Selecting a Battery for a Motorized Kayak: Type, Capacity, and Life
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Selecting a Battery for a Motorized Kayak: Type, Capacity, and Life

Selecting a Battery for a Motorized Kayak: Type, Capacity, and Life

If you’re considering the purchase of a fishfinder for your kayak, or pondering going all in on an Old Town Sportsman AutoPilot motorized kayak, you’ve probably found yourself wading into the world of marine batteries. The questions surrounding type, capacity, and duration are relevant, important, and at times, a bit overwhelming. These questions have led you here, where I hope to provide a basic knowledge of batteries and some empirical advice to ensure you’re purchasing the right battery for you.

Kayak Battery Type:

There are two general types of battery: lead-acid and lithium-ion. Each comes with pros and cons. Lead-acid batteries cost less, but they have a shorter lifespan and require regular maintenance to keep them operating properly. Conversely, lithium-ion batteries are much more expensive up front, but they are maintenance-free and have a much longer lifespan. Most lithium-ion batteries are 95% efficient or more, whereas lead acid batteries should not be discharged to much more than 50% before you risk causing loss of the battery's lifespan. In terms of weight, lithium-ion batteries weigh roughly 30% less than their lead-acid counterparts, which is a definite factor when you consider loading and unloading it each trip as well as the overall load your kayak can handle.

As is often the case with consumerism in general, if you buy cheap you’re most likely going to need to buy often. That is to say, saving money on a lead-acid battery will probably feel good in the short term, but there’s a high likelihood you need to replace it within a year or two. For this reason, I recommend lithium-ion batteries. Choosing lithium-ion will not only reduce the hassle of loading and unloading a hefty battery, but it will also help increase the distance you can cover just by its reduced weight alone. Most importantly, your wallet will thank you. Perhaps not right away, but over time the cost-effectiveness of lithium-ion makes it a no-brainer.

Battery Capacity:

You’re going to want to familiarize yourself with the term “amp hours,” often abbreviated “Ah.” Battery capacity (how long it will last on a single charge with consistent output), is measured in amp hours. The higher the amp hours, the longer the battery can power the motor. With higher amp hours, you are also going to look at a higher cost and a longer charge time. For this reason, it’s important to tailor your battery purchase to the type of fishing you do. You don’t want to buy too small a battery and end up running out of juice, but you also might not need a 100Ah battery if you’re mainly fishing smaller lakes and ponds. To give you an idea of battery life and travel distance, refer to the chart on the right. It is based on an Old Town Sportsman Autopilot 120 kayak outfitted with a 100Ah lithium-ion battery. Essentially, this chart offers a look at how far you can go on a single charge. However, be aware that there are numerous variables which will alter the travel distance possible from a single charge. These variables are covered in the next section.


Speed Setting Motor Amp Draw GPS Speed 100AH Battery Run Time (in hours) Distance (in miles)
0.5 0.8 0.3 125.00 37.50
1 1.2 0.5 83.33 41.67
1.5 1.8 0.8 55.56 44.44
2 2.3 1.1 43.48 47.83
2.5 2.8 1.3 35.71 46.43
3 3.9 1.6 25.64 41.03
3.5 4.8 1.9 20.83 39.58
4 5 2 16.67 33.33
4.5 7.4 2.4 13.51 32.43
5 9 2.6 11.11 28.89
5.5 10.5 2.7 9.52 25.71
6 12.5 2.8 8.00 22.40
6.5 14.9 3.1 6.71 20.81
7 17 3.2 5.88 18.82
7.5 19.3 3.4 5.18 17.62
8 21.8 3.6 4.59 16.51
8.5 24.9 3.7 4.02 14.86
9 27.5 3.8 3.64 13.82
9.5 30 4 3.33 13.33
10 35 4.2 2.86 12.00

Battery Duration and its Impacting Factors:

This has to be the most asked question I hear from those considering purchasing a battery-powered kayak like the Old Town Sportsman Autopilot: “How far can you go on a single charge?” As insinuated above, that's not a question with a simple answer, because many factors will alter the output you get from a single charge, and of course the size of your battery will play a big role. For this reason, battery duration and angler behavior are mutually inclusive topics. Simply put, how far you can go depends significantly on water conditions, load weight (including yourself), type of battery, battery capacity, and your behavior as an angler.

When it comes to draining your battery, how you choose to fish on a given day will have a big impact. Oftentimes, your day is spent cruising the bank at speed settings 1 to 3 with occasional Spot Lock to really work a particular structure. Perhaps throw in a few short stints at speed 10 to hurry towards the next honey hole, then some more time spent in Spot Lock mode or using more low speeds, and we are looking at a generally accurate hypothetical fishing day. I use a 100Ah Dakota Lithium battery and the aforementioned “style” is often how I spend my days fishing. With 100Ah, this type of fishing has never fully drained my battery, and I am confident in the amp hours I have available.

In order to discern how much battery you’ll need, or how quickly it drains, you’ll need to do some reflection on your style of angling. For example, if your day is full of high speeds jumping from spot to spot, or if you often cover long distances trolling or exploring a vast amount of water, you’ll need a battery with enough amp hours to keep you cruising. Keep in mind that on a given day, environmental factors like wind, swell, and tide will impact how quickly your battery drains. Additionally, heading out with just the bare essentials or loading your kayak up with a weekend's worth of gear can also play a large part. Trolling at a constant speed is one way to get an idea of just how far you can go in your local waters. However, if you really want to avoid the stress of worrying about your battery life, I recommend a battery meter.

Battery meters are a great way to put your mind at ease while on the water. Some anglers have what we like to call “battery anxiety.” This is the constant feeling that you will drain your battery and be left paddling your way back to the launch. I had the same feeling until I installed a meter. If you plan on sticking with a traditional lead-acid battery, the meter built into the AutoPilot powered by MinnKota will work just fine. However, if using a lithium-ion battery, you will need to install a meter designed for lithium batteries. The reason for this is that lead acid batteries drop in voltage output as they drain. Lithium batteries output a constant voltage regardless of the capacity left in them, leaving you no warning that they’re running low until they’re dead. For this reason, installing a meter or having your local shop install one is an anxiety-reducing cost you’ll be happy to have invested in.

Lastly, you may be wondering about pairing a fishfinder with a motorized kayak. Selecting the right battery for your fishfinder is an important task, and the same basic principles discussed above still apply here. The first step is to look up the power draw for the fishfinder you plan to use. This can be found on most manufacturer’s websites. Sometimes, the power draw will be given in milliamps. You can use a simple online conversion website to translate the amps. As an example, the Humminbird Helix 7 Chirp Mega SI draws 0.8 amps. This means that when using a 10Ah battery, you would get 12.5 hours of battery life (10 divided by 0.8). That is more than enough for your average day on the water. However, the Humminbird Solix 10 Mega SI draws 2.5 amps. This would mean that the same 10Ah battery only lasts for about 4 hours, and you’d be hard pressed to enjoy a day on the water without being constantly worried about your battery dying. So, for a larger, more power consuming fishfinder, you’ll need to invest in a higher amp hour battery which gives you more than enough charge to last for what you’d consider your typical day on the water. When in doubt, it’s a safe bet to purchase too big of a battery rather than one that’s too small.

In summary, it should be clear that choosing a battery is something that takes research, reflection, and a financial investment on the part of the angler. The more data and knowledge you arm yourself with as you begin the process, the more likely you’ll be to make the correct choice the first time you purchase a battery for your kayak motor, fishfinder, or both. Once the purchase and installation are complete, you can enjoy the fun part: get out there fishing and use some of that battery life!

Since 1999, Black Hall Outfitters has been southern New England’s premier kayak fishing and paddle sports destination. From kayak accessories, lighting, and transport, to bait, tackle, and marine gear, BHO has everything you need to make the most of your on-water adventures. For more information, stop by either of our two locations in Westbrook or Old Lyme, Connecticut or visit us online at

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