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Whether it’s off-roading, camping, fishing or storing power for longer road trips, a deep-cycle battery has all the juice you’d need. This supplies power to any appliances, equipment or vehicle accessories when on the road, and spares your car battery. It also plays a central role in off-grid solar setups, storing generated power for later use.
What are Deep Cycle Batteries?
Deep-cycle batteries are power storage units designed to be ‘deep-cycled’ or discharged to very low levels (over 80 per cent) regularly. They differ in construction, use and purpose from standard starter batteries that you’d find in your car. The main differences are the thicker battery plates and denser active paste material, allowing a 12V deep cycle battery to discharge at a slower rate and supply stable voltage over a longer period.
Starter batteries, on the other hand, provide very short bursts of high voltage and discharge only a small portion (2 to 5 per cent) of the rated battery capacity. They have the grunt to turn over engines, and supply power to starter motors and alternators, but won’t last long in continual power supply. Discharging them to rates often seen in deep-cycle variants leads to battery damage and safety concerns, such as gassing, leaks or even explosions.
Types of Deep Cycle Batteries
Battery tech has developed at breakneck speeds, with constant improvements and different types of batteries. There are a few things to know before setting out to buy deep-cycle batteries. One of your first concerns is choosing the right type:
- Flooded Lead Acid (FLA) – this is the most common type, widely available and relatively cheap. They’re based on lead plates flooded in an electrolyte mix of sulfuric acid and water. The batteries can be discharged to roughly 50 per cent capacity, making them a good choice for lower power needs, such as the odd weekend getaway. The low price is down to a few downsides. Some have been known to leak hydrogen and oxygen during operation, so they require careful placement and more maintenance. Moreover, they’re some of the heaviest 12-volt deep-cycle batteries, with most over 30 kilos.
- Absorbed Glass Mat (AGM) – sealed batteries like these offer higher safety and require less maintenance. Here fibreglass layers separate the lead plates, offering higher efficiency with longer life cycles and higher discharge rates of over 80 per cent. The batteries are also much lighter, with standard 100Ah types coming in at around 25 kilos.
- Gel – these batteries get their name from gel-like silica electrolytes. The material is denser and less viscous, so there’s a lower risk of leakage. This type is comparable to AGM batteries, benefiting from low maintenance, good discharge rates of around 75 per cent, and similar weights for the rated capacity.
- Lithium-Ion – the newest version, offering considerable advantages where it matters. The batteries can be discharged to very low rates (around 95 per cent) without causing physical damage or related safety concerns, they come in more compact designs and at half the weight of FLAs, and have some of the highest rated capacities to power connected appliances, devices or equipment for longer. They’re also more durable, don’t get as hot compared to other types, and offer faster charging rates. And they have the highest discharge and recharge cycles (roughly 5000 times), meaning they’ll outlast any other 12V deep cycle battery. All these advantages do come at a cost, but if you’re a regular camper, off-roader or need off-grid power more often, this is the type to choose.
Common Uses
Deep cycle batteries are a main component in solar setups, where they store generated power. Here they can be used alone or in battery packs when energy needs are higher, such as powering power-hungry appliances like ovens, fridges and microwaves. The devices are seen in golf carts, electric scooters, wheelchairs, and electric forklifts. And they’re a reliable off-grid power source for marine and off-roading uses, where they supply power to auxiliary systems like off-road lights or winches, and basic tools like compressors, and double as a secondary power source to top up depleted starter batteries.
What to Look For
When buying a deep cycle battery, first consider your power needs, where and how the battery will be used, and whether you plan to add other devices or equipment to your setup. The first thing to look for is the rated capacity in Ampere hours. This ranges between 50Ah to 300Ah, with 100Ah and 200/225Ah being more common for outdoor use. The higher capacity means you can run one or more devices or appliances for longer periods before the batteries need recharging. This of course will depend on what’s connected.
Next, consider safe discharge rates. Lithium-ion batteries fare best here and are the best option for frequent and heavy users. AGM and Gel types are decent options for most uses, and FLAs will be enough for short bush breaks with basic camping gear. Related are the overall charging cycles. Again lithium-ion batteries top the list, with averages of 3000 cycles, compared to less than 500 cycles in flooded acid batteries.
And lastly, consider maintenance needs, and specifics like size and weight. Sealed batteries are virtually maintenance-free, whereas FLAs need frequent inspections to check for possible gas leaks or overheating. This also limits where batteries can be safely used. Lithium batteries for instance have no issues in enclosed spaces compared to lead-based types. Sizes will also impact whether batteries can fit in designated spaces (such as under bonnets or in car boots) while weight determines the required hardware (trays, battery boxes etc) for safe usage and the physical demands when they need to be relocated.
