1. You may have lower performance settings for Battery than for AC power. Go to Settings | Power & Sleep | Additional power settings | Change plan settings | Change advanced power settings. Compare the settings of Battery and AC power and adjust the Battery settings as desired. 2. That laptop is eight years old. If it's the original battery, it is just a shadow of what it used to be. Test it: Open an Administrator CMD prompt (CMD, run as Administrator).Paste this command, and then press Enter:powercfg /batteryreport That will show a figure for the designed battery capacity (when new) and the current capacity. How to Generate a Battery Report in Windows 10[URL]
so hi i need help with my dell latitudee5430 non-vpro so when i disconnect the AC my laptop start to lagg alottt i mean alot i think the problem is with the motherbored or with the battery.      if someone can help? 
why my laptop is lagging when when AC is not connected