Charge it, again & again ect.
I don't know much about your trickle charger, but I would buy a trickle charger made for transmitters unless you know a lot about electronics and how to make one. I don't, thats why I buy commercial equipt. I used one someone made one time and ruined 2 batteries with it. You do need to fully charge a new battery, not trickle it. I would charge and cycle it a couple times before use just to make sure it is in good shape. Then charge if fully and put the trickle charger on it. That way it is going to hold a full charge. If you put the trickle charger on it when it is dead, it will still be dead when you go to use it.