Whether you need to jumpstart a car, learn how to choose a battery or find out how to store one, just take a tour through Battery Basics and you'll be ready to go.
The standard automotive battery in today's vehicles is 12 volts. Each battery has six cells with 2.1 volts. A car battery is considered fully charged at 12.6 volts
When a battery drops voltage, even a small amount, it makes a big difference. For instance, when a battery drops from 12.6 to 12.0 volts, its power drops from 100% to 25%. At 12.4 volts, a car battery is 75% charged. At 12.2 volts, it's 50% charged.*
A car battery is considered charged at 12.4 volts or higher. It is considered discharged when it's at 12.39 volts or less.
Voltage is produced by a chemical reaction. Inside a battery there are positive and negative lead plates that sit in a liquid called electrolyte solution. Electrolyte solution is a mixture of water and sulfuric acid.
When this solution interacts with the lead plates, there's a chemical reaction. This chemical reaction creates pressure that we call "voltage."
The pressure (voltage) pushes the current out of the battery's negative terminal through the "load", the equipment drawing the power. The current returns through the positive terminal.
To achieve the chemical reaction that creates voltage in an automotive battery, the electrolyte solution inside the battery must have the correct mix of water and sulfuric acid. As you know, when a car battery is at 12.6 volts, it's charged at 100 percent.
At 12.6 volts, the electrolyte solution is 65 percent water and 35 percent sulfuric acid. This is the ideal combination!
Sometimes electrolyte "breaks down" and the acid moves onto the plates. So, there's less acid in the water. Whenever the percentage of acid in the solution decreases, the charge drops.
As the temperature drops, the cranking power required by the car increases. However, as more cranking power is used, the amount of battery power available decreases.
Cold Cranking Amps (CCA) is critical for good cranking ability. It refers to the number of amps a battery can support for 30 seconds at 0°F until the battery voltage drops to unusable levels. For example, a 12 volt battery with 600 CCAs means the battery will provide 600 amps for 30 seconds at 0°F before the voltage falls to 7.20 volts (six cells). The higher the CCA, the more powerful the cranking ability.
If you live in a cold climate, you should consider the CCA rating when choosing a battery. If you live in a very hot climate, you don't need as much CCA.
Selecting the Right Battery
How do you know which battery is right for your vehicle?
Here are some quick tips to help you make the right choice.
Check your vehicle manual for the original equipment manufacturer's recommendations for:
Battery group size indicates the battery size that will best fit the physical dimensions of your vehicle. Many vehicles can accommodate more than one group size.
- Battery group size
- Cold cranking amps (CCA)
- Reserve capacity (RC) for your vehicle
CCA is critical for good cranking ability. It's the number of amps a battery can support for 30 seconds at a temperature of 0 degrees F until the battery voltage drops to unusable levels. A 12V battery with a rating of 600 CCA means the battery will provide 600 amps for 30 seconds at 0 degrees before the voltage falls to 7.20 V (six cells).
RC helps to power your vehicle's electrical system if the alternator fails. It indicates the battery's "staying power" -- how many minutes the battery can supply ample power without falling below the minimum voltage needed to run your vehicle.
In general for both CCA and RC, the higher the number the better. HOWEVER, if you live in a cold climate, the CCA rating should be an important consideration in choosing a battery. Conversely, if you live in a high heat climate, you don't need as much CCA.
If you're looking for a deep cycle battery for marine or RV use, you must consider:
Multiply the Amps by the Hours to determine the Amp Hours, or AH, required.
- The type of equipment to be powered
- The current (amps) needed to run the equipment
- The number of hours you'll be using the equipment
Current Draw (Amps)
TOTAL 75 AH