Is it worth considering being able to connect/disconect the battery while the eppg it’s on your back (like the positive wire if having individual bullet connectors)?
Or there is no way the engine could go up throttle on the ground or in the air because of a failure like others found out when they started their gas ppg on the ground and it went full throttle?
Also for an esc like the Mad 300A what do you think would be the recomanded maximum lenght of the battery wires (including the wire inside the battery) excluding the esc wires? I’m having about 30cm inside the battery and would like to have about 20 outside so 50cm plus the esc wires, is that easy on the capacitors?
I see the SP battery has the red wire of about 1m, I presume the negative has to have the same lenght.
It looks nice but I see trouble ahead, sorry! You need as much play as possible to really look up at your glider during forward inflations, and it will be even worse doing reverse.
Take a look at this video from two days ago with my students - it is unlisted for now but will depict better the important of being able to look up and back/I hope it will help.
The black wire is not the same length. It is very short. BTW, the Anderson connectors are much easier to connect and disconnect…unlike bullet connectors and the XT style connectors.
Bill
I’ve finished my paramotor project and I love it. It has 35kg with the reserve and 17kg battery. More than what I anticipated, as usual .
During tests it peaked at 17kw but the 2.8kw batt has a huge voltage drop at that power, don’t know why. But I did the maiden and needed only 3.8kw for level flight and 5-6kw climb.
Other specs: 24min flight time, 13.4Ah left from 32Ah (41% left) 86v and 3.6v/cell no load. Think I could fly a little longer. Battery temp 45C. During ground test at average 4-5kw I’ve got 27min and temp went to 55C…kind of high, maybe I’ve enclosed it too much.
At hanging test I’ve got 15-16 degrees with 2.5cm of foam at my back, then added another 1cm layer and I was surprise to see in the video a what I believe to be very good angle during level flight power, almost vertical prop.
The higher battery behind the head was not a problem.
Video posted in the video category. Flight details at the end of video.
Thank you OpenPPG and members for your support!
Marius, that looks super cool, well done!
Would you be happy to share the details of the parts you used and any thoughts one them? I’m thinking of doing a similar project using a non-sp140 frame.
Well done for getting the project completed, it looks amazing!
Steve
Thank you Steven!
The parts I’ve used are:
-SP140 frame
-MAD M50 34kv 20kw motor just like on SP. I love it. Recently someone noticed me about the Mad V135L motor that is also 24s, 35kv, 70kg with an 135cm prop, 20kw and only 2.24kg not 4kg. And has the same prop attaching bolt patern as M50 6xM6x50mm. So you might want to look into that if you’re not very heavy and want lighter…if I knew about it, I think it would have been more than enough for me, IF it’s a good motor that is which I don’t know.
-Custom battery (see the begining of the project on this page for it)
-Custom hand controller (See topic A simple throttle in Throttle controller field)
-Custom motor mount. See above on this topic.
-Custom battery thermometers display if you don’t put bms.
-Mad Ampx 300A Esc. If you’re in US might consider the openppg power pack because I’ve didn’t come cheaper buying from EU but did come cheaper than buying from US and paying shipping and VAT.
-120v wireless coulometer.(lcd in the handle, main board in a black plastic box bellow the Esc on the frame, in which I also have a step down from main batt voltage to 12v to power the coulometers main board and the thermometers. The coulometers main board has an 5v usb output to power the lcd and I’ve also powered the servo tester in the handle with 5v bacause the Mad Esc has no bec.
-Dudec PowerSeat Comfort Low U(underseat reserve) very confortable harness, love it.
-Supair 105kg Shine M 1.4kg reserve
-Openppg cnc arms. Love the finish on them.
-140cm Eprop with openppg quick release that is awsome.
-A pvc light plate at the back and 3cm of foame to push me in front and achive the desired hang angle.
That’s about all that comes to mind right now. Tell me if you want to talk more about certain items.
note: here the pilot should weigh a maximum of 55 kg and should fly a high-performance wing. the motor produces too little torque for eppg because it simply has too little copper mass and magnets that are too small. however, it puts more strain on the battery than the sp140 motor with significantly less power output
I need battery knowers help again regarding two things on a 2.8kw 24s8p custom battery made out of Samsung INR 40t3 4A, 35A new cells:
At a ground test of 27minutes, an average of 4-5kw load and 2.1kw pulled out of the total 2.8kw (3/4) to about 85v (3,5v/cell) without load, the battery reaches 55C temp.
I know the limit is generaly 60C so why this high temp? Because I have 24s8p and Openppg uses even the 6p pack no problem.
I have one 10x0.15mm pure nikel strip on the cells in parallel and six 14awg(50A rated, barely warm at 20A/wire or 120A total (20Ax6pcs).
So why this high temp at an 8p pack (with 4-5kw load, 7-9A/cell) when a 6p works fine?
At ground tests, at full throttle it pulled 17kw out of a freshly charged to 4.15v/cell battery and in three seconds the alarms set at 3.3v/cell (80v) went on. How is it possible to have this voltage drop when I read somebody climbed 7 minutes with the 4kw batt at full throtle in chill mode 17.5kw?! I know 4kw is bigger than 2.8 but not that big to have minutes on one at full and three seconds on the other.
That’s why I babyed the throttle on my first flight.
Note: (I’ve received the cells from the well known company in Netherlands, all at 3.44v, some say it’s too low for storage others that it’s okay if they all have same voltage). Individual cell capacity test on four cells got in 4050-4128mA from 2.5 - 4.2v.
In short:
Why a huge voltage drop to about 3.3v/cell at 17kw in seconds on a fresh battery?
Why such high temp of 55C at 4-5kw load?
There could be a few issues on why you see the high temps.
First of all you use 0.15 nickel. That is very brittle and too thin. Use at least 0.2x10mm better with 0.2x12mm or wider
Second is that your spot welder is way to week, the dots are overheated due to long pulse and you have to make a lot of them(like 12!), compared to using a good power source makes 4 dots more than enough, see:
You have a lot of soldering, between each cell, and at each module and then from module to main wire, all that solder creates a lot of losses. You may decrease the actual resistance in the module by spot welding series connection rather than soldering, but then again you need to have a proper welder and thick and wide enought nickel, someting like 0.2x12mm or more.
Thats why you may experience hight voltage drop at 17kW.
See if you can discarge one cell at 7Amps and compare the temp. If it is lower than the problem is actually in your connections. So a cell in the system might actually put out more amps during load to deliver that avarage 7-9A due to all the losses on the soldering joints with a combination of thin nickel and potentially weak spot welds.
That’s super useful, thank you!
It looks like the mad M50 would be the way to go… Plenty of grunt!
Are you based in the US?
I’m not and I’m asking because being based in the UK I will need to pay import duties and VAT which add ~ 25% to the cost> So I’m looking at my options. Still not convinced I’ll take the leap but I’ve done 2ebikes and I can’t lie… It looks great fun and I’m tempted!
Any thoughts more your reflecting on your successful project? Worthwhile?
The cells used for the Sp140 are Molicel 21700 P42A 4200mAh 45A so they are higher discharge cells then the ones used for your project. You could test the two side by side, you just need one cell to test and pull same power and measure the temp of each so you can see. This will show why you have higher temps.
Well sh…t Alex, when I was finally starting to enjoy the eppg after almost a year of working and investing time, money and dreams.
Thank you for finding the time to truly analize my battery.
-I can’t use wider nikel because the plastic cell holders won’t permit it, 10mm is max.
-I thought that between cells in parallel a 0.15x10 is enough if you have enough series wires because the high current travels in series but I might be wrong and nikel is heating up.
-Regarding resistance, I think the use of cooper wires (1.68 resistance) instead of nikel strip (7 resistance) should compensate for the soldering points (22 resistance)?
I mean instead of 5m of a metal that has 7 resistance(nikel strip) I have 5m of a metal that has just 1.68 resistance(cooper wire). Does that make sens?
-Regarding spot welds, I thought that 12 smaler will make for 4 stronger…I’ve posted my concerns about this, here in march… afterwards, I did what I could.
-Heat: I knew they heat up more than molicell but everyone said Samsung are good cells. From the graph I see that at 10A the cell reaches 44C so ther’s the answer…put together tens of cells and enclose them thight and I have my 55C temp. I’ve exposed the cells to air and will see if it drops a bit.
Anyone know what temp the half hr SP140 batt get?
Botom line:
-If I stay below 10kw and 55C temp, can I use the battery as it is? Any drawbacks in doing so?
-Is it normal to get 27min flight at 4-6kw load and 50C temp? Or do I loose lots of power by heat and it’s worth consider redoing it?
Don’t think I have the will and energy to start it all over again, wait months for parts and fly it in spring…just to get 5min plus and 5C minus…
I’m from Europe, and the shipping and vat were the reason of building myself, well I think I went cheaper but not by much…I’ve lost counting on the way.
I don’t know about successful project, I’ll tell you later…For now the battery gives me headaches.
If it turns out I can use it than yes, it can be named successful considering being first time of many things for me on this project.
Other than this, I’m satisfied with everything else on the build.
Ha ha! Thanks Marius, I’m in the same position, and it’s not clear to me that there’s a cost saving. Probably not is my guess, but it does also offer the opportunity to customise, and the joy of showing people what you built!
Are there documents available on the open PPG that you referenced? I have looked but can’t find anything other than a git hub repository for the controller code. I can’t even find a motor specification, in fact if you hadn’t given the details earlier I would still be in the dark
I use the T40 Cells in my DIY battery pack 15S10P. The average current is 60A, shorttherm max. 80A during my 40min flights at 150m AGL. The max cell temperature are <50°C after my full powered flights, also here in summertime (30°C air temperature).
For the battery connection i used 0,2x10mm nickel + 0,1mm copper layer. The temperature measurement via IR camera with full power (150A-200A) shows no hot connection.
This would be also my advice to buy/rent an IR camera and check with full power were hot areas are.
I flew my 15S10p battery since a half year with 60-70 flights and it works fine. I done probably also to much welding points and this could damage my cells/electrolyte. I can recognize this after one week storage of my precharge pack: Some cells lost they capacity faster than other cells and i have to rebalance the pack.
Did you say you keept the battery charged one week?
People say that it’s good practice not to keep it charged not even 24hrs because the rapid chemistry changes at full charge.
I can’t use the battery when it’s open to measure temp, because of the many bolts that keep it together and in the huge wind generated by the prop I don’t know how the temperatures would mach the enclosed batt box.
I will spot weld three cells in series with the same nikel, soldering points etc and draw 7-8A with an brushless motor and prop for some minutes. And measure with IR gun.
How can welding points destroy the cells if you don’t penetrate it?
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