Blade mcx - battery problems?

Do you have this heli? If yes, what flyingtime do you get with the standard battery charged using the standard charger?
I got 7,5mins the first few flights, then something happend to either the charger or the battery - now I've only 2mins before it goes down.
Usually I charged with the stock charger until the led was completly off or there were 20secs pause between blinking - that's what the manual said. Suddenly the charger didn't start to blink but rather he was lit the whole time (even beyound 40mins).

Solution: I now use the 5g battery taken from the Silverlit TandemZ (130mah)

and I also solderd a better connector to the copter

so now I can charge the battery with a professional lipocharger. The new battery gives me again about 7.5mins - and this after only about 25mins charging (with 300ma).
Next I'll order an 200mah lipo with 5,1g - this should be the perfect battery for the blade mcx.

Hope this helps,
Greetings,
RCSchim