MAC's 2nd build


Using 18650 batteries, I believe I have enough room in my electrical electrical enclosure to hold two 7Sx14P batteries. One on each side of the enclosure. Totaling 14s x 14P.


Yes, I’m still noodling on how exactly to mount the mast to a hollow board :slight_smile: My current crazy strategy is to make a big 0.125 aluminum plate with press-fit nuts for the mast mount, then a zillion small holes around the outside. rough up the bottom of the board, then epoxy the plate to it and then epoxy another layer of fiberglass over that.

This will either distribute the forces enough to keep it together or it will tear itself apart.

The idea for this originated with this, which is basically a repair plate with a lot of UHB tape underneath.

But I’d guess this mount assumes a foam filled board rather than hollow core.

I’m open to suggestions. I thought about a big complex extruded rail infrastructure on the inside of the board but I’d rather not go down that route unless I have to.


On my first build, my foam board was not very strong, especially after I cut through one of the wooden rips. I ended up sandwiching the board between 2 3/16" aluminum plates.
There might be some foam or ribs in your board. At some point you need to drill for your wires. I would do some very small holes to explore what you have.
If you use a aluminum plate make sure the wire holes are very smooth, same with all the holes in your mast top and bottom. The silicone wire jacket we all use gets razor like cuts very easy.


I pulled the trigger on my battery purchase. 205 18650 Samsung 30Q, 15AMP max continuous.


Hey Mac,
Were did you buy yout Samsung 30Q cells? I am looking for reliable source


What’s the damage haha??


Two Hundred and Five! that’s a lot of cells…

I’ve been spending a bit of time today looking at welders. Once again I think I’m overthinking the problem. There’s a guy (he’s here I think) that is doing it with a starter solenoid and a motorcycle battery.

So I ordered a starter solenoid. I already have the motorcycle battery. Bike doesn’t run anyway.

He manually times his welds, but I think I’ll work up a little timer circuit thingie.


I live in NY (USA). I bought them from IMR batteries. They are located in Houston TX. I don’t know yet if I will be happy with my decision. They have lots of positive reviews on their web site. I did not find much negative when I looked. They were competitively priced. After I pulled the trigger I got a quick Email response back acknowledging the sale. A couple hours after that I received a E-mail saying they have shipped. With tracking number. I should receive them next week. We are having a bad snow storm now so that might effect delivery. I will let you guys know.
Shipping was only $20.28. The prices for all their batteries are listed on their web site with quantity pricing.


Total $789.67
These were the names of places that I considered.

  1. Liion. seems good.
  2. IMR battery : this is who I went with.
  3. 18650batterystore. seems good.
  4. Bad Bro: seems good but for what ever reason they gave me a crazy high shipping cost. So no go.
  5. Ebay: best price, free shipping, many warnings about fake batteries. I just did not want to risk it.
  6. Battery junction: seems ok. But was higher than the others.
  7. Nkon. Good reviews but they don’t sell to the US.
  8. Alibaba,many warnings about fake batteries. I just did not want to risk it.
  9. ALiexpress,many warnings about fake batteries. I just did not want to risk it.
  10. Jehusgroupbuy: They were out of stock at this time.
  11. ERC: They only deal with recycled stuff.
  12. Luna cycles: they just sell packs.


I need 196 cells for a 14s x14P battery. I got a few extra because I might spot weld a hole in a few and let the smoke out. I have never spot welded deliberately.
I spent the last few days reading about making the battery. I ran across that video of the guy using the car battery and a relay. I did consider it. I already have all the parts. There are no shortage of DIY spot welders on the web. I just don’t want to risk messing up expensive new batteries. Today I ordered a Spot welder, Kapton tape, heat shrink to cover the battery, Nickel strips. Some of the those little round insulator things that they put on ends of the 18650 cells.


What type of spot welder did you order? You can test on 2 nickel strip to find the correct power or welding Time , then try with 18650 … Weld and test pull , usually you waste 1 or 2 cells not more


I bought the SunKKO 709A, Price 169.99 from SUNKKO. Shipping is high, Order total 218.59 USD. I bought the 220VAC 50Hz version. I saw some reviews that said they were unhappy with the 110 version. We have 220 VAC 60 Hz power so that should work. They also make a 709AD, and a 709 AD +. Those up grades have a fan and a digital display. This one comes with the hand held remote welder thing. I think that would be important to reach cells in a large pack.


@MAC thanks for the detail. I am using this welder pretty good results


I saw that one. Are you going to buy the handheld electrode thing. Or are you going to make your own. I saw somewhere they used copper nails for electrodes. I really wanted to give that a try. It seems like the car battery is the perfect thing for putting out lots of current for a very short time. I just decided to play it safe, and hopefully go the easy route.


It actually comes with copper electrodes. But needs a holder holf them in proper distance for consistent welds. I am planning to male a 3d printed holder.


Please let me know how the 220v version of this works out. I have a 120vac 788 and it pooped out after maybe 100 welds so I’m loathe to get another Sunkko but it is handy to have the controls and the foot pedal.


i have this welder as well , it is perfect for this job, but yes a holder needs to be build, and the car battery need to be fully charged to keep the same “welding time”"


No car battery, just buy a 4s 65 to 100c lipo battery, very convenient


Than you might face the next problem: Apply the same pressure to both.
I think the distance is less important than the pressure. And the distance has to be rather high, to force the current flow through the contact into the cell connector and back again and not short circuit the current through the connector only.


The spot welder is suppose to be delivered by end of day Friday. If I get some time this weekend I will mess with it and let you know what I learn.