There can be a few things why this is happening.

1) Could be your battery requires replacement.

2) Background apps or programs are running all the time in high power state.

3) Device has not been restarted in a few days.

1) If you device is still under warranty with either where you purchased the device or with the manufacture, then we would recommend logging your device with them.

If your device is out of warranty completely and you can identify your brand and model you could purchase a replacement battery from a trusted eBay seller online.

We recommend if you choose this option to only buy from trusted seller and within your country if possible.

2) There are other things that can cause your battery to run out of charge quickly. Background applications and programs can keep your device overly active never giving it a chance to run in a lower power state.

3) Always ensure we shutdown and even a simple restart is healthy for your device. We recommend doing so daily if possible.

Another option to confirm your issue is to run Windows Battery Report.

Windows Key + R (This will open run)

Open: cmd

At the prompt type: powercfg /batteryreport

Then press Enter.