Is my XS-1300LCD dead

[PA-WOODCHUCK]

Yep, it's 14 years or so old and started beeping but battery indicator shows 2 bars and sometimes no bars and has no bad battery indicator. Power it up and 4-5 seconds later shuts down. Batteries  test as 25.6 volts on bench and are 3.5 years old. In the past they last about 4 years. Another test I did once it did shut down was load it w/led lamp and pulled plug even with 2 bars on display but shut down. So... is it just batteries or other internal issue? I did notice UPS is warmer than I can remember. Time to replace unit?

thanks