How insecure does a battery have to be to fail an MOT Test?

Q.    How insecure does a battery have to be before it should be failed?

A.     The battery must be so insecure such that it is unrestrained and likely to fall from its vertical position when the vehicle is in its presented condition (i.e. bonnet / access panels closed). A battery that is not strapped down and is moving around inside a battery box does not justify a failure, as it cannot fall from the carrier.

How insecure does a battery have to be before it should be failed?

1.9 Electrical Wiring and Battery

Information

This inspection applies to all vehicles other than Class 3.

Some tow bar electrical sockets are ‘hidden’ behind an access panel in the bumper or bodywork.  Unless requiring the use of tools or specialist equipment, these panels must be removed to facilitate the inspection of the towbar socket.

If a tow ball or pin is not fitted at the time of test, e.g. because it is detachable, has been unbolted or otherwise removed, but the attachment brackets are still in place, any trailer electrical socket should still be assessed.

This does not apply if the attachment brackets have been deliberately rendered unfit for further use.

A trailer electrical socket with a defective or missing cover flap that incorporates a lug and spring to hold the plug in place is not a Reason for Rejection.

Method of Inspection

1. Check the condition and security of the battery(ies).

2. Check the condition and security of all visible electrical wiring.

3. On vehicles fitted with a towbar, check the condition and security of the trailer electrical socket. Note: This check applies to both 7 pin (12N) and 13 pin electrical sockets.

4. On vehicles fitted with a towbar that have a trailer 13 pin Euro-socket, use an approved device to check that the socket is wired to correctly operate the trailer:

  • Position lamps  
  • Stop lamps
  • Direction indicators
  • Rear fog lamp

Reason for Rejection

1. A battery insecure or leaking electrolyte.

2. Electrical wiring:

a. insecure or inadequately supported so that it is likely to become damaged

b. damaged or deteriorated to the extent that it is likely to cause a short circuit or become detached

c. insulation damaged or deteriorated to the extent that bare wiring or connectors are exposed.

3. A trailer electrical socket:

a. insecure  

b. damaged or deteriorated to the extent that the connecting lead could not be securely connected.

4. A trailer 13 pin Euro-socket not operating the trailer lamps as intended.

https://www.mot-testing.service.gov.uk/documents/manuals/m4s01000901.htm