Calculating the Run Time of Motor

Almost every customer asks “How long can I expect the motor to run for on a single battery charge?”. This actually depends on a number of factors such as the weather and water conditions, how fast you run the motor, the weight of the boat and so on. But there are two major things that determine the run-time: the amperage capacity of the battery and the amperage draw rate of the motor. Fairly simple science really!

Amperage Hour Rating – Every battery whether lead acid, gel cell or lithium has an amperage rating ie 105Ah (amperage hours) which is an indication of how long a battery can supply a continual amperage. So a battery with a larger amperage rating will last longer than a smaller rated battery. A simple guide is as follows, a 105Ah battery is theoretically capable of supplying 25 amps of power for 4.2 hours (25 amps x 4.2 hrs = 105 amp hours) before it will become flat and require recharging. But if you only draw 10 amps of power then you could expect to get up to 10.5 hours of running time.

Amperage Draw of the Motor – Now compute the estimated motor run-time based on amperage draw. The actual amperage draw of the motor is how much amperage (or current) the motor draws at a particular speed. The slower the speed you operate the motor, the lower the amperage being used. Conversely, if the run the motor at full speed, the higher the amperage draw rate and the shorter the run time will be. We recommend 105 Ah plus battery for most of the Haswing motors for a 12V model, whereas a 24V requires two of these or 1 x 24V InfinitiPower lithium and a 36V model requires 3 x 105Ah deep cycle batteries or 1 x 36V InfinitiPower lithium.

Variable speed motors (vs fixed speed motors) will generally provide longer running times.

Extending Battery Life and Running Time – It is best to recharge an AGM battery before it is fully depleted of charge, because by fully depleting the charge regularly it can shorten the life span of the battery. Whereas a lithium battery has a BMS (battery management system) that switches the battery cells off when it reaches maximum Depth of Discharge, thus protecting the cells. And when the battery is not in use, it is a good idea to trickle charge the battery with a suitable charger. Doing these things can extend the battery life and the running time on the water and enable you to get the most out of your Haswing trolling motor.

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