Very smart idea
Ill probably be doing something like that myself until then Iâm keeping close the the water which is not that much better:)
Also Iâve considered a small sized bailout rig static lined to the paramotor. Inflation happens in less than 100ft You can see this in videos of skydiving âskyhookâ or âmardâ
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Sorry, I misread your original post⊠I get it now⊠none of the four that you flew with had any damage. So the first current the damaged ones saw was a charge current just to top them off.
Yes, you should top them off to make the voltage match the other packs. If you connect packs in parallel with different voltage the high pack will charge the low pack at an extremely high amperage and could cause a fire. That brings up another question⊠were you charging packs in parallel? Did you try to charge a full pack in parallel with an empty pack?
I guess you canât tell us what the damage looked like because you didnât see the damage before putting them on the charger? There must have been a short between the layers inside in such a way that the current flow triggered an ignition but remained stable prior to adding the charge current. If you were to fly with them I imagine the same thing would have happened while drawing current from them. Iâm glad that happened on the ground and not in the air!
How reliable are your chargers at stopping when full and at balancing cells? A good charger should detect that the battery is full and not overcharge it but what if the fire was caused by overcharging? How long was it charging before the fire started? If I put a full battery on my charger it will say charge complete within a minute.
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I use the same chargers as you. It must have been damage since it was one of the two bottom batteries. And the other oneâs mount broke from impacting the ground. This leads me to the conclusion that the two batteries both hit the ground when the motor fell over, and the one with the broken mount had a bit of give when it hit and didnât get damaged. The mount acted like a crumple zone.
When I first saw the puffing I figured it was the one with the broken mount. I thought it had hit the ground hardest and then broke off. When I saw the one with the broken mount was still left after the fire I checked which battery it was by process of elimination and found it was the other lower pack.
I use one charger per battery in fact hobby king sent me a few extra if anyone is interested in some at a lower cost.
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I charge my batteries the night before my flight and wake up early before work, when I tip my batteries off sometimes there as low as 4.16 from being charged to 4.2 the night before. With that being said the battery started to puff about 5-10 mins after I put it in the charger. Iâm confident in these chargers based on how much they beep. That tells me they are calibrating regularly
I had the same thought. Iâm so glad the mount broke off one of them. What temp would the plastic you used on the battery rails melt? Iâd be curious to find if they could be shaken off in a fire even with the flush mounts.
I think the zip ties would be the first to melt and release the batteries but the wires plug in perpendicular which would keep them from unplugging on their own. 
I think a good solution for a dropsystem would enable to drop the whole baterysystem via a 3 ring solution - maybe drop into a 7 meter webbing that can be cut extra :
For fireprotection we could use
And for automatic firefight on top of the batteries :
http://www.fire-defender.com/en/bonpet-3/bonpet-2/
I use both on a boat where the loading devices are, it can be 600 amperes at 14 volt so a lot of heat build up, as the area is build from wood i covered all with weldmats and mounted the auto firefight bonpets.
To handle the amps i had to use 2x75 mm2 parallel or even 90 mm2 cables.
For anyone still interesting in this design, please use the attached file. This corrects the placement of the M3 bolt and includes better slip-fit tolerances for the pull-pinBattery Jettison Frame Spacer.stl (513.5 KB)
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Instead of a full box, I used a single CF plate. Two very shallow âkeysâ on the back of the plate eliminate any side to side movementâŠyet allow the entire battery assembly to fall away. After reading the recent description of the battery fire, I have no desire to fly without this mod. Itâs frightening when you multiply the fire by 4.
Iâve been a parachute rigger for 6 years and have built many three rings myself. For sure a 2 ring setup would be better. Or even a ring-less design like what paragliders use when winching. The reason is simplicity. Each additional ring reduces the force needed to keep it closed, three rings are only needed when your pulling gâs in a diving malfunction. Just one wrap around should do , the second is way over kill for 40-60lbs
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I love the idea to drop them down first, and then cut them away. This could buy us plenty of time to âaimâ
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Yes the weight is not so high but if you have to drop them in a spiral fall gs would be extrem, so i think its a safty plus - but for normal flight you are right, than it is not necesseryâŠ
Scenario: you have a silent flight, clean air all ok 500 meters over ground.
Fire starts on your back.
When you keep cool and drop your batteries than all is ok but if you cant drop it before trying to go down you will want to go down fast as possible becouse you dont see whats going on there, so you will have to spiral or b stall, and there you will have a lot of gs.
If you cant stop it or drop it it could be quick desent to hold a fullstall and end it with the reserve 150 meters over ground, you have to land to get awayâŠ
thats why i am thinking about a bonpet firestop it weights only 1 kg and maybe stops the fireâŠ
Or keeps it smaller than without
And 3 ring should cut away in any g situation.
Or we land it 7 meters under usâŠand dont have to drop them total at all.
But i think they could burn thru the webbing and fall by themseve after some time.
All depending how violent the burning is.
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A 30 pound drop on a 7 foot tether would be quite the jolt!
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Plus dragging 30 lbs. across the ground and the possibility of it catching on something could result in a really interesting face plant. It might even provide a whole new dimension to âDirt Divingâ. Add in the potential for a grass fire and the offending pilot might even get roasted while trying to pick up his teeth. Coming to YouTube soonâŠ
I have seen gliders with low flying accessories of their outfit at the Coupe Icare during the annual PG costume competition and that made interesting landings at times, such as banners getting caught in tree branches. I tow paragliders for a living and I have seen less experienced tow operators towing at the wrong time and wrong place in the wrong conditions with the tow line snagging in fences, farming equipment or trees , and the end result was always epic.
Found cool video there you see what i mean
Fully loadet milttary skydivers
2 min. 50 sec. You see 2 landings 1 filmed from the air and 2. The filmer himself.
They always drop theyr luggage when under canopy and land forward like paraglidersâŠ
Not always found that video:
No idea how he could land thatâŠ
Here you see how it works ( at 3 min. 15 sec.) At the end the guy talks about theyr job:
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Skydivers flare a lot higher and have a much steeper glide. With a tether that long the load would hit the ground long before I ever initiate my flare. My wing is fast and responsive and Iâm usually less then 5 feet high when I start my flare.
You are right
I do both skydiving and paragliding but my parachute flys faster and is way more agile than my paraglider.
I always feel like driving a bus when on the same day i fly my paraglider after some skydivelandings.
But the canopy size is less than half of the glider so the wingload is double.
My weight is 190 pound 85kg without gear and my canopy is 120 sqft.
11 m2.
Also the landing in the last video does not look so slow.
It will definitly be challanging to land such a load on a webbing thats for sure.
Btw. It will be an emercencylanding, could use the reserve high up over ground too⊠than no problems with forwardspeedâŠ
Or drop the reserve in 2 meters height it will open and you can land standing, i did practice that in my paraglidingschool 20 years ago-
not sure how that could work with the motor on the backâŠ
But if it is possible not to drop that high weight and land safe that would be the most responsible way to handle that situation.
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