Best Way to Charge Trolling Motor Batteries

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Best Way to Charge Trolling Motor Batteries

Best Way to Charge Trolling Motor Batteries

Best Way to Charge Trolling Motor Batteries

As we power towards the 2020s, fishing has never been more popular as a pastime. And with that, trolling motors, used to power fishing boats, have never been more widely used.

Deep cycle batteries are commonly used in trolling motors, and due to their longer and steadier supply of power are a great fit and eminently suitable.

Although with advancing technologies li-ion batteries are becoming more popular, the traditional lead-acid deep cycle battery is currently cheaper and more widely used.

Deep cycle batteries are designed to supply charge when between 45% and 75% of their total capacity, depending on each battery’s usage and chemical composition.

These batteries fall into two distinct categories: Flooded Lead Acid (FLA) and Valve Regulated Lead Acid (VRLA). The valve regulated batteries are further divided into Absorbed Glass Mat (AGM) and Gel batteries.

Battery Maintenance

Modern AGM batteries require no complex maintenance and are therefore the most popular deep cycles.

However, other deep cycle batteries will usually require appropriate maintenance.

Most deep cycle batteries are manufactured with thick plating and a strong plastic case which protects the battery from vibration and shock damage.

Within the batteries are plates made up of lead and lead dioxide. These are partly or completely submerged in the fluid or semi-fluid state of chemical composition.

Therefore it is necessary to keep the electrolyte checked and at a constant level


The following are some points that can safeguard the battery from severe damage.

  • The battery nodes should be kept clean and tightened at regular intervals, as loose connections and accumulation of dirt on the plates can result in premature aging and general poor performance.
  • Keep a check on the fluid level inside the battery; it should not overflow or be left unfilled – either can damage the battery.
  • Always fill the battery with distilled water to the marked level. Do NOT use tap water, as it can contain chemicals and minerals that can react with chemical components within the battery.
  • Apply dielectric grease, NO-OX-ID or even Vaseline to the battery terminals whenever the battery is unused for a long period; this will prevent corrosion and contamination.
  • Recharge the battery regularly while not in use; this will prevent sulfation, which reduces the battery life.
  • Never abruptly disconnect the charging process and leave the battery partially charged. This can cause the phenomenon of battery stratification which disrupts the balance of chemicals inside the battery.

Another factor that contributes to maintaining the battery by ensuring its optimum performance is to conduct periodic equalization. This is the process of recharging the battery with a low current for 3 hours, which keeps the cell in a balanced state.

Battery Testing

While battery maintenance ensures the optimum performance of deep cycle batteries, appropriate testing determines the ideal mode with which to charge it.

Testing starts with determining the electrolyte level and the voltage of the battery. Measure the specific gravity (relative density) of the electrolyte and voltage of the battery with a hydrometer and digital voltmeter respectively.


In order to start the testing process, the battery should be completely charged. The surface charge should be removed prior to the testing. If you are not able to remove the surface charge by yourself, then let the battery settle for at least 6 hours before initiating the test.

The simple way to test the battery is to inject 20 amps charge into the battery for 3 minutes. Record the results and match it with the table given below that shows the ideal rate of voltage and gravity.

State of ChargeGravityVoltage (12v)Voltage (6v)
Note: Sulfation in the battery occurs when gravity measures less than 1.225 and voltage falls below the capacity of 12.4volts (12V) or 6.2volts (6V). Sulfation stiffens the battery plates and eventually reduce battery’s ability to generate desired volts and amps.
Load testing is a more complex method of testing the battery, performed when the battery is at full charge. Usually, the amp load for testing is mentioned on the battery and is generally ½ of the CCA rating.

The results of load testing should be as follows:

  • Hydrometer ratings should not exceed 0.5 of difference between the cells.
  • Digital voltmeter readings should not be higher than 12.9volts
  • If the voltage reading falls below 10.5volts, it may be that your battery contains defective cells.

Trolling Motor Battery Charging

From all of the deep cycle batteries sold in a year, only 30% are able to reach 48 months of functionality.

It is therefore essential to replace the charge removed from the battery by regular use. This will prevent battery sulfation and other things that adversely affect performance.

There are various methods to charge deep cycle batteries, but the charging always proceeds through the three stages of bulk, absorbed and float.

When it comes to charging trolling motor batteries, there are several possible methods. When trolling motors were in their infancy batteries were charged by turning the battery acid in the battery container. But as technology has advanced, more practical charging methods have emerged.

Solar Panel

Although it might not be a reliable source of power depending on the weather, solar energy can be used to provide the charge when the battery is not in use.

Portable Charger

With the benefits of mobility and fast charging, portable chargers are the most preferred mode of supplying power to the battery. They have quite a lasting impact on the battery and provide stable charge for a specific period of time.

Onboard Charger

When the boat is on water, the battery can be charged with an onboard charger. This provides a fast, convenient charge, but for a relatively short period only.

Best Way to Charge Trolling Motor Batteries – Our Verdict

The ideal method depends upon the circumstances. However, charging the battery through proper means and understanding its characteristics will ensure a long and productive battery life.

And remember, it could also save you from the situation of running out of charge on the water.

Like Best Way to Charge Trolling Motor Batteries? Click here for our reviews of household battery chargers

Steve Brown


Steve is a gadget enthusiast who's always been intrigued by batteries. The founder and editor of Battery Chargers Info, he's assembled a group of like-minded experts to cover every facet of portable power His aim is to help you learn more about your favorite gadgets and their batteries so you can maximize both their performance and their life.

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