Nice. What’s the battery pack weight?
It’s 46lbs. Etienne how do you have your temps set? I ran it tonight on ground and got “power high temp protection” go off, it was set to 30° as default I changed it now to 45°. I’m guessing this is the temp of the bms itself?
Man this thing has a lot of power hoping to do first flight this weekend been busy with work.
It’s that more energy density per lb than bonkas?
These seem way better. What are the cons with 18650’s?
Not really. If you compare to 6 7s bonkas the weight is 33.6lbs. If your just comparing the weight of the actual battery then lithium ion are lighter but once you add all the hardware, case, wiring then it’s heavier. 18650’s should last significantly longer then lipos, it’s easier To have a bms for lithium ion, pack. In my opinion lithium ions are much safer then lipos just from working with them on drones for many years and seeing them explode if damaged or used when swollen. I’ve personally seen two drones go up in flames so I prefer to use lithium ion.
you need to tag me, like this @dzubot (just with my name) otherwise I only see your post by chance 
when the battery is in action, it starts to heat up, 60 degrees celsius is the maximum temperature that would still be acceptable, so I have set my BMS to just that.
It’s the Discharge high temperature protection value, yours is at 60°C as well.
on my first flight, my battery was wrapped in rubber foam and shrink wrap. it overheated only after 9 minutes.
Hence why I built the case with ventilation holes and even three active fans (that I don’t need, which I found out afterwards).
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I need some advice from you all. I built the case out of acrylic but as you can see after doing a couple test runs on the ground the case has cracked like crazy. My question is what should I use? I can’t use anything conductive. I’m thinking about lexan or polycarbonate which is supposed to be stronger and much less prone to this happening.
Was planning to fly first flight tonight but I think I need to make new side pieces as this is how the battery is held onto the paramotor frame.
The only thing acrylic is good for is picture frames and display items. Polycarbonate will work really well. Lexan is a brand name for polycarbonate.
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Appreciate that Paul. I didn’t realize acrylic was so brittle. Now I know why Aircraft only use poly/lexan.
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Got the case re-built with lexan/poly, much better choice of material. Ran it now for 9 min then the bms hit 60ºc cut off, i’m assuming it won’t get this hot when flying. Voltage start was 57.5v, end voltage after 9 min static runnup 53.2v. So used 4.3v in 9 min, if this stayed constant and I ran it down to 35v this would be 47 min run time. Hope to fly this weekend.
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Was that full throttle for 9 minutes? What was your amp draw?
I varied the throttle but nothing less then 150amps, did steady 280amps for a few min then eased off as the bms temp got close to 60º. I’d say my average was 200amps for the 9 min.
Micah posted an EbikeSchool.com video about the new Vruzend kit: New & improved Vruzend V2.1 no-weld 18650 kit
@dzubot he talks about beta testers and mentions your project at about 9:33, here’s a direct link: New & improved Vruzend V2.1 no-weld 18650 kit - YouTube
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Yeah I sent them video. They will probably be doing a feature video solely on the openppg when I get some footage flying it
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Absolutely beautiful! Not what you want to see when you want to fly though!
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Thank you for the thread dzubot. I was eyeing vruzend pack as an alternative to getting bonkas shipped to Canada. I was calculating a 14s X 12P pack using the 3500mah lghg2 batteries vruzend sells.
About a 25lb pack instead of almost 40. Perhaps that’d not be enough to supply the motors. I’m not a big guy (170lbs) so it might work ok with smaller props/less thrust and get more run time.
Doing the math even those 3500mah cells have slightly less energy density once you get a pack built up. About 11-12lbs/kwh vs only 10lbs/kwh for the Bonkas. The trade offs are safety, cycle life* (80%cap at 400cycles) and maybe availability.
*How many cycles are the Bonkas rated for?
No Problem! It was fun building the pack. Eventually will build second pack maybe when there’s a better battery cell to be used. The lghg2 is 3000mah not 3500. Do not buy any after market cells, only buy originals.
I wouldn’t recommend anything under 14s20p pack or else you will get lots of heat build up and the bms will shut battery off. Also you don’t want to get these plastic vruzend caps hot or they could melt I’m told. The bigger the pack the better it is for the cells, the longer it’ll last as well. I’m hoping my pack will last forever. Already I’ve seen many people kill their bonka packs, puffed cells. I use lipo in drones and they never last more then couple years before they start puffing up. If you are very careful not to push the pack or get them too hot then they will last their 300 recharges probably. 18650 cells should last 2000 cycles. I also like having the bms to monitor the pack.
Even with my pack I’m pulling 15amps per parallel group at 300amp draw.
Nice pix even if a NoGo on this one. Always a next time! Good luck!
Why did you choose for 18650? I recently replaced these cells in my ebike with 20700 and they perform better.
The vruzend caps are designed for 18650 cells, they are also easy to come by for good cells. 20700 are not as common yet, the best cells are from panasonic/tesla and are almost double the cost vs 18650.