So I think you might not understand C. C is how fast a battery is charging or discharging. It is measured using the capacity of your battery in mah. So 1C is the same as your battery's capacity in amps, so if you had a 2200 battery 1C would be 2.2 amps. For charging, if you want to charge at 2C, multiply your capacity by 2 and you will get the charge rate that you want. I'm gonna use a 2200 again for this. To charge it at 2C, multiply 2200 by 2 and you get 4400mah, which is 4.4 amps. To calculate your battery's max discharge rate, multiply the C rating by battery capacity and you will get your max discharge rate in mah, divide that by 1000 to get the discharge rate in amps. So if a 2200 has a 20C discharge rate and you want to know how many amps you can safely pull from it, multiply 2200 by 20 to get 44000mah, and divide by 1000 to get 44 amps. Sorry if my explanation is a bit complicated, it's hard to fit in one post.
So basically you can charge your battery at 1.5A, but you will be charging at around 1.7C, so just know that.