what is balancing charge is it nesessary?

Balancing equalizes the cells in the pack. Opinions differ on how often you should balance, and it also depends on the cells used.

Use a volt meter to check each cell as it charges, each cell should never go above 4.2 volts. Much above that is when lipos get exciting, I think 4.25 is the absolute limit, some say 4.22 I think. If they are all the same voltage or at least within a couple hundreths you are good to go. If not, either a bad pack or you need a balancer.

You can try charging 1 cell at a time to manually balance, assuming you charger does 1 cell. You are using a lipo charger right?

i use 7,2v rx pack and 11v tx pack my charger have a built in balancer function but not the balance plug..should i get the plugs for balance charging or just a volt meter? also is it possible to charge more than one pack at the same time? thanx for the answers...

If you already have the balancing charger I would suggest going for the balance plugs. That said, a good multimeter is always a handy tool to have, great for troubleshooting and such.

Keep up the good work!