I have five smartphones in my drawer, all in perfect condition except for a battery that won't hold more than two to three hours. I wish I could at least buy b

I have five smartphones in my drawer, all in perfect condition except for a battery that won't hold more than two to three hours. I wish I could at least buy battery replacements and change it easily. The other problem is the selling cost: whoever I will sell the smartphone to will very likely not keep it and sell it right away to someone else in need, at a higher cost. I may be alone on this but that disturbs me to the highest level and I end up keeping them in my drawers.