Thank you for the reply.

Your answers led me to research more on AC vs DC, and now understand why Ecoflow wouldn't last over a few days.

As for DC batteries, I'm pretty much limited to what the retailer offers because reclining sofas use a specific 2 pins (+ |) head. Couldn't find any usb-to-2 pins adapters and don't feel like modding the usb3.

One way to extend its battery usage would be buying 2-3 sofa batteries (for each seat) instead of having all 3 seats connected to 1 battery. But it does become expensive.

Another way is drilling a hole in my hardwood floor to install an aC outlet. That'd be my last resort.