What is an AGM battery?
5 January 2026
Your vehicle might have one, or you might be wondering if you should get one, but what exactly is an AGM battery?
The letters AGM stand for Absorbent Glass Mat. AGM are a type of lead-acid battery where the electrolyte is absorbed into fibreglass mats rather than being in liquid form. This design makes AGM batteries spill-proof, maintenance-free and able to provide higher power output compared to traditional flooded batteries.
They have a higher cranking capacity because more plates can fit into the battery casing. That’s also why AGM batteries are heavier.
They are also more resistant to vibration and can be mounted in a variety of positions, making them a favourite for seasonally used vehicles such as snow mobiles and boats and in back-up power systems.
Let us look at those advantages of AGM batteries in more detail:
- Maintenance free: no need to top up with distilled water
- Longer lifespan: they typically last longer due to their robust internal construction
- High performance: they deliver strong starting power and cope well with high electrical demands
- Safe and reliable: the sealed design prevents leaks and allows for flexible installation.
Charging AGM batteries: why it matters
Regular and optimised charging is crucial to maximising the lifespan and performance of AGM batteries. Unlike standard lead-acid batteries, some AGM models benefit from a slightly higher charging voltage to ensure optimal performance and longevity. Using a charger that recognises these needs can make a significant difference.
CTEK’s new NXT 5 battery charger combines high performance, reliability and ease of use – and it has a specific mode optimised for AGM batteries. The AGM mode delivers a slightly higher charging voltage tailored for those AGM batteries that require it.
Just connect the charger and press the Mode button to access charging that is tailored for AGM batteries. The NXT 5 also has spark-free operation, reverse polarity protection and CTEK’s hallmark connect-and-forget functionality.
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