2018 Macbook Service Battery warning

"Service Battery" indicates macOS has detected a hardware fault with the Battery which will need replaced. Have Apple or an Apple Authorized Service Provider examine the laptop to provide you with a repair estimate. In some regions you may be able to mail the laptop to Apple for the repair. Click the "Get Support" link at the top right of this page to see your options.

Batteries are considered Consumable Products. Over time it will degrade to a point where it needs to be replaced. The usage is normal as the capacity will go up and down all the time and never stay always at 100%. Apple Batteries are rated for 1000 Full Battery Cycles and / or 80% Capacity before needing Evaluation or replacement.

Hi.

Reseting PRAM/NVRAM (https://support.apple.com/en-gb/HT204063) may clear some defective data around the MB or the charging circuitry.

If nothing changes I would take it to an Apple repair center.