LBA10 balancer defect?

Hi!

Today It was the first time I charged my Flightmax 5000mAh 5S 30C battery. While I was charging the LEDS 1,2,3 and 5 were constantly on and number 4 was only off. Is this right? Or is the LBA10 defect or just the LED? After I charged it I measured up the voltage of each cell which was around 4.2V, which is good, right? But how can I check if the balancer is still doing his job good or if the LED is only deffective?
And another question; what does a balancer exactly? Does it take away amps from the battery or does it put amps in the battery? (Sorry I'ma noob at balancers...)

Thanks,

Patrick