Guide: Choosing Best Deep Cycle Batteries For Your Solar And Inverter System

This article on how to choose the best deep cycle battery was originally written by us but has appeared in several other websites.

Now let’s look at the best Deep cycle batteries you can use for your solar power and Inverter system. The batteries in your Inverter system is one of the most critical components you will find. The primary purpose of a battery is to store energy, in this case –Electrical energy. So when your grid is down, that is when there is a power failure from your diesel generator or grid ( popularly known as NEPA in Nigeria) or when your Photovoltaic system isn’t producing power during the night, it is the stored electrical energy in your battery that will provide an uninterrupted power supply during this period.

Of course, at this point, you know that the recommended battery type you need for your renewable energy system is a Deep Cycle Battery.

Having said this, it is imperative that the Inverter battery that will be added to your system should be of the very best quality and brand.

Just in case you are not very familiar with the working principle of Deep Cycle Batteries, I will in the next sub-heading give a refresher introduction to it.

What is a Deep cycle battery?

Deep cycle batteries as the name implies are built to withstand longer use and draining of battery up to 80%. In other words, with a deep cycle battery, you can discharge it almost completely leaving only about 20% power for further recharging. They have a greater depth of discharge and are designed to continuously provide power for long period of time

In contrast, the other Shallow cycle starter batteries are designed to deliver short high current bursts for a short period which is needed to start the engine thus frequently discharging only small part of their capacity. Once the engine starts the battery is recharged by the engine-driven charging system. Starter batteries are intended to have a low depth of discharge on each use.

In battery terminology, a cycle in your battery occurs when you discharge your battery and charge it back to the same level. So what I am saying is that the way the deep cycle battery is built, they are designed to withstand greater number of cycles than any other lead-acid battery type hence deep cycle batteries have longer life span.

Now I believe you have seen the major reasons why deep cycle batteries are preferred in an Inverter system. The scope of this article will not accommodate further discuss on the technology behind it including the arrangement and thickness of the plates.

Best Deep cycle batteries for your Power Inverter system

Now back to the main topic of this article. Generally, Inverter battery buyers wholly rely on the vendor’s information about deep cycle batteries in their decision making. The essence of this article is to enlighten you more and further equip you in your final decision.

Because of the different types or categories or kinds of Deep cycle batteries available in the market, it is not enough to simply recommend ‘deep cycle’ batteries to clients. I shall now introduce the different kinds or categories of deep cycle batteries to further narrow your choice to the one best for your project and quickly eliminate the ‘unfavorable’ choice.

Types of Deep cycle batteries:

Flooded Lead Acid battery:
This is the oldest deep cycle battery type and it is still very popular today. It has the simplest design and also referred to as Wet cells. This type of battery is still very much in use because of the advantage it has over all the other battery type especially its cost effectiveness. Flooded Lead Acid batteries are very cheap and affordable. The downside is that they are not maintenance free. The user will have to regularly remove the caps and top the acid with distill water when low, etc.


Sealed Absorbed Glass Mat Batteries (AGM):
In Absorbed Glass Mat Batteries (AGM), instead of flooding the plates with Lead-acid, the electrolyte is held in glass mats or matted glass fibers which in turn is wrapped around the positive electrode or plate. If you have seen a disassembled AGM battery, you will easily notice this ‘white’ glass matt that is wrapped around the dark positive plate.

Here is a Wikipedia entry on the glass mats of AGM batteries:

Very thin glass fibers are woven into a mat to increase surface area enough to hold sufficient electrolyte on the cells for their lifetime. The fibers that compose the fine glass mat do not absorb nor are they affected by the acidic electrolyte.

Some of the merits of using a Sealed Absorbed Glass Mat Battery (AGM) include the fact that they have low internal resistance making them easier to charge faster than other types. AGM batteries are more tolerant to temperature variations and can resist vibration unlike other Lead-Acid counterparts. They don’t leak acid and can perform if tipped on its side or tilted. Also they are maintenance free.


Gelled Electrolyte Sealed Lead Acid Battery:

This type of battery is a lot like the Flooded Lead Acid battery except that the liquid Lead-Acid electrolyte solution is ‘thickened’ into gel form with silica. So it makes it a dry cell although it is technically not.

The introduced silica only serves as a thickening agent and doesn’t actively participate in the electrolyte reactions. This kind of battery is Valve-regulated. These valves are the tiny outlets for the escape of gases produced during the use of the battery. The major reason for thickening the electrolyte with silica is to immobilize the electrolyte. This in turns gives the battery an edge over flooded Lead Acid batteries. For example, if there is a crack on the battery container, the battery continues to perform, even with the crack.Also unlike the flooded cells, the Gelled battery will continue to work if tipped on its side.

One other merit of Gelled Electrolyte Sealed Lead Acid batteries that people don’t often put into consideration while making a battery choice is that this type of battery actually have a superior deep discharge resiliency and tend to have a greater number of life cycles.

Other:
There are still other types of batteries which are mostly non-Lead Acid batteries. These includes: Lithium ion (Li-ion) batteries, Nickel-Cadmium batteries, etc. We are not going to be talking about these types of batteries because of their high cost of acquisition for a renewable energy system application. They are not yet manufactured in very large quantities for renewable energy applications as in Lead-Acid batteries and most of them are still in the research stage.

Until many manufacturers go into the production of these batteries, there will be no competitive advantage that can drive down the cost of production and the final selling price of product