Ran 2 new batteries again with full charge. Got 12 minutes and 15 at hover no wind. Sent them back to Yuneec. They are sending two new batteries. Bought a third battery and it got 22 minutes at hover. Much better. Also tried Venom 7300 mAh battery and only got 21 minutes. Surprised. Thought it would increase flight time. What multi charger do I need?