Bert Coules wrote:
"The Natural Philosopher" wrote:

And how can I tell when the battery is sufficiently charged?

when the terminal voltage is over 13V

But how do I tell that? There's no meter or any other indicator sort of on
the charger.

Do you have a multimeter?

If not, it sounds like a fairly old and dumb charger. On those the current
starts high (say that 6A) and then gradually drops as the battery charges.
At the end of charge it's only taking 1A which is something the battery can
handle indefinitely (although I wouldn't leave it on for weeks).

So I'd charge it for say 8 hours and see if there's any life from the
battery.

Theo