Q: Macbook Pro 15" not charging properly after new buying/using new charger

Hi everyone,

I had my last charger for 6 or 7 years and it finally broke. I purchased a new one for my macbook 15" and ever since then, my computer loses charge very quickly and will die at 30-40%. The battery bar will be in the red and say I need to plug it in or it will die, even thought it should have lots of charge left. Could this have anything to do with buying a charger with the improper wattage? The guy that helped me pick out the charger never mentioned anything like that. I'm also wondering if the battery just needs to be replaced, which is kinda of a weird coincidence, that ever since I replaced the charger it needs to be changed. I'm hoping someone can help me out!

Thanks,

Hannah