u/Ed-luvr

I recently purchased a new portable car jumper with 65W max capable charging input. I initially connected it to an older (10W?) USB charger and it took it about a day to charge from 50% to 99%. I waited and it did never did reach 100%, so after disconnecting it from the charger, I noticed that the stored battery capacity decreased from 99% to less than 50% in about an hour, with nothing connected to it. I then connected it to a 60W charger and saw that the 'fast' charge indicator illuminated, and within a few hours, the unit battery capacity reached 100%. I've now watched it for three days, and it remains at 100%. I would have expected that a charge from any source would be the same, is this normal behavior?