Eppg project - 2.8kw battery

Hi, I would like to post my eppg project here. I’ve tried to find most of the components in Europe.
My project will not be dyi homebuild, but more like home assembling and the components are:

  • SP-140 frame and loop with netting.
  • MAD M50 34kw motor with 140cm prop and openppg prop quick release
  • MAD AMPX 300A 24S ESC (not totaly decided yet…)
  • Custom made 24s 8p (2,8kw) li ion battery from Samsung INR21700-40T (40T3) 4000mAh - 35A cells.
  • Dudek comfort harness
  • Aluminium arms from Simplify (not sure yet)
  • homemade hand controller
  • custom made 20mm/100-130mm aluminium motor standoffs with M6 or M8 bolt through them.
  • custom made motor plate from 6mm 7075 aluminium aloy.

About the battery
Because I’ve never built li ion batteries, reading through here about high voltages above 60v made me decide to split it in three and make smaller 8s 8p packs.
The individual 30v batteries will be each one in its aluminium case, separated one from another, with cables connected on the outside.
-I won’t be using an BMS, and I’ll be able to balance charge them with my ISDT T8 battery charger.
-Each pack will have a temperature probe in the middle, that gows to a 12V Temperature Controller that activates an alarm when a preset temp is reached, also I’ll be able to monitor the temp in flight.
-Each pack will have an xt60 plug for charging and an 8s balance plug to which I will have voltage alarm dispalys that will monitor the individual cell voltage.
-The connections between packs like from the positive of one to the negative of the other I will have two 10AWG wires with same polarity going to both terminals of an xt90 connector so I think it will handle the amps.
-For the main plugs to the ESC I went for the AS 150 antispark that are rated at 150-200A. The reason for thinking they will be enough is that I’ll have consumption like 50-100A (4-9kw) most of the time and above that probably just for seconds…

  • On the cells in paralel I’ve used one 0.15/10mm of pure nickel strip and between series 7 pcs of 14 AWG (rated 55A each) silicone cables. I’m also new to spot welding.
  • The alu batt case walls on the interior will be insulated with fiberglass and maybe some foam to secure them inside.

The reasons I went for a more complicated and with lots of cables three pack design:

  • I feel better knowing I’m working, and storing in the apartment smaller 30v li-ion batteries.
  • I can use my hobby charger which I’m familiar with and see very often the state of balance between cells on it or on the small volt dispalys on the batt case.
  • If something happens to o cell or a pack, it’s 1/3 of the whole batt not whole of it.
  • If the voltage of a group of series cells drops, the alarm gows on, if one pack overheats, the alarm gows on, in both cases I AM the one deciding what to do, if I need another 10 sec of power to pass an obstacle or turn into wind and land safely I’ll have it. Of course, I would land immediately.

The three aluminium batt boxes will be held together into one single battery by aluminium corner profile bolted along the four corners. Unfortunately, because the cells are in plastic holders and distances in the boxes, the total battery will be very long, about 62cm/22cm/9cm (the SP 140 has it at 48/26/9,6cm). But because I’ll have some distance between the frame and motor plate I’ll be able to recline it so it won’t hit the cage when handling it…in theory.

Any advice, idea and opinion are welcome!
Thermometer probe:


a nice project! a note. It would be good if you laid the cables that have more than 60 V with an orange hose or, better, orange cables. that is the cable to the esc and the cable from the esc to the motor. so the rescue workers and firefighters know what’s going on technically. also possibly make stickers that show the volts. It’s not just about whether there was an accident while flying, but also maybe a car accident through no fault of your own. everyone knows then through the orange color that one is careful. It’s just a safety tip. with many electric drives today, which often have 80 volts and more, it is now a problem for insurance companies how it is treated if there is no marking. a fireman who works as a volunteer has a shock in his heart because he only wants to help. that should not be.

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Thank you, I was thinking of sticking on the battery the yellow high voltage triangle, and smaller ones on each power cable exit from the case.

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that’s a good solution how you do it! in the automotive industry, fire brigade, police, etc., many helpers will be trained in the next few months. I noticed the currently “orange” cable which is synonymous with dangerous DC current. Hence my comments on this because it is becoming a standard worldwide - even the small e-motocross with 72 volts or more have now all been given orange cables, I just saw them a few minutes ago. sur ron storm bee and others in the scenne.

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For the spot welding knowers:
I’ve noticed that some of the welding points look smaller and that they pop out when flex a smal screwdriver underneath the nickel plate. Then I’ve increased the power of the device beyond of step 30 which is not recomended with a new max.45A car battery, and I made other welds. How can I check them without detaching the nickel because I have no more space on it to make new welds…but It gives me a feeling of insecurity not checking them… Of course I’ve practiced on spare cells, different power levels, and most of them were good. Thing is, if you press too hard the welds are weak, I’ve seen it on youtube more people sayng that, then I start with very gentle press and I had somme blow up burned holes through the nickel and sparks that freak me out, I’m guessing because was no contact between the nickel and battery from not enough presure. Although I use a hard, rounded woden stick to force the nickel to lay on the batteryes because the plastic holders together with the ring caps and the fact that I’ve soldered the wires so I won’t heat the batteryes, made the nickel not to lay perfect on them, but after cleaning it and force it down it stays down on them.
Don’t know why my copper wire electrodes get blunt after ten welds either…articles say too much courrent, how the hell is too much if it makes tini welds that don’t hold…
I think I’ll check some of them with the screwdriver, make some more welds if needed at level 50 from 99 and see…then I’ll put some hard foam in rows to press on the welds when I’ll wrap the battery in shrink tube to hold it together. And that’s it. Not a fan of this spot welding…I might have to change the electrodes after making one battery that’s how short they got after so much sharpening. And the new 44A-390A car batt gets from 13v to 12.6 after welding one side of a 8s8p pack…