Best cheap spotwelder?

So after years of messing with ebikes, I've decided to make the switch to 18650s. But every bike I have is unconventional, and will take custom batteries. The only real solution is for me to start building my own.

I'm saving to put a down payment on a house, so I don't have a ton of free cash. Whats the best cheap spot welder going? I don't mind buying one I'll have to modify to make work well.

The Malectrics, boss level, and Riba seem to work very well. They are simple precision timers that use a large car battery as the welding pulse. The last I checked, they were roughly $100, but check to see the current price.

The kWeld is a little over $200, and some builders feel that it's extra features are worth the price. All of these welders are naked and open-source, so a fried component is easy to find and replace, although they have all been improved to the point where they don't seem to have any failures now. They all use a bank of FET's as the on/off switch.

Thanks! All 3 of those look great, and that style wasn't even something I had thought of before asking.

I also recommend the malectrics, I have the original version that first came out. My recommendation is use 6 gauge pure copper welding cables for the probes cables. At first I was using the cheaper 8 gauge copper clad and the cables got too hot to hold after about 10 welds, the power setting also had to be very high to get good welds.
With pure copper you can use a lower power setting and cables only got warm.

Using a 12 volt battery as a power source you don't have to worry about house circuit breakers tripping. The 12 volt spot welders look small but they are quite powerful. At the 3 power setting I get good welds on 0.15 nickle strip, power setting goes all the way to 9. The new malectrics also can use a 3s lipo as a power source. The latest version cost the same as the original version but has many new feature and a better LED screen. Cost is less then 100 dollars. 6 gauge pure copper wire you can buy for less then 20 dollars. For probe tips you can use pure copper nails, they also cheap.

I have made many DIY spot welders, capacitor discharge, rewound MOTs and car battery type. The cheapest and easiest to get going is a group 24 - 27 car battery, solenoid and momentary push button or micro switch. All other types require alot of things that they don't tell you on youtube DIY spot welder vids. I use a rewound MOT transformer and foot switch as a RSU and solder because I like copper strips, internal resistance of a battery pack adds up quick when using nickel strips spot welds. Once again if I were you and wanted to spot weld my packs then the battery, solenoid type is the cheapest and easiest by leaps and bounds.

I was/am about to go down the car battery route, I read your comments re internal resistance with interest. At what point does the use of Ni/Cu become apparent. Im looking at building a 7s13p, with the possibility of adding a further set, ie 7S14P, if weight allows. I dont really intend to build many batteries so had thought the relative cost of a spot welder was a no brainer but hadnt considered this point.

I strongly recommend the Kweld. It isn't cheap in price but it's exceptionally in quality and design.

I went down the build-your-own route with the solenoid, momentary switch etc and the results were less than desirable. The real issue is the lack of consistency as I had no control over the amount of heat/energy. With the Kweld, you can control the amount of energy (measured in Joules), dialing it up or down depending on the tab material and thickness. The Kweld has some smarts such that it measures the actual amount of energy used by the weld and will confirm a good weld with a beep. It's either a good weld or no weld at all. You need to assemble it and bring-your-own-power-supply. Assembly is easy (if you can build a battery pack, you can put the Kweld together with your eyes closed) and for power I took the simple route of using a good car battery.

I'm not an electrical engineer or precision craftsman (not by a long shot) but the results with the Kweld made it look like I knew what I was doing. The unit is a piece of brilliant German engineering IMHO. The designer is Frank Boeh. He was very responsive to all my inquiries.

BTW, I bought mine from Frank's US distributor, 18650 Shrink & Cell Holders. https://18650shrinkandcellholders.com/kweld/ The owner, Keith, was also exceptionally responsive. Ordered and received the unit in less than a week. It was shipped from Rhode Island to Canada.

I just bought a Malelectrics spot welder - came to $140 shipped to the US, plus $60 for a 3S 75C lipo from Hobbyking. Great instructions and super easy to put together. Only done a few tests so far, but works a treat. I went this route rather than one of the Suncko (?) ones as they have pretty mixed reviews, plus I didn't want to have to find space to store another largeish tool

Thanks for the suggestions. I went with Malectrics. It seems to be a well thought out kit, and the quick test welds I did with it all look good. I hope to rebuild a tool battery with it tonight to test it out.
And they threw in some real German Gummi candy. Can't go wrong with that.

jonyjoe303 said:

I also recommend the malectrics, I have the original version that first came out. My recommendation is use 6 gauge pure copper welding cables for the probes cables. At first I was using the cheaper 8 gauge copper clad and the cables got too hot to hold after about 10 welds, the power setting also had to be very high to get good welds.
With pure copper you can use a lower power setting and cables only got warm.

Using a 12 volt battery as a power source you don't have to worry about house circuit breakers tripping. The 12 volt spot welders look small but they are quite powerful. At the 3 power setting I get good welds on 0.15 nickle strip, power setting goes all the way to 9. The new malectrics also can use a 3s lipo as a power source. The latest version cost the same as the original version but has many new feature and a better LED screen. Cost is less then 100 dollars. 6 gauge pure copper wire you can buy for less then 20 dollars. For probe tips you can use pure copper nails, they also cheap.

Click to expand...

do you have a pic, or instructions for your probe setup? i didn't realize that the probes get hot till you mentioned it. I realized i had to take little breaks for it to cool down. PS love the Malectrics spot welder.

spinningmagnets said:

The Malectrics, boss level, and Riba seem to work very well. They are simple precision timers that use a large car battery as the welding pulse. The last I checked, they were roughly $100, but check to see the current price.

The kWeld is a little over $200, and some builders feel that it's extra features are worth the price. All of these welders are naked and open-source, so a fried component is easy to find and replace, although they have all been improved to the point where they don't seem to have any failures now. They all use a bank of FET's as the on/off switch.

Click to expand...

I'm very curious to hear what those extra features are? Do you know?

The main feature appears to this devices ability to measure the current passing through it in real-time, and it automatically adjusts the pulse timing on the fly to compensate for any change in voltage, or amperage droop.

If you have a large low-resistance battery (*or possibly two in parallel?), the variance in volts and amps should not be an issue.

However, with the kWeld, if there is any change over the course of welding dozens of cells, it will shorten or lengthen the pulse timing (*measured in milliseconds) to ensure that each weld recieves the same amount of energy (*measured in joules).

It also has a test mode before starting, to let you know if the battery you plan on using will be able to provide the amount of welding energy you hope to use. The most common complaint from new users (before this feature was added) was that the welds were weak at the highest setting. In this situation, upgrading to a better battery always solved that issue.

The positive electrode of an 18650 cell is very robust, but the negative end is sensitive to heat. When welding to the negative end, consistency is very important. A weak weld can become a bottleneck to current, but too much welding energy can cause internal damage.

Have just found this funny welder from China. Looks pretty crazy. https://www.aliexpress.com/item/32824649533.html?spm=a2g0o.detail.1000023.14.409d55b7YiGTF2

zzoing said:

Have just found this funny welder from China. Looks pretty crazy. https://www.aliexpress.com/item/32824649533.html?spm=a2g0o.detail.1000023.14.409d55b7YiGTF2

Click to expand...

Its only control board for MOT welder. I tried it and works 100%.

spinningmagnets said:

The main feature appears to this devices ability to measure the current passing through it in real-time, and it automatically adjusts the pulse timing on the fly to compensate for any change in voltage, or amperage droop.

If you have a large low-resistance battery (*or possibly two in parallel?), the variance in volts and amps should not be an issue.

However, with the kWeld, if there is any change over the course of welding dozens of cells, it will shorten or lengthen the pulse timing (*measured in milliseconds) to ensure that each weld recieves the same amount of energy (*measured in joules).

It also has a test mode before starting, to let you know if the battery you plan on using will be able to provide the amount of welding energy you hope to use. The most common complaint from new users (before this feature was added) was that the welds were weak at the highest setting. In this situation, upgrading to a better battery always solved that issue.

The positive electrode of an 18650 cell is very robust, but the negative end is sensitive to heat. When welding to the negative end, consistency is very important. A weak weld can become a bottleneck to current, but too much welding energy can cause internal damage.

Click to expand...

Many things. I have this in consideration when i will buy a welder.
Looking at which one i should buy.
It's between Malectrics and Kweld.
My biggest headeach is i don't know which battery to chose
A car battery is expensive and takes space.

Best cheap spot welder for me is MOT spot welder. 100-200€ plus battery is not cheap for me. If i need to pay 150-250€ for spot welder than i suppose money is not the problem. In that case best option is to buy some branded battery.
I guess at least 50% of people cant afford that 150-250€ spot welder. Especially if they use it 1-2 times per year or less.
Maybe im wrong but thats my opinion.
My MOT spot welder is good for my needs. Total cost about 20-25€. And welds are very good.

heres a picture of the 6 gauge pure copper welding cables I use on my malectrics, I use copper nails as the actual probes, I solder the nails to the cable.

This is one of the early version of the malectrics, I use xt90 connectors to connect to the 12 volt battery. Instead of foot pedal, I use a momentary switch on the actual probe, It works excellent. I been using power setting 4.1 on 015 nickle strip, it works good without heating up.

You have to find the lowest power setting in your situation where you get good welds, if your power setting is too high it won't really be a better weld but it will definitely heat up your cables.

spinningmagnets said:

The main feature appears to this devices ability to measure the current passing through it in real-time, and it automatically adjusts the pulse timing on the fly to compensate for any change in voltage, or amperage droop.

If you have a large low-resistance battery (*or possibly two in parallel?), the variance in volts and amps should not be an issue.

However, with the kWeld, if there is any change over the course of welding dozens of cells, it will shorten or lengthen the pulse timing (*measured in milliseconds) to ensure that each weld recieves the same amount of energy (*measured in joules).

It also has a test mode before starting, to let you know if the battery you plan on using will be able to provide the amount of welding energy you hope to use. The most common complaint from new users (before this feature was added) was that the welds were weak at the highest setting. In this situation, upgrading to a better battery always solved that issue.

The positive electrode of an 18650 cell is very robust, but the negative end is sensitive to heat. When welding to the negative end, consistency is very important. A weak weld can become a bottleneck to current, but too much welding energy can cause internal damage.

Click to expand...

It sounds like the kweld would give more consistent welds throughout a session as the welding battery discharges?

Of course the malectrics allows the builder to adjust the welding pulse-time manually, but the actual amount of energy delivered is entirely up to the output of the battery that is used (meaning, if you switch to a different battery, the proper settings will be different).

If you are welding the common 0.15 nickel strips, it appears to function quite well. (I haven't used one yet, but I track the posts of users). If you stick to using a large and fairly new battery (low resistance) from their list of recommended batteries, you should get consistent results.

Although neither company recommends this, if you already own a Malectrics, I suppose the 8.2V kCap should work fine as the power source, and it can be "filled" by any 8.2V source, even a low-amp source such as a large bank of 2S 18650 cells charged to 4.1V each, taken from a laptop pack recycler (cells that are often often near-free). Once discharged, the kCap is safe to transport or ship by mail, unlike a charged LiPo. It's not bulky or heavy, like a car battery of the acceptable type (800CCA+).

The kWeld is more expensive, but I consider it a lifetime purchase, and the feature of consistent welds is worth it to me. I am no longer pursuing the welding of copper [by itself] onto 18650's ever since discovering the "sandwich" method, which uses power in the normal ranges to accomplish.

However, one of the features that appealed to me was the kWelds ability to pass 1400A without damage. It is the amps that provide the heat, and it's high amp-rating provided me with a very wide performance range for experiments.

Of course the 1400A pulse was at lower voltages so it would not exceed the total wattage power limit, and at that amp-flow, the cables and probes would get hot, requiring a cooling-off period between welds. The Malectrics is not rated for this power level.

When using either one, start at a lower power level and work your way up, plus...test the anticipated method on dead cells before moving onto the expensive new cells. On the positive tip, a good weld is easily tested and observed. But on the negative end, it is important to accomplish an adequate weld with the minimum amount of heat.

Another issue that appealed to me was for the spot-welding of fuse-wire to the negative end of an 18650. When welding a nickel strip onto he positive ends, there is a wide range of settings that will work. However, for a thin fuse wire, it is vital to have a very consistent pulse of energy. If using different cells on occasion (MJ1, 30Q, VTC6, etc), the appropriate fuse wire will also vary Iin thickness.

spinningmagnets said:

Of course the malectrics allows the builder to adjust the welding pulse-time manually, but the actual amount of energy delivered is entirely up to the output of the battery that is used. If you are welding the common 0.15 nickel strips, it appears to function quite well. (I haven't used one yet, but I track the posts of users). If you stick to using a large and fairly new battery (low resistance) from their list of recommended batteries, you should get consistent results.

Although neither company recommends this, if you already own a Malectrics, I suppose the 8.2V kCap should work fine as the power source, and it can be "filled" by any 8.2V source, even a low-amp source such as a large bank of 2S 18650 cells charged to 4.1V each, taken from a laptop pack recycler (cells that are often often near-free). Once discharged, the kCap is safe to transport, unlike a charged LiPo, and it's not bulky or heavy, like a car battery of the acceptable type.

The kWeld is more expensive, but I consider it a lifetime purchase, and the feature of consistent welds is worth it to me. I am no longer pursuing the welding of copper [by itself] onto 18650's ever since discovering the "sandwich" method, which uses power in the normal ranges to accomplish. however, one of the features that appealed to me was the kWelds ability to pass 1900A without damage. It is the amps that provide the heat, and it's high amp-rating provided me with a very wide performance range for experiments.

Of course the 1900A pulse was at lower voltages so it would not exceed the total wattage power limit, and at that amp-flow, the cables and probes would get hot, requiring a cooling-off period between welds. The Malectrics is not rated for this power level.

When using either one, start at a lower power level and work your way up, plus...test the anticipated method on dead cells before moving onto the expensive new cells. On the positive tip, a good weld is easily tested and observed. But on the negative end, it is important to accomplish an adequate weld with the minimum amount of heat.

Another issue that appealed to me was for the spot-welding of fuse-wire to the negative end of an 18650. When welding a nickel strip onto he positive ends, there is a wide range of settings that will work. However, for a thin fuse wire, it is vital to have a very consistent pulse of energy. If using different cells on occasion (MJ1, 30Q, VTC6, etc), the appropriate fuse wire will also vary.

Click to expand...

Great summary.
Thanks for it.
I know what to do now.

It just took me a while to understand what you meant by "Sandwich" method. Had to read through a lot of posts in this forum but it was worth it
You want to weld copper strips and to get it working, you use a piece of nickel strip on top.
Thanks.