Only 12-volt, lead acid, batteries can be recharged by an electrical battery charging device. There are two basic physical types of the lead acid battery, an SLA (sealed lead acid), and an open top maintainable battery. The SLA is just as the name applies; it allows no access to check the level of battery fluid inside each individual battery cell. The open top or maintainable battery allows the user to check and add fluid to the battery. Both of these types of batteries can be easily tested for a full charge.
Things You'll Need
- 12-volt car headlamp
Attach the 12-volt car headlamp to the positive(+) and negative(-) terminals of the battery. Keep the lamp connected for approximately three minutes. This will remove any surface charge to the battery if it was freshly charged. A surface charge occurs through the charging process and can give a false result to the following test.
Insert the red lead for the voltmeter into the connector identified as “Volts.” Place the black lead for the meter into the connector marked as “com.” Turn the switch on the meter to the position of “DC Volts.”
Touch the red lead to the positive terminal on the battery. Connect the black lead to the negative terminal.
Read the value in DC volts on the face of the meter.
Observe the following values to assess the condition of the battery through the meter reading. A voltage value of 12.7 volts and above indicates a 100 percent charged battery. The voltage reading of 12.4 volts will indicate that the battery is only 75 percent charged. A meter reading of 12.2 volts or 12.0 volts will indicate a charge rate of 50 percent and 25 percent, respectively. Any readings below 11.9 volts will indicate a fully discharged battery, and damage may have occurred to the storage device. Voltage readings that are 10.5 volts and below show that the battery is severely damaged and needs to be replaced.
Tips & Warnings
- Follow the battery manufacturer's specifications and maintenance details whenever servicing any lead acid battery. Special precautions may apply for some types of batteries.
- Always charge any lead acid battery in a well ventilated area. The charging process emits a highly flammable gas that can be ignited by any open flames.
How to Charge a 12V Battery
Most vehicles use 12-volt batteries to start the engine and power the accessories while the engine is running. The vehicle's alternator, generator...
How to Tell If a Car Battery Is Charged
If you're like most people, you've experienced a dead car battery at some point in your life. Often, a drained battery strikes...
How to Charge a 12-Volt Deep Cycle Battery
There are three basic types of deep cycle batteries: standard wet cell, absorbed glass mat and gel cell. The batteries are rated...
How to Know When an Auto Battery Is Fully Charged
A 12-volt car battery must maintain a full charge not only to start your vehicle, but also to ensure that the battery...
The Battery Won't Charge on My John Deere
One of the most frustrating things that can occur when trying to garden or work on your lawn is to have a...
How to Tell If a 12 Volt Battery Is Bad?
Battery problems can lead to a no-start or crank problem. In many of these cases, lack of maintenance is the root of...