I have an OverLander RC6-VSP charger and a selection of batteries, all 3s
1x Hobbyzone branded 1300mah
1x E-Flite branded 1300mah
2x OverLander super sport 1350mah
2x OverLander sport 2200mah
All of these batteries are taking at least twice as long as you would expect to charge. From storage state ~50% charge, at 2C Settings they were taking an hour each. Even though the charger seemed fine. It was taking ages to do the last bit... That is... Charging seemed quick until one cell hit 4.2v and then the balancing at low current was taking ages.
This never happened before this time, but I haven't used the batteries for a month or so. All voltages were pretty well balanced while stored and I always use balance charging and not just charging mode.
Any ideas as to why this might have happened? Once charged the batteries flew as normal, but taking so long to charge is far from ideal... Have they simply lost balance and will be OK next time, or is this a sign of faulty charger and/or batteries?
I'm slightly concerned, being a bit of a noob with lithium batteries.
Were they fully charged when stored or were they stored in a warm place? If so then it will likely have caused some damage which means that the cells have higher internal resistance and so take longer to balance.
Try flying them, sometimes you find a battery reluctant to balance but which will balance fine next cycle. Otherwise a charger with more balance drain current (yours has 0.3A) would balance them quicker.
People seem to get very very concerned if a battery doesn't balance out at 0.0x or the like.
1. It's likely the actual electronics to measure it aren't THAT accurate.
2. That amount of 'imbalance' is effectively trivial.
You can just simply curtail balancing/charging at that point if you care to and go fly. The [Fast Charge] option effectively truncates that last little bit of balancing to work that way. It doesn't go "faster", it stops earlier. It doesn't charge your battery quite as full so may be a bit easier on it also.
If you're going to learn to fly them, you have to learn to fix them.