Trolling Motor Batteries – The Complete Buying, Charging, and Maintenance Guide

Buying the perfect inflatable boat is easy… trolling motors aren’t that difficult either…

The hard part is choosing the right trolling motor battery.

Things can go bad if you get the wrong one. I’m talking about the battery dying in the middle of a lake, or even your boat catching fire!

You HAVE to be careful when buying one of these. There’s NO room for error – you could seriously hurt yourself.

Sound scary?

The good news is that with a few pointers, buying the perfect trolling motor battery is super easy.

That’s why I’m here… To give you the complete guide to trolling motor batteries.

By the end of this article, you’ll know:

• The battery types you should and should NEVER use
• The difference between popular marine batteries (wet-cell, AGM, and lithium)
• What AH rating is and how to calculate battery life 
• The best batteries in the market today
• How to PROPERLY charge your batteries

Plus, I’ll also throw in a bunch of tips on how to get the most out of your battery.

We’re going in-depth today, so buckle up, and let’s dive in!

Batteries You Should NEVER Buy (and those you should)

NEVER use a car battery.

Shocked?

Most people are when I tell them this. After all, trolling motor batteries look exactly like the ones we see in our car engines.

But there is a big difference:

Car batteries are starter batteries, trolling motors batteries are deep-cycle batteries.

Starter batteries give a surge of power to get an engine running. Once running, the car’s alternator charges the battery so it never runs out.

Without a steady charge, starter batteries drain quickly and die. Even if they don’t completely drain, you can’t use a starter battery if its power drops below 50%. Remember, they need a surge of power to get started.

Even worse, the starting power surge can also damage your trolling motor. So NEVER use a car battery for your trolling motor. It’s a terrible idea.

Instead, you need a deep-cycle battery for your trolling motor. No other type of battery will do.

Here’s why:

Deep-cycle batteries give slow and even power. Your motor can run for hours and hours thanks to this.

Plus, you can use 80% of their power without worrying they won’t start up anymore. No matter how low the battery gets, you can always recharge it (no alternators needed here!).

Starter batteries go bad if they drain completely… but deep-cycle batteries were designed to be discharged and recharged. Good batteries can last hundreds, even thousands, of cycles before needing to be replaced.

Deep-cycle batteries are the only way to go for trolling motors. Other batteries may work, but they’ll always be either dangerous or ineffective.

Note: Ever heard the term “marine battery?” It’s a very tricky one…

Sometimes, this term is used interchangeably with the word “deep-cycle”. Other times, it’s used to describe any battery used on a boat – such as starting batteries for outboard motors. To avoid confusion, look for deep-cycle batteries, not marine batteries.

The 3 Types of Deep-Cycle Batteries

Get any deep-cycle battery, and you shouldn’t have any problems.

That said, it’s a good idea to learn about the 3 popular types of deep-cycle batteries: wet-cell, AGM, and lithium-ion.

1. Wet-Cell Batteries

These are the oldest, cheapest, and perhaps most common type of deep-cycle battery around. That said, they are losing popularity to AGMs for several reasons.

For one, they need regular maintenance. If you leave your wet-cell battery alone, it will die a lot sooner than it should.

Electrolyte fluid (water and sulfuric acid) fills these batteries. If this fluid ever drops below the critical point (usually due to overcharging), it will destroy the battery.

It sounds scary, but it’s not difficult to avoid. All you have to do is check the fluid levels once in a while. Too low? Pour in some distilled water and you’re good to go.

Spilling is another issue wet-cells have. You shouldn’t flip or rock these batteries. If you do, their electrolyte fluid will spill off – which, in turn, will destroy the battery.

Finally, they don’t last very long. With proper maintenance and use, wet-cell batteries last around 2-3 years. Which is okay, but not quite at AGMs level.

2. AGM Batteries

AGM stands for Absorbed Glass Mat. It’s a newer, more expensive, deep-cycle battery.

Unlike wet-cells, AGM batteries store their electrolytes in thin glass mats. This makes them lighter, spill-proof, and longer-lasting. With a 3-4 year lifespan, AGMs can outlive wet-cells by a couple of years.

The best part?

AGM batteries are completely maintenance-free.

You’ll have zero worries with AGM batteries. No fluid can escape since it’s completely sealed. You never have to refill it with distilled water like wet-cells.

They do cost more, but what you get makes it so worth it. That’s why AGM batteries are super popular nowadays.

3. Lithium-Ion Batteries

Then there are lithium-ion batteries.

These batteries are incredible. They are longer-running, longer-lasting, more durable, and a LOT lighter than AGM batteries.

Is this the best battery for trolling motors then?

No.

In fact, it’s hard to find anyone using these batteries for their inflatable boat.

But why???

Aren’t they much better than AGMs?

Well, yes… but they’re super expensive.

If you thought AGMs were pricey, lithium batteries make them look cheap.

Plus, they’re overkill. Recreational boaters aren’t going to war… they don’t need military-grade equipment.

Unless you really need the extra run-time or lifespan, I wouldn’t recommend a lithium battery. AGM batteries give you more than you’ll ever need, and there’s no need to break the bank for them.

How to Calculate Run Time With AH Rating

Alright! We’re getting closer to choosing the perfect battery for you. Next up: check the AH rating.

AH rating stands for “Amperage Hour rating”.

This is easily one of the most important specs of batteries. The higher the AH rating, the longer the battery life. Go for the highest AH rating possible in your budget.

Knowing your AH rating also allows you to accurately estimate how long your battery will last. It’s quite technical, so let me break it down for you in layman’s terms.

You can picture your AH rating as the “fuel capacity” of your battery. Divide this number by your motor’s amperage draw (check your motor’s specs for this number), the result will be how long your motor can run in hours.

Example: A 120AH battery powering a 30amp trolling motor can run for 4 hours – 120AH / 30amps = 4 hours.

Can’t find your motor’s amperage draw?

You can also use the wattage. Divide your motor’s wattage by its volts (let’s say 12), you’ll get its amperage draw.

Example: 360 watts / 12 volts = 30amp.

With this, you never have to guess how long your battery can run. If you combine a 120AH battery and a motor using 360 watts, you know you can go for at least 4 hours (if you’re good at math, that is).

High-end trolling motors have battery meters, so you don’t have to worry about this.

But if yours doesn’t, you DO NOT want to take your chances. Trust me, running out of battery in the middle of the sea is the last thing you want. So keep this trick in mind.

The Best Trolling Motor Batteries

By now, you should have a good idea of what you’re looking for.

Need more help? Here are my top picks for each battery type.

1. Wet-Cell Batteries

Wet-cell batteries are the most common, but it’s difficult to buy them online. Remember, they spill. Shipping is a big problem because of this.

For wet-cell batteries, your best bet is to head to your local battery shop and buy it there.

Don’t want to? You can check out the Trojan SCS200.

Trojan SCS200

Buy on Amazon

The Trojan SCS200 isn’t your ordinary wet-cell battery. It’s a flooded battery, which keeps it running longer than its counterparts.

It costs more than traditional wet cells due to its high AH rating. At 115amps, you can keep your motor running for a long, long time.

That said, you will need to maintain it properly. Regular water checks and cleaning will prolong its lifespan by far. So don’t forget these.

Should you get one?

It’s hard to say. Wet-cells are great because they’re supposed to be affordable. This one costs quite a lot.

It does perform better than other wet-cells, but you can already afford an AGM with its price.

2. AGM Batteries

If you have more to spend for quality and longer life, AGM is your best choice.

These are much better than wet-cells, and they’re not too expensive either (unlike lithium).

Casil CA12350

Need a small, lightweight battery? Casil’s CA12350 is a great choice.

Sure, 35AH isn’t a lot. But for smaller motors, a great day at the lake doesn’t need more than this.

Plus, it only weighs 25 lbs., allowing you to bring more gear along.

You can mount it in any position without worrying about spilling. It is, after all, an AGM battery.

That said, this battery won’t do for bigger, more powerful motors. For these, you’ll need something like the…

Weize LFP1255

For stronger motors and bigger boats, the Weize LFP 1255 is here for you.

Yes, it is heavier and bigger than the 12350, but its 55AH rating lets you cruise longer.

Its shape isn’t standard – it has a taller dimension – but it can fit in most battery mounts without any problems.

Still want more Amp Hours? Go for the…

Mighty Max ML100-12

Now we’re talking serious boaters here. 

There’s not much to say here – you already know the benefits of AGMs. 

One thing though: this battery is quite expensive. But if you’re looking for that long-lasting 100AH battery, this won’t be a problem at all.

VMax SLR125

Last but not least, the VMax SLR 125. 

It’s big, it’s heavy, it’s expensive, but once you see how long it lasts, you’ll find it’s well worth it. 

But be careful! At 75 lbs., a lot of lighter inflatable boats can’t carry these. Check your boat’s limits before buying. 

This isn’t the highest AH rating you can get – there are other AGMs with more. But for trolling motors and recreational boating, it’s unlikely you’ll need them. The Vmax SLR125 will provide you with everything you and your trolling motor could ask for.

3. Lithium Batteries

Not satisfied with your AGM batteries? Go for lithium.

Remember, these are very expensive – much more than AGMs. And I’ll say it again… to me, you don’t need lithium batteries for a trolling motor.

But if you insist, here are some of the best lithium batteries around.

Renogy Lithium-Iron Phosphate

Buy on Amazon

Just by glancing at the specs, you can see how lightweight lithium batteries get. It’s half the weight of AGM’s with the same AH rating!

And that’s not all.

Lithium batteries can live two-times longer than wet-cell batteries. AGMs can’t live as long as them either.

Plus, they’re slower to discharge when not in use (more on this later!).

Sounds great… doesn’t it?

Well, it is. But once you see the price, you’ll understand why very few people use these for trolling motors.

Mighty Max ML100-12Li

Mighty Max produces both AGM and lithium batteries. By comparing the two, you can see how much better lithium batteries are.

Scroll up, you’ll see the AH rating is the same, the size is the same (pretty much), but the weight is cut in half!

Like Renogy’s lithium battery, the ML 100-12Li also has all the advantages of lithium batteries. It lives longer and it discharges slower than AGMs.

But like Renogy, it’s also very expensive. Compared to its AGM sister, this battery costs over 3x more.

So unless you’re going to do some heavy-duty work, a battery like this won’t be necessary.

How to Charge Your Battery The Proper Way

Charging a battery for the first time can be terrifying.

There’s something about these big, heavy boxes of electricity that scares a lot of people. You may have also heard disaster stories – getting fried by electricity isn’t something you want… is it?

However, there’s nothing to be afraid of.

There are a few things you need to know, yes. But when you do things properly, it’s not only completely safe, it’s also very easy.

What do you need to know?

Let me tell you…

1. Chargers to Avoid

Not every charger will work for your deep-cycle battery.

I’ve seen people complain about their batteries not charging while using trickle chargers. Trickle chargers are for preventing battery drainage, not putting power in! Don’t use these.

Also, avoid the old-fashioned bulk chargers. These chargers charge and charge without ever stopping (until you unplug them). Overcharged and damaged batteries are too common with these chargers.

And you can NEVER fully charge a battery with these… even if you time everything to perfection.

Why?

Picture yourself pouring soda into a glass. If you don’t slow down, you’ll fill it to the brim quickly… but half will be fizz. When the bubbles go down, you’ll find your glass only half-full.

Batteries work in a similar way. Old chargers don’t slow down as they fill up, so your battery will never be truly full. It’ll keep “fizzing” out instead of staying.

Years ago, bulk chargers were the only option. But thanks to technology, we now have newer and better chargers.

2. The Proper Charger

Your best option is to get an ultra-specific deep-cycle automatic charger.

Ultra-specific meaning if you have an AGM battery, get an AGM charger. If you have a wet-cell, get a wet-cell charger.

Nothing can go wrong when you do this.

Can’t find specific chargers? Ask the manufacturer if it works for your type of battery. Never make assumptions.

Getting a deep-cycle charger is also very important. Not every AGM charger is a deep-cycle charger (some of them are trickle chargers), so make sure of this.

Finally, it needs to be automatic.

Automatic chargers can detect the battery level. They slow down as the battery fills up. This way, the battery gets to fill up completely (there’s no “fizz” to worry about).

There’s no risk of overcharging either. Once the battery is full, automatic chargers go to trickle mode and keep it there.

Looking for a good AGM charger? Check out Black and Decker’s BC2WBD here:

3. How Long Should You Charge Your Battery?

With the proper charger, all you have to do is plug it in and charge it.

Important: Make sure you connect the positive clamp to the positive terminal and negative clamp to the negative terminal.

But now the question arises… how long should you charge your battery?

With an automatic charger, this won’t be a big problem. The meter will tell you the exact power level of your battery.

That said, it’s nice to have an idea of how long charging will take. There’s a simple trick for this:

Chargers are measured by amp power. With this, all you have to do is divide your battery’s AH rating by this amp power – you’ll get the charging time in hours.

Example: A 5amp charger will take about 7 hours to charge a drained 35AH battery. 35 / 5 = 7.

The higher the amps, the faster your battery will charge.

4. Charging While Running

Can you charge your battery while on the move?

Yes, there are several ways to do this.

But with a trolling motor and a decent sized battery, you don’t need to. It’s not something I recommend for recreational boaters (it’s expensive and can be a hassle).

If you really need it, you can use solar power, or hook your battery to an outboard motor with an alternator.

But that’s a topic for another time, so let’s move on…

Battery Maintenance Tips

Want your battery to live its full lifespan?

Here are some tips to help you with that:

1. DO NOT Mix Old and New Batteries

If you’re using two or more batteries together, never mix old with new. If you do, not only will you get poor performance, but you can rupture the batteries as well.

2. DO NOT Mix Battery Types

Not only should your batteries be the same age, but they should also be the same type. Using AGM and wet-cell together is NOT a good idea.

3. Clean Terminals Regularly

If your battery’s terminals are covered with dirt or rust, clean it out. Your motor and charging will be more efficient this way. Too many people panic when their battery isn’t performing, only to find out all it needs is cleaning.

4. Use Baking Soda to Clean

I like using a combination of baking soda and toothpaste for cleaning. It gets rid of the corrosion in the terminals well. Remember to dry it off completely after.

5. DO NOT Half Charge Your Batteries

Always make sure you charge all the way up. If you don’t, sulfate will build up inside your battery and destroy it.

6. Charge After Every Use

In the same way, you want to charge your batteries after every use. If your battery is always full, sulfates won’t have a chance to accumulate.

7. Use a Trickle Charger

If you aren’t going to use your battery for a while, use a trickle charger to keep it in good shape. Batteries drain slowly if you don’t use them. By now, you should know that that is never a good thing (because of sulfates).

Conclusion

Phew!

That was quite a lot to take in.

And no wonder… trolling motor batteries are misunderstood by so many boaters.

But if you’ve made it here, you now know all there is to know about trolling motor batteries. So get out there and grab a battery for your trolling motor!

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