Andrew Gabriel wrote:

It's a car battery.

If it's been taking 3A for a few hours, it will have 9Ahrs
(less a bit for inefficiency) added to it, which is plenty
enough to start a car many times, unless there's something
wrong. The car will then charge it properly, and much faster,
whilst you do your regular driving (don't sit on the drive
reving the engine, as that's pretty pointless).

It's a 60Ah battery. The terminal voltage isn't yet up to 13V.

It's a fairly new battery, yet either there is something wrong with it,
or there is something wrong with the car (that is draining it rapidly
while it sits on the driveway).

The other day it was flat, so I charged it for an hour or so, it started
up right away, then later that morning it was flat again.

Daniele