If you have a lithium battery you may find the battery will not charge using the lithium charger. Lithium batteries are quite sensitive and if this happens it means the battery has disscharged to much. 

If this happens you can post the battery back to us and we will charge it up for you using a direct charger and then in the future you just need to make sure that you don't let the battery get to flat. 

It is possible for you to direct charge the battery yourself to correct the problem but THIS CAN BE DANGEROUS and we advise you not to do it unless you know what you are doing. We will not be responsible for any damage or injury caused by direct charging a lithium battery. If done wrong it could cause the battery to explode. If you do decide to direct charge it yourself you should only give it a 5 - 10 minute direct charge using a normal direct charger (like used to charge normal heli batteries etc) and then use the lithium charger to fully charge the battery. WARNING - do not direct charge a lithium battery for more than 10 minutes which could be dangerous and cause the battery to explode. 

You can stop this happening again in the future by stopping using the helicopter as soon as the battery is at a level where it does not have enough power to lift the heli off the ground.