DIY Spotwelder

[Hassan]

Hi Guys,
I want to build a 18650 batterypack of 403VDC of an Electric vehicle. The battery has 5 Segments of 19s8p. The connections are done via copper-nickel(0.1mm copper and 0.1mm Pure nickel) sandwich method. I have built my own spotwelder using MOT. i have used 35mm2 copper wire for secondary with 2 turns. Pure copper electrodes. Output Voltage is 1.8 volts and current is >400A (Maximum i could read via my clampmeter).Theoratically it should be >1200A.i am using arduino and a relay for control. The pulse is set for 220ms through Trial and error. If the pulse is set for less than 100ms, it doesnt weld properly.
I am getting consistent welds, but the cell is heating up considerably. Now i do not know that it is normal or not but i can feel the heat with my bare hands throughout the cell. Its not too hot but one can easily feel it.
I do not want to damage cells, so i am considering using a thinner wire and more turns on the secondary winding to increase the voltage to around 12V so that the heating issue is resolved.
What are the other ways i can do to prevent this.

 

[amberwolf]

I don't have the specifics on correcting the problem, but it sounds like you have to have way too long a weld time, so current is flowing so long that it's causing the cell heating. You may also not have sufficient probe pressure, so there is too high a resistance from probe to surface or from strips to cell, creating excess heat.


Have you looked thru the various copper/nickel sandwich threads; or the Kweld threads? They may have useful info on weld times, power, etc. A few are linked below:

"Copper/nickel sandwich" buses for series connections

There is a popular thread called: "Spot Welding Copper Strips to 18650 Battery Cells" Spot Welding Copper Strips to 18650 Battery Cells It is the place where the copper/nickel sandwich method was first reported, and enough interest has been shown that some members have asked that this method...

endless-sphere.com

kWeld - "Next level" DIY battery spot welder

Hi guys, as part of my kicksurfer project (I was tired of my battery pack manufacturer of wanting >700€ each time I am asking him to prepare a few samples of packs from another cell type), I have started desigining a DIY spot welder. After some googling, I realized that even when building it...

endless-sphere.com

Other pages / sites that may have relevant info:

Google Search

www.google.com

 

[Hassan]

I don't have the specifics on correcting the problem, but it sounds like you have to have way too long a weld time, so current is flowing so long that it's causing the cell heating. You may also not have sufficient probe pressure, so there is too high a resistance from probe to surface or from strips to cell, creating excess heat.


Have you looked thru the various copper/nickel sandwich threads; or the Kweld threads? They may have useful info on weld times, power, etc. A few are linked below:

"Copper/nickel sandwich" buses for series connections

There is a popular thread called: "Spot Welding Copper Strips to 18650 Battery Cells" Spot Welding Copper Strips to 18650 Battery Cells It is the place where the copper/nickel sandwich method was first reported, and enough interest has been shown that some members have asked that this method...

endless-sphere.com

kWeld - "Next level" DIY battery spot welder

Hi guys, as part of my kicksurfer project (I was tired of my battery pack manufacturer of wanting >700€ each time I am asking him to prepare a few samples of packs from another cell type), I have started desigining a DIY spot welder. After some googling, I realized that even when building it...

endless-sphere.com

Other pages / sites that may have relevant info:

Google Search

www.google.com

Thankyou for suggestion. Yes i have looked into those threads before posting but i couldn't find anything specific to my problem . If i decrease my weldtime pulse, it doesn't weld properly so after over an hour of trial and error i found 220ms to be the best pulse time. I donot have the budget for Kweld.

 

[amberwolf]

I wasn't suggesting to use the Kweld itself, just to see what weld currents, voltages, and times are used for the specific type of welding you are doing; some info about those has been posted in various kweld threads, and in other copper/nickel sandwich threads.

If your welder can't achieve the necessary current/voltage/time/etc you may need to modify it or replace it with one that can to avoid whatever problems you're having.

There are also alternate ways to make such a sandwich; JonesCG has one in his latest battery-build threads.