Batteries and Battery Testing

1. Batteries and Battery Testing

2. A typical battery showing all of its component parts.

3. As a battery is discharging the lead peroxide, sponge lead and sulfuric acid chemically react to each other. This causes the positive & negative plates to turn to lead sulfate. The sulfuric acid turns to water.

4. As the battery is recharged, the lead plates & acid return to their original state.

5. As the battery is discharged, the acid content decreases and the water increases.

6. Lead-alloy grid. The active battery materials are “pasted” onto these grids.

7. Absorbed Glass Mat Batteries The acid used in an absorbed glass mat (AGM) battery is totally absorbed into the separator making the battery leak proof and spill proof. The battery is assembled by compressing the cell about 20 percent, then inserting it into the container. The compressed cell helps reduce damage caused by vibration and helps keep the acid tightly against the plates. The sealed maintenance-free design uses a pressure release valve in each cell. Unlike conventional batteries, called flooded cell batteries, most of the hydrogen and oxygen given off during charging remains inside the battery. The separator or mat is only 90% to 95% saturated with electrolyte, thereby allowing a portion of the mat to be filled with gas. There gas spaces provide channels to allow the hydrogen and oxygen gases to recombine rapidly and safely. Because the acid is totally absorbed into the glass mat separator, an AGM battery can be mounted in any direction. AGM batteries also have a longer service life often lasting seven to ten years. ASM batteries are also called sealed lead acid (SLA) batteries.

8. Maintenance-free.

9. Diagnostic Story Chemical reaction for a lead-acid battery that is fully charged being discharged by the attached electrical load.

10. SAFETY TIP Chemical reaction for a lead-acid battery that is fully discharged being charged by the attached generator.

11. As the battery becomes discharged, the specific gravity of the battery acid decreases. Frequently Asked Question Frequently Asked Question

12. Typical battery charge indicator. If the specific gravity is low (battery discharged), the ball drops away from the reflective prism. When the battery is charged enough, the ball floats and reflects the color of the ball (usually green) back up through the sight glass and the sight glass is dark.

13. When testing a battery using a hydrometer, the reading must be corrected if the temperature is above or below 80°F (27°C).

14. (a) Memory saver. The part numbers represent components from Radio Shack. (b) A schematic drawing of the same memory saver. Some experts recommend using a 12-volt lantern battery instead of a small 9-volt battery to help ensure that there will be enough voltage in the event that a door is opened while the vehicle battery is disconnected. Interior lights could quickly drain a small 9-volt battery.

15. Jumper cable usage guide. Notice that the last connection should be the engine block of the disabled vehicle to help prevent the spark that normally occurs from igniting the gases from the battery.

16. Courtesy of Fluke Corporation Measuring battery electrical drain using a multimeter set to read DC amperes.

17. A capacitance-type battery tester. The up and down arrow keys are used to answer questions about the battery before it is tested.