The instruction booklet does say that under 10.5v it will pulse charge, as opposed to straight trickle charge. And under 7.5v it wont charge at all.

Kind of defeats the point of a battery charger imo, as you primarily would require it when yr battery is flat! lol

But the one I bought was clearly faulty as even when given a few hrs kick start with an old style charger it still failed to charge the battery overnight despite saying it was.

Oh well, live and learn.

cheeRS