If your battery is over 2-3 years old it needs to be replaced. 

FAQ - Laptop battery articles - Dell Community

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@Viktorija 27 wrote:

Hi! 

My Dell Vostro 15 3000 is not turning on and my battery light is on even when it is not plugged in. I pressed the power button for 30 seconds but nothing happened. It is still the same. What do I do?

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There can be several causes but to startwith, you can try following. Please try these options one by one and check after each option.
1. Troubleshoot Power
Type troubleshoot in Windows Start Search box > Click Troubleshoot > Scroll down > Click Power > Run the troubleshooter > Follow on-screen direction.

2. Restore Default for Power Settings
Right click on battery icon in system tray > Power options > Click Change Plan Settings > Click Restore default settings for this plan

3. Disable Fast Startup
Right click on battery icon in system tray > Power options > Click Choose what the power buttons do > Click Change settings that are currently unavailable > Scroll down to Shutdown settings and uncheck Turn on fast startup > Click Save changes

4. Uninstall / Install Battery Driver
Shut down your computer > Detach power chord > Remove battery > Attach power chord > Reboot your computer
Windows Key+X > Device Manager > Expand Batteries > Right-click Microsoft ACPI-Compliant System > Uninstall > Shutdown the computer > Remove the power chord > Attach your battery > Attach your power chord > Reboot the computer to automatically install the driver