Is this circuit ok for charging SLA gel cell batteries?

Sorry to revive this thread, but the charger is running way slower then it should be. It should be charging at 600 miliamps with a 1.1 ohm resistor, but I monitored the current for a couple hours and it stayed at 40.2-40.3 miliamps. Should I adjust the potentiometer so that it puts out 600 miliamps?
Edit: I tested the current through a 390 ohm resistor and even tried shorting the charger for a split second. Both times it only put out around 40 miliamps.