Heat Calculations

How to calculate the decrease in the heat an electric vest produces when connected to the battery through a harness or controller

This procedure can be used to calculate the decrease in the heat an electric vest produces when connected to the battery through a harness or controller. Ideally there should be no loss, but since wire, switches, connectors, and circuitry all have resistance, there will be some loss. Harnesses and controllers with large wire and few, high-current connectors will have less loss than harnesses with small wire and many connectors or low-current connectors.

Step 1) Measure and record vest resistance. Be sure to compensate for meter lead resistance.

Step 2) Connect vest to either the battery harness or a controller and to the battery.

Step 3) Turn on vest (full on if controller is adjustable).

Step 4) Measure and record the voltage across the battery.

Step 5) Measure and record the voltage across the leads at the vest.

Step 6) Calculate vest current at the voltage recorded in Step 5:

Current = Step 5 Voltage / Step 1 resistance

Step 7) Calculate vest wattage at the voltage recorded in Step 5:

Vest wattage through harness = Step 5 voltage X Step 6 current

Step 8) Calculate vest current if directly connected to battery:

Current = Step 4 voltage / Step 1 resistance

Step 9) Calculate vest wattage at the voltage recorded in Step 4:

Vest wattage at battery = Step 4 voltage X Step 8 current

Step 10) Subtract Step 7 wattage from Step 9 wattage to get wattage loss of harness/controller.

Step 11) Divide the Step 10 wattage by the Step 9 wattage and multiply the result by 100.

This gives the percentage loss of the harness/controller.

For example, if the vest resistance is 4.0 Ohms, the battery voltage is 13.8

volts, and the voltage at the vest is 12.8 volts:

Step 6 vest current is 12.8 / 4 = 3.2 A

Step 7 vest wattage is 12.8 X 3.2 = 42 Watts

Step 8 vest current is 13.8 / 4 = 3.45 A

Step 9 vest wattage is 13.8 X 3.45 = 47.6 Watts

Step 10 wattage loss is 47.6 - 42 = 5.6 Watts

Step 11 percentage is 5.6/47.6 = .1176, or 11.76 % loss in the harness/controller

Our HEAT-TROLLER and battery harness has a 1.4% loss! Check our competitors products.

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