12V lead-acid battery charger with LM317 current limiter
Charging a Lead Acid battery is quite easy. You should first apply a constant current (CC) of max. 1C (in your case 9A) until the voltage reaches 14.4V. Hold this voltage for at least one hour, at most 10 house to balance the cells inside the battery. At the end of the constant (CV) period the current should be below 1/20 of C (in your case 450mA).
Do not apply voltage above 14.4V, this will reduce the capacity of the battery over time because of water loss.