LiPo battery, as the heaviest single element of any racer quadcopter, is mostly the first one to fell off during crash. Or displace in high-g maneuvers. Or simple fell off in flight. Like on this picture below I’ve found on Reddit. Grrrr… for sure this is something I would like not to see personally again. And I’ve seen it on my first build based on X525 frame.
So, solid and strong battery mount is a must. Battery strap for sure. Even few in case of heavier ones. But battery strap is not enough. LiPo can always slip out. To prohibit that, I’ve been using velcro strips and it worked fine. But velcro has a few drawbacks: it is not very strong connection, allows some movement, and looses strength after some time. Few weeks ago I’ve discovered something that is way way better than regular velcro: 3M SJ3550 Dual Lock Reclosable Fastener.
General idea is similar to velcro, but instead hooks and naps, it is made from interlocking plastic “nail heads” on both sides. This creates much stronger and more secure connection than velcro.
3M Sj3550 Dual Lock has only one problem: price. It is rather expensive. 3 meters (10 ft.) can cost up to $50. Comparing to velcro it is a lot. Costly, but worth it!