What is a deep-cycle battery?

A deep-cycle battery is designed to be discharged to 80% of its capacity and recharged repeatedly without losing lifespan. Unlike starter (SLI) batteries, it does not deliver high current peaks but sustains a constant load over hours — ideal for fridges, lights and electric trolling motors in boats or caravans.

When do I need a deep-cycle battery?

Whenever you power equipment for long periods: caravan fridge, electric outboard, solar panels, mobility scooter, golf cart, medical life support. A standard car battery will NOT survive this regime — it would degrade within weeks.

How long does a deep-cycle battery last?

Between 4 and 12 years depending on technology (AGM deep-cycle: 5-8; GEL: 6-10; LiFePO4: 10-15). The biggest factor is depth of discharge (DoD): at 50% DoD they last twice as many cycles as at 80% DoD. A smart charger with deep-cycle mode is mandatory.

Can I use a deep-cycle battery for engine starting?

Not recommended as your only starter battery: deep-cycle batteries deliver less cranking amps (CCA) than an SLI or starter AGM. The correct setup is two batteries in parallel: a starter (SLI/AGM) and a service (deep-cycle), separated by a relay or BMS. Some "dual purpose" hybrid batteries cover both uses with intermediate performance.

Do deep-cycle batteries need maintenance?

Modern AGM and GEL deep-cycle batteries are sealed and maintenance-free. Open lead-acid batteries (flooded deep-cycle, like Trojan) do require periodic distilled water top-ups every 1-3 months depending on use. LiFePO4 require absolutely no maintenance.

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Deep-cycle batteries

Deep-cycle batteries are designed for applications that demand sustained discharge: golf carts, industrial scrubbers, mobility scooters and solar systems.

Extreme cyclic capacity: hundreds of cycles at high depth of discharge.
Thick plates built for slow, sustained discharge — not for cranking.
Do not mix with starter batteries: using a starter in a cyclic application will destroy it within months.

See all AGM batteries → · See all GEL batteries →

Compatible batteries

Receive them tomorrow before 5 PM if you order before 6 PM (Spain mainland and Portugal only).

Before you buy: check 3 key points

Although the batteries shown are sourced from information provided by manufacturers, we recommend checking on your current battery:

Dimensions (length × width × height, including terminals and protrusions)
The dimensions shown are the maximum of the battery and include the height of the terminals, small ridges at the base and any lateral protrusions. Measure your current battery completely, from edge to edge. The new one must be the same size or slightly smaller — never larger, it would not fit in the housing.
Positive terminal (left or right viewed from the front — check the battery photo carefully)
Stand facing the battery, with the manufacturer's label facing you and the terminals on top. Locate the terminal marked with +: if it is on your right, it is "positive right"; if it is on your left, it is "positive left". Do not rely on how the battery is mounted in the car — the position is always measured looking only at the battery itself.
Technology (AGM, EFB or conventional — the same as your current battery or higher)
Depending on the manufacturer, the same technology may be labelled differently: AGM may also appear as VRLA, AGM Start-Stop or AGM Deep Cycle. EFB may appear as EF, EFB+ or Enhanced Flooded Battery. Conventional may appear as SLI, Lead-Acid, Wet or Standard. If your vehicle has Start-Stop, the battery must be AGM or EFB — never conventional.

If you have any questions, just ask us and we'll be glad to advise you with no obligation.

This engine comes with an AGM/EFB battery as standard: the car's charging system requires it even without Start-Stop. If in doubt, message us and we will confirm.