Lets clear some things about BMS ( Battery Management System) . There are 3 different types of modules used for the battery packs , as following:
Protection Modules , that are meeting the basic requirements :
Over current protection at charging & discharging ( any value from 1-100A and above , chosen by the manufacturer of the battery pack )
Over charge protection for each cell , at a max. 4.25V
Over discharge protection , at 2.9V.
Balancing Modules ,that actively stops the charging and discharging of a weaker battery from the pack, and adjust the charging current in order not to undercharge some and overcharge some others .
BMS Modules , that are combining in one, the 2 described above.
These modules are a must in the laptops and professional cordless machines , in order to expand at maximum ,the life of a battery pack.
On the other hand , for the hobby machines is accepted not to have this modules , due to the lower price and the fact that , not being heavily used , the unbalancing process will be slower .
About the chargers :
A professional one will have a feed back from the battery pack ( via 2 extra slots ) , stoping the charge process as soon as the charging current is dropping under a certain value.
A hobby charger is likely to have a timer for charging process due to the fact that is missing the feed back , and as a protection measure. For this particular type is more likely to get an incomplete or overcharged battery pack
As a simple rule : if you have a battery pack with all 5 slots populated with connections ( not only 3 like , like in your case ) , and the charger with the same number of slots connected to the internal PCB , there is a good chance to have a reliable charger and a protected and balanced battery pack .
But , most of the time , the price will tell you what you paid for...
Discharging completely a li-ion pack is not a must , by contrary , only the Ni-Cd ones has to be like that , due to the well known memory effect of those .
In your particular case I have to ask you one question : does your charger have some indication about the charging process ( ex. red led = charging , green led=fully charged ) or something else ? Even on the cheapest chargers an indication of this type is present !!!...