Swelled Batteries?

[VEGASROBBI]

A couple weeks ago my trusty S2 with over 300 flights just dropped from the sky. It was about 100° out and I was only going 3-4 mph - about 6 feet agl. It just dropped like the battery was disconnected, but it wasn't. It fell flat and the battery took the hit, so no damage.

A dozen flights later I'm going 20 mph following from the rear; again my S2 just fell like power was disconnected. This time I broke a couple props and cracked the shell.

Both flights were at about 100° ambient, both towards the end of the flight; but the batteries were over 30%. No hot warnings and following great.

My batteries are slightly swelled but not enough to affect contact. Interestingly the video was saved on both drops and ended at the exact second of the drop; like it knew the drop was coming.

Fortunately I have a backup S2 I purchased when they were on sale.

I sent the flight logs in and the offer I got was a $150 inspection fee that will be applied to the repair which will not exceed $800.

Of course I'm sending it in, I'm not looking for warranty since it has had a long and fruitful life but I am interested in what went wrong.

 

[Ridefreak]

Sorry to hear that VR, I've experienced one of those events and it makes no sense, like you said, running along fine, video stops and the drone drops out of the sky like a rock. It's be nice if they had some pointers to help avoid those meteor type landings.

 

[VEGASROBBI]

I changed the name of this thread for what I believe to be a possible cause for the sudden drop.

As you know my first S2 dropped twice in as many weeks, both times it was hot out and near the end of the flight. With S2 number 1 out for repair I pulled out my backup S2.

First flight was awesome, I was very happy how it was following. Second flight not so good, halfway through the flight it dropped

I was only a few feet up so no damage. It was 100* out and the S2 was hot. The battery detached, I picked it up and examined it carefully. The upper surface was swelled, I'd say about 1/8" from the center to the edge. After wiping everything down I installed the battery, I was able to rock it enough to get a 1/16" gap at the back where the contacts are

It's my theory batteries can swell to create enough offset of the battery to cause it to disconnect. I installed the new battery that came with the spare drone and flew an entire flight with no issue, that battery was flat.

My original batteries have a couple hundred flights, they have been flown in the heat and the cold and they are slightly swelled. It may be in hot weather they swell more and with the G forces associated with flight it can cause disconnection.

Most drones I own have a battery compartment that will allow the battery to swell a bit, but the S2 seems to have little tolerance for that. It may have been a good idea to build in a cavity to allow the battery to swell without pushing it away from the body.

I'm getting new batteries.

 

[MileHi_Skydio]

Thanks for the follow up! That explanation makes complete sense and I can see with tight tolerances combined with swelling of the battery that it forces the battery to disconnect mid flight in hot weather

 

[Ridefreak]

I noticed most of my GoPro batteries have swelled up recently, I need to check the SD batteries, you and I are probably approaching the useful life of these LiPos. It's been what, 2.5 years at least.