I had no idea my camera had a second battery!

I have an older Cannon Rebel XT and I’ve charged my many batteries and used different chargers to ensure nothing was faulty. The camera will not even power up let alone take a photo! Anyone have this problem before? I’m looking for advice/ solutions.

I haven’t used my camera for a few years and I’ve charged all my batteries and even used different chargers to make sure nothing was faulty. My camera refuses to power up! Anyone else have this frustration with this camera? Cannon Rebel XT digital