BIFRC Spot Welder Uprated Voltage.

[Sunder]

Hi All,

Right before Covid, I bought a spot welder identical to this:

https://www.reddit.com/r/18650masterrace/comments/evvs44/bifrc_spot_welder_from_aliexpressebay/

But as I was bogged down with work, and working from home under covid lockdown, I never had a chance to assemble it or use it. I'm finally getting around to it, and noticed that the voltage operating was listed as 7 to 12.6v. I was planning on using a 6S LTO battery (10.8 to 16.2v), because when someone says 12V, there's usually a fairly generous leeway of what 12V means, given that cars can get up to 14.8v with the generator on.

I've looked at the parts, and the only voltage sensitive devices I could think of were the Mosfets and the Capacitors. The mosfet is a 4NO4R7, which I searched to be rated as 40v, and the supplied big green capacitor (which wasn't soldered on), is 25v @ 2200uF. I've got a spare 50v 4700uF I was going to use instead, as it appears the capacitor is only used as a "buffer" (It solders directly on to the input terminals.)

Is there anything I've missed checking before I power this thing up? Is it likely that any of the other components on the board are voltage sensitive?

Thanks.

 

[amberwolf]

Does it have an SMPS or other type of low voltage power supply inside? Something that runs off the input voltage and regulates things for any MCU or other control electronics inside? If so, that will have a designed input voltage range, and it is possible it wont' operate correctly (or at all) if outside the range, depending on what kind of safeties they've built in (if any).

Other than that, any non-passive components (and passive ones like elecrolytic or tantalum capacitors) will have voltage limits, so you could verify that all of those are well able to tolerate whatever you're going to use (or that they are not on that voltage circuit).

If there is an HVC in the control electronics, it may also refuse to operate above whatever that point is, even though it might function if it didn't disable itself.


is also possible some of ti's parts have *power* limits, where if you go higher than teh specified voltage limit, the total power then allowed thru some parts may be more than they have ability to dissipate heat from, and you could get smoke from that.

FWIW, its' pretty strange to me to release a spot welder (that poeple commonly run off car batteries and the like) that can't handle at least 14v+ on it's input....to only handle 12.6v is positively strange...no commonly-used battery (for DIY spotwelders) is going to be at/just under the 12.6v, though one (or more) cell(s) less could be well under that. Just not what's typically used. :?

 

[Sunder]

Thanks Amberwolf. I'm wondering if 12.6v was used because it's 3S x 4.2v (Fully charged LiPo). and 7.0v, because it's 2S x 3.5v (flat LiPo)

There's no SMPS circuitry there that I can see. However, there is some kind of microcontroller that detects a short (so it can start the weld without a trigger button), and controls the welding time.

I'm going to try it. Worst case, it was only $40.

 

[LewTwo]

Any update on this ...
I was thinking of using 4S LiFeP04 (A123) cells = 10 to 14.5 Volts

Edit: I note in this video the individual states 16.8 volts is the max
https://youtu.be/ETc9J3A2_zA

 

[Bicyclops]

I just bought the BIFRC welder for $20-21 with probes here:
https://www.aliexpress.com/item/4000381745277.html

I chose the BIFRC after watching endless review videos. The only other one that was a close second choice was a $50 on with a lipo built into it but I wanted the cheaper one and I don't like the short lifespan on lipos, and having to store them near 50% SOC to get the full 2-3 year lifespan.

I chose the BIFRC because:
- cheap
- can weld up to 0.2mm nickel strip thickness (add extra wires to the probes to carry enough current for 0.2mm strips)
- can use my marine 12V lead acid battery which I already own for use as a house power backup, connected to a cheap Cyberpower pure sine UPS with it's little 12v included battery removed and swapped for the marine battery.
- only requires small effort (adding second 12v power supply and heat sinks) to modify it for longevity https://www.youtube.com/watch?v=VggXUXeHtLI