What the difference actually is
A conventional flooded battery is built to be kept near full charge and to deliver a large current for a few seconds when you start the car. That is the whole job.
A stop-start car asks for something different. The engine restarts many times per trip, and while it is stopped the battery is running the lights, the climate fan and the electronics on its own. EFB and AGM batteries are built to take that repeated partial cycling. AGM handles the heaviest duty of the two.
Why fitting the wrong one is expensive
An ordinary battery in a stop-start car is cycled far harder than it was designed for. It does not fail immediately — it fails early, often well inside what you would consider a reasonable life, and the failure is not a manufacturing defect. It is the wrong application.
Some vehicles also need the new battery registered to the car's battery management system. Skipping that leaves the charging strategy set for the old battery.
How to know which you need
If the car has stop-start, assume it needs EFB or AGM and confirm before buying. The lookup on this page flags it where we hold the information, and asks you where we do not — we would rather ask than guess. AGM sizes are supplied in the Premium range.
Find your battery
Which NOVAX® fits your car?
Read the code off the top or side of your current battery — three digits, sometimes with letters after them, like 628 or 646.
NOVAX® is fitted and warranted through Global Batteries Xpress and authorised resellers. Find your nearest outlet — they confirm the size against the car before anything is fitted.
Where to go
NOVAX® is tested, fitted and warranted at Global Batteries Xpress outlets and at resellers we have appointed in writing. The test is free whether you buy anything or not.