First of all, unless your range has decreased considerably, or the battery is cutting out during use, I would say that the battery is working correctly.
The following graph is of an 8 cell 5Ah LiPo pack being recharged after using just over 1 Ah capacity:
I should also point out that I do not have a
BMS on any of my LiPo packs, but I do keep a close eye on the balance of the individual cells and will occasionally carry out a balance charge, which takes a lot longer than the standard charge shown above.
The charging current at the beginning of the charged peaked at 4.7 Amps and then continues to charge at high current
(which is limited by the 150 watt charger output) until the target voltage of 33.6V is reached at around the 10 minute mark.
The charging then continues at this constant voltage and the current gradually diminishes as less current is required to maintain the pre-determined battery voltage.
The charging process ends after 21 minutes and 10 seconds, and during more than half of this time it was charging at less current than the charger is capable of providing.
The GM charger only has a 2 Amp output which only 43% of my 4.7 amps so it will take a lot longer to recharge the 1Ah capacity that was used.
A 10Ah pack is probably going to require more time to fully re-charge than my tiny 5Ah pack, but this would ultimately depend on how much of its capacity had been used in the first place.
Here is a graph showing a balance charge on a 7 cell 10Ah LiPo pack as a comparison:
The first few minutes of this charge are missing from the graph as the monitor software was not running when the charging was started, but it clearly shows how much longer the fine balancing of the cells can take at the end of the normal charge.
I don't think that 6 hours is too long for a 10Ah battery being charged at just 2 Amps while all the cells are also being properly balanced each time, so I would say that your charger, battery and
BMS are probably fine.
If the green light was not coming on and the battery or charger was excessively hot after 6 hour then I would be concerned.
The heating up and cooling down of the charger indicates to me that it is working normally and if you look at the charger temperature in the above graph
(the stepped line) you can see that mine does this too.
Also, just to clarify you query, it's the charger itself that automatically reduces the current throughout the constant voltage phase after the maximum battery voltage has been reached using constant current
(not the BMS).
In simple terms, a fully depleted 10Ah battery charging at 2 Amps cannot be fully charged in just 5 hours charge as you might at first expect
(i.e. 5hr x 2A = 10Ah).
I hope this all makes sense and gives you a better understanding of how the charging process works and why it can take longer than you might expect.
Alan 
