What does AGM mean on a battery?

AGM (Absorbent Glass Mat) is a sealed lead-acid technology where the electrolyte is absorbed into a glass fibre mat. It is leak-proof, withstands more charge/discharge cycles and tolerates heat better than conventional batteries. AGM is fitted to boats with advanced Start-Stop and regenerative braking.

Which boats use AGM batteries?

boats with advanced Start-Stop, regenerative braking or high electrical loads (advanced driver assists, permanent climate control, heated seats). Brands like BMW, Audi, Mercedes-Benz and Volvo have fitted AGM as standard since around 2010 on their efficient-engine models.

How long does an AGM battery last?

Between 5 and 8 years under normal conditions — 50% to 100% longer than a conventional battery. Real-world life depends on Start-Stop usage, extreme temperatures and short-trip frequency. If the vehicle does many short trips or has very active Start-Stop, check the battery from year 5 onwards.

Can I fit an AGM in place of an EFB or conventional battery?

Yes — AGM can replace EFB or conventional batteries (AGM is the superior technology). What you must NEVER do is the opposite: fit an EFB or conventional in a vehicle that originally had AGM — it would degrade within months and Start-Stop would fail.

Do I need to register the AGM battery when I replace it?

Yes — most modern cars with a BMS (Battery Management System) require the new battery to be registered via OBD so the alternator applies the correct charging profile. Without this step the battery will be charged incorrectly and lifespan will be cut significantly. Any workshop with a basic OBD tool can do it (~£10-20).

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AGM marine batteries

AGM marine batteries combine strong cranking with cyclic capacity — perfect for inboard/outboard boats with on-board electronics.

Vibration-resistant and fully sealed: safe in marine conditions.
Zero maintenance: ideal for marinas or long lay-ups.
Cyclic capacity: power fridge, sounder, lights and auxiliary gear without penalising cranking.

See all AGM batteries →

Compatible batteries

Receive them tomorrow before 2 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 — Start-Stop requires AGM or EFB)
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.

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AGM marine batteries

Compatible batteries

Start-Stop battery Varta A9 12V 50Ah 540A AGM

Marine battery Varta LA95 12V 85Ah AGM

Marine battery Exide EP1500 12V 180Ah 900A AGM

Caravan battery Ritar EV12-150S 12V 150Ah 715A AGM

Marine battery Exide EQ800 12V 95Ah 850A AGM

Auxiliary battery Tudor TK500 12V 50Ah 570A AGM

Auxiliary battery Exide EK500 12V 50Ah 570A AGM

Caravan battery Ritar EV12-150 12V 150Ah 715A AGM

Caravan battery Ritar EV12-240 12V 240Ah 840A AGM

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