Do I always need to fully charge my MacBook Pro 13"?

SiThuLin wrote:

battery

About Mac notebook batteries - Apple Support

https://support.apple.com/en-us/HT204054

Determine battery cycle count for Mac notebooks - Apple Support

https://support.apple.com/en-us/HT201585

Batteries - Maximizing Performance - Apple

https://www.apple.com/batteries/maximizing-performance/


If your USB-C power adapter isn't charging your Mac notebook

https://support.apple.com/en-us/HT204652

Apple Portables: Troubleshooting MagSafe adapters

https://support.apple.com/en-us/HT203207

SiThuLin wrote:

1. Do I always need to fully charge my MacBook Pro 13"?

2. Should I keep my MacBook Pro 13" plugged while I am working and does it damage my battery?

3. If my battery has 100% charge and it is charged continuously, does the power is used from my battery or from the charger?

1. Since I never know when I'll want to pick up my MB and go I always keep it on a charger when I have access to mains
2. Your computer has a 'smart' battery. It quick charges until it is almost fully charged. When it reaches about 95% it moves into trickle charge. When it is fully charged the battery stops charging until it drops down to about 95-97% and begins trickle charging again. This avoids damage.
3. As noted above, it stops charging at 100%.

dwb gave you some great answers, so there is very little to add.

There is a subtle twist when you are doing very intensive work. The computer is free to use everything provided by the power adapter PLUS "borrow" from the battery, unless it starts to overheat.

This allows you to do everything you ask of it, at maximum speed, provided the power adapter is connected and the battery has charge to spare. When on battery alone, it may compute more slowly to conserve power.