Hi, I have on order a 6x 18650 LCD Display Power Bank. It is this one from Kaidomain. http://www.kaidomain.com/Product/Details.S022369
I know the cells must be balanced before i put them in, but what happens when they become unbalanced from use?
The cells will be hard wired in so I can’t pull them to balance.
Because they’re hard wired, it is impossible that they become unbalanced.
All cells have no choice but to obey each other. 
Just charge the cells full before putting them together.
They will probably be wired in parallel, i.e. they will stay in balance.
The easiest way to initially balance the cells is to charge them.
HKJ, do you have a suggestion as to how much voltage difference is allowed before you connect cells parallel?
Some people sound rather panicky about it, so.
I would not be that worried. I tried it once while measuring:
With a 1 volt difference between the batteries the peak current was 6A, but only for a very short time.
Generally I would prefer to stay below 0.2V
I would be more careful with High drain (low resistance) cells though…
What batteries will u be using in this?
Thanks for the reply guys, really helpful!
I will be using the Samsung ICR18650-26C
Wouldn't they be better able to handle the current though?
With 6 cells in parallel, what kind of current are we talking about here? 50-75 amps?? Are we going to use the thing to power a riding lawnmower or something? I really doubt the circuit board on the thing would be able to handle even the full rated current of normal low-drain cells.