There is no manual?

It's logical one has to be attached to + and one to -.
However, I really have no idea if it makes a difference which one.

Suggest you google it or contact laptop mate

I think that perhaps djensen and I must have different versions of the same charger, as mine does NOT have the charger tabs placed on the first and last contacts of the batteries four contacts.  If you view the battery from the front(Anker logo facing you and four contacts on the top right of the battery), there are three circles in the upper right hand corner of the label.  In the first circle a negative symbol, the second contains the letter "T", and the last a positive symbol.  Each of these coincide with a contact on the top of the battery.  The first contact has no marking, the second is negative, the third is the letter "T", and the fourth and last contact is positive.

 The tabs of the charger connect to the second contact(labeled with a negative on my battery, perhaps different on yours) and the other tab of the charger connects with the fourth contact(labeled posative on my battery, once again maybe not the same on yours).  When connected correctly to the charger while NOT plugged into the electrical outlet the small indicator light on the charger may momentarily turn red and then turn off(this is correct).  When plugged into the wall the indicator light that had come on red and then turned off will now appear red again(A-OK this correct).  The indicator light will remain red until the battery is fully charged whereupon it will turn Blue.