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Trolling Motor Run Time: How To Calculate Run Time

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Looking for an efficient trolling motor for your boat? Check out our full line of transom mounted saltwater trolling motors.

When calculating trolling motor run time, there are two things you need to know: Battery amperage hour rating and a motor’s amperage or watt draw.

Amp Hour Rating

Marine batteries are rated by “Amperage Hours”. This unit measures how long a battery can maintain a consistent amperage output. The larger the amperage hours (AH) rating, the longer it will last and more power it will be able to hold.

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Motor Amperage Draw

Motor amperage draw describes how much amperage/watts a motor draws at a certain speed. In order to calculate an estimate of how long your current or soon to be motor will last, you divide the AH rating and divide it by the amperage draw. If the only information given by the manufacturer is watts, you divide watts by the voltage of the battery to calculate how many amps are being drawn. You then compare this to the AH rating on your battery.

If Only Amperage Drawn Is Given
50 AH / 52 amps drawn = .96 hours

If Only Watts Is Given
624 watts drawn / 12 volt battery = 52 amps drawn
50 AH / 52 amp drawn = .96 hours

Most manufacturers will only list the amps/watts being drawn at top speed. You can calculate an estimate of amp drawn at different speeds using the max speed provided as your starting point. Note, these estimates do not factor in weight, wind or water resistance or other external factors.

Watt Draw For NV Motors At Different Speeds*

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*These are approximate ratings taken during a factory test

Weather

Weather can greatly affect battery performance and life. The stronger the weather, the more energy/power will be used to combat the resistance. This is something to take into account when choosing a battery.

Extending Battery Life

-Larger Motor:

24v multi-battery trolling motors and larger can have the same thrust as smaller motors with fewer amps being drawn.

-Don’t Completely Empty Your Battery:

Making this a regular routine can deteriorate the life of your battery. Recharging your battery before it is completely drained and using battery life indicators can help you keep your battery strong as well as keeping it adequately charged. Our Smart Battery Box is equipped with a LED battery life indicator which helps estimate how much battery charge you have left.

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Leaving Your Battery Uncharged

It is detrimental to battery health to leave it uncharged for months. If you are not using your battery, utilizing a battery tender or trickle charger can be invaluable. These devices help keep a slim amount of current running through your battery. Charging your battery about every month can greatly increase the longevity of your battery as well.

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