Deep Cycle Battery Life Expectancy

Wondering how long does a deep cycle battery last?A floored lead acid cell, also more popularly known as a wet cell, is one of the most common battery types in use for many different applications today. It is not surprising that many people will want to know the specifics of such batteries, especially those in the automotive and marine industry.

Things such as starting viability and deep cycle battery life expectancy are points of curiosity, and it is the aim of the article to answer those questions. Lifespan is one of the most important battery specifications a user should know, perhaps next only to type and purpose in significance.

It needs to be considered because it is the amount of time the battery will be useful to the people after all, and the people who use the battery could plan their purchase, maintenance (if any are needed), and replacement schedules around that date.

When the battery fails, lifespan is also one indicator that the battery needs to be recycled and replaced, with no hope for repairs, as repairs could only be less cost-efficient than getting a fresh energy cell.

Battery Lifespan: Years, Cycles, And Depth of Discharge

When people talk about battery lifespan, they expect to talk about it in terms of years. This is reasonable, as the number of years can be a good indicator of how long a battery will last. But it is never accurate, and there are factors such as weather, purpose, and climate that make predicting the years of service very unreliable. This is why some people express the lifespan of a battery in cycles.

A cycle, simply put, is the process of a complete discharge and recharge. So for example, if a battery is said to have a lifespan of 1000 cycles, it means that it can undergo up to 1000 discharge and recharge procedures before you can expect it to deteriorate in performance. Cycles do not always mean a battery discharge to zero percent then back up to 100 percent again, though. In fact, it does not mean that at all.

Different batteries have different definitions of a reasonable cycle, but the three most common is a discharge point is up to 10 percent, 20 percent, or 50 percent. This discharge point is also more commonly known as the depth of discharge, or DOD, and it plays an important role in determining the actual lifespan of a battery.

For example, a battery maker may advertise itself to last for twenty years, while in checking the fine print you may notice that this measurement is only if the battery was cycled only up to a 5 percent discharge. Now, cycle depth and battery life is correlated, so the advertised 20-year battery will have a considerably shorter lifespan when cycled to a depth lower than 5%.

This shows that the optimal depth of discharge is an important consideration in measuring battery lifespan, too. It is not enough that we know how may cycles the battery is good for. It also helps to know the cycle depth the battery will be used with. For instance, a battery that lasts for two years when consistently discharged to 50 percent will last for four years when discharged to 80 percent.

A battery lasting for one year when discharged to 10 percent will have a lifespan of five years when discharged to fifty percent.

Lifespan Comparisons: Starting Vs. Deep Cycle

So if the depth of discharge is tied closely to a battery’s lifespan, why can’t we just use our batteries up to the maximum lowest discharge depth that we can to make their lifespan last longer then? There are several reasons for this, mainly hinging on convenience and purpose.

For one thing, not all people have tons of reserve batteries so that they could easily get a replacement when the one they currently use is in 10 percent discharge. Some may have the luxury of using interchangeable batteries, some do not.

But another, more compelling reason is that there are batteries that are not designed to work well when constantly brought to a very low cycle depth. This is why we have the term “deep cycle” batteries, as these are designed to perform great even when cycled below 20 percent.

Other battery types are just not built for that purpose. For example, consider a starting battery class that is composed of lead acid. Starting batteries are so named because they are designed to start a car engine. These have thin lead plates which are reminiscent of sponges, like foam.

This gives them a much larger surface area exposed to the solution, allowing them to draw currents more quickly than standard deep cycle batteries. However, this type of battery is designed to be used at only a shallow depth of discharge, which is around 2 to 5 percent. On that depth, it can last for thousands of cycles. Yet if this kind of battery is frequently discharged around the 20 percent to 50 percent level, it could be a dead battery after merely 150 cycles.

Deep cycle batteries, on the other hand, have much thicker lead plates and they are much tougher compared to the sponge-like stuff found in Starting batteries. They have less surface area in the battery solution, which means they do not draw current as quickly as Starting batteries could. But their tough composition enables them to operate at much deeper discharge cycles than the average starting battery.

In any case, there are general expectations regarding the lifespan of these kinds of batteries. A Starting battery used for automotive purposes will last anywhere from three to 13 months. As for deep cycle batteries, the lifespan really depends on the type. An AGM class battery will last anywhere from four to seven years, while a deep cycle gel cell battery can last from two to five years. Floored lead acid types have the greatest life expectancy, as these batteries can last from four to eight years.

If you are interested in reading more about this topic, then check our in depth review of marine starting battery vs. deep cycle.

Tips For Prolonging Battery Lifespan

If you really, really want to prolong your battery life, you must of course make sure that they are in tiptop or almost perfect state every time. Proper and consistent maintenance of these batteries will go a long way to ensure a better lifespan. For example, checking the water levels so that they are not drained, or making sure they do not stray too far from the fifty percent discharge rate are some of the best ways to make your battery life last longer.

If you plan to put your batteries on storage, you might want to utilize a trickle or maintenance charge so that the batteries do not get discharged or drained completely over time. Also, make sure that the ports and terminals of the battery are cleaned before putting them in your storage space.

Climate, or more specifically temperature, is also proven to affect battery lifespan. It is common knowledge that batteries perform better in colder weather. Meanwhile, they suffer in hotter temperatures, especially those with active wet cell components, as the heat can contribute significantly to the vaporization of the liquids within the cells.

Charging methods also contribute to battery life, and most people prefer slow charging over fast charging because it has less risk of overcharging. Slower recharge and discharge rates are believed to be more efficient, because of a factor called internal resistance — this is the loss of electricity that is converted to heat, and is also the reason why batteries heat up when charging.

Anyway, without going into the details, what you should know is that internal resistance is not a constant value that will be consistent throughout the life of your battery. A much higher amperage results in a higher internal resistance value, and vice versa. This is why a battery that is said to rate 180 amp hours in six hours may be rated 220 amp hours in 20 hours of charging, and 260 amp hours with 48 hours of charging.

There are many things you can do to prolong the life of your battery, but basically it all boils down to taking really good care of the product. Obviously, neglect will make result in an unsatisfactory performance, and it will be in your best interests to be aware of the battery’s state. (You can also read about how to recondition a deep cycle battery in order to not buy a battery).


Now you know the different factors that contribute to the lifespan of a typical battery, most especially deep cycle cells and starting batteries. It is a combination of different factors, which are included but not limited to the type, the number of cycles it is expected to run until it deteriorates, and the depth of discharge it can be optimally used with.

The amount of maintenance the battery receives plus the charging and storage methods and the climate are some of the most important factors as well. Starting and deep cycle battery life expectancy is a fluctuating value, and i hope this article would give you an idea of how these things are measured. To be on the safe side, you can always consult your battery manual for further specifics.