I built a 6s battery from old li-ion 18650 laptop batteries (4 in parallell). I did put a balance cable on it and I have a balance charger. The first time i charged it at 1amp and currently im charging it for the second time with 1,5amp. To speed things up how high can I go?
It entirely depends on what kind of cells they are. But if you aren’t sure and they’re old, I wouldn’t go more than 2amps.
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Thanks, ill stay at 1,5 then as im doing it in a confined space where I live 
I hear the fumes can be quite bad if it starts to burn.
Also I can confirm you get a good workout when the battery stops.
How many Mah are the batteries ?
If the batteries get overly warm or hot during charging then you will need to back off a bit during charging. Charging at 1/2 C is better for pack life though.
That pack will only be good for 150 watts constant and 300 watt burst so you will need some serious reduction on your drive system to give it a happy life otherwise you will cook the cells every time you accelerate.
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Batteries were around 1750 mah each, when I discharged them with my fake charger.
What does 1/2 C mean?
Also 150 watts constant 300 burst, dont really know what you are saying. Im using a Turnigy Aerodrive SK3 - 5055-280kv motor. Max Power: 1510W, but thats with a 10S Lipoly? I have reduced the ESC to 50% Power as i can barely stand on the board, was going to increase it but maybe not after what you said. How long do you think the pack will last? What happens when you Cook the cells too many times, will they peacefully die or start a fire?
C rate is discharge rate. To convert this amps its C x capacity. So 1/2C is 875ma for your cell. Dont use laptop cells for eskate. Your pack will die very fast and potentially catch fire.
I think using laptop cells is OK if make sure each paralleled pack is equal in Ah’s. You do have to use at least 80 to a hundred cells to make it work. It takes a huge amount of time to sort the good from the bad so in the end, if you value your time, it is cheaper to use new cells.