You have reverse connected the charger and shorted it out !!!!
the charger you have is pretty much a float charger and will not charge a flat battery.
There's not enough Amps to reactivate the SLA
Get one of these for a great result :
http://www.radioparts.com.au/product...switching-mode
Note: You have only 9Ah of recomended use (50% discharge)
Charge the battery after every use (Minimun 6 hours)
The charger will go into a float mode when the battery is full