Choosing a Battery

There are a number of factors to consider in selecting a battery to power the PowerUp Propulsion System, and a range of choices for each factor.  For that reason, we have not included the battery in our purchase package – we’ve left that decision to the customer.  We recommend, however, that you use a 12-volt deep-cycle, marine battery.  Those batteries are designed to be “deeply”, or totally discharged with each use, and are ideal for this application.

Discharge capacity of the battery is the most significant factor for our discussion.  That factor will actually influence all other factors with your choice.  Typically, discharge capacity is expressed as amp hours…and, simply put, the more amp hours you have, the more time on the water you get.  Also, the greater the amp hour rating of a battery, the larger, heavier and higher priced it will be.  The motor in our system draws 50+ amps at full-throttle.  Therefore, if you want to experience your top-end speed, for at least an hour, you should chose a battery with an amp hour rating of at least 50+ amp hours.  Doubling the rating to 100+ amp hours will effectively double your time on the water, if throttle settings remain the same.

As I mentioned, increasing amp hours in your battery, increases the size and weight of the battery.  Another factor that significantly affects those issues is whether you chose a lead acid or lithium ion battery.  In general, a lithium ion battery is much more expensive, but much lighter in weight, than a lead acid battery, with the same amp hour rating.  Additionally, we’ve found some significant differences between lithium ion and lead acid batteries with performance.  A lead acid battery discharges initially with a voltage in the range of 13.5 volts.  As the battery continues to discharge, the voltage drops slowly, and the motor will slow, at a given throttle setting.  A lithium ion battery, however, provides a higher voltage with discharge – around 14.5 volts.  That results in an increase in the performance of the motor (i.e. slightly higher speeds).  Furthermore, the lithium ion battery will maintain the higher voltage for most of the discharge cycle, so a slowing of the motor with time, is not as apparent.  In practice, you need to pay closer attention to your battery monitor with a lithium ion battery, as your day on the water progresses, to prevent running completely out of power before your outing is complete.  A reserve battery is always a good idea, pending the limits of your kayak’s weight capacity…and your budget.

Our system has received extensive testing with lead acid batteries of 105 amp hours, and lithium ion batteries of 100 amp hours. Assuming a range of throttle levels, occasional periods of slow trolling and/or 0 mph speed, that capacity level will provide a “full day” on the water. The lithium ion battery is 8-10 times the cost of the lead acid battery…but it’s less than half the weight.

I hope you’ve found the information above useful, and it helps you make the best battery choice for your propulsion system. Your questions or comments are always welcome!

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