Napa Essentials 85-303 manual Electrical Condition of Battery

9.ELECTRICAL CONDITION OF BATTERY

9.1The state of charge of refillable-top batteries can be checked by using a hydrometer. A hydrometer is a bulb-type syringe which is used to extract a small quantity of the electrolyte from each battery cell. Types are calibrated in terms of specific gravity (a common scale being 1.120 to 1.265) or the type which uses four colored balls to indicate the state of charge. A float in the hydrometer barrel indicates the specific gravity of the electrolyte. This specific gravity reading indicates the battery’s state of charge at a given temperature, as shown in the table below:

State of Charge of		** Initial Specific Gravity Reading
Battery at 80°F (27°C)	1.280		1.265	1.225	Floating Balls
100%	1.280		1.265	1.225	4
75%	1.240		1.225	1.185	3
50%	1.200		1.190	1.150	2
25%	1.170		1.155	1.115	1
Discharged	1.140		1.120	1.080	*

**Initial specific gravity readings vary, depending on battery type and manufacturer. Contact the seller or manufacturer of the battery for this specification.

*No balls float in the barrel of the hydrometer.

9.2The state of charge of sealed-top (maintenance-free and recombination- type) batteries must be checked with a high resolution voltage tester.

9.3If uncertain about type of battery you will be charging, or the correct procedure for checking the battery’s state of charge, contact the seller or manufacturer of the battery.

9.4The temperature of the battery and the equipment the battery is used with has a dramatic effect on battery efficiency and system power requirements. For example, at 0°F (–18°C ), a battery is operating at 40% of its rated efficiency, while the engine it is attempting to start requires over twice as much power as would be necessary at 80°F (27°C).

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