figure 303.

[Fig. 301 Cover of Prest-O-Light farm lighting cell]

[Fig. 302 Parts of Prest-O-Light farm lighting cell: nut, stud, terminal, hard rubber bus.h.i.+ng]

[Fig. 303a Parts of Prest-O-Light farming light cell: gla.s.s jar, rubber jar, rubber cell connector, gla.s.s cell connector]

[Fig. 303b Parts of Prest-O-Light farm lighting cell: positive plate and outside negative plate]

[Fig. 303c Parts of Prest-O-Light farm lighting cell: long lead jumper, jumper, separator, short lead jumper]

Specific Gravity of Electrolyte. The values of the specific gravity of Prest-O-Lite farm lighting batteries are as follows:

Battery fully charged reads 1.250 Battery three-fourths charged reads 1.230 Battery one-half charged reads 1.215 Battery one-fourth charged reads 1.200 Battery discharged completely reads 1.180

These readings are to be taken with the electrolyte at a temperature of 80 Fahrenheit. Readings taken at other temperatures should be converted to 80. To convert readings at a lower temperature to the values they would have at 80, subtract one point for every two and one-half degrees temperature difference. For example, suppose a cell reads 1.225 gravity at 60. To find what the gravity would be if the temperature of the electrolyte were 80 divide the difference between 80 and 60 by 2-1/2, or 80 minus 60 divided by 21/2 equals 8. The gravity at 80 would therefore be 1.225 minus .008, or 1.217, which is the value of specific gravity to use. If the specific gravity is read at a higher temperature than 80, divide the difference between 80 and the temperature at which the gravity reading was taken by 21/2, and add the result to the actual gravity reading obtained. If, for example, the gravity were 1.225 at 100, the gravity at 80 would be 1.225 plus .008, or 1.233.

Charging Rates. The normal charging rate to be used in giving Prest-O-Lite batteries a regular charge or overcharge are as follows:

Battery Charging Rate ------- ---- 5 F.P.L. 5.0 amps.

7 F.P.L. 7.5 amps.

9 F.P.L. 10.0 amps.

11 F.P.L. 12.5 amps.

13 F.P.L. 15.0 amps.

15 F.P.L. 17.5 amps.

Rebuilding Prest-O-Lite Farm Lighting Batteries

Opening the Cell.

1. Make sure that the cell is as fully charged as possible. Since it is not very convenient to charge a single cell, a good time to open a cell for cleaning and repairing is immediately after the battery has been given an overcharge. See page 455.

2. Disconnect the cell from the adjoining ones.

3. Heat a thin bladed putty knife and insert it under the edge of the lead-antimony cover to melt the sealing compound. Run the knife all round the cover, heating it again if it should become too cool to cut the compound readily.

4. Grasp the lead posts above the cover and lift up gradually. This will bring up the cover, plates, and separators.

5. Place the plates on a clean board for examination. Use the instructions given on pages 339 to 346. Do not keep the plates out of the electrolyte long enough to let them dry, and the negatives heat up. If you cannot examine the plates as soon as you have removed them immerse them in 1.250 acid contained in a lead or non-metallic vessel until you can examine them.

6. In renewing the electrolyte, pour in as much new 1.250 acid as there was old electrolyte in the jar. (It is a.s.sumed that the electrolyte was up to the lower ridge of the gla.s.s jar before the cell was opened.) The new electrolyte must not have a temperature above 100 degrees when it is poured into the jar.

7. The separators can be pulled out easily when the plates are laid on their sides. All that is necessary is to remove the small rubber bridge at the bottom corners of the plates. The separators can then be pulled out. If the old separators are to be used again brush off any material that may be adhering to them, and keep them wet with 1.250 acid until they are replaced between the plates. Any separators that show cracks or holes, or that split while being replaced between the plates should be thrown away and new ones used.

8. It is not necessary to remove the sediment from the bottom of the jar unless it is within one half inch of the bottom of the plates. If the sediment is to be removed, carefully pour off the clear electrolyte into a lead, hard rubber, or earthenware jar, if the electrolyte is to be used again.

9. If one or two of the plates in either positive or negative groups need to be replaced it is best to burn a new plate to the strap without removing the peened cover. This is done by blocking under the row of plate lugs with metal blocks after cutting off old plate and cleaning the surface of strap. Insert new plate, the lug of which has been cut about 1/4 inch short, to allow for new metal. Choosing small oblong iron blocks of suitable size, build a form about the plate lug which fits same well. Now with a torch and burning lead fuse the new plate onto the old strap. When cool remove and test joint by pulling and slightly twisting the plate at the same time.

Sometimes one group of a starting and lighting battery may be in sufficiently good condition to pay to combine it with a new group, but this condition will very rarely, if ever, be met in farm lighting cell service. We advise the replacement of the complete cell element if either group is worn out, for the cost of repairs and of new group will probably not be warranted by the short additional life which the remaining old group will give.

10. Putting Repaired Cell Back into Service. After having finished all necessary cleaning, replacement, or repairs, remove all old sealing material, return the element with attached lead cover to the cell jar.

It is not necessary to reseal the cover to the jars this sealing is essential only for insurance against breakage or leakage in s.h.i.+pment.

Add through the vent plug opening sufficient cool acid of 1.250 Sp.

Gr. to reestablish the proper electrolyte level, which means that the electrolyte is brought up to the lower moulded gla.s.s ridge near the top of jar.

Connect the cell with any other repaired cells and charge at normal rate already indicated under "charging rates" until dell voltage reads 2.5 or above, at 80. The positive to cadmium voltage should be at least 0.10 volts less than cell voltage itself. When this condition is obtained cell may be replaced in operating circuit with others and should give satisfactory service.

EXIDE FARM LIGHTING BATTERIES.