Car Battery Ah Calculator

For example batteries rated in ampere hours ah also called amp hours are designed to deliver low currents for an extended period.

Car battery ah calculator.

C rate of the battery. Caveat manufacturers test and rate batteries according to a certain discharge time in the automotive industry usually 20 hours. Drawing 10 amps from a 10 amp hour battery or 1c you will only get half of the rated capacity or 5 amp hours from a 10 amp hour battery. Last example a lead acid battery with a c10 or c 10 rated capacity of 3000 ah should be charge or discharge in 10 hours with a current charge or discharge of 300 a.

For example a 1c battery needs one hour at 100 a to load 100 ah. Amp hours are also heavily based on the relative capacity between two batteries which reduces accuracy levels in helping determine the exact time of use. Cca x 0 7 ah. Using the inverter calculator indicates 14 35 amps dc load and then running the sizing calculator suggests that i need battery capacity of 306 ah 20 hrs.

When you can calculate the amp hours from a cca battery it will be easier to find the correct replacement when your car battery goes bad. Or you may have a battery showing the ah rating only and you need to convert it to cca to have a better idea about its performance in the cold season. C rate is used to describe how fast a battery charges and discharges. However when the 2 105 20 hrs batteries in parallel are used and then put on charge after use the batteries typically register 50 charged.

Charts that detail this effect for different discharge rate can be used for greater accuracy. Why is it important to know the c rate or c rating of a battery. To determine the ah rating of a 12 volt battery use a multi meter. A rule of thumb is that for a 1 hour discharge rate i e.

With this formula you can calculate any car battery ah from a given cca. The auxiliary battery should be connected to the alternator through an isolator module to prevent the inverter from discharging the engine start battery when the engine is off. Connect a basic resistor across the battery s terminals then monitor the discharge over time until the voltage decreases to 12 volts. The number you get is amp hours which is 420ah.

Divide the battery s 100 amp hour capacity by 83 3 and you get 1 2 hours or about 1 hour and 12 minutes of tunes before the battery dies. Deep cycle batteries most commonly available are 27 90 ah 4d 150 ah 8d 220 ah capacity. This is the current i used for either charging or discharging your. Just use the method mentioned above.

Take the current cca number from your car battery for example 600 and multiply it by 0 7.