The battery isn't held down properly, or it's leaking electrolyte. A loose battery can move about and short against the bonnet or bodywork, which is a genuine fire risk, and leaking acid damages everything it touches.
Wording as it commonly appears on an MOT certificate: “Battery insecure or leaking”.
What does it mean?
The battery isn't held down properly, or it's leaking electrolyte. A loose battery can move about and short against the bonnet or bodywork, which is a genuine fire risk, and leaking acid damages everything it touches.
How serious is it?
Usually recorded as: Major. The tester assesses the actual vehicle on the day, so your certificate is what counts.
What normally causes it?
- A missing or corroded battery clamp, often left off after a battery change
- A swollen battery case from overcharging or heat
- Corroded terminals letting acid creep out around the posts
What a mechanic would check
Try to move the battery by hand — it shouldn't budge. Then check the case for swelling or damp, the terminals for that white-green fur, and the tray underneath for corrosion, which is where the acid ends up.
What might need replacing
- A battery clamp or hold-down bracket
- A battery, if the case is swollen or leaking
- Terminal clamps and a clean-up of the tray
Can you still drive it?
It's a failure. A loose battery under the bonnet is a fire risk, and it's about the quickest thing on the whole certificate to put right.
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This is general guidance from a UK mechanic, not a substitute for a physical inspection. Only the tester who inspected your vehicle can confirm what was recorded and why.