This is completely untested and I'm too lazy to figure out the proper resistor values. Basically it acts as a constant current charger during bulk charging and a constant voltage charger at float charging.
R10 and R9 should be sized to set the LM317 to 14.4V (bulk charge). When the transistor (any small signal transistor) is set on the resistance of R8 will be in parallel with R9 and cause the output voltage to drop, and would be set to the float of 13.2V. Should have labeled that "set float charge".
R7 sets charge current, but that current regulation would be negligible when the previous LM317 is set to the float voltage. R11 would be 22K and R10 at 10K to act as a voltage divider so you can read the battery voltage with the Arduino.
