Choosing the right marine batteries is more than a matter of going with a reliable brand that your customers can trust. Even the best battery is only as good as its application and maintenance. This starts, of course, with knowing the differences between the two most common types of marine batteries: cranking batteries and deep cycle marine batteries.
What is a Cranking starter Battery-- and what design features matter?
A cranking battery allows a marine vessel to start by sending power to the engine when the ignition switch is activated. For this reason these batteries are also known as starter batteries. To start a motor, short and strong bursts of energy must be sent from the battery.
The more plate surface area inside the battery, the easier it is for that battery to provide the necessary power. That is exactly why cranking batteries have many thin plates; they increase surface area and make starting a marine vessel as smooth and reliable as possible.
The same elements that make a starting battery ideal for cranking an engine also make them less than ideal for continuous discharge or “cyclic” use.
That's why deep cycle marine batteries are another necessity for boaters.
What is a Deep Cycle Marine Battery?
Once a boat's engine has started, it no longer needs the same quick and powerful bursts of energy that come from a starter battery. Instead, the boat needs continuous, reliable power for trolling-- including running electronics like sonar, GPS, and radios.
That’s where deep cycle marine batteries come in.
A deep cycle marine battery, or trolling battery, has several design differences. One key is plates: It has fewer, thicker plates allowing the battery to provide continuous power output over long time periods. Deep cycle batteries can be entirely drained and recharged many times over, cranking batteries can't.
In other words:
- A cranking battery ensures a boat can easily start and get out on the water.
- A deep-cycle (trolling) battery keeps it operating and runs electronics in any conditions.
Why You Can't Use the same Battery for Cranking & Trolling
We get it: It can be tempting for any boater to want to minimize accessories and additions to their vessel.
But that approach will cost you more money and time in the long run. It is very difficult to combine the performance of a cranking battery and a deep cycle battery into one battery -- because they’re both intentionally engineered to do completely different things. When a cranking battery is subjected to continuous use, (e.g. trolling), it is subject to overheating and depletion of available capacity. By that same regard, when a deep cycle battery is called upon to provide the bursts of energy necessary to start an engine, it won't always perform.
Put another, you’ll usually get the best results and smallest operating costs when you use two separate marine batteries.
A third option (for some people):Dual Purpose Marine Batteries
As with many rules - there can be exceptions.
Some dual purpose batteries can work for both cranking and trolling. However, these dual purpose batteries are not necessarily the right option for every boat. Although they do mean one less battery to purchase and maintain, like many "2-in-1" options; they do not always allow a vessel to perform at the same level as two batteries would.
For instance, deep cycle batteries are built to withstand many discharges and recharges while cranking batteries are not. A dual purpose battery, therefore, falls somewhere in between. Many do not stand up well to total discharges (discharge beyond 50% of usable capacity). A dual purpose battery can also be more prone to overheating in harsh conditions, which is certainly not ideal while a boat is out to sea. Still, these types of batteries can work well for short trips and if they are used and maintained properly.
Now that you know which battery options you need -- which chemistry is right for you?