At present, there is at least WhatsApp Web and WhatsApp Desktop to be used on PCs. But to do this, you still need connection access from your PC to your WhatsApp account on your mobile. According to TheNextWeb.com , this may change soon. This is indicated by the information reference distributed by WABetaInfo, which is known to routinely provide leaks about WhatsApp. In its words, WABetaInfo said that WhatsApp is developing a Universal Windows Platform (UWP) application along with a multi-platform system that makes WhatsApp services still work even if the user’s cellphone is not active.
— WABetaInfo (@WABetaInfo) July 26, 2019 If so, one of the things that will be possible is that WhatsApp users can still chat with the people in their contacts (via the desktop) even though the smartphone battery is exhausted. However, there is no further information about when the feature will be officially applied by WhatsApp.