So I found a copper bus bar that should fit, on ebay. I asked the seller if they can cut it to size and whether they can drill the holes and cut the threads, the flat copper material is 20x4mm, I am planning to have it cut to 286mm which is exactly the length of the 15 cells in parallel.
Here’s the sketch for my inquiry:
The threaded holes will be for these M3 Screws:
M3, 4mm length, large flat head
Any word from veconcepts on pricing for a battery? And specs?
I haven’t heard back for a while so I messaged him again.
So as mentioned above, I ordered and received a flat piece of copper (4x20mm with 1000mm length).
I had to cut it accordingly and add the threaded holes for the M3 Screws, so that it does make a nice bus bar.
It turned out quite well:
Next step was to measure the required length for the nickel strips, cut them to size and also drill a hole to be able to connect them with the copper bus bar
quite a good plan, however it didn’t turn out so well. drilling holes in such a thin material apparently isn’t working.
However I have an idea that I’ll be testing in the next couple of minutes. will keep you posted. 
So since I have access to a couple of lasers, one of them being a fibre laser to cut and engrave metal, I thought I could just laser the hole.
It just worked great.
Cut and drill at the same time:
this is three of the strips at each cell-position attached to the bus bar:
I can now spot weld each strip, three per cell, one by one to each cell:
Looking great! How do you get to a bad cell?
Nice build. Do you have an estimate of the current weight, estimated flight time and capacity of the pack once done? Also, can you post more pictures of your build showing overall size, construction and configuration? (newbie still learning about 18650 battery pack builds)
how about you scroll up a bit?
Busbar with two 8AWG wires soldered to it. On the other end the RC ProPlus.
It was not too easy to solder the RC ProPlus connectors, plus the casing, it was all a very tight fit.
Here’s the negative busbar with the BMS soldered in between:
I added some double sided tape (the strong type from 3M with some thickness), before putting it together:
this is how it looks alltogether.
The triple layer board on top is the BMS, which is right now only lying on there. still have to find a way to attach it to the battery somewhere.
And the other side, which shows the not-yet connected balancing wires of the BMS.
still looks kind of messy, as mentioned above, I’ll need to find a way to put it all together.
The tricky thing is, that I really really need to pay attention to not shorting the battery by accident.
I have purchased a large sheet of foamed rubber, which I will use for insulation and wrapping the battery.
However before I start wrapping this battery up, I want to make sure how and at what position I will attach the battery to the OpenPPG frame.
By the way, I received my batch 3 kit a couple of days ago, and I am already at 80% completion.
As I am eager to get in the air with this thing, I will be wrapping up things pretty quickly now.
Note that the OpenPPG now comes with two switches, and that the community has come up with an idea of how to prevent the arcing effect, when turning on the power circuit (a lot of current going from the batteries to charge the capacitors when connecting the circuit), and that is the pre-charge solution
with a 22 ohm Resistor and a special 3D printed switch with a very smart feature
Thanks @GliderPilot
(explanation and files here: Paul B & Braedin B (GliderPilot & Glydrfreak) Flights & Build Modifications - #76 by GliderPilot)
So my two sets of 8 AWG wires are on one hand to dissipate the current onto two sets of wires,
and to be able to connect both switches to the battery at the same time.
Great looking battery well done! Hope it works as good as it looks. Could you build a plexiglass or thick plastic box around it with vent holes? This would protect it from getting touch by any metal screw head on the paramotor frame. Then mount with industrial Velcro and strap around it to the frame as well.
Amazing you built your kit to 80% 2 days. Would like to know how to battery fits between the motors, lots of room?
Could you connect to the copper bus bars to power cables by tapping holes and securing the cables down with bolts? Add an eyelet crimp connector to attach the wires to the bolts.
After I was done, I kind of thought about the same thing. Soldering the thick 8 AWG cables to a thick copper bus bar requires a strong soldering iron and a lot of heat. (I ended up using a small gas torch to solder).
Using ring terminals and screws would probably have been much more elegant. But hey, hindsight is easier than foresight!
I am scratching my head about what kind of enclosing would be best.
I was first thinking about acrylic sheets as well, lasercut and with fittings just like the carbon sandwich concept of the OpenPPG, a couple of screws, done!
The I was thinking about a sleek aluminum case.
Last, I decided to wait until I actually receive the openPPG kit, to actually see how and where it would fit.
To be able to handle the battery with the conductive screws and carbon plates, I needed to wrap the battery first. This is crucial to avoid an explosion!
This is what I used: a sheet of foamed rubber (I bought two thicknesses, to have a choice whatever is best) and stretch film
And finally, the OpenPPG aaaaand the battery.
the OpenPPG is laid flat on the floor, battery just loose on top, quickly wrapped in the stretch film to roughly protect all the contacts.
Nice build - looking forward to seeing static test run numbers - wishing you all the best, you put a lot of effort into this and I hope it pays offs - it looks very promising.
I tried building a pack from old laptop batteries some yrs ago for my E-bike. It did not work out and I no longer have the patience for these detailed projects. That is on of the reasons I picked the headway kit for my bike after that.
Thus I admire those that attempt them and envy them when they are successful - I hope to envy you!
Cheers
Thanks @E-pusher!
So after I finally wired everything up (OpenPPG as well as the Battery) I was finally able to fire Up the Battery.
And it looks like as if I had scratched my head to much about the pre-charge circuit and the switches,
as the BMS seems to allow me to turn on and off the Power from the Battery.
The display also reads the Voltage and the Current/Amps once it’s running:
This is a picture of the BMS’s display before I charged the battery. That’s the state the battery is in since the cells were delivered (I never charged or discharged them).
