How to Make Trolling Motor Batteries Last Longer

If you’re an avid trolling enthusiast, you know how important it is to have a reliable trolling motor. Hauling in an amazing catch depends on your ability to drag your lines through the water at a slow, steady pace; if your motor fails, you’re quite literally “dead in the water,” likely with no choice but to return to shore.

Aside from mechanical failure, battery life is the most common reason for trolling and outboard motors to quit, and several different factors can affect your battery’s performance. Batteries function differently depending on their type and design, and each type has its own operational and maintenance requirements.

Battery Types

According to power boat manufacturers, trolling boats that are 14 to 16 feet long should be equipped with a 12-volt motor. Longer boats require a 24 or 36-volt motor.  Any of these motors will run on a deep-cycle 12-volt battery; unlike starter batteries, deep-cycle batteries are made to discharge a small amount of current over a long period. They require frequent recharging, but they are perfect for producing the kind of slow, steady power your trolling boat requires. Deep-cycle batteries are available in two kinds: lead-acid wet cell batteries and absorbed glass mat or AGM batteries.

Lead-acid wet cell batteries are a popular choice because they’re cheaper than AGMs, and they handle being drained and recharged fairly well. However, they require regular maintenance: you need to check the water levels in the cells and keep the terminals clean to avoid corrosion. Additionally, these batteries can leak or spill, causing damage the battery housing, terminals, and even the boat, so make sure they’re firmly positioned and check them often.

By contrast, AGM batteries last longer, and they are completely sealed, so there’s no danger of spillage. They also typically have a longer life-span: a lead-acid wet cell battery might last two years, while an AGM cell can last up to four. However, they’re also about twice as expensive.  

Lithium-ion batteries represent a third option. They’re attractive because they’re very reliable, efficient, fully sealed, and lightweight. However, they are very expensive, and they pose a unique set of safety challenges: lithium-ion battery fires are among the most difficult to extinguish, and if your battery catches fire, simply dousing it in lake water won’t work. To stop the chemical reactions that are occurring, you need a foam or dry chemical extinguisher, and your boat might sustain serious damage before you’re able to bring the fire under control. For these reasons, most boaters steer clear of lithium-ion cells unless there’s a pressing reason to prioritize weight and efficiency over safety.

Maximizing Battery Life

To make your trolling motor’s batteries last longer and perform more reliably, keep these troubleshooting and maintenance tips in mind.

  • Battery and boat manufacturers recommend that you fully recharge your trolling motor battery as soon as possible after use. Batteries that are left to sit with less than 12.4 volts are prone to the formation of lead sulfate inside the cells, which will severely impact their performance and lifespan.
  • It’s a good idea to use a trickle charger during the offseason to keep power flowing through the battery, or to re-charge them every month. Allowing your battery to sit uncharged for a long time will reduce its performance and shorten its lifespan.
  • As much as possible, drain your battery fully, and then recharge it fully. Repeated partial discharge and recharge creates a condition called stratification, in which the chemicals in the cells are out of balance. Essentially, the acid sinks to the bottom of the battery, limiting the performance and life of the unit.
  • Allow your battery to cool off after recharging. The recharging cycle produces a significant amount of heat inside the cells, and Immediately putting a hot battery to use can cause damage or total failure.
  • After each recharge, be sure to equalize the charge to keep battery cells in balance. Most battery chargers have an equalizing cycle, which applies an extended, low-current charge for a long period (usually 1 to 3 hours).
  • For lead-acid wet cell batteries, check water levels at least once each month, topping them off with distilled water as needed.
  • Be sure to clean the battery and its terminals before you put it in storage for the offseason, and store it in a dry, temperate environment. Don’t let your battery get too hot or too cold, as extreme temperatures are damaging.
  • When you take your battery out of storage, thoroughly inspect it for signs of damage. Bulging, cracks, frayed cables, and corrosion will severely impact your battery’s performance and could pose a health and safety hazard. If the damage is severe, you may have no choice be to replace the battery. Be sure to dispose of old batteries correctly.
  • If you have a lead-acid wet cell battery, perform routine voltage and specific gravity tests on the electrolyte solution in each cell to identify problems like over-watering and inadequate charge. You’ll need a hydrometer and a voltmeter for these tests, but you can purchase a reliable model of each for ten to fifteen dollars.
  • Invest in a high-quality charger. Cheap charging units never do a great job of charging the battery to full capacity.

General Guidelines

Following best practices for maintenance and storage can go a long way towards maximizing your trolling motor battery’s life. However, you should also keep the following general guidelines in mind:

  • If you’re unfamiliar with your boat’s power requirements, do some reading to solidify your understanding of how batteries work. In the long run, it will make you a more confident and capable boater.
  • If possible, match your battery’s discharge rate with the motor’s power consumption. For example, a 55-pound thrust motor requires a battery load of 120 amp hours. (An amperage hour is a means of quantifying the amount of energy a battery can store and discharge. More amperage hours equates to higher energy storage capacity, which means it can power your motor for longer.)
  • Use your trolling motor in calm water as much as possible. When the motor has to fight against chop, strong winds, and strong currents, it requires more power and will drain the battery more quickly.
  • As batteries age, their capacity will generally decline, while their internal resistance increases. This makes it harder to charge the battery, and harder for the battery to deliver its energy to the motor. If it’s not already present, write the date of purchase on your battery, and keep an eye on the passage of time. Even the best-maintained battery will begin to fade with age.
  • When using your trolling motor, keep the load steady and moderate and make changes to your speed gradually. Sharp, heavy shifts in speed will cost you more power, and if you overtax the motor by running at a higher speed for long periods, you’ll drain the battery more quickly.
  • Be careful when moving lead-acid wet cell batteries – vibrations and sudden jolts can break the internal plates and render the cells incapable of holding a charge.

Conclusion

Maintaining a proper charge affects the longevity of your trolling motor battery more than any other single factor. For best performance, service your battery regularly, store it in a clean, dry, and temperature-controlled place, and use a trickle charger to keep it at maximum charge throughout the offseason.

Use a hydrometer and a voltmeter to test lead-acid wet cell batteries properly, and if you’re concerned about vibrations or jostling that might damage the cells, opt for a more stable AGM battery. When trolling, minimize drain by keeping your speed low and steady and staying in calm waters as much as possible.

By understanding your boat’s power consumption needs, taking proper care of your battery, and exercising discretion while on the water, you’ll enjoy reliable, hassle-free performance from your trolling motor, season after season.