What are Deep Cycle Batteries?

Deep cycle batteries, sometimes also referred to as deep cell batteries, are designed to be deeply discharged on a regular basis. In contrast to starter batteries, which are designed to be constantly topped up and deliver short, high-current bursts of power (e.g. for starting a car engine), a deep cycle battery is designed to deliver sustained, lower-current power over a long period of time. It can also be discharged to less than half of its capacity for many charge cycles.

Physically, the main differences between deep cycle and starter batteries is that the deep cycle battery has thicker battery plates and denser active paste material, allowing it to withstand the deeper charge cycles.

Uses of Deep Cycle Batteries

Deep cycle batteries are employed for use in situations where steady, low-current power delivery is required. They are commonly used as 4x4 batteries, caravan batteries, recreational vehicle batteries, marine batteries and in dual-battery systems.

What’s The Best Deep Cycle Battery For Camping?

For 4x4 recreational use with a solar camping setup an AGM battery is adequate and by far the most popular choice due to the price point. For the ultimate in performance and for serious off-road adventure enthusiasts, lithium is the best deep cycle battery money can buy.

The AGM Battery

The AGM battery (Absorbent Glass Mat) contains electrolytes which has been absorbed into porous fibreglass mats. Compared to wet cell batteries, AGM deep cycle batteries can handle higher temperatures, will self-discharge at a much lower rate, and have lower internal resistance, meaning they can accept a higher charge current and thus will charge more quickly.

Because the AGM battery is fully sealed, it is much easier and safer to transport. It does not have to be mounted upright in a sealed container vented to the outside; rather, it can be mounted either on its sides or on its ends and can vent to the atmosphere. An AGM battery is also maintenance-free, in that it does not require topping up with distilled water like wet cell batteries. This makes AGM a great choice for use as a marine battery or boat battery.

The Lithium Deep Cycle Battery

The Lithium deep cycle battery represents the very latest in battery technology. Lithium batteries are generally composed of Lithium Iron Phosphate (LiFePO4), which is considered the best battery material available on the market today.

The advantages of lithium deep cycle batteries compared to their sealed lead acid (SLA) forebears are numerous. Firstly, they are much lighter, generally weighing about one-third to half that of equivalent capacity SLA’s. They can handle up to 8 times as many charge cycles as an SLA battery, and can discharge very close to 100% of their capacity without damaging the cells, compared to just over 50% for SLA batteries. Lithium batteries have extremely low internal resistance, meaning they can charge very quickly and efficiently. They will charge to more than 90% of capacity in 1-3 hours, compared to SLA batteries which will generally charge to around 80% of capacity in around 5-8 hours. More so on boats, but also in caravans, weight is an important factor and Lithium is by far the best marine battery or caravan battery for sale today.

Other Types

AGM and Lithium are the most common types of deep cycle batteries on the market. There are also a couple of other types available:

Flooded Lead Acid batteries (wet cell) were the first type of deep cycle battery produced, and they are still somewhat popular today due primarily to their low cost, despite being heavy and maintenance-intensive making them unsuitable for use as a boat battery

Gel Lead Acid Batteries are similar to wet cell batteries but have a gel-based electrolyte, which eliminates evaporation and makes them much more resistant to extreme temperatures and vibration.

Battery Capacity & Calculating Requirements

Battery capacity is measured in Ampere hours (Ah). This measure represents how long one Ampere of current can flow out of the battery.

To calculate your requirements, consider the current draw of each piece of electrical equipment you wish to run from the battery. For example:

1 x set LED camp lights (3A per hour) x 5 hours = 15Ah
1 x portable fridge (1.5A per hour) x 24 hours = 36Ah
Total = 51Ah

Add a safety net (say 50%) = 51Ah x 1.5 = 76.5Ah

You would select a deep cycle battery with a capacity of at least 76.5Ah. The greater the capacity, the more power you have in reserve. This is particularly important if you are using portable solar panels to charge the battery, due to the possibility of inclement weather.