# Battery Size Calculator

Complete the following input data to calculate the required battery size to achieve the desired runtime

Kw Load:

Inv Eff %:

Number Of Batt In String:

Number Of Parallel Batt Strings:

Desired Runtime Minutes:

Battery Rating =    Watts

Battery Power =    Watts Per Battery

Battery Power =    Watts Per Cell

Battery Current =  Amps

##### // <![CDATA[ function calc() { kw = (kw.value); eff = (eff.value); nobatts = (nobatts.value); nostrings = (nostrings.value); runtime = (runtime.value); if (kw < 1 || eff < 1 || nobatts < 1 || nostrings < 1 || runtime < 1) { alert("- ERROR - All user input fields must contain a positive number greater than zero. Clear the form before proceeding"); } amps = ((kw * 1000) / (eff / 100)) / (nobatts * 12); wpb = ((kw * 1000) / (eff / 100)) / (nobatts) / nostrings; wpc = wpb / 6; logruntime = Math.log(runtime); //Uses Math.function to use variables in higher order math problems. Sets variable logruntime to find the log of runtime in the formula below powruntime = Math.pow(runtime, 2); //Sets variable powruntime to find the exponent of runtime in the formula below Av = -0.0282419922029529; Bv = 0.0946569178501977; Cv = 0.357650908275154; multiplier = Av + Bv * runtime / logruntime + Cv / powruntime; capacity = multiplier * amps; battsize = (capacity * 4) / nostrings; battrating = Math.round(battsize); // Rounds value of battery watt rating to nearest integer wattsperbattery = wpb.toFixed(1); // Formats value to 1 place wattspercell = wpc.toFixed(1); batterycurrent = amps.toFixed(1); box1.value = battrating; box2.value = wattsperbattery; box3.value = wattspercell; box4.value = batterycurrent; } // ]]>

*Battery size calculation assumes 1.67 volts / cell cutoff
*Actual battery performance may vary from calculated values due to condition of the battery, operating temperature, and other factors