Choosing the right marine batteries is more than a matter of going with a reliable brand that your customers can trust. The right battery is only right if it is utilized in the proper place and treated to proper maintenance. This starts, of course, with knowing the difference between the two most common types of marine batteries: cranking batteries and deep cycle marine batteries.
What is a Cranking Battery?
A cranking battery is the battery that allows a marine vessel to start, 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 exists in the battery, the easier it is for that battery to provide the necessary power. That is exactly why cranking batteries have many thin plates, to increase surface area and make starting a marine vessel as smooth and reliable as possible. Of course, those elements that make a starting battery ideal for cranking an engine also make them less than ideal for continuous discharge or “cyclic” use, which is 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, which is where deep cycle marine batteries come in. A deep cycle marine battery, or trolling battery, consists of fewer plates, but those plates are thicker. This allows the battery to provide continuous power output over long periods of time. It also means that the battery can be entirely drained and recharged many times over, which is not the case with cranking batteries. A cranking battery ensures a boat can easily start and get out on the water while a trolling battery lets it keep humming along in any conditions. Deep cycle marine batteries are also much less likely to overheat since their thicker plate construction can withstand high temperatures during heavy currents.
Why You Can't Use One Battery for Cranking & Trolling
It can be tempting for any boater to want to minimize accessories and additions to their vessel, but the truth is that it is very difficult to combine the performance of a cranking battery and a deep cycle battery into one. The main reason for this is that when a cranking battery is subjected to continuous use, such as during 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. Most marine applications require two batteries for best results.
Dual Purpose Marine Batteries
With many rules - there can be exceptions. There are dual purpose batteries can that 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.
Overall deep cycle marine batteries and cranking batteries are both necessary components of a safe and reliable marine vessel, but knowing the difference is key.
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