Looked at the comments, many seem new or are confused. This charger will charge at 3 Amps Max. (with heatsink on Regulator) The circuit works by monitoring the current through the voltage drop through the series output R7 (the more current, the lower the voltage). The op-amp (as a comparator) compares the output with the reference voltage provided by the R4/R5 Voltage divider. When "on", the output of the op-amp is high, no current flows through Q1 or R6. When the charging current drops (batteries draw less current from charger the closer they are to 'full'), the voltage drop across R7 decreases, increasing the voltage at the inverting input of the op amp. When that voltage is higher than the reference from the R4/R5 voltage divider, the ouput of the op-amp goes low, putting R6 in parallel with R2, and turning on Q1 which turns on the LED. R6 in parallel with R2 lowers the voltage on the adjust pin of the regulator, effectively turning it off. The circuit allows a 30mA trickle charge through R1, which also provides power to the circuit. My opnion is that a 3 Amp charger IS a trickle charger, There are lots of other circuits around that use several paralell MOSFETs to get high/normal charge rates. 2 amps on a half-dead battery would take over a day to charge. However, the low current method is the only way to salvage a fully discharged lead acid battery, if at all. Hope that answers everybody's questions. (no, I didn't create this circuit, just came across it and thought I'd comment)