A deep cycle battery provides stored electric power at a high depth of discharge, for an extended time period. The types of deep cycle batteries are flooded lead acid, gel cell, absorbent glass mat, and lithium ion batteries.
Based on these types, the deep cycle battery is extensively discussed in this article, according to the following outline;
Types of Deep Cycle Battery: A Broad Classification
Based on composition, the deep cycle battery can occur as any of two main types; lead-acid and lithium ion batteries.
-Lead Acid Battery
The lead acid battery is the first type of rechargeable battery to have been invented, and dates back to 1859, when Gaston Planté, a French physicist, developed the earliest model, based on electrochemical principles .
Components of the lead acid battery include two electrodes, which are immersed in dilute sulfuric acid electrolyte.
Grains of metallic lead oxide comprise the positive electrode, while the negative electrode is composed of porous lead .
Subsequent modifications of the lead acid battery have led to an improved design in terms of resiliency and versatile applicability.
The lead acid deep cycle battery is of two main types, which are the flooded lead acid battery (FLA), and the valve-regulated lead acid battery (VRLA).
The main difference between flooded lead acid battery and valve-regulated lead acid battery, is the presence of a seal in the latter, by reason of which the valve-regulated lead acid battery is also referred to as the sealed lead acid battery.
Flooded lead acid batteries require the addition of water to the electrolyte, so as to supply oxygen required for the redox electrochemical reactions that occur in the battery.
On the contrary, the valve-regulated lead acid battery is equipped with a spontaneous oxygen-recombination mechanism, which replaces the need for maintenance by addition of water .
The valve-regulated lead acid battery is also of two types. These are the gel cell and absorbed glass mat (AGM) batteries.
Also known as the lithium-ion (Li-ion) battery, this type is composed of electrolytic material which is chemically dominated by lithium.
Lithium batteries are a relatively recent power storage technology, and is elaborated in further detail in this article.
For an overall classification of the deep cycle battery, there are four (4) types altogether, which are discussed below;
1). Flooded Lead-Acid Deep Cycle Battery
Flooded lead acid (FLA) battery derives its name from the fact it is composed of electrolyte which submerges the electrode plates .
The electrolyte itself is composed of sulfuric acid (H2SO4) while the electrode plates are usually composed of lead.
Because of the electrochemical redox reactions that occur in the process of charging and discharging this type of deep cycle battery, hydrogen and oxygen ions are lost from the electrolyte with time.
To replace these lost ions, distilled water is added regularly to the electrolyte . This is the most important maintenance measure for the flooded lead acid deep cycle battery.
Because of the need to add water to the electrolyte, the flooded lead-acid deep cycle battery is not usually sealed. For the same reason, FLA batteries are sometimes referred to as “wet cell batteries”.
In addition to being the oldest and most common type of battery, the flooded lead-acid battery has the advantage of being relatively cheap. They are also fairly efficient in terms of output power delivery, and can tolerate overcharging.
However, the maintenance needs of this type of deep cycle battery, are relatively high. This includes regular addition of distilled water, provision of proper ventilation, and temperature regulation.
The average charging efficiency of the flooded lead-acid deep cycle battery is about 75%, and it has a depth of discharge of up to 80%.
2). Gel Cell Deep Cycle Battery
The gel cell battery is a valve-regulated lead acid battery (VRLA) which uses a gel-like electrolyte, and operates based on an oxygen-recombination mechanism.
In the gel cell deep cycle battery, the electrolyte is usually sulfuric acid, which is suspended in a silica compound .
Electrolytic reactions which occur with every cycle of discharge and recharge of the gel cell deep cycle battery, are sustained by the continuous recombination of hydrogen (produced at the cathode) and oxygen (produced as the anode), thereby preventing the loss of water from the cell.
The gel cell deep cycle battery is heat-tolerant, mechanically resilient, and spill-proof. It also a charge efficiency of 80-95%.
It has an average lifespan of 3.5 years and can operate at a depth of discharge of 75% for a lifecycle of up to 1,000 (number of charges and discharges before losing performance).
3). Absorbed Glass Mat Deep Cycle Battery
Absorbed Glass Mat (AGM) battery was invented in the 1980s, as an advanced model of the lead acid battery.
The AGM deep cycle battery has some notable advantages like spill-free characteristics, durability, resilience, safe usage and minimal need for maintenance .
It is also a valve-regulated battery (VRLA), and the electrolyte is contained by a fiberglass mesh that occurs between the electrode plates . This design makes the battery mechanically resilient, and temperature tolerant.
On average, the AGM deep cycle battery has a Depth of Discharge (DoD) of 80%, and can operate with an efficiency of up to 95%.
4). Lithium Ion Battery
Developed on the basis of separate research works conducted by M. Stanley Whittingham, John Goodenough, Rachid Yazami and Koichi Mizushima in the 1970s , the lithium ion (Li-ion) battery represents a milestone in the field of energy conservation.
As a deep cycle battery, the lithium ion model has found significant relevance in the development of solar batteries for backup in buildings and other facilities.
Components of a lithium-ion deep cycle battery include a separator, cathode, anode, and electrolyte .
The electrolyte is usually composed of lithium iron phosphate (LiFePO4, LFP) or lithium nickel cobalt oxide (LiNiMnCoO2, LNMC) .
Advantages of the lithium ion deep cycle battery include its lightweight, which is about 30% less than the weight of the flooded lead acid battery (FLA) .
Li-ion deep cycle battery is also capable of rapid recharge and stable output, as well as energy efficiency and a depth of discharge of 80-100%.
Deep Cycle Battery Maintenance: How to Maintain a Deep Cycle Battery
The method of maintenance for a deep cycle battery, varies based on the type. Below, deep cycle battery maintenance is addressed in terms of the lead acid and lithium ion types respectively;
-Lead-Acid Battery Maintenance
Measures for the effective maintenance of a lead-acid deep cycle battery include;
- Do not leave the battery uncharged for long periods of time.
This helps to prevent sulfation, which occurs when the sulfate component of the electrolyte, crystalizes, thereby forming sulfate crystals on the electrode plates .
This is caused by deprivation of a full battery charge for a long period, and can cause early failure of the deep cycle battery is left unchecked.
- Charge the lead acid deep cycle battery in ventilated areas.
This measure ensures that the hydrogen and oxygen ions of the electrolyte are not decomposed at an excessively-high rate
- Use the battery under tolerable temperature conditions.
Because of the exposure of the electrolyte, lead-acid batteries are generally intolerant of excessively high or low temperature.
- The battery should be kept free of dirt
- Electrode plates should be constantly immersed in electrolyte.
This reduces the rate and chances of corrosion.
-Lithium Ion Battery Maintenance
Ways to maintain a lithium ion deep cycle battery include;
- Battery should be only partially discharged.
This will help to extend the lifecycle of the battery .
- Overcharging of the deep cycle battery should be prevented.
A fully charged state can shorten the lifespan of the battery .
- Check the charge status of the deep cycle battery regularly.
- Energy storage should be done at moderate temperature.
Exposing the lithium ion deep cycle battery to high temperature, increases the risk of damage. At room temperature, chemical reactions in the battery will occur at a slower rate, thereby extending service life.
The deep cycle battery can be disengaged from its connection, and stored at temperature of between 5-20°C.
A deep cycle battery is known for its ability to discharge at a high fraction of its total capacity, for extended periods of time.
The types of deep cycle batteries can be differentiated based on attributes such as composition, design, and durability.
Generally, there are two main types of deep cycle batteries, which are; lead-acid deep cycle battery, and lithium ion deep cycle battery.
The lead-acid battery can be differentiated into flooded and sealed (or valve-regulated) lead acid battery types.
Valve-regulated lead acid batteries include gel cell and absorbed glass mat (AGM) batteries. Therefore, in total, four distinct deep cycle battery types can be identified.
The four (4) types of deep cycle batteries are;
- Flooded Lead-Acid Deep Cycle Battery
- Gel Cell Deep Cycle Battery
- Absorbed Glass Mat Deep Cycle Battery
- Lithium Ion Deep Cycle Battery
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