Cranking battery vs deep cycle marine battery

On store shelves, next to standard batteries intended for use in most techniques, you can find deep cycle batteries. Despite the similar voltage and capacitance parameters, these energy sources cannot be considered interchangeable. Why this is so and what is the difference between the deep cycle and a starting (starter) battery, you will learn from this article.

Starter batteries

Batteries designed to start an internal combustion engine are called marine starting batteries. Any starter motor operates under heavy load conditions, so its starting current can be as high as 300 A. Accordingly, the starting batteries are capable of delivering high current for a short period during engine cranking.

Let’s list the main parameters of the battery to compare them with the values of the deep cycle battery in the future:

• The current range is from 250 to 1000 A.
• Voltage – 12.7 V (the most common value).
• The capacity is from 55 to 65 Ah (the most common value).

The key feature in the operation of this type of battery is its sensitivity to strong discharge. Manufacturers do not recommend using the battery at a stage when the voltage in it drops below 10V. According to experts, several tens of such discharges will disable the unit.

Deep cycle batteries

This type of storage battery is used to power the engines and the electrical system of the on-board network. The requirements for them differ greatly from those that must be met by starting batteries. Deep cycle marine batteries must give energy for a long time and withstand deep discharge without consequences.

Depending on the internal device, deep cycle batteries are of two types:

• Lead-acid (there are two plates inside, between which there is a liquid electrolyte).
• AGM (do not have liquid electrolyte in their device).
• AGM batteries are much more helpful in comparison with the first type. First, they are resistant to temperature changes and vibrations, and second, they do not require maintenance and are more durable. The advantage of the lead-acid type is its affordable cost.

Different operational requirements determine different device designs.

• Plates. Starter batteries have thin plates close together. This makes it possible to reduce their dimensions and deliver a large current. The deep cycle battery plates are thick, which increases their service life and reduces sensitivity to deep discharge.
• Weight. Due to the thick plates, a deep cycle battery of similar power weighs 3-4 times more than the starting one.
• Dimensions. The deep cycle battery takes up much more space than the starting battery.
• Maximum current. According to this parameter, the starter battery is far superior to the “competitor”. Accordingly, the deep cycle battery cannot provide sufficient current to operate the engine starter.