How to Measure Battery Voltage

You should check the voltage of your car's battery on a regular basis. By doing this maintenance, you decrease the likeliness of having the battery die while you are away from home. Low voltage in a young battery may also indicate an alternator problem. Confronting this small problem can prevent it from becoming bigger a one.

Difficulty: Easy

Instructions

Things You'll Need:

• Voltmeter
• Battery
• Wrench

1. Locate your car's battery and remove the ground (negative) wire. You will need to use a wrench that fits the clasp.

2. Remove the live (positive) wire using the same method. It is important that you remove them in this order to insure that you don't accidentally short circuit the battery while you remove the live wire. It will also ensure that you don't shock yourself while testing the battery. The chances that this could happen with the battery hooked up to the car is unlikely, but removing will give you zero chance of hurting yourself.

3. Take your voltmeter and find the red and black wires. Voltmeters can be bought at many hardware and automotive stores. Places like Radio Shack and Autozone will have several for you to choose from.

4. Place the red wire to the positive (live) end of the battery. Typically the positive side will also be colored red.

5. Touch the black wire to the negative (grounded) end of the battery. Typically the negative side of the battery will be colored black just like the wire you are touching to it.

6. Check to make sure that your voltmeter reads that the battery is putting out at least 12 volts. If it is, then your battery has enough voltage to power the car. If the meter reads fewer than 12 volts, then it is time for you to replace the battery with a new one.

7. Reattach the battery to the clamps.

Tips & Warnings

• If you want to make sure that your alternator is working, measure the volts from the battery while it is at rest and then compare it to the volts while it is hooked up to the running car. If the meter reads 13.5 to 15 volts, then the alternator is working.
• While checking the battery's voltage, you may also want to make sure that the electrical contacts are clean. If you suspect that your car isn't getting enough power, it may be cause by corrosion rather than a problem with the battery.

[toshiba]

on 9/25/2008 well it depend on the connection mode of the battery cells, if parallel connection, the voltage keep one cell's voltage, and if series connection, the voltage add by the number of the cells, for example, if the voltage of one cell is 3V, the series connection mode for 4 cells may generate 12V voltage

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