It's generally better to buy a replacement from the original laptop maker than the cheapest compatible option from a third party. Replace your battery—if you can—if you see its capacity drop ...
Read How to test a MacBook battery: see if it needs replacing & replace it. Our list starts ... The larger the laptop, the higher wattage is the battery—as they generally require more power ...
This could be caused by any number of issues, like the battery being damaged ... expensive component to replace. Troubleshooting itself can be difficult. Every laptop requires a different amount ...