How can avoid using my battery in my XPS 9365-70?

Thank you for your message. There is no option to disable the charging when plugged in unless you remove the battery.

The system will stop charging when it has reached the optimum level, only once you unplug the power cord the battery power will be used.

This system does not support hybrid power so there is no battery power used when high intensity applications are used

@SreejithR's answer isn't completely correct.

@thawbeanif you go into your BIOS Setup, you can configure minimum and maximum charge levels.  For example, on my XPS 15 9530 I have my minimum charge level set to 50% and my maximum set to 80%.  That means that when my battery reaches 80% charge, then the system stops charging even if it remains connected to AC power.  But since I also have a minimum charge level, it does not START charging again until the battery naturally self-discharges down to 50%, which can take quite a long time.  So the battery during that time is effectively disconnected, because the system is not drawing from it, but it's not charging it either.  The catch of course is that if I need to disconnect my laptop from wall power unexpectedly, then I might have as low as a 50% charge, but I almost never use my laptop on battery power anyway.  And I believe newer systems support the Dell Power Manager application that allows you to tell your system to temporarily override those settings and charge itself up to 100% once, so as long as you have SOME advance notice, you'd be able to top up your battery without having to reconfigure your BIOS settings.  Hopefully this helps.