When it comes to selecting trolling motor batteries, there are a few things you will want to consider: Battery type, battery amperage hour rating, size and budget.
For many years, there were two primary types of deep-cycle 12-volt batteries recommended for use with trolling motors: Lead Acid Wet-Cell and AGM Batteries.
The term “Deep-cycle” means that the batteries are designed for discharging smaller amounts of current over a longer period of time and for more frequent recharging.
The “traditional” batteries are still -by far- the most popular trolling motor batteries but Lithium batteries are catching on.
Lead Acid Wet-Cell
Lead acid batteries remain the most common deep cycle batteries for trolling motors. They can handle frequent draining and re-charging associated with trolling motor use and they are the most affordable option. Depending on quality, lead acid batteries will last between 2-3 years. These batteries can be purchased for less than $100 and are readily available in a variety retail outlets. The downside of lead acid batteries is that they can require occasional maintenance – topping off the water – and they are also prone to vibration and spillage.
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AGM (Absorbed Glass Mat) Batteries are a type of lead acid battery that are completely sealed, generally last longer on a charge and typically have a longer life-span. While a traditional deep cycle battery might last approximately 2-3 years, an AGM deep cycle battery can last up to three or four years. AGM’s *cost more than standard lead acid wet-cell batteries – up to 2x more – and may not be an option for those on a tight budget. While more expensive, they provide increased longevity and performance out on the water. AGM’s also have the added benefit of being 100% maintenance free.
*The good news is that the prices of AGM’s have been dropping pretty consistently over the last couple of years.
Lithium batteries are starting to become more and more popular for a variety of reasons:
1. Extremely Lightweight – For the smaller boats and boats where weight can be a considerable factor, lithium batteries offer a 70% average reduction in weight compared to traditional batteries.
2. Significantly Longer Battery Life – Lithium batteries can last up to 10 years whereas lead acid wet-cell and AGM batteries have an average life span of 2-4 years. Even though there is a higher up-front cost for lithium batteries, they can save you money in the long run. If you calculate the cost of replacing your batteries every 2-3 years as opposed to every 10 years with lithium, you’ll most likely be spending less on batteries when all is said and done.
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3. 100% Depth of Discharge – This essentially means that you’ll have full power regardless of the level of charge. Traditional batteries tend to lose power and capacity as their charge is depleted. By the way, the new Minn Kota Precision chargers are compatible with lithium batteries.
4. More Power – Due to the consistent, sudden fluctuation in speeds, trolling motors require a fair amount of cranking torque (aka thrust). Lithium batteries supply more power due to their negligible voltage drop when rapid acceleration is required.
5. Smaller Footprint: Not only are lithium batteries lighter, they also take up less space. For instance, you can buy a 24v lithium battery that is the same size as a 12v, group 27 deep cycle battery.
My more detailed description of lithiums may indicate a bias on my part but that’s not necessarily true. Due to the lack of awareness in lithium batteries, I wanted to describe the technology in more detail. Ultimately, good quality batteries with the right specs (see below), will provide adequate power for a full day of fishing.
In the end, your choice will depend on your budget, your installation specifications and your priorities.
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Amperage Hour Rating
You can think of a battery’s amperage hour rating as being similar to the gas tank of a car. Everything else equal, a battery with a 115 amp hour rating will last longer than a 100 amp hour rated battery. In more technical terms, a 100 amp hour rated battery can deliver 100 amp hours of current to a trolling motor. So if a motor was running at low speed and pulling 4 amps, the battery should last around 25 hours. (100 amp hour rating / 4 amps = 25 hours). Similarly, if the motor was running at top speed and pulling 40 amps, the battery would last for 2.5 hours (100 amp hour rating / 40 amps = 2.5 hours). For more information on understanding battery run times, please see our guide on understanding trolling motor run time.
For trolling motors use, we recommend a battery with AT LEAST a 100 amperage hour rating, a Group 27 rating and 175 minutes of Reserve Capacity (RC). Due to shipping restrictions, we do not sell marine batteries at TrollingMotors.net. However, both types listed above should be widely available in most areas. Lithium batteries are more difficult to find but we recommend Lithium Battery Power LLC if you decide to go that route.
- Never mix battery types, nor old batteries with new batteries.
- Charge batteries as soon as possible after each use – leaving batteries in a discharged state will decrease their longevity and performance.
- Periodically check wet-cell battery fluid levels and top-off as needed
- Check terminal connectors periodically for signs of corrosion – clean with a paste of baking soda and water.
- Store batteries in a cool, dry place in the off-season and maintain a trickle charge.