Is 4G Falcon Z 917 Hotspot still good for future use?

I have a Falcon Z 917 Hotspot purchased in 2019. 

The battery is now dead. 

Would you just replace the battery, or do I need to consider a newer model? 

Looking at the limited doc, I see “portable”. 

There’s no description of that. - Is that the reason it needs a battery? 

Thanks