Absolutely. If the battery is reversed, the FETs will conduct through the body diode so the output will always be on. You'd see a big spark when you touch the electrodes to the cell. This may or may not damage the circuit.18650dude said:
JP spot welder
- Thread starter riba2233
- Start date
atomek1000
100 W
fechter said:
Are you sure? Fets will not conduct if they are not activated by electronics i think.
I'm sure.
The FETs will act like a diode in the reverse direction.
The FETs will act like a diode in the reverse direction.
Depends what polarity, of 12V logic supply no, it has protection diode (if it doesn't work, just reverse the polarity), but don't mix the polarity from the welding battery. Welder goes to the negative pole. If you have any doubts please ask before trying, thanks! 
tomjasz
1 GW
I tried the probes from the Sunkko 709A welder and they work fine. A little easier to use, being more flexible. A bit easier to weld with the small tip, especially in the recycled parallel hold I'm using. But with a simple base jig as JP uses in the video the JP welding pens are very usable. I imagine they will hold up much longer than the Sunkko tips.
Attachments
eleven6
1 W
hey riba2233,
I'm interested in purchasing one of your spot welders. Reading through the thread it looks like there was a waiting list for your first batch. Are you in-between production runs, or can I place an order now?
I'm interested in purchasing one of your spot welders. Reading through the thread it looks like there was a waiting list for your first batch. Are you in-between production runs, or can I place an order now?
eleven6
1 W
10-4, I'll keep checking
ridethelightning
1 MW
- Joined
- Jul 21, 2013
- Messages
- 2,010
make plenty of em riba, once word gets round they will probably fly out the door :wink:
tomjasz
1 GW
I tried the welding pens from my Sunkko 709A. A total disappointment of a welder that went bad in the first uses.
The JP is SO much easier.
I do like the more flexible cables and small tips. I don't know how long their tips will last. They do tend to stick to the weld more often.
I think the tips supplied by JP will last much longer. They are a little large for the jig I have but then it's not that great of a setup. Pretty much useless when making other than rectangles and squares. I intend to make a wooden jig for each size battery I construct. While there has been some criticism of butting the cells closely with glue, I prefer that method for saving space. I learned with recovered cells to rewrap any damaged shrink wrap. It's really easy and cheap to do. My thinking is I'd rather save the space and if I have a repair that damages the shrink wrap, I simply rewrap. In trials with junk batts it works very well and the wraps are cheap. You can even by some fake Samsung sleeves. (asshat suppliers)
Here's the two probes. JP is DEFINITELY higher quality materials. The welding pens on Aliexpress and with the 709A are really pricey and are spring loaded offering no improvement for the additional complexity. As always IMHO.
The JP is SO much easier.
I do like the more flexible cables and small tips. I don't know how long their tips will last. They do tend to stick to the weld more often.
I think the tips supplied by JP will last much longer. They are a little large for the jig I have but then it's not that great of a setup. Pretty much useless when making other than rectangles and squares. I intend to make a wooden jig for each size battery I construct. While there has been some criticism of butting the cells closely with glue, I prefer that method for saving space. I learned with recovered cells to rewrap any damaged shrink wrap. It's really easy and cheap to do. My thinking is I'd rather save the space and if I have a repair that damages the shrink wrap, I simply rewrap. In trials with junk batts it works very well and the wraps are cheap. You can even by some fake Samsung sleeves. (asshat suppliers)
Here's the two probes. JP is DEFINITELY higher quality materials. The welding pens on Aliexpress and with the 709A are really pricey and are spring loaded offering no improvement for the additional complexity. As always IMHO.
Attachments
John in CR
100 TW
Riba2233,
This is probably a noob question, but that's what I am when it comes to battery tab welding. Will this welder work for joining the aluminum tabs of cells like A123amp20's?
This is probably a noob question, but that's what I am when it comes to battery tab welding. Will this welder work for joining the aluminum tabs of cells like A123amp20's?
Unfortunately not, those tabs are too thick, not to mention copper tabs. For proper welding of those cells you need highly specialized welders, and also ultrasonic welder for joining copper to aluminum tabs. It's all described in a123 manual, I think they even recommend welder models
Just made my first 18650 battery pack with Jakov's welder. This is an awesome product. High quality, easy to use and very effective. Making these packs are a lot of fun now with this spot welder. Keep up the development of this product, you are on to something big here.
ebikeaddict
1 mW
The welder arrived in today's mail. It's awesome looking, very well done. Thank you again Jakov for all your efforts on the welder.
What size wire are you using for the welding cables?
I'm thinking about building an analog version using junk I have lying around. For the price, I should just buy one of yours but I like to tinker.
I'd be interested to hear from anyone who has one and an oscilloscope. It would be interesting to put a scope across the battery to see how much it sags during the pulse. It would also be interesting to measure across the welding electrodes during a pulse. There could be a significant voltage spike at turn-off due to inductance in the wires. It may not be a bad idea to put a diode reverse biased across the output cables to catch any spikes. An actual measurement of weld current would be cool also.
I'm thinking about building an analog version using junk I have lying around. For the price, I should just buy one of yours but I like to tinker.
I'd be interested to hear from anyone who has one and an oscilloscope. It would be interesting to put a scope across the battery to see how much it sags during the pulse. It would also be interesting to measure across the welding electrodes during a pulse. There could be a significant voltage spike at turn-off due to inductance in the wires. It may not be a bad idea to put a diode reverse biased across the output cables to catch any spikes. An actual measurement of weld current would be cool also.
fechter said:
Hi, wire is 25 mm2 (around 3 gauge, but 4 gauge or 20 mm2 works, but don't go below).
I already did scope tests, but it was some time ago, I don't remember what each picture represents, some are current over 1 mohm inline shunt, and some are voltage over electrodes. Battery voltage doesn't drop noticeably because it's short pulse.
Yeah, there is negative spike on turn off, but not critical for these mosfets. And that's the reason why you shouldn't use too long wires.
Actually I remember that 4th picture is for current, and it's not 2.22 A, but 2220 A :lol: It's 2.22 V over 1 mohm shunt. It's only second pulse.
Tests are done with prototype welder, but it's the same thing as current one, although it has bit weaker mosfets, but they behave the same.
tomjasz
1 GW
riba2233 said:
Thanks for posting the scope shots. The spike is there for sure, but not too big. I guess having a dead short for a load damps it out pretty fast. 2220A is a pretty respectable current. 370A per FET. This helps with calculations.
