Battery tech can be confusing, and with a wide range of battery types and options on the market, it can get downright complicated to know which is the right battery for you.
One question we get asked a lot is, “Can I use a car battery to power my trolling motor?”
The short answer is no.
This battery looks fine for running a trolling motor, but it’s really not!
While a car battery and a dedicated trolling motor battery look a lot alike, and while they’re both 12V systems, they’re nothing alike on the inside or in the way they deliver power and handle deep discharging.
Instead, you need to use a deep cycle battery, like the ones we review in this article:
If you want to know more about why you can’t use a car battery to power a trolling motor, keep reading!
Table of Contents (clickable)
- What Size Battery Do I Need For A Trolling Motor?
- Best Marine Battery - Dual Use, Starting, and Deep Cycle Batteries Explained and Reviewed
- Best Trolling Motor Batteries For Fishing Kayaks
Battery Tech 101: Battery Types
All batteries accomplish the same basic task: they store electricity and deliver it as needed.
But the way a battery is engineered, and the tasks for which it is designed, are very different.
Let’s take a closer look at common battery types.
Starter or cranking batteries
Starter batteries are designed to produce short bursts of very high power, allowing them to turn over an engine. They’re perfect in cars and trucks, where the alternator keeps them charged as electronics like lights, your radio, and your air conditioning create a constant draw.
But the moment the alternator fails, that low-level draw starts to discharge your starter battery, and you’ll quickly find that your vehicle stops dead.
That’s because starter batteries just aren’t designed to deliver low levels of power over a long period. They’re only able to start an engine and demand an alternator to keep them alive during prolonged use.
Without constant recharging by an alternator, they’ll quickly discharge and suffer damage.
That doesn’t make them inappropriate for the water, however, and they’re just what you need to start an outboard. Even then, they’re best when paired with an onboard charger to keep them topped up properly.
Deep cycle batteries are basically the opposite design of a starting battery. They’re engineered to provide low levels of power over long periods of time, and they can tolerate very deep drains - down to 20 percent of their capacity - without being damaged.
That makes them perfect for running electronics like fish finders and electric trolling motors.
What they can’t do, however, is produce the short burst of high power necessary to start an engine.
Dual-use batteries are engineered for both basic battery tasks, and they can provide the short burst of power necessary to turn over an engine while also being able to supply long-term, low-level juice to electronics.
But the downside to a dual-use battery is that it’s not as good as a dedicated starter battery at getting an engine running, nor is it as good at supplying low-lower power all day. Typically, they can only tolerate a discharge of about 50 percent of their capacity without damage.
These batteries are simply a compromise, allowing anglers to run a single battery to get both tasks done.
Sometimes used as a synonym for “deep cycle,” marine batteries can consist of any of the other types, depending on their purpose.
What Happens if You Run a Trolling Motor with a Car Battery?
The batteries in vehicles are always starter batteries. They’re designed to crank an engine and then rely on constant recharging from an alternator to stay alive as your car’s electronics draw long-term power.
If you connect a car battery to a trolling motor, everything will be fine at the start.
Your trolling motor will come alive instantly and will run fine - until your car battery starts to lose its charge. That will happen pretty quickly, and depending on the throttle setting you use, you’ll start to notice diminished power within a few minutes.
The battery will die pretty quickly depending on the total draw, and the engine will stop.
There’s a very good chance that you’ll damage the car battery, too, as it’s not designed for deep discharging.
If you want to power a trolling motor, you really need a dedicated deep cycle battery that’s designed for just that kind of use.
And whether you fish from a kayak, a center console, or a bass boat, a good deep cycle battery is an investment you won’t regret making.
As always, we’re here to answer any questions you might have, so feel free to drop us a line!