Kohler 20-3250 kW manual Specific Gravity Check, Charge Battery

3.11.3 Specific Gravity Check

Use a battery hydrometer to check the specific gravity of the electrolyte in each battery cell of batteries with filler caps. Holding the hydrometer vertically, read the number on the glass bulb at the top of the electrolyte level or the number adjacent to the pointer. If the hydrometer used does not have a correction table, consult Figure 3-20. Determine the specific gravity and electrolyte temperature of the battery cells. Locate the temperature in Figure 3-20 and correct the specific gravity by the amount shown. The battery is fully charged if the specific gravity is 1.260 at an electrolyte temperature of 26.7_C (80_F). Maintain the specific gravities between cells within ±0.01 of each other. Charge the battery if the specific gravity is below 1.215 at an electrolyte temperature of 26.7_C (80_F).

Note: Some battery testers have four or five beads in a test tube. Draw electrolyte into the tube as with the battery hydrometer described in this section or use the manufacturer’s instructions. Use Figure 3-21 to interpret typical test results.

3.11.4 Charge Battery

Use a battery charger to maintain a fully charged battery when the generator set is used in a standby application. The engine battery-charging alternator charges the battery while the generator set is running.

Note: If the generator set is in a temporary prime power application in which the generator set has periods of inactivity, the controller circuitry may drain the battery. If there is no power source for a battery charger, place the controller in the prime power mode, if equipped, or disconnect the battery from the generator set.

°C °F

71.1160

65.6150

60.0140

54.4130

48.9120

43.3110

37.8100

32.290

26.780

21.170

15.660

10 50

4.440

- 1.1 30

- 6.7 20

- 12.2 10

Correction

+ .032
+ .030
+ .028	Example No. 1
+ .026

+ .024	Temperature below 26.7°C (80°F)
+ .022	Hydrometer Reading 1.250
+ .020	Acid Temperature --6.7°C (20°F)

+.018

+.016 Subtract .024 Specific Gravity

+ .014	Corrected Specific Gravity is 1.226
+ .012	1.250 -- .024 = 1.226
+ .010
+ .008
+ .006	Example No. 2
+ .004	Temperature above 26.7°C (80°F)
+ .002
0	Hydrometer Reading 1.235
- .002	Acid Temperature 37.8°C (100°F)
- .004
-. 006	Add .008 Specific Gravity
- .008	Corrected Specific Gravity is
	1.243
- .010
- .012	1.235 + .008 = 1.243
- .014
- .016
- .018
- .020
- .022
- .024
- .026
- .028

The temperature correction amounts to about .004 (4 points) of specific gravity for each 5.5°C (10°F) change in temperature.

1-787

Figure 3-20 Specific Gravity Temperature Correction

Number of Floating Beads

5

4

3

1 or 2

0

Battery Condition

Overcharged

Fully charged

A good charge

A low charge

A dead battery

Figure 3-21 Bead-Type Test Interpretation

TP-6200 10/12 Section 3 Scheduled Maintenance 151