How to turn bass up in car?

Okay so i have a honda civic and the other day my battery died and when i finally got it on the stereo wouldnt let me turn the bass up higher than 8, before my car died i was able to go up to 15 but now it stops at 8?

Now a question for you. Does your radio have an aftermarket amplifier? If so your alternator does not have enough amperage to operate it. The maker of the amplifier can tell you how many more amps it must have to keep the electrical system in your car operating properly.