Calculate the Amount of Time and Amperes to Charge your 12v Battery

Instructions: Input the number of Ampere-Hours or Cold Cranking Amperes, than choose the unit for the number. The unit options are Ampere-Hours and Cold Cranking Amperes (CCA). You can find this information by looking at the specifications for your battery at the manufacturers website, the information packet that came with the battery, or it is usually printed on the battery label. Click calculate and the calculator will determine the amount of amperes and time to charge your battery. The information provided by the calculator is a general rule of thumb, and the time and ampere's may vary depending on the condition of your battery. The answer will appear below.

Number (Ah or CCA):
Units: Ampere-Hours Cold Cranking Amps


(Answer will appear here)

Cold Cranking Amperes or CCA is a battery rating used to show how much power a battery can deliver to start your motorcycle or outdoor power equipment. The larger your engine the more CCA's your battery will need to produce to turn over the engine. This is one reason why it is always important to replace your battery with the correct one. The definition of CCA is the number of amps a fully charged battery can deliver at 0 degrees fahrenheit while maintaining at least 7.2 volts across the battery terminals for 30 seconds. Its important not to confuse cold cranking amps with another rating called CA or Cranking Amps. The definition of CA is identical to CCA, but the temperature is 32 degrees fahrenheit and not 0 degrees. Weaker batteries can score a higher CA rating, than CCA, and some manufacturers will try and confuse the consumer into thinking a weaker battery is stronger by displaying the batteries CA rating on the label.

The definition of Ampere-Hour is the amount of current a fully charged battery can deliver for 20 hours at 80 degrees fahrenheit while maintaining at least 10.5 volts across the battery terminals. If a fully charged battery can deliver 2 amps for 20 hours at 80 degrees fahrenheit while maintaining at least 10.5 volts across the battery terminals, than the battery is given a Amp-Hour rating of 40 ampere-hours. It is not as common to see amp hours rating displayed on the battery label as it is to see cold cranking amps.

Most methods used to test the condition of a battery require special tools, and it goes beyond the scope of this webpage. However, a simple voltage meter can be used to measure the voltage across the battery terminals and will indicate the batteries state of charge. The state of charge will not tell you the condition of the battery. It is possible to have a bad battery that measures high voltage across the terminals when it is not supplying current or is not under a load. Below is a table which lists the battery terminal voltage and relative percent charge.

Voltage Percent Charge
12.60 Volts 100%
12.45 Volts 75%
12.30 Volts 50%
12.15 Volts 25%
Less than 12.15 Volts Discharged