Swapped out the 850mAh battery for this 2500mAh. Had to snip the wires on the original connector and splice in the new wires as it had a different connector. Warranty probably voided I know.
I let it run a factory (1-16) pattern with headphones connected (not listening) for 7 hours straight before the charge light turned red. Better than the specified 3 hours.
Only downside. It’s going to take a lot longer to charge up to full again
.But it does charge no problem.