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An Introduction to Marine/RV-Deep Cycle Batteries
There are many misunderstandings regarding marine/RV-Deep cycle batteries. This booklet is designed to clarify terminology and misconceptions and to assist you, the customer, in 1) making an informed decision regarding proper usage, 2) extending overall battery service life, and 3) maintaining battery performance at optimum levels.

Deep Cycle Batteries
The term “deep cycle” refers, in general, to a battery that has the capability of deeply discharging hundreds of times. How does it differ from other batteries? An automotive starting battery is manufactured specifically to provide a quick burst of energy thousands of times in its lifetime while only being able to deeply discharge less than 50 cycles during its life.

Proper Deep Cycle Application
A marine/RV-Deep cycle battery can be used for various applications including boats, motor homes, sail boats, travel trailers, tent campers, etc. Anytime an application indicates a need for batteries which can provide repeated deep discharge, you need marine/RV-deep cycle batteries.

What is a Cycle?
A cycle refers to one battery discharge and recharge of any depth (See Figure 1). The amount of battery discharge (in percent) compared to its full capacity determines the need for a shallow, moderate or deep cycle. This is appropriately called battery depth of discharge (DOD) and is measured in percent. For example, 40% DOD indicates a battery has been discharged by 40% of its total capacity and has a 60% state of charge remaining.

Types of Cycles
There are three primary types of battery discharge cycles: shallow, moderate and deep. These terms help us to understand the type of cycling that batteries are required to experience. To clarify, let’s take a look at all three types. Shallow cycles occur when only a small percent of the total battery capacity is discharged. Following that same line of thought, moderate or deep cycles are discharged by a higher percent of the total battery’s capacity. (See Figure 2).

Ratings and Specifications
Marine/RV-deep cycle batteries have rating specifications which include cold cranking amps (CCA), marine cranking amps (MCA), reserve capacity (RC) and ampere hours (Ah). RC and approximate Ah ratings may not be listed on the battery decal. However, they are available through your local Interstate Batteries distributor. Unless specified, the Ah ratings are based on a 20-hour discharge.
Cold Cranking Amps (CCA) –

The amount of current (amps) a battery at 0 degrees Fahrenheit (-17.8 degrees Celsius) can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12 volt-battery).
 

Marine Cranking Amps (MCA)
The amount of discharge current a battery tested at 32 degrees Fahrenheit (0 degrees Celsius) can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts on a 12 volt-battery).
Reserve Capacity (RC)
The amount of time a battery can deliver 25 amps at 80 degrees Fahrenheit (26 degrees Celsius) without falling below 1.75 volts per cell (10.5 volts on a 12-volt battery).

Note: Interstate Batteries uses the RC rating established by Battery Council International (BCI). Some manufacturers use a 15 or 22-amp discharge rate rather than 25-amp discharge. The lower discharge level allows a higher number of minutes to be displayed (on the battery label) which does not reflect the true RC minutes at a 25-amp discharge.


Ampere hours (Ah)
Tested at 80 degrees Fahrenheit. It is the amount of current (in amps) a battery can deliver, multiplied by the amount of hours, without falling below 1.75 volts per cell (10.5 volts on a 12-volt). Most marine/RV-deep cycle batteries are rated on a 20-hour discharge rate. Example: a 100 Ah battery can deliver 5 amps for 20 hours (amps x hours = Ah).

Please contact us if you are interested in ordering or learning more.

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