MacBook Pro 2018 says it needs battery charging on start up while battery is charged >15%

"MacBook Pro 2018 says it needs battery charging on start up while battery is charged >15%: [...]When I insert my charging cable however, it often has a battery percentage of more than 15% left. Does anyone have any suggestion on how to fix this problem? I would like to use my MacBook normally when it has a 15% battery charge left.[...]"

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Troubleshoot the Mac's Power:

As for replacing that battery, that may not be necessary. So, try troubleshooting it.

A. Black Mac Screen:

Go Here: If your Mac doesn't Turn On or Start Up - Apple Support

Using External Devices: Try Resetting the SMC and NVRAM, but this time, using an external keyboard. Connect an external monitor and see if you get an output. This applies to Intel-Based Macs only.

B. Mac Power Issues:

Try a New Charger:

If it is currently charging from a charger, then use a new charger:

• Power & Cables - Mac Accessories - Apple - Select "Mac Compatibility" on the left
• Find the right power adapter and cable for your Mac notebook - Apple Support

C. A Few Links to Refer to Power:

• How to Turn your Mac On or Off - Apple Support

• About Mac Notebook Batteries - Apple Support

• Charge the MacBook Pro Battery - Apple Support

• If your Mac Battery won't Charge - Apple Support

Are you checking the battery charge level on the login screen? If so, that information is many times incorrect. To get the actual battery charge level, make sure to first log into macOS.

I have seen these USB-C Intel Macs behave this way all the time. I even saw it happen with a brand new Apple OEM battery from Apple. I suspect that on occasion the Logic Board loses communication with the Battery. When this happens, the power adapter needs to be connected before the laptop will start.

If this is the original factory battery, then perhaps this battery is beginning to show signs of failure.

"MacBook Pro 2018 says it needs battery charging on start up while battery is charged >15%: [...]When I insert my charging cable however, it often has a battery percentage of more than 15% left. Does anyone have any suggestion on how to fix this problem? I would like to use my MacBook normally when it has a 15% battery charge left.[...]"

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Battery Issues on a 2018 Mac:

View the Battery Health:

On iOS13, Battery Health is now called Maximum Capacity. Once it reaches below 80%, Apple recommends you get a new battery.

1. Go to: Settings
2. Tap: Battery
3. Click: entitled " " on the top-right corner
4. View: Maximum Capacity

If below 80%, it is time for a new screen.

Where to get a new battery:

Take this in for a Genius Bar Appointment at your local Apple Store. Bring a proof pf purchase with you.

Contact Apple:

• Contact Us - Choose Locations
• Proceed from there as Necessary

Or...

B. Contact an AASP: 

1. Go Here: Find Locations - Apple Authorized Reseller
2. Click: Service & Support
3. Enter: your location information
4. See: if there is an AASP nearby
5. Contact: an AASP that shows up, and find out more about the services that they offer to fix the Mac