Deep Cycle Batteries: Types, Benefits and Buying Tips
Utes, boats, motorhomes and caravans all rely on deep-cycle batteries for power. They run everything from winches and off-roading lights to fridges and ovens, and store backup power from vehicle solar installations. Unlike starter batteries that provide short power bursts to get engines going, deep-cycle batteries are designed to give a consistent charge over a longer period. This makes them ideal for keeping the AC on in hot weather, pumping fresh water, lighting camp sites or binge watching your favourite shows.
A major benefit is that the batteries can be repeatedly discharged to much lower levels (often lower than 50 per cent) than their starter siblings, and recharged thousands of times without losing capacity or enduring physical damage. Several types exist, from simple lead-acid to lithium deep cycle batteries with higher discharge rates and longer lifespans.
Flooded Lead-Acid (FLA)Deep-cycle Batteries
These are the oldest type of deep-cycle batteries. Built around thick lead plates flooded in an electrolyte solution, they can be safely discharged to 50 per cent of full capacity. Drawcards are the low price, decent cycle life (recharge rates) of up to 1000 cycles, and relatively low maintenance with the occasional need for distilled water. They do, however, drain faster than other types, especially in warmer settings. The larger size and weight are also factors to consider.
Absorbent Glass Mat (AGM)
AGM batteries have electrolyte absorbed in a fibreglass mat, meaning they’re maintenance-free and sealed and can safely be used in enclosed areas, without the risk of gassing. They have higher safe depth of discharge rates than FLA batteries (some up to 80 per cent), longer life cycles (between 500 to 1500) and are faster to charge. And they’re smaller and lighter for the comparable power output without costing much more.
Lithium Ion
If your power needs are higher, you require fast charging and have limited space, then choosing a long-lasting lithium deep cycle battery for sale over other types makes more sense. Common deep-cycle variants known as LiFePO4 or Lithium Iron Phosphate are the same batteries you’d find in mobile devices (although in a much lower capacity), EVs, electric bikes, scooters and industrial equipment.
They store and move energy by cycling lithium ions between an iron phosphate cathode and a graphite anode, with lithium salts acting as electrolytes. Compared to other technologies, lithium batteries are preferred for their:
- Longer lifespan – lithium-ion batteries have lifespans ranging between 3000 and 5000 charging cycles, essentially lasting 10 years or more with a consistent power supply. This reduces costs over the long term.
- High power density – for the same size, these batteries hold up to twice the power density, meaning they’re almost half the size and weight of conventional FLA batteries with the same power output. Good news for users with limited space, especially vehicles.
- Lower weight- related is the much lower weight. Typical FLA batteries weigh over 30 kilos, can be hard to move and maintain and require more attention in mounting. Smaller and lighter lithium variants are portable (especially as a backup power supply) and easily configured into existing setups.
- Super fast charging – the design and materials used in these batteries ensure very fast charging times. Lithium-ion batteries accept higher current, meaning a full charge within 1 to 4 hours, compared to 6 to 8 hours in AGM, and up to 12 hours in larger capacity FLA batteries.
- Higher depth of discharge – lithium batteries can safely discharge 80 per cent of total capacity, with some going up to 100 per cent before recharging. LiFePO4 types also compare well against other lithium chemistry types, including Nickel Manganese Cobalt (NMC) and Nickel Cobalt Aluminium (NCA).
- Consistent power supply – these batteries ensure consistent voltage through much of their discharge cycle, with voltage drop only near depletion. This ensures all connected appliances and equipment work properly. Consistent power also means less overheating.
- Safety – look for a lithium deep cycle battery for sale if you also prioritise safety. They have built-in overcharge protection, short circuit protection, and effectively counter overheating, with a wider operable temperature range. Moreover, they won’t leak or gas, have safety valves to manage pressure, and complex battery management systems that constantly monitor parameters like voltage, current and temperature, and shut down the battery to prevent accidents and damage.
Choosing the Right Deep Cycle Battery for Your Needs
First, determine your overall power needs. Consider how and where the battery will be used and the power drain from connected equipment. Battery capacity, stated in Amp-hours (Ah), determines how much current the battery provides over a given time. Sizes generally start at 100Ah (enough for weekend getaways with basics like lights, charging devices, and powering smaller 12V appliances); 200Ah for longer camping and off-roading trips, and 240Ah for power-hungry appliances including air-conditioning systems, water pumps, heaters and other equipment in fully featured motorhomes, caravans and boats.
Next, consider nominal voltage. This ensures compatibility with powered equipment. 12V types are the most common, though 24V types are seen in larger boats and industrial equipment. Weight and size also matter, as they limit where the battery can be mounted. Lastly, the type of deep-cycle battery you choose determines vital factors such as lifespan, depth of discharge, charging speeds, overall safety and of course, price. With improved chemistries, lower weight, and high capacity in a small, sealed and safe package, lithium batteries are your safest bet.
