2012 Chevrolet Malibu bad

Are you still under warranty? If so, I'd take it to the dealership. If not, I'd have to check the battery and charging system.

Another possibility is too much drain with the key off. Usually less than 50 ma, that .050amp, not even a tenth. If the drain is too much, you pull/replace fuses one at a time. When you pull the fuse on the problem circuit, the excess drain goes away.

Sometimes it can drain through the alternator?

Just to add, if the battery is down, you will have to get it charged up to do any testing.

They said it was the battery

I'm not sure of engine litre, it may not make a difference? There are battery&charging system trouble codes, I'd have to check codes. Some of the national brand auto stores will check codes for free. If you want to check codes, yourself, at the least, you need an obd2 code reader that will work with your vehicle.

I did look at service bulletins for your vehicle, didn't see anything that caught my attention.

There is the battery connections, alternator connections/wiring. OK, have the new battery tested, if you think that is the issue?

Unless you can do a little testing, I'm going to have trouble trying to help you.