Spot welder question

[airborne spoon]

I want to make a spot welder because the ones that are plug and go are like $300+ and the reviews are usually 1-2 stars.

I came across https://www.keenlab.de/index.php/product/kweld-complete-kit/ and was wondering if anyone had used one of their kits? Seems like a pretty solid design and build but i don't wanna spend almost $200 if its not known to be good.

 

I made a battery pack for my skateboard a few years ago and soldered all the tabs on there 2x 6S4P (50v) but one joint came loose and caused the thing to stop in its tracks and i ate shit at 35 mph. Although about 3 years of riding and it took this long for something to break is pretty good considering how much vibration those things suffer through.

So now i want to redo the pack and spot weld all the tabs on there for better connections so this doesn't happen again because that was excessively painful. Can i just spot weld over the solder joints or do i need to grind off all the solder before doing a weld?

[DoctorNick]

Havent tried, but you need to remove solder in order to spot weld. You could also get new batteries

[airborne spoon]

8 hours ago, DoctorNick said:

Havent tried, but you need to remove solder in order to spot weld. You could also get new batteries

yeah since batteries are only like $1.5/ea its doable but not ideal because shipping from China takes forever. And these batteries are still in good condition, no reason to toss good batteries.

What's the best way to remove the solder? i know heat is bad and that's why i was quick with my solder joints last time. I was thinking maybe using a Dremel or a buffing them against my belt sander.

[DoctorNick]

18 minutes ago, airborne spoon said:

yeah since batteries are only like $1.5/ea its doable but not ideal because shipping from China takes forever. And these batteries are still in good condition, no reason to toss good batteries.

What's the best way to remove the solder? i know heat is bad and that's why i was quick with my solder joints last time. I was thinking maybe using a Dremel or a buffing them against my belt sander.

Idk, maybe check YouTube, must be something

[microwar]

Have you seen this one?
Around 50 usd from Ali Express.

 

[akio123008]

Personally I prefer to use Li-Po batteries instead. It avoids the hassle involved with li-ion cells, and they're not that expensive. They can be bought on websites or in stores that sell RC parts.

 

The nice thing about those lipos, (which is why I use them) is that the cells can support far more current, so you don't need parallel cells. For instance my ebike battery can easily do 150A without having multiple cells in parallel (it's a 6s battery, only series, no parallel). The downside is that the energy density is a bit smaller, you can't go as far for a given volume of batteries.

[airborne spoon]

On 5/2/2021 at 12:34 AM, microwar said:

Have you seen this one?
Around 50 usd from Ali Express.

That thing screams crap, I've seen a few reviews on nearly identical products from amazon and if you want to weld more than like 10 welds it is useless and the welds aren't very good anyway.

22 hours ago, akio123008 said:

Personally I prefer to use Li-Po batteries instead. It avoids the hassle involved with li-ion cells, and they're not that expensive. They can be bought on websites or in stores that sell RC parts.

 

The nice thing about those lipos, (which is why I use them) is that the cells can support far more current, so you don't need parallel cells. For instance my ebike battery can easily do 150A without having multiple cells in parallel (it's a 6s battery, only series, no parallel). The downside is that the energy density is a bit smaller, you can't go as far for a given volume of batteries.

Lipos for an eskate are not ideal, i am looking for range not power, (although i can do 38 mph on my board and it has plenty of bottom torque). i can also do 14 miles of range which is very important. If i used lipos they would cost a fortune compared to liion (i paid $0.90 each battery from alibaba) and the size is not ideal because lipos are bigger and you don't get the mAh for range needed in the form factor. I can see on a bike the power draw is needed just like an RC car where you have huge ramp up power draw that decreases as you even out the speed. but on a skate its all about the range because they are so light and the motors are so torquey they rock on without needing super high amounts of power draw.

 

Anyway i bought the kWeld and it works amazing, i hooked it up to a cheep car battery from AutoZone ($70) and i was off welding all my batteries without issue. I was welding at about 65J each hit and did 6 spots on each battery and the welds are super strong and hard to tear apart using .2 nickel strips.

[ColinLTT]

Trust me, just buy one. 
 

 

[airborne spoon]

19 hours ago, ColinLTT said:

Trust me, just buy one. 

I remember that video and was thinking of building one originally but buying a 95% ready to go one was a better option for the price. Glad i went with the kWeld because it works amazing