What is a Deep cycle Battery? | Detailed Explanation

So you’ve been thinking about buying a battery for a while now you are still confused about what kind of battery you exactly need. You have been hearing all sorts of terms like cranking batteries and deep cycle batteries and you’re confused.

Don’t worry. In this article we’ll find out everything we need to know about deep cycle batteries and help you find the best battery for you.

What is a deep cycle battery?

A deep cycle battery is a battery that is designed to provide a steady amount of current for a long period of time. This is the kind of battery you’d install with your inverter or as your solar system battery.

The term “deep cycle” refers to the deep discharging capability of the batteries. Unlike car batteries, who only can discharge upto a very less amount before requiring recharging, deep cycle batteries can discharge nearly upto 80% before needing recharging. Car batteries are designed to discharge a lot of electricity quickly whereas deep cycle batteries are specifically designed to last longer.

There are deep cycle batteries. Traditional flooded batteries or the new AGM or Gel technologies. Each type has its own advantage and disadvantage and you can select the right one based on your needs.

Where can I use a deep cycle battery?

Deep cycle batteries have a huge array of applications but here are some of the most prominent ones.

  • Solar/Off-Grid  battery.
  • Inverter/UPS battery.
  • Marine battery.
  • In recreational vehicles to power electronics.

What is the lifespan of a deep cycle battery?

While it generally depends on a lot of factors like battery type and brand, a decent deep cycle battery can last anywhere between 3-10 years. Usually AGM type batteries or gel batteries last longer than traditional batteries. It is recommended to discharge deep cycle batteries upto maximum 50% to increase their lifespan. 

Temperature also affects the overall performance and lifespan of your deep cycle battery. Batteries generally perform better in warm weather than colder climates. Traditional batteries have a tendency to freeze if the weather is too cold outside, which generally renders the battery useless. Apart from this, maintenance is also a key factor. Although AGM batteries or Gel batteries require very low maintenance, traditional batteries must be taken care of properly and regular maintenance is necessary to get the best out of the battery. 

How to charge a deep cycle battery?

A deep cycle battery generally charges in three stages. Firstly, the bulk charge phase when the most amount of current is sent to the battery. After a while when the battery is mostly charged, the charging moves onto the absorption stage where the battery gets charged slowly until the battery is almost completely charged in which case it moves on to the trickle charge stage which is mostly done to maintain the battery charge at a 100%.

Some batteries have poor shelf lives. AGM batteries when left without a load for a long time can start to discharge and if an empty battery is stored away for too long, it may become unusable completely. That is why it is recommended to always store away a charged battery. 

The time taken to charge a battery depends on two factors. The capacity of the battery generally rated in Amp-Hours and the current rating of the charger itself. For example, a charger rated at 10amps will charge a 100AH battery in almost 10 hours.

Different battery types have different chargers and it is recommended to pick a charger carefully as using the wrong charger can be dangerous and harm your battery.

There are various types of chargers for deep cycle batteries. The most commonly used is the electric charger. Inverters and UPSs have built in circuitry to automatically charge a discharged battery. 

Other than that, some batteries can also be charged using your car’s alternator. 

Lastly, one of the better and economical ways to charge a battery would be using a solar panel. 12V solar panels can be used to charge batteries. Although, a charge controller is needed to monitor the amount of electricity flowing into the battery. 

Most charge controllers also have built in functionality to detect if the battery is fully charged and switch to trickle charging automatically. 

Deep cycle batteries as solar batteries

Deep cycle batteries are a key component in any off-grid powering  system. Like we discussed, deep cycle batteries are an excellent option for storing power and discharging it steadily. In an off-grid, renewable energy system, it is very important to be able to store the energy when the source is not present.

In off-grid solar systems, batteries help power the system at night when the sun isn’t around to power it. During the day, the sun only powers the setup as well as charges the battery and the cycle goes on. 

Usually, in demanding setups, multiple batteries are used to overcome the power requirement. 12V batteries are connected in parallel thus increasing the overall capacity of the system.  

What is the best deep cycle battery?

Picking the best battery depends on a lot of factors. Different battery types offer different advantages. Before buying a battery some factors you should con sider are: your budget, the nature of your necessity, battery life.

If you need mobility, AGM batteries are best as they are vibration resistant and thus can be transported easily. 

If you have a stationary setup and are on a budget, you can go for flooded batteries. BUt they need a bit of maintenance so also keep that in mind.

Lastly, look for a trusted brand that is known to provide quality. Some good brands would be Optima, Odyssey, ACDelco, etc.  

What do amp-hours mean in a deep cycle battery? 

The capacity of a deep cycle battery is measured in amp-hours. Technically, it is the number of hours the battery can provide a steady current for. The amp hours are basically a unit of charge stored in the battery.  Some batteries do not follow this analogy and it is sometimes difficult to find the rating of such batteries.

To understand the concept better, let us assume this. Say you have a current draw of 5A per hour, in that case, an 100Ah battery will last you 20 hours when the battery is fully charged.

A huge range of batteries having different Ah ratings are available in the market. Batteries with higher ratings are generally bulkier and more expensive. 

To get the best out of your battery, it is important to weigh your requirement. Home setups generally need a lot of power and might even need multiple batteries. On the other hand, mobile setups do not need as much power and can work with batteries having a low rating.

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