How to Calculate Amp Draw on Garmin Marine Equipment

To calculate the Amperage, draw of a Garmin marine chartplotter, radar, or sonar module, use the following formula:

• Amp draw = maximum watts / battery voltage

The maximum wattage of a Garmin device can be found in the Appendix under the Specifications section of its Owner’s Manual. It may list as Max Power Usage or Max Power at 10 Vdc, depending on the model the Owner’s Manuals may also provide both maximum power and current draw. If the model comes either with built-in sonar or non-sonar units’ look for separate tables in the appendix.

When calculating Amp Draw use the Following Inputs:

Use the Max Power or Max Power Usage at 10 Vdc as the baseline for all calculations.

Battery Voltage - 12 Vdc is the minimum recommended operating voltage for Garmin devices. Use the vessels dc power distribution voltage that the Garmin devices connect to typically, most recreational vessels use the following dc power distribution voltage systems: 12 Vdc, 18 Vdc, 24 Vdc, 32 Vdc, 48 Vdc. Devices may function at lower voltages but may have limited abilities due to low power.

If the vessel has a dc voltage above or below the operating parameters of a Garmin device, verify installation of the correct conversion equipment dc to dc. Consult an Authorized Garmin dealer or installer for more information

NOTE:  All figures are approximate and are based on "MAX draw at 10 Vdc". Data may be lower or higher, depending on other circumstances.