do a recalibration of the batterie. use the op1 or let it turned on until the batterie is fully empty ao it shuts down by itself. you can do thia over night for example. needs up to 18 hours. then turn the op1 OFF plug in the charger. either wall or pc, no difference. the leds should turn on normal now. so one after the other from 1 to 5. let it do that for about 10 seconds, then turn the op1 ON and wait about 10 seconds at the tape screen and turn it OFF again. and let it charge until its full. can also take a long time or maybe just 3 hours. thats always different. thats it, the batterie should be calibrated and the led indicator should be accurate now.
also: always shut the op1 on after plugging it in for some seconds and wait, then turn it of. this way the op1 registers that its in charging mode and only then it will charge fully!
hope that helped