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[Full Guide] Starting Battery vs. Deep-Cycle Battery

Mike Smith
Mike Smith
—
09/05/2023

When it comes to powering marines and RVs, finding the right battery is crucial. Two popular types of batteries are starting (cranking or starter) batteries and deep-cycle batteries. But what are the differences between them, and which one is the best for your needs? Let's take a closer look at these two battery types.

Part 1: Understanding Marine Starter Batteries

Marine starter batteries, often referred to as marine cranking batteries or marine engine start batteries, are a specialized type of lead-acid battery engineered specifically to initiate boat engines. Their primary design focuses on delivering a significant burst of power, measured in cranking amps (CA) and cold-cranking amps (CCA), to ensure rapid engine ignition.

The term "cranking amps" (CA) quantifies a battery's capacity to provide a surge of power at 32°F (0°C) for a duration of 30 seconds, all while sustaining a minimum voltage. This particular rating is generally used to evaluate a battery's starting capability in milder or moderate climates, where extreme cold is not a significant factor.

In contrast, "cold-cranking amps" (CCA) represent a more demanding assessment of a battery's starting strength. This metric is defined as the maximum current a battery can discharge at a frigid 0°F (-18°C) for 30 seconds, again, while maintaining a minimum voltage level. Why is this distinction important? CCA becomes particularly critical when attempting to start an engine in cold weather conditions. Lower temperatures can cause engine oil to thicken, thereby increasing the resistance the engine must overcome to turn over. For those interested in a deeper dive into this specific rating, our blog post, "What are CCAs?", offers further information.

Part 2: Exploring Deep-Cycle Marine Batteries

Engineered for endurance, deep-cycle marine batteries are specifically constructed to deliver a consistent and sustained power output over prolonged durations. This characteristic makes them perfectly suited for applications demanding continuous energy. Unlike their counterparts, starting batteries, which are optimized to provide brief, high-current surges for engine ignition, deep-cycle marine batteries feature more robust construction. They incorporate thicker lead plates, a design element that allows them to endure repeated deep discharging and subsequent recharging cycles without incurring damage.

What kind of onboard equipment relies on such a power source? These batteries are commonly employed to energize a wide array of electrical systems and appliances found on boats. This includes essential items like lighting, as well as equipment such as trolling motors, fish finders, radios, and so on. Consequently, deep-cycle marine batteries play a crucial role in boating activities where a dependable and long-lasting power supply is paramount. Their reliable performance ensures that boaters can fully enjoy their time on the water, free from concerns about unexpected power interruptions.

Part 3: Comparison of Starting Battery Vs. Deep-Cycle Battery

1. Differences in Function:

Starting batteries are designed to provide a burst of high current to start an engine, and then be quickly recharged by the alternator. They are made to supply high electrical current for a short period of time, but not for an extended period of time. They are not designed to be deeply discharged and recharged repeatedly like deep-cycle batteries.

Deep-cycle batteries, on the other hand, are designed to provide a steady, lower current for a longer period of time. They are typically used for applications such as RV house batteries, off grid life, trolling motor batteries, and solar panel batteries. They are designed to provide a sustained flow of electrical power over an extended period of time and to be deeply discharged and recharged repeatedly.

2. Differences in construction:

In terms of construction, starting batteries typically use thinner and more numerous lead plates to increase the surface area and provide a high current output. They are designed to withstand a high number of shallow discharges and recharges.

Deep cycle batteries, on the other hand, use thicker and fewer lead plates which can handle deep cycling. Deep cycle batteries are designed to discharge to a much greater percentage of their full capacity while remaining functional, whereas starting batteries will quickly fail if deeply discharged.

starter vs deep cycle battery

 

Part 4: A Third Option: Dual-Purpose Marine Batteries

Attempting to bridge the gap between starting power and sustained energy, dual-purpose batteries are engineered to offer a compromise between the distinct characteristics of cranking batteries and deep-cycle batteries. Their design allows them to deliver the significant burst of power required to initiate an engine, while also possessing the capability to supply a moderate, continuous flow of electricity for operating onboard electronics and various accessories.

Interestingly, many deep-cycle marine batteries available in today's market are actually designed with this dual-purpose functionality in mind. For individuals with smaller boats that have less demanding engine starting requirements, a high-quality dual-purpose deep-cycle marine battery might indeed provide sufficient power for both starting the engine and running accessories. However, what about situations involving larger vessels or more power-hungry systems? In scenarios with larger boats that have more powerful engines, or if there's a substantial array of onboard electronics and accessories, the generally recommended approach is to utilize a dedicated cranking battery specifically for engine starting. This would then be complemented by a separate deep-cycle battery, or even a bank of batteries, to handle the demands of accessory power.

 

FAQS about Deep Cycle and Cranking Battery

1. Can You Use A Deep Cycle Battery As A Starting Battery

While a deep cycle battery can be used as a starting battery in a pinch, it is not an ideal choice. Deep cycle batteries have lower cranking amps (CCA) than starting batteries, which means they may struggle to deliver the initial burst of power necessary to start an engine, especially in colder temperatures. Additionally, using a deep cycle battery as a starting battery may decrease its lifespan since the repeated high current draws during engine starts can cause internal damage.

2.Can lithium batteries be used for engine starting?

LiTime Lithium dual-purpose batteries give you 1,000 cold cranking amps of engine starting power.

3. Can you run a cranking battery and deep cycle in parallel?

It's not recommended to connect a cranking battery and a deep-cycle battery directly in parallel for long-term use. They have different designs and will charge/discharge unevenly, which can shorten the lifespan of both batteries.

4. Can You Use a Marine Battery in a Car?

Using the wrong type can lead to poor performance, shorter battery life, and potential issues with your car's electrical system. Always best to use a battery specifically designed for automotive use in your car.

Conclusion

Choosing the correct battery is fundamental to ensuring reliable power for your marine vessel or RV, directly impacting your safety and enjoyment.  

By carefully considering the unique roles of starting, deep-cycle, and dual-purpose batteries, you can select the right power source—or combination of sources—to keep your adventures running smoothly and without interruption.

Mike Smith
Mike Smith
Mike Smith is a marine energy expert with 15+ years of experience and a Master’s in Electrical Engineering from Stanford. Passionate about lithium battery integration, he also enjoys sailing and exploring coastal waters in his free time.

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