Yes, it's possible if your device is rooted running [Advanced Charging Controller-Acc](https://forum.xda-developers.com/apps/magisk/module-magic-charging-switch-cs-v2017-9-t3668427) Magisk module
*and* device kernel supports 

* Battery Idle Mode: To activate this feature at a user defined battery level. 

And/Or 

* Custom Charging Voltage Limits: Activates this feature at a user defined voltage level. This method is superior to first method since granular voltage control is possible and keeping in mind that battery charge level is *not* an accurate indication of voltage. Kernels that support this, include support for first mode too.



First step is to configure charging to be stopped at a safe level, in my case, 75%, using the Acc module

Next step is to use the charging power to run the phone *only*

**How does it work?**


In either methods, the charger is fooled into "believing" temperature conditions aren't good for charging (either the reported battery temperature is too high or too low, so battery charging is discontinued as a safety precaution). 


That means the device is drawing power from the external power supply alone - which is exactly what we wanted! And the battery doesn't get drained because it is not being used (of course over a long period of time it would drop a percentage point) 

On my OnePlus 7, battery idle mode is supported by [Kirisakura kernel](https://forum.xda-developers.com/oneplus-7-pro/development/kernel-kirisakura-1-0-0-op7-pro-aka-t3933916). Interestingly, beta versions of stock ROM have this feature in stock kernel but one doesn't know if it makes it to next stable version. 

When this feature is running, a low USB  equivalent power is fed to the phone and conventional charging indicators show charging with zero power. Note that the second screenshot (Ampere app) shows "not charging" and no word about discharging, so the battery is at status quo

[![enter image description here][1]][1]


[![enter image description here][2]][2]


This screenshot below is from ACCA (Acc App, optional companion app of Acc magisk module ) which offers all the command line options (believe me, a ton of them) in a user friendly GUI. It shows battery charging idle mode at 75%

[![enter image description here][3]][3]


  [1]: https://i.sstatic.net/etek3m.jpg
  [2]: https://i.sstatic.net/F3MHVm.jpg
  [3]: https://i.sstatic.net/PRMqrm.jpg