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A good marine battery is essential if you want to make the most of your time on the water.

AGM Batteries are currently the most popular choice because they are sealed and virtually maintenance-free.

In this article, you’ll learn about how to pick the right AGM battery for your boat and what our recommendations are.

Let’s get started!

If you’re looking for an AGM battery for your trolling motor, we’ve handpicked the best products depending on the size you need:

Best Large AGM Batteries – 100 Ah

Renogy
12V 100Ah
Universal Power
Group 12V 100Ah
WindyNation
100Ah 12V
Voltage12V12V12V
Capacity100 Ah100 Ah100 Ah
Cell TypeLead-acid, AGMLead-acid, AGMLead-acid, AGM
Dimensions LxWxH13.1 x 6.9 x 8.6 in12.2 x 6.6 x 9.2 in13 x 6.8 x 8.7 in
Weight63.9 lb64 lb66 lb

Best Medium AGM Batteries – 75 Ah

Weize
12V 75AH
Mighty Max
12V 75Ah
Universal Power
12V 75AH
PricingCHECKCHECKCHECK
Voltage12V12V12V
Capacity75 Ah75 Ah75 Ah
Cell TypeLead-acid, AGMLead-acid, AGMLead-acid, AGM
Dimensions LxWxH10.02 x 6.65 x 8.94 in10.24 x 6.61 x 8.27 in10.24 x 6.61 x 9.13 in
Weight46.7 lb50.7 lb49.1 lb

Best Small AGM Batteries – 35 Ah

Mighty Max
12V 35Ah
Weize
12V 35AH
Interstate Batteries
12V 35AH
PricingCHECKCHECKCHECK
Voltage12V12V12V
Capacity35 Ah35 Ah35 Ah
Cell TypeLead-acid, AGMLead-acid, AGMLead-acid, AGM
Dimensions LxWxH7.68 x 5.16 x 7.13 in7.68 x 5.12 x 7.09 in7.68 x 5.16 x 6.42 in
Weight24 lb23.1 lb22.9 lb

8 Things to Consider When Buying AGM Batteries

1. Advantages of Using AGM Batteries

Lead-acid AGM batteries are built with a well-known and safe technology. They’ve been constantly improved since the 1980s, and they can last many seasons if looked after properly.

They’re also relatively inexpensive if the alternative is using lithium batteries.

Another great thing about them is that you can charge them with a regular car battery charger.

2. Downsides of AGM Batteries

If you ever carried a car battery, you know how heavy lead-acid batteries are. AGM batteries are just as heavy or even heavier if you opt for a larger capacity.

AGM batteries can’t be discharged below 50% of their capacity without a significant drop in their lifespan.

Good AGM batteries will give you 200-300 charge/discharge cycles, which you can consider good enough, depending on how often you go out fishing. However, lithium batteries can do even over 3000 cycles, which means you don’t have to worry about buying new batteries for a long time.

Another important limitation is that AGM batteries have to be stored fully charged. Otherwise, they will quickly start deteriorating and losing capacity.

3. Know the System Voltage

The voltage of your trolling motor will determine how many 12 volt batteries you need.

A 12V trolling motor requires just one 12V battery; for 24V and 36V systems, you will need to connect 2 or 3 batteries in series. More batteries of the same size mean more capacity and more range available.

4. How to Select the Right Size?

How much run time you will get out of your battery mainly depends on two factors: battery capacity and current draw of your trolling motor.

Battery capacity is measured in Ampere-hours or Ah and current draw in amperes (amps). In theory, if your battery has 100Ah capacity and your motor draws 20 amps of current, then you can calculate its run time by dividing 100/20 = 5 hours.

However, as we said before, if you want to keep your AGM in good condition, you should only use 50% of its rated capacity. In the case of a 100Ah battery, you really only have 50Ah available, so your run time at the same speed will be 2.5 hours.

5. Check Available Space and Battery Dimensions

It’s tempting to use large AGM batteries that will give you more run time.

However, do check how much space you have available, and remember that you will need more than one marine battery if you have a 24v or 36v trolling motor.

If you have enough space but your boat is light, think about how the extra weight in the desired location could affect your boat’s balance and handling.

If you want to keep your battery in a specially designed battery box, you will need to check if the fuse is the right size for your motor.

6. What Type of Terminals Should a Battery Have?

Battery terminals are frequently overlooked when choosing a battery. There are several different types, with all their pros and cons. Have a closer look at the terminals, and – if possible – read user reviews.

If your battery has threaded terminals, you should read the battery specifications and find out what torque you should use to tighten them.

You will need to get an appropriate torque wrench to do that.

7. What About Flooded Lead-Acid Batteries?

Both flooded and AGM batteries are lead-acid batteries. The main advantage of an AGM battery is that it’s encapsulated and spill-proof.

You can also charge an AGM battery much faster (up to 5 times), and it can better withstand freezing temperatures.

Another reason why I recommend AGM over flooded batteries is that they are better suited for a boating environment, where motion and vibration are commonplace.

8. Get the Correct Battery Charger

You can charge a 12v AGM battery with a car battery charger, but make sure it has the correct current output for the size of the battery you want to charge.

It is normally recommended to charge your deep-cycle AGM battery with a current limited to 20% of rated capacity. For a 100Ah battery, this equals 20A of current.

Now, if you took a 20A battery charger and connected it to a small 35Ah AGM battery, this could lead to the battery heating up and gassing, and damage to the battery.

AGM Trolling Motor Battery Reviews

1. Renogy 12V 100Ah

Renogy builds some of the most reliable AGM batteries in the market today. They use high purity materials and special alloy plates that allow extremely high discharge currents (a whopping 1100A) and a low self-discharge rate of less than 3% per month.

One thing to be careful about is to be careful not to overtighten the battery terminals. If you have a torque wrench, set it to less than 109.8 inch-lb. (12.4 Nm)

2. Universal Power Group 12V 100Ah

Universal Power Group offers some of the best value AGM batteries currently. They are also sealed and spill-proof and can be mounted in any position.

The first thing you notice is the terminals which work great with those found on many trolling motors. They are not threaded, which means you can’t damage them.

The main drawback is only one year warranty, which is less than competition.

3. WindyNation 100Ah 12V

WindyNation is another good choice for a deep-cycle AGM battery. It’s made with high-purity lead, which results in a very low internal resistance.

It has threaded terminals, which means you have to be careful not to overtighten them.

4. Weize 12V 75AH

If you need slightly smaller batteries, for example, to connect two in series for a 24-volt system, a 75Ah capacity AGM battery might be a better choice.

We love Weize batteries and how they are designed. You can’t overtighten the terminals, and each battery comes with terminal bolts and a convenient handle.

It’s a heavy-duty battery that will have no problem powering your trolling motor.

5. Mighty Max 12V 75AH

Mighty Max is one of the better-known brands in the industry. They have a good reputation for long life and reliability.

They are 100% spill-proof and is shock and vibration resistant.

Mighty Max offers a full 1-year warranty and a 30-day refund policy.

6. Universal Power Group 12V 75AH

This Universal Power Group battery is a smaller version of the popular UPG 100Ah battery.

It’s popular among trolling motor owners due to its smaller form factor. This is especially useful if you need to connect two batteries in series to achieve 24 volts.

Very good value with a 1-year warranty.

7. Weize 12V 35AH

This is a great little battery for a fishing kayak or a canoe, where trolling motors tend to be in 24-36lb thrust territory.

Many small boat fishermen like them for the small factor and ease of installation. It weighs only 23 pounds.

8. Mighty Max 12V 35AH

This Mighty Max battery has a high maximum discharge current of 330A.

Its container is made of durable ABS that resists vibrations often found in marine environment.

The reviews are mostly positive, although they stress that if you have a 12v trolling motor, this battery is only suitable for small boats.

9. Interstate Batteries 12V 35AH

Last on our list is Interstate Batteries product. Don’t get me wrong, it is still a very good battery.

However, it is also quite a bit more expensive than the two batteries above, which means you get less value for your money.

Frequently Asked Questions

What size battery do I need for a trolling motor with 30 lb thrust?

It will most certainly be a 12v battery. When it comes to its Ah rating, It really depends on how heavy your boat is. On an aluminum jon boat, your 30-lb motor will draw much more current than on a kayak.

Can I install my AGM battery on its side?

Most AGM battery makers allow installing a sealed AGM battery on its side. However, you should check it with your battery manufacturer. It is always recommended to install the battery upright and NEVER upside down.

How do I wire an AGM battery for a 12v trolling motor?

If you have a 12 volt trolling motor with just a single battery, the wiring of your system is straightforward:

  1. Make sure the speed of the motor is set to “0”
  2. Connect positive (+) of the motor to positive (+) of the battery
  3. Connect negative (-) of the battery to negative (-) of the motor

How do I connect AGM batteries in series for 24 volts?

If you have a 24 volt trolling motor, you will need to connect two 12 Volt batteries in series:

  1. Make sure the speed of the motor is set to “0”
  2. Connect positive (+) of the motor to positive (+) of Battery 1
  3. Connect negative (-) of Battery 1 to positive (+) of Battery 2
  4. Connect negative (-) of Battery 2 to negative (-) of the motor

How long can you store an AGM battery?

AGM batteries can be store for up to seven years. However, it doesn’t mean you can leave it for that long unattended and hope it will perform like new. If you want it to last that long, you will have to keep it fully charged.

Still, there will always be some chemical aging and damage affecting the plates, which means you will have significantly less available capacity than before when it was new.