In battery buddy a negative charge means discharging and positive means changing the battery.
I also have this strange dependency on the cable: with the same power supply some cables charge the Sailfish Xperia 10 iii, and after swapping to another cable on the identical power supply the phone doesn’t charge. This is reproducible and depend on the cable. I can’t tell which specifications the cable must meet to be able to charge. Additionally, I don’t know if this ‘charging refuse’ with some cables also occurs with Android on the affected Xperia 10 iii. Would be interesting to know, but reflashing effort is too time consuming for me right now to find out.