Read a few threads in the battery FAQ section, though it sounds like maybe you have. It can be a lot to take in all at once. BTW 15s lico is in the range we'd consider to be "48v" Your usable voltage range will be about 62v to 53v actually measured, and best if you stop by 55v. Or at least slow way down and start milking it with lots of pedaling below 55v.
KFF happens when you screw up, normaly it's not a problem. What happens to me at least, Is I have some packs that I am series connecting. Starting from + to the controller, you are connecting + to - of each pack, aiming to connect the last - to the controller. If you do this, all will be well, but there will be a spark when the last connection is made to the controller. Not going to burn your hands though.
When you screw it up, you have grabbed the wrong wire from a jumble of them, and instead of connecting + of pack one to pack 2-, you grab a wire that connects pack 1+ to pack 1- !!!! Now you will have a melting connector in your hands, and possibly even set the entire pack on fire by dead shorting it.
The solutions is to be slow and methodical about it when connecting up packs. Do it exactly the same way every time, just like a pilot doing a preflight checklist.
There are threads out there on fitting a resistor to your controller connection, for eliminating the spark when you connect up. I don't consider the connection spark a problem at 48v.
For charging, I'm still a fraidy cat recomending breaking the pack into three sections to charge at 5s with a decent RC charger. You can paralell the whole pack to charge it as one great big 5s pack. Charging done in a fire resistant location, if not outdoors, at least where you can get a shovel and flip that burning pack out the door with a shovel fast if needed. No sleeping, no leaving the house for just a minuite, etc.
Bulk charging, if you choose to, is best done with a back up protection, such as Methods sells. There are some commercially avaliable paralell harneses, Ice Cube 57 makes some nice custom ones, but others are avaliable. EP Buddy is one source ( in the usa though) with a nice selection of paralelling stuff. Have a look just to see what is out there anyway. Making your own is easy too. Just buy 12g wire, and connectors or your choice for the main y harnesses, and chop up Jst extensions to make the y harnesses for your balance wires, or balance charger using a paraboard.
Monitoring, like charging, has as many methods you can use as there are shoe styles, all more or less good. The gold standard is monitoring every cell or every set of paralelled cells in the whole pack. Three cellog 8's would accomplish this. In addition you want a main pack voltage readout, to give you a clue when a peek at the cellogs should be done. The main pack readout is idealy done with a cycleanalyst, or at least some type of wattmeter.
A lot of using RC lipo correctly is all about knowing your pack intimately. Once you establish that all the packs with runt cells in them, if any, have been weeded out, then you have a pack you can monitor a lot less. With such a set of packs that I know tend to stay balanced, I can just watch my CA and by knowing what my typical voltage is when I have discharged say half of it measured by the wattmeter, I can smell a rat early if something is not right. What I mean is, if I discharge 4 ah, and my voltage looks low, I get suspicious and get a cellog out of my pocket and start looking for the pack that is lower than it should be.
But if all looks normal on the CA, I can ride till 80% discharged with very few worries that a cell is going too low in there somewhere. The key thing is buy some extra packs, so you can use only the best ones. Then use a cellog or whatever device to get to know every cell by checking voltages often till you get enough cycles on the pack to know very well how it behaves in use.
