Top Tips for Buying a 12V Deep Cycle Battery

Alessandro Volta's first battery, the voltaic pile, was invented in 1799. Since then, deep cycle batteries have become an important, society-altering invention. He also had the volt named after him, in honour of his achievement.

Everyone owns a 12V deep cycle battery if they own a car and almost all of them take it for granted — until it's dead. From marine applications to vehicles and solar batteries, it's important to know what you're buying.

Don't worry, we've got all the tips you need for buying the right 12V deep cycle batteries for your application.

Keep reading to find out more.

Types of Deep Cycle Batteries and Their Construction

First things first, you shouldn't use a car battery for your boat and vice versa. You may be putting unnecessary strain on a battery not meant to do what you want it to.

There are two main kinds of batteries.

• Starting batteries
• Deep cycle batteries

Starting batteries make a strong surge of energy delivered to a starter motor. That motor gets a combustion engine moving so it can start to power itself. This is typically seen in car batteries.

This kind of battery also gives power to other features of the car or through a USB or lighter port provides power to other devices. But it isn't designed to take the deep cycle strains that an RV battery or marine battery is. It's designed to do a lot of work at once and recharge over time.

Deep cycle batteries, on the other hand,  provide a steady rate of power over long periods of time. The internal design of these batteries differs significantly from starter batteries. There are many different designs of true deep cycle batteries available, such as:

• Lithium-Ion
• Flooded lead-acid
• Gel lead-acid
• Absorbant Glass Mat (AGM) lead-acid

Lead-acid batteries come in sealed (also called valve-regulated) and flooded design types. AGM and Gel batteries are sealed, so no liquid can be spilt unless the casing is damaged. Despite better performance and safety, flooded lead-acid batteries continue to be a popular choice.

All of these batteries are suitable for a range of common deep cycle applications but often shine most in a specific category.

Deep cycle batteries are often used for electric vehicles, emergency equipment and lighting, off-grid energy storage like solar and wind, or as an uninterruptible power supply (UPS) backup.

How Long Does a Battery Last?

The answer is different between the two categories of Lithium-based and lead acid-based batteries, and even between each lead-acid battery design. Further still, the strain the battery endures in the application you're using it in will factor into the life of the battery.

There's a difference between cycles and lifespan.

The lifespan of an AGM battery is typically six years. The battery will still retain 80 per cent of the original capacity after this point, so it can still have 50 per cent available capacity for use.

However, AGM batteries are only rated to 500 cycles. What makes a deep cycle battery "deep" is that you can go as low as 80 per cent of the available capacity of a battery. The lower you go will reduce the cycles you can use the battery.

AGM batteries will have various cycle lives at capacity withdrawn. For example:

• 200 cycles at 100 per cent
• 250 cycles at 80 per cent
• 500 cycles at 50 per cent
• 1,200 cycles at 25 per cent
• 3,200 cycles at 10 per cent

The recommended depth of discharge on an AGM battery is only 50 per cent. That means you must buy your system based on how much energy you want available for use.

If you want 50 KWh of electricity available, you need to build a system of 100 KWh.

What Are the Differences Between Batteries?

12V deep cycle battery technology is quite varied. Between the two categories of lithium-ion and lead-acid, there are some big differences in performance.

Lithium-ion battery technology has advanced greatly in the past 40 years from an interesting idea to enabling the digital world. It has, without a doubt, revolutionized marine, solar, and other deep cycle applications as well.

Some reasons that lithium-ion batteries are highly desired are:

• 95 per cent efficiency
• 85 per cent or deeper depth of discharge
• 2,500 to 10,000 cycles
• Low internal resistance
• Shelf-life of more than 10 years
• 30 per cent the weight of lead-acid battery systems

Flooded lead-acid batteries remain popular for a variety of reasons. One reason is that they are a commonly understood technology, compared to lithium-ion. They also require little maintenance once they're set up, aside from adding distilled water.

Other lead-acid batteries need no maintenance at all.

AGM batteries are a significant improvement over flooded lead-acid batteries, but gel batteries continue to offer more benefits. Flooded lead-acid and AGM batteries benefit from one advantage over all the rest of the battery technologies you could be looking at.

Still, nothing beats lead-acid technology in cost.

A Sample Solar System

A lithium-ion 12V deep cycle solar battery doesn't need a replacement for 10 years, but let's take a look at up-front pricing.

The cost of a lithium-ion battery could cost up to 500€ per KWh. If you have a 50KWh system, that's 25,000€ straight away. Installation and transport costs together would likely cost around 3,000€.

The total cost of the lithium-ion system is 28,000€.

The same system done in lead-acid with lower efficiency and capacity ratings means you need to build for 100KWh. The 100KWh system will have a usable capacity of 50KWh.

The upfront cost of each kilowatt-hour would be 50€ or less. For this system you're looking at 8,000€ if you have the same installation and transport costs. A hefty savings of far more than 50 per cent to get your system up and running.

Gel batteries would cost more, and flooded lead-acid batteries would require too much maintenance and space. AGM has a higher capacity, more available power, and lower cost than Gel batteries.

AGM also has a faster charge than flooded batteries and better cycle life with less sulfation issues.

12V Deep Cycle Battery: All You Need to Know

When looking for a 12V deep cycle battery system such as a 12V deep cycle marine battery or 12V deep cycle solar battery, you now know what you need to look for.

Depth of discharge ratings will affect cycle life and available energy. This lets you know how many batteries to buy. Choosing lead-acid is much cheaper than lithium-ion, but there's still a lot of variation in the type of lead-acid battery to look at.

Need more help? RB Battery has been the leading supplier of deep-cycle and automotive battery solutions for more than 25 years. We are a premier supplier in Asia, Africa, and the Middle East.

Get in touch with us today to learn how we can help you create your next deep cycle battery system!