jon wrote:
I used an old 19v x 4A laptop power supply with a couple of 55W headlight
bulbs in series to charge my flat battery. It started at 2.5 amps and
dropped to 1.8 amps over a couple of days, giving a full charge.

That's a handy idea. I have some 12V 20A PSUs, and a headlight bulb in
series would limit the initial current to 4.5A which would be sensible.
That would be enough to get it off the floor, and then a regular charger can
take over. It wouldn't be the fastest but it would be good enough to begin
with.

Theo