On Sat, 30 May 2020 08:22:22 -0000 (UTC), Smolley wrote:

Further to a post a few weeks ago, about the battery being flat in my car
after standing idle for a few weeks. I subsequently charged the battery in
the house using a laptop power supply and a couple of headlight bulbs in
series to deliver a charging current of ~2 amps over several days. I
eventually put the battery back in the car and fitted a knife switch
isolator. Yesterday I went out in the car and returned after about 10
miles. This morning after the engine fan had stopped I measured the
standing current across the open knife switch and was surprised to see the
meter was reading 3.26 amps. No wonder the battery flat!

The current will start high, but will settle down after a few minutes
as things go to sleep. You need to wait for a while before measuring
the quiescent current draw.