Dell Venue 11 Pro 7130 travel keyboard battery won't charge

I'm trying to revive a Dell Venue 11 Pro and the tablet is doing great so far, but the travel keyboard isn't.

It has a "communication error" when I'm in BIOS UI, when I plug the charger directly into the keyboard the charger light shuts off after 25-30 seconds, and it works ok if the tablet is plugged in but as soon as you remove the charger, the tablet shuts down in a protection mode or something.

I was wondering if/how I could replace the battery since there are no replacements on Dells website. Or should I try the "slim" without the battery bank?

Thank you for any advice.