[BrianG]

The only downside to balancing after charging is that the balancer does its job by discharging the higher cells until they all reach the same voltage. Consider this: You have a 4s pack and and decide to charge without the balancer. At the end of the charge 3 of the cells are at 4.15v and last cell is at 4.35v. This will still look like 16.8v to the charger (4.2v X 4 cells). So, three cells aren't getting the full charge and one is getting too much. If you hook the balancer up after the charge, it will discharge the high cell until it reaches the same level as the others, which will further reduce the total capacity of the pack when you come to use it since it will be at only 16.6v. No, it doesn't sound like much, but is when you consider that the constant voltage portion of the charge is roughly 1/4 to 1/3 of the charge cycle.

Also, if you balance after the charge, it's a good idea to balance before charging as well. After a pack is depleted, each cell might not be at the same voltage. So, the charger is starting with an unbalanced pack. It is possible they could even themselves out during the charge process, but not guaranteed. Balancing before charging equalizes all the cells from the get go, which minimizes the chance of an out of balance condition by the end of the charge. The only exception to this that I can think of is if you are using an LVC that monitors each individual cell instead of the total pack voltage.

If you balance while charging, all the cells will reach an even 4.2v by the end of the charge so you have full pack capacity.