No.4 Battery was built some three hundred and fifty metres to the North East of Ardagh Martello. The battery site still has some above ground remains including part of the parapet wall and a defensible building (guard house) which may also have been used as a magazine. It would appear to have be armed with two smoothbore guns, probably 24 or 32-pdrs. The battery has commanding views over Lawrence Cover, the Fleet Anchorage.
It would appear that the tower and battery was used by the military until at least the 1860s, possibly later.