I get the seriousness of the matter but I am tired of seeing the same example of a nail through the pack videos
I like to see a pack shorted via the wires - not that it would be any less but it is more unlikely to happen then a puncture IMHO
Heres a vid of an emergency landing from what I think is just battery used for starting an ICE PPG - the dont give much detail - guess he is luck small pack and close to shallow water!
Bat fire
Rgs, Patrick
That would be really useful.
Test #2 has affected me deeply. I’ve watched a bunch of lipo battery fire videos, but this was an absolute show stopper for me. I hadn’t seen anything like this video up until this moment. In that second test, there was one single battery of exactly the capacity and configuration I’ve prepared to use with the OpenPPG. There is absolutely no way a fire like that would be survivable in the air, and I’ve been planning on carrying 4 times that amount. What if a flaw develops in a battery over a period of use? How common is this sort of experience among careful users of lipo batteries? Is this an inevitability for some unfortunate user, or does this really never happen if batteries are well cared for? Is there a way to test lipo units to assure within a truly safe margin that each battery is stable? I’d rather carry twice the weight and fly half as long if there’s any chance this is to be expected.
IMO not impossible but unlikely to have a fire like this on your back if you follow the rules.
This video is purposefully detonating the batteries by deliberately over-charging them. Like dropping a match in a fuel tank and filming it.
This situation COULD occur on the charging bench if you used a cheap charger that doesn’t monitor them at the cell level - Remedy: Get a quality charger and keep an eye on them while charging - Don’t leave them to cook all night as your sleeping. Read up on Lipo charging safety
This situation COULD occur in flight when using low C rating batteries (eg: Multistars 10C) and your only running 2 of them. The large current draw with the batteries high internal resistance COULD cause thermal runaway. - Remedy: run 4 batteries of higher C rating (25C Bonka, Tattu, Gensace, maxAmps etc) Less strain on each battery, cooler the pack runs.
This situation COULD occur in flight if the pack suffers mechanical damage or short circuit.
A prop strike on a poorly secured pack or any of it’s wiring COULD lead to a fire. - Remedy: Make an outer case for all the batteries to sit in,then strap it to the frame to protect the pack. Also consider using a fuse on the positive wire just after the connector to the mainPPG wiring harness
EG: Amazon.com
That’s allI can think of right now. And how I plan to deal with it when mine arrives. Feel free to add to this rant or call me out if you think something is wrong with what I’ve said. You only get one chance to make this mistake. And remember that carbon is very electrically conductive!
Test, test, test, test before maiden flight
Rationally, this response is correct, of course. But, years ago I added a large gas tank (commercially produced by the manufacturer) to my Fresh Breeze Monster, took up a tandem student, and when we landed, we found that the muffler had melted a gaping 10 inch hole in this newly designed plastic tank. I once watched a gas tank get hit by a prop (on a well known commercially-produced machine) and cover my friend with a thick cloud of gasoline spray. I once watched a friend fall from 100’ up and get medevaced to the hospital - he survived miraculously. I’ve experienced some extreme accidents myself - one of which threatened my livelihood, required nearly a year of physical therapy, and stopped my normal life during that period. Most of the pilots I know, who’ve flown for a long time have experienced accidents which occurred due to a mix of human error, conditions, unique situations etc. I’ve really experienced quite a few myself.
Most of the dangers inherent in aviation can be dealt with reasonably and reduced to an acceptable level, especially with some experience. The dangers inherent with lipo are new to me, though, and I have no experience or knowledge of the statistics related to their fragility. My concern is that they can simply fail, even when taken care of properly - I just have no perspective about how likely that is. Gasoline in a tank doesn’t simply explode. I did read that there’s anywhere from a 1/100000 to a 1/ten million chance that any sort of perfectly healthy and well maintained lithium battery can randomly explode do to microscopic particles which can be introduced during the manufacturing process. Your chances of getting hit by lightning are 1 in 13000, so this is a comforting statistic, if it’s true.
I actually lost a lot of sleeping last night coping with my reaction to that video and the reality of a danger which was far more intense than I had understood. Before that video, I was ready to change the direction of my entire life to focus on OpenPPG. Now I’ve managed to work myself into a bit of terror about the prospect that the entire rig could explode in a fireball, unexpectedly at any moment, and without warning, if, for example, any of the batteries gets physically damaged without my knowledge.
I’ve always been willing to take calculated risks, but there’s an unknown here, about which I haven’t become educated enough yet. I’ve done everything I should: I bought storage packs and boxes for all my lipos, I bought the correct chargers, I’ve read every day for several weeks now to learn as much as possible about use and care of lipos, etc. But I’ve done all that with other systems in the past too, and still run into real jeopardy, and watched others run into hazards, because of unknown or misunderstood dangers. Right now, my alarms are all going off, and I need to learn more about documented cases of lipo failure, to ease my concerns.
I guess what I’m looking for is more research. Lipos have been around for many years, so I imagine the industry knows the risks (about well maintained batteries). If anyone has links to studies or more information which can put the potential for uncontrollable danger into perspective, I think that would be helpful for everyone.
At this point I’m not sure if I can cope with the potential for such a serious situation arising because of simple physical damage, in a sport which often involves heavy physical activity.
As I ramble here, I guess my main question comes down to how fragile lipo batteries are, and is there any viable option which is safer (less likely to fail catastrophically if subjected to a shock)? As I said, I’d rather fly half as long with twice the weight, if there is any option which is safer.
Nick, while I applaud you, and others, for having a safety first mentality, I do think that the fire risk is being overstated here. I feel that any risk can be greatly mitigated with proper care and procedure.
The videos posted are a result of intentional overcharging. This thermal runaway is a real thing! But that is not likely to occur in discharge.
My background, for what it is worth: I work in the auto industry as an engineer on electric cars. I work on electric motor calibration now, but spent the first part of my career in HV batteries and their management systems. I have seen first hand the consequences of a battery fire and take it seriously.
I think Lukas summarized it well, though. Charging is the greatest risk time by a large margin. Care should be taken if charging in the home or garage. I charge all my large lipos in an ammo case or cement block. Charging with balance leads connected, in a safe place, and you are fine.
I think your concern is about something happening in air. If the pack is sized right for the discharge current, connections are good (not high resistance) and not going to short, I consider the risk practically nil. OpenPPG does not push the packs as hard as most RC applications do in terms of C rate discharge.
I feel an easy piece of mind is to put the lipos in a burn bag on the frame. These are cheap and lightweight and should contain an issue while you get to the ground. You could also build the lipos into some sort of FR4 box for extra redundancy. That would be lightweight and maybe convenient for mounting.
I think there was talk about a BMS being made for OpenPPG? Cell temperature monitoring would be the next step in a safety system.
We need to make sure users know how to handle lipos properly, certainly. But I do not lose sleep about my batteries.
I drive an EV daily. I feel much better about having a battery under my butt than 15 gallons of highly flammable liquid! I think with most things, the unknown of battery technology scares some folks.
It’s the severity of the fire in the video example above (test #2 in the video, about 1:30 in), which has caused such a reaction for me. It’s totally devastating - the lipo bag in which it was stored was utterly useless against the massive sustained spewing firestorm created by just 1 16000mah 6s battery. There’s absolutely no way to provide protection from this outcome, and according to what I understand more and more, the only way to really avoid running into this situation is to maintain the batteries (with zero tolerance for any error) and to provide fantastic protection by the battery management system (which we don’t have yet), to help deal with potential failures, damage, etc. during use.
EDIT: jhair, I wrote this before, and posted right as you posted. Thank you for your response. That’s very helpful and reassuring. Keep it coming guys 
What about flying with a battery box? That’s what some other ePPG systems apparently do…
What I don’t understand there is if they get ‘too hot’ since there is less air circulation.
A thin metal box, similar to an ammo box, would be the most robust. Someone could probably fabricate something fairly light weight. I suggested FR4 as an option too as it has fire resistance and is an insulator. I’ll have to investigate that more.
If this scares you, that might be the best option. Just make sure there is no shorting risk to any battery leads or terminals if the case is metal.
Thank you so much for your response. The most comforting understanding is that there’s not as much danger during discharge
NIck - If you find that you are not able to move past these concerns. Another option is to get a pack built from18650 cells. There’s a thread on it here somewhere. Nofireballs ( a good username:)
My hope is to move us to 18650s, but the trick is getting the peak currents. The plan is current using a BMS but ONLY for Cell voltage and temp monitoring (not putting more FETs inline for shutoff/safety). I do think we should fuse things however.
If we do 18650s, we’ll want a frame/case anyways, which can double as a fire Shield.
Hey guys there are certainly some good discussions here but Im making this topic unlisted for the time being. The original question was about doing a battery release by @dpack, glad you were able to get some good answers (Battery/motor quick release - #28)
I want to reiterate that we take safety very seriously. After all gasoline is highly flammable yet the industry has come up with solutions that many of us seem more that happy to strap onto our backs. The OpenPPG is designed to make flying safe, easy, and affordable. In the spirit of openness thanks for all the feedback
dpack’s original post was about fire safety:
Biggest safety concern I have with this design are the batteries catching fire, either due to a defect in the battery …or from damage during an accident …It would suck to burn to death…
Every post in this discussion has been directly related to that topic. This sort of discussion is the purpose of an open source community. It’s not always neat, pleasant, or organized directly according to the agenda of the technology’s original founders, but it’s very productive. The net result of this discussion, for me, is that I want to dig in and contribute to the design of the battery system. If that’s not the point of starting and fostering and open source community, then I don’t know what is…
I agree with @NickAntonaccio – a lot of great information has been discussed here. Not directly related to the emergency battery release system that I suggested, but all about battery safety, which was why I was thinking of emergency battery release in the first place.
Though these discussions may give a few people pause in embracing this awesome new system in the short run because it brings up concerns they haven’t thought of, as these issues are discussed and worked out, it will make this project MUCH stronger, and safer, in the long term. So I think it’s better to keep the thread listed.
I renamed the thread ‘Battery Safety discussion’ to make things clearer.
Very much appreciate all the amazing work you guys are doing, @zjwhitehead and @Pdwhite
Delisted?
Why?
Battery safety is perhaps the most important topic to be discussed in an “openPPG” forum…
in the wrong part of thread–lost context
The battery on my Pedego ebike is a simple plug and play… BMS is in the battery pack itself. Im guessing 18650’s are used… very safe,
plug them right in to the wall charger…
But i have a feeling there isnt enough juice to run a PM with this without having 10 packs — I havent researched the power needs for this PPG— and I dont know what size my batteries are–i am thinking maybe 20ah 48v