My friends Astell&Kern AK100 (aka iriver-rwa-ak100) stopped working, and I think the battery finally has died. The battery has the following markings: PR-665354N F121 00701AA 7.4WH 472246454746 3.7V 2000mAh. Li-ion battery. All links I have found (on this forum) seem to be dead, so if anyone...