hi,
Finally found it.
For the invertor, assume 100% conversion with a 240V/40Watt lamp load, it would draw about 3 amps, so a 6AHr battery would last just under 2 hours.
Usually conversion eff is around 80%, so I would estimate 1.5 hours for a fully charged battery. End voltage not less than 10.8V.
IIRC,the output of the charger at 12V is only a few tens of milliamps, say 24mA.
Recharge time at 100%, 6/0.02 = 300 hrs!!!
I will re-examine the charger, Ill will come back if I have made an error in reading it.
Where are you in SA.?