MOSFET for spot welding

Hello, sorry for such a vague question, but I don't really understand mosfet datasheets. Are two IRL40B209 logic level FETs in parallel, capable of handling 400-600 CCA from a battery for a few milli's? (under 50ms)

Also how many of these can I safely run from 1 digital arduino pin?

Many Thanks

What's "CCA" in this context?

Cold Cranking Amps?

If you mean 400 - 600 amps, no chance. Instant magic smoke.

You have to take MOSFET max current ratings with a pinch of salt - they’re typically for a short pulse.
For this device 400uS is specified at a < 2% duty cycle.

Look at the TO220 package - do you really think those puny leads will take many amps for long? Think how fat car starter leads or welding cables are to take a couple of hundred amps.

You need a MUCH bigger device - probably one with nuts and bolts for the connections. 50mS is probably long enough for you to look at continuous dc ratings.

And to make them switch fast ( and hence with low loss) your really need a suitable driver capable of providing >1A peak. Not an arduino pin. And to drive the specified device a much higher gate drive voltage to ensure saturation - suggest > 10V

Allan

ps why do you think car starter motors still use solenoids to switch the current? They’d use big MOSFETs if they could…

Have a look how commercial spot welders work

pylon:
What's "CCA" in this context?

Cold cranking amps. Basically short circuiting a small car battery for 10ms maybe.

Similar things have been doing using arduino and mosfets, but I'm unsure of the exact design.

wkdkris:
Cold cranking amps. Basically short circuiting a small car battery for 10ms maybe.

Similar things have been doing using arduino and mosfets, but I'm unsure of the exact design.

No...cold cranking amps is the ability of a battery to run a starter motor in a vehicle in a cold environment.
This could continue for 20 seconds or more.

I am going to make a spot welder similar to this, however, I need some spare time to do so.

The Arduino could control the starting relay which in turn controls the high current to the area being welded.

Suggest you use this idea for a spot welder.

Short-circuiting even a small car battery could easily give you getting on for 1000 amps.

What's this for ?

Allan

http://www.pittnerovi.com/jiri/hobby/electronics/welder/index.html

bluejets:
No...cold cranking amps is the ability of a battery to run a starter motor in a vehicle in a cold environment.
This could continue for 20 seconds or more.

Thanks, I understand how long a starter can be used for being a mechanic.

I know this is maybe a little out of the ordinary, to want to short a car battery through mosfets, but similar has definitely been done......

The time I'm requesting is extremely short amount of time. Possibly under 10ms. No where near the amount of time needed to crank a car via a solenoid etc. I also doubt a solenoid could deal with switching fast enough.

I shall try and post two YouTube videos of similar projects. Any feedback would be greatly appreciated

allanhurst:
Short-circuiting even a small car battery could easily give you getting on for 1000 amps.

What's this for ?

Allan

Its to weld nickel strip to 18650 battery cells. For an ebike battery :slight_smile:

Larry, I have already watched the video you have posted using the solenoid. However a lot of his welds have burn marks. I was hoping to advance the idea and get slightly better welds.

Like this example

wkdkris:
I know this is maybe a little out of the ordinary, to want to short a car battery through mosfets, but similar has definitely been done......

Last time I saw an attempt at anything LIKE shorting out a car battery, it ended up with bit of the battery scattered for yonks and acid into the bargain. ( yonks == b***** long way)

For €109,00 why not support the guy and get his kit :wink:

wkdkris:
Thanks, I understand how long a starter can be used for being a mechanic.

I know this is maybe a little out of the ordinary, to want to short a car battery through mosfets, but similar has definitely been done......

The time I'm requesting is extremely short amount of time. Possibly under 10ms. No where near the amount of time needed to crank a car via a solenoid etc. I also doubt a solenoid could deal with switching fast enough.

I shall try and post two YouTube videos of similar projects. Any feedback would be greatly appreciated

Its to weld nickel strip to 18650 battery cells. For an ebike battery :slight_smile:

Larry, I have already watched the video you have posted using the solenoid. However a lot of his welds have burn marks. I was hoping to advance the idea and get slightly better welds.

Like this example
DIY Arduino Spot Welder V3 - YouTube

The burn marks are the result of doing the weld in an oxygen rich atmosphere. Try a nitrogen rich atmosphere.

Paul

larryd:
For €109,00 why not support the guy and get his kit :wink:

DIY Arduino Battery Spot Welder Kit V4 Full Bundle Car Battery - Malectrics

Tbh, I could almost ask you the same thing hehehe.

129 euro is a lot for a single time use probably. And why? I'm capable of programming myself. In fact I've already written a code to do what I want. But I need a way of handling the pulse via mosfets like he has. I wanted to avoid the "you can't do this or that, or the battery will explode etc"

So back to my original discussion.

Irfb7430 is a similar FET to the one I suggested IRL40B209 from my understanding? Except I think the 7430 is not logic level? If so, how is 6x 7430 being ran? And how could I run 6x IRL40B209.

Some explanation between the two fets would be greatly appreciated.

I am a fan of using relays in high current situations like this 8) .

The programming would be quite simple.

You don’t need a logic level MOSFET if you drive it (them) with 12v as the author does.
See the schematic as offered.

Placing several MOSFETs in parallel, as he did, gets switching resistance down to less than 1mΩ

I like his idea of a mother of a fuse.

Schematic PDF

MCP1407

I like the kit, do not get me wrong. Wish I had the spare money available to buy it. But for now, I need to live with a little DIY. I have everything needed available to me, including the logic level FETs Ive mentioned.

Would it be possible to run 4x IRL40B209 from 1 arduino digital pin? I do not understand the gate ohm, and how much power a gate requires from the digital pin.

Since you are driving parallel transistors, the load capacitance will be quite high.
Use a proper driver like the one linked or risk letting the smoke out of the transistors.