Calculator | Determine Run Time for Specific Load

This calculator is intended to help you figure out how long your lead-acid (Wet, AGM, Gel) battery will last under a specified load. In order to use this calculator you will need two separate AH ratings, given by the manufacturer, as well as the amperage, in direct current of your load. For an explanation of why a calculator is necessary to figure out the true run time of your battery see Puekert’s Law.

Walkthrough

	This calculator is designed to tell you exactly how long your battery will last given a set amperage load that is put on it.  It requires 2 separate AH ratings at different hour ratings.  If you do not know, you will need to contact the manufacturer to find out.  Typically you will have a 100hr rate, a 20 hr rate and a 10 hr rate readily available from the manufacturer.
Example	C1 and R1 - The first field of this calculator is for the first AH rating for the battery.  In our example, it is 200 AH.  This leads to the second field, which is the hour rate that the AH is given at.  In our example it is the 20 Hr rate.
Example	C2 and R2 - The third and fourth fields are for the second set of ratings, in this case 216AH at a 100 Hr rate.
Example	Battery Temperature and Age - The fifth field is to adjust for extreme environmental temperatures, in our example it is over 85 deg F. The sixth field accounts for age of the battery.
Example	Peukert's Constant - The seventh field is Peukert’s constant, and is figured using the previously given information. If you want to see the formula yourself, see our Math behind the Magic article.
Example	Amperage of Load Applied - The next field is where the amperage of the load you are placing on the battery is entered. This is figured in DC amperage, so if your load is being ran through an inverter; use our AC to DC amperage conversion calculator. For our example, we have calculated a total load of 15 amps.
Example	Capacity At Given Load - The nineth field tells you exactly what the adjusted capacity of this battery is at your specific load.
Example	Runtime with 50% Safe Discharge Level - The last field tells you approximately how long your battery will last under the given load and circumstances. Under a 15 amp load, our 100 AH Battery should be discharged no more than 6 hours and 9 minutes.

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