I intend on sharing it. To start I’m going to use it to get a better understanding and optimize my machine, but hope to be able to produce them for others too. What kind of features would you be looking for?
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Awesome!! Temp monitoring and emergency power off in case of unsafe temp level would be the most important thing I think.
I would also love a system where you can charge 4 or 8 batteries at once with a single charger so you don’t have to switch the batteries multiple times to charge them all.
Anything that can increase efficiency or safety is a major plus.
Any news on the battery box Paul?
I’ve been working on a design which uses a cable release to disconnect straps. A board protects the batteries from falling into the prop(s) and the XT150s are used (potentially at varying lengths) to give the best chance of clean disconnect. If anyone’s interested PM me.
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I love this! And I’m assuming that since it’s been 9 months that you’ve long since completed this project. I just started working with the ESP32 and I was thinking that it would be perfect for such an application. Bravo!
dropping them would be great?
you do realise, that
- you’d have no control over the impact zone, if you have high altitude
- they’d get damaged with probably a 100% certainty, and could even explode, not even mentioning the damage to the environment
- you’d be dropping an item worth over a thousand dollars
Drop them for emergency, but not for no reason!
This might be overly complex but I am wondering if it’s possible to incorporate a small inertial reel into a drop-box type design so that the batteries, if dropped, end up say 20-30ft below the pilot. This would be enough to dissipate enough heat, would ensure they follow you down, and assure they don’t ‘land’…I like that term, but it’s more like ‘bomb drop’…on something or someone unsuspecting below.
Probably over complicating this, but may be an idea.
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I am new to the OPenPPG Community, this was the first thing I was thinking to tell you the truth. I have been flying and building large drones for many many years. I have seen large lipo battery packs that have gone bad for no reason at all? Even after keeping them in there perfect conditions recommended by the manufacturer? I like the pull dump idea. but with any aircraft failure. there is a negative impact on what the parts hit for sure. Nomex fire suet wrap is an idea. But I have not used in this type of application. bag the packs sealed in Nomex style fire wrap. maybe spring launches it like a drag dragster parachute. it would help push away from you, not hang there on one positive cable burning you back up. just thinking of what could happen. lol
It’s really hard to make a LiPo “vent with flame” from over discharge. LiPo fires typically happen due to overcharging or puncture. What could happen with a 2 stroke and explosive fuel?
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I have been using that for over a year now (Batch2). If $#@! was to happen, I would not worry about $25.00 props. Just pull and let gravity takeover. 26lbs of Bonkas are enough for a clean XT disconnect. The system I made for my harness dfoes not have any pins, buckles, rings, etc… just one strap and a small piece of Paragliding line - can’t be any lighter system than that😄
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Hi Voltair. I am finally coming to the stage of the design of battery mounting… I very much like the idea of your jettison system: can you pls give more details/photos of the design.
Hi Andy,
I do not use it anymore - maybe I should😆 It was basically a 2 inch wide strap wrapping the 4 Bonka and secure it at the top. I had a small line from the pin running to my left shoulder (attached to the shoulder strap with a velcro). The idea was to pull the pin, the strap would slide through its buckle and release the batteries attached together as one pack - the sheer weight of the batteries was enough to disconnect the cable connectors but, I actually found a flaw with the design later and the battery pack actually fell inside the cage net and did not go any further. So, more research must be done on that level.
Ok thanks for that. I guess the risk of fire in flight must be very low if most on this forum do not have a jettison system? Any advice on the risk? Maybe I should at least have a carbon plate between the batteries & the harness?
It is. Probably lower than for a two stroke engine if you don’t abuse the batteries. The bonka fire reported was caused by inadvertently attempting to charge damaged cells. Like re-filling a damaged propane tank. Don’t. Also he reported they were already at 4.18-4.20. I consider that 100% fully charged already. Additionally he reported packs charged to 4.2V in the evening would be down to 4.16V the next day. That is very suspect. LiPo batteries should not be doing that. Storage at 100% should be minimized but I’ve not seen even a millivolt drop over a few days.
I baby my batteries. I charge them to 4.15V/cell indicated on the chargers which is 4.17V per my multimeter. I don’t watch the charge like a hawk but I do make sure i’m present at the end of the charge and check on them every 30 minutes or so. After flying I charge to 3.85V. If I plan to fly in a given evening I complete the charge that afternoon. I hope to get more than a couple hundred cycles from them.
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Thanks for that Greg. I guess just to secure the batteries with webbing? Or I’ve seen the rail system on the forum. I’ve already sorted the surface mount XT150 connectors and worked out how to avoid loops of wire which may get close to the props. On another topic, I’m using the Maytech anti-spark switch as opposed to the “2 manual twist switches + pre-charge”.
Originally I just used velcro strapping through some of the slots in the back plate. It was a bit of a PITA to strap up individual batteries every flight and I wanted to go to eight. I went with a shelf system.
There’s no provision for jettisoning the packs. If they got that hot they might burn the strapping and tape then fall away. Or not. 
I also have no additional impact protection for the batteries but anything that might hit them would literally have to come through me first 
so…?
The system is light, safe, simple, and easy. What else does an aviator need?