Can a Trolling Motor Battery Get Wet? Are Marine Batteries Waterproof?

Whenever my trolling motor battery acts up, the first thing I do is check to make sure the battery compartment is sealed correctly. It may seem unnecessary since marine batteries are made for the water, but they’re more vulnerable than you think.

A trolling motor battery cannot get wet. Exposing a marine battery to saltwater will create an electrical pathway that drains out energy. Furthermore, continued exposure to freshwater and saltwater can erode your battery. 

There are many ways that water can negatively affect your trolling motor battery. Fortunately, there’s a lot that you can do to care for your marine battery and keep it working longer.

Trolling motor laying on side for inspection.

How Moisture Affects Your Trolling Motor Battery

When installed correctly, marine batteries can effectively handle water activities. Still, direct exposure to water will negatively affect how the battery functions. Corrosion and rust are one concern. However, it’s even more common for electricity to leave the battery through the water. These situations can either gradually damage your battery or leave you stalled altogether.

Terminal Side Issues

Water damage to a marine battery’s terminal can result in severe power issues. Ideally, battery terminals should vibrate as little as possible. The terminal sits in very secure housing on the top side of the battery to prevent this occurrence. However, this housing is not infallible to leaks.

So, what could happen if water infiltrated your battery’s terminal? Consider this hypothetical:

Suppose water drips onto and penetrates the terminals. In this case, the water will collect between the terminal chambers. The water between the chambers will act as a conduit of electrical current, forcing the battery to expel discharges at increasing speed. In a worst-case scenario, this kind of drainage can leave you stranded in the middle of the water.

Marine battery up close.

Base Issues

While the base of the marine battery is insulated, it’s not fully protected from water. It’s essential to check your battery’s housing compartment to prevent any possible water contact with the base.

If saltwater touches the base, its insulation will slow down discharge, but it won’t stop entirely. The salt in the water will create an electrical pathway out of the battery. In this case, your battery will slowly discharge.

Placing your battery in a battery box will reduce exposure to moisture and corrosion. I highly recommend the Minn Kota 1820175 Trolling Motor Battery Power Center Marine Battery Box.

Exposed Wire

If the base and terminal are both isolated from water, what else do you need to consider? Another possible battery vulnerability is the wiring. Even if the wires are insulated, contact with water (especially saltwater) can expel energy from the battery via the wires. 

Can I Leave My Trolling Motor Out in the Rain?

If a marine battery cannot get wet, what does that mean for your trolling motor? For instance, is it okay to leave a trolling motor in the rain? While some rain shouldn’t be a problem, there are certain things you should know.

You can leave your trolling motor out in the rain. While excess moisture is detrimental to marine batteries, trolling motors are designed to get wet. Avoid letting trolling motor plugs get wet as these connect directly to the battery.

The good news is that manufacturers often seal the trolling motor shaft, making it almost impossible for water to get in. Therefore, you need not worry if the motor falls into a body of water for a brief moment.

However, the more significant concern, in this case, is the battery. After all, while some rain may not do significant damage, a heavy downpour is a different story.

Where to Store Trolling Motor Batteries

When possible, put the battery inside one of the boat’s hatches. Batteries should not be exposed on the deck of the vessel.

You are much better off buying a battery box. Not only will it protect your battery from the elements, but it will also protect you and your boat from your battery.

Storage for trolling motor batteries

Why would you need protection from your battery? Allow me to explain. 

Most trolling motor batteries are lead-acid wet cell batteries. Suppose your lead-acid marine battery got damaged. In this case, the battery could leak extremely harmful components, like toxic lead and corrosive sulfuric acid.

Furthermore, most battery boxes contain vents near the top that regulate the emission of hydrogen gas. Limiting hydrogen gas build-up from your battery is vital. Otherwise, the fumes could gather in the cabin of your boat. If its concentration surpasses 4%, this gas becomes highly explosive.

Beyond the undeniable necessities of a battery box, newer models can also offer fantastic conveniences. For instance, smart battery boxes, like the Newport Vessels Trolling Motor Smart Battery Box Power Center (available on, offer USB and DC ports for your phone and other electronic devices. This commodity will come in a pinch if you need to call emergency services on your cell phone.

How Can I Keep My Trolling Motor Battery in Great Shape?

As you can see, while trolling motor batteries are relatively durable, they still require care and maintenance to work at their best. So, how can you keep your trolling motor battery running safely and smoothly for years to come?

You can keep your trolling motor battery in great shape with regular maintenance and proper storage. For instance, it’s essential to keep your battery fully charged and regularly equalized. Furthermore, trolling motor batteries should be stored in dry areas that aren’t too hot or too cold.

There’s a lot more to this question than one paragraph could surmise. However, I would say the basics of marine battery maintenance come down to these basics: usage, charging, equalization, cleaning, storage, and testing.


How you use your marine battery affects its performance just as much as before or aftercare. Every time you use your marine battery, try to drain its energy entirely and don’t hesitate to charge it after use. Frequent partial charges and discharges can cause stratification (the chemicals in the battery cells go out of whack). This fluid imbalance can cause battery acid to sink to the bottom of the cells, resulting in corrosion.


Overcharging and undercharging a regular battery can result in less desirable effects. However, this issue becomes doubly imperative with marine batteries. When a marine battery charges too fast or slow, its lifespan will decrease.

To avoid this problem, invest in a multi-stage charger. For instance, the Minn Kota Precision On-Board Charger (available at is a brilliant resource for this purpose. Minn Kota’s revolutionary charger features a sensor that can detect when the battery is charging too much or too little and adjust accordingly. Furthermore, it has adjustable settings for AGMgel, or flood-leaded acid batteries. 


If you are using a flood-leaded acid battery, equalization is necessary at least twice a year. Equalization not only keeps your battery clean but ensures it a longer life. For more information, here is a video from Minn Kota Motors:

Cleaning and Storage

You should clean out the battery and its terminals thoroughly before storing it for long periods, like during the off-season. Furthermore, it’s necessary to store your battery in a dry, climate-controlled area. Extreme temperatures can cause damage to your battery.

Inspection and Testing

Take a close examination of your marine battery whenever you remove it from long periods of storage. It would help if you looked for any signs of damage, like frayed wires, bulgings, cracks, or corrosion.

Inspecting a trolling motor battery.

Furthermore, you should regularly test your marine battery. For instance, lead-acid wet cell battery owners should perform voltage and gravity tests on the electrolyte solution. These tests can diagnose problems like over-watering or an unsuitable charge. To conduct such tests, you will need two tools: a hydrometer and a voltmeter.

Final Thoughts

Trolling motors are quite durable and highly convenient, but the battery that runs them is less so. Marine battery voltage is lower than household appliances and does not present as much imminent danger in the water. However, water exposure is still a concern.

However, the more common issue is the effect water can have on a battery’s lifespan and usage. Under no circumstance can a trolling motor battery get wet. Therefore, if you want to get the most out of your marine battery, protecting it from moisture with a battery box is the best way to go.