- Joined
- Oct 18, 2017
- Messages
- 12
I'm in the market for ultracaps. Those Skels look good but they come in 10 packs and are weld only. I would need another welder to weld the ultracaps for my welder.
kWeld - "Next level" DIY battery spot welder
- Thread starter tatus1969
- Start date
spinningmagnets
100 TW
If anyone is having difficulty finding a small quantity of copper rod in 1/4-inch__0.25-inch diameter (roughly 6mm), I have purchased several feet, and can sell it by the inch, plus postage.
My local hardware store stocks solid copper wire in 6ga and 4ga as grounding wire for large junction boxes. This 6mm had to be ordered, and is considered 2ga.
My local hardware store stocks solid copper wire in 6ga and 4ga as grounding wire for large junction boxes. This 6mm had to be ordered, and is considered 2ga.
- Joined
- Oct 18, 2017
- Messages
- 12
I don't know if these are new or if I just didn't notice them, but Thunder Power has some 120C stuff right now.
http://www.thunderpowerrc.com/CAR_BATTERIES/Reaper
The specs on these are getting pretty insane now.
Are there any plans for pulse arc capabilities on the kWeld? Of course it would need the proper solenoid tungsten holder. I'm thinking it could be useful for welding ultracaps etc.
http://www.thunderpowerrc.com/CAR_BATTERIES/Reaper
The specs on these are getting pretty insane now.
Are there any plans for pulse arc capabilities on the kWeld? Of course it would need the proper solenoid tungsten holder. I'm thinking it could be useful for welding ultracaps etc.
Pulse arc is interesting. I did some experiments using a non-contact electrode and high voltage starter. I've never tried using a solenoid but it might work.
The "4800mAh 2-Cell/2S 7.4V Reaper 120C LiPo, Shorty" sounds really promising, they state 1152A max burst discharge. But can someone tell them that Deans/EC3/EC5/Traxxas/XT60 connectors are all hopelessly underrated for a battery that is rated for 576A continuous?The Lightning Stalker said:
I have received the first batch of laser-cut housing parts for kWeld. Here is a picture of the first build, they will be available in my shop soon. These are much more affordable than 3D printed housings (unless you have a printer yourself), so I stopped the development of those.
andrew.box
100 W
Wow, nice project. If you end up selling boards or kits please say so here. I bet we could get a number of people who'd reserve a board and parts. Also try the DIY power wall forums, those folks love spot welders.
andrew.box
100 W
Cool, thanks! I'm currently wasting all my money on a Volt module based battery backup portable inverter project, but I may want to pick one of these up eventually. They look like great quality little spot welders and price is reasonable.
okashira
10 kW
I just ordered one for some testing. 
How soon will it ship?
How soon will it ship?
okashira said:I just ordered one for some testing.
How soon will it ship?
Shipping is planned in week 9, but I am not sure if I can keep that because I have trouble with foreign customs at my board assembly service location. I will keep you updated.
Cheers
Frank
spinningmagnets
100 TW
Those electrodes look good!
This is what Kweld looks like with 4AWG cables
I’m very excited to find out what resistance I have after calibration. The length of the cables are the same as per manual with shorter electrodes holders but with this bigger wires I guess I can make them longer.
I’m very excited to find out what resistance I have after calibration. The length of the cables are the same as per manual with shorter electrodes holders but with this bigger wires I guess I can make them longer.
What a monster! :wink:bigbore said:
That'll probably depends most on your battery, I forgot what type you plan to use? The welder itself accounts for 0.33mOhm (switch path) + 0.78mOhm (fuse path) from terminal to terminal (actual measurement data).bigbore said:
EDIT:
Keep in mind that this also adds inductance, and to dial the total round trip length into the unit if you exceed EDIT: 1 meter.bigbore said:
tatus1969 said:
I will be using a 3S5P lipo made with very old zippy lipo 5000mAh 40C cells; this one
Then from calibration il will get Ri+Rc1+Rc2+Rc3+Rc4+Rs. Is it correct?
Also could you tell me the total length of both electrode cables you obtain with your electrode holders? I would like to know the length from electrode tip to the center of the ring cable shoe hole.
That looks like it has very low ESR, together with your thick wires you may exceed the 2kA limit. You'll see during calibration, maybe you need to reduce to 2S. Just guessing, anyway.bigbore said:
No, calibration only measures between the two output terminals of the module, that is Rc3+Rc4. But as Rc1/Rc2 should be extremely low in your case, you can estimate the battery ESR from the current that is displayed, and the other known values.bigbore said:Then from calibration il will get Ri+Rc1+Rc2+Rc3+Rc4+Rs. Is it correct?
EDIT: here is the full picture of what I get with the Turnigy nanotech:
(milliOhms | Where measured)
1.87 Probe system, measured between terminal screws
0.33 Power switch, measured between terminal screws
0.78 Fuse, measured between terminal screws
0.19 Battery plus cable, measured between terminal screw and cable end
0.19 Battery minus cable, measured between terminal screw and cable end
3.34 Complete system, measured between kWeld cable ends
4.89 Battery ESR including leads and XT150 connector
It is 0.4m each for both electrode wires, and 0.1m each for the battery wires. The total is 1.0m, not including the lengths through the module, those of the electrode holders and electrodes, and of the wires on the Lipo itself. I wasn't too accurate here, but there is quite some safety margin.bigbore said:
spinningmagnets
100 TW
The listed 3S 130C 5000-mAh Turnigy Nanotech cells seem to be working fine for several builders. However, some potential customers have concerns about using LiPo, so I am investigating what an alternative power supply might look like.
I am currently thinking a hybrid pack that uses four high-current LiFePO4 cells (Headway 38120?), and a 12V capacitor bank. The impedance on the Headway cells is listed at a very low 4-mOhms, peak burst amps are 150A... If using six 2.7V Maxwell super capacitors, they are listed as 3.3-mOhms. [There are recently many 12V super cap banks being marketed right now as a car starter boost unit, to help a car battery on cold mornings]
Frank has mentioned that lower voltages might be slightly better (smaller inductance spikes?), and it is possible to build a power bank made only from six capacitors (one possible configuration is 3S X 2P for 8V). However, then you must find a power supply to keep the 8V Supercap bank charged. Some very large high-amp car battery chargers have a transformer with two coils on the output that can be configured by a simple switch to provide 12V at "X" amps, or 6V at "2X" amps.
We must find the best balance. Higher amps would cause more heat on the unit, but higher volts would cause more inductance? (I am still learning). If using a 4S Headway pack, the 12V car battery charger as a power supply could easily be found locally. However, adding super caps might make the jolts easier on the LiFePO4 cells.
I am open to any suggestions for a LiPo alternative that would work. The current default is to use one large new car lead-acid battery, or possibly two car batteries in parallel (still at 12V, but twice the amps).
edit, just ordered six Maxwell 350 Farad super caps (D cell size), 2.7V each, 3.2-mOhms...
I am currently thinking a hybrid pack that uses four high-current LiFePO4 cells (Headway 38120?), and a 12V capacitor bank. The impedance on the Headway cells is listed at a very low 4-mOhms, peak burst amps are 150A... If using six 2.7V Maxwell super capacitors, they are listed as 3.3-mOhms. [There are recently many 12V super cap banks being marketed right now as a car starter boost unit, to help a car battery on cold mornings]
Frank has mentioned that lower voltages might be slightly better (smaller inductance spikes?), and it is possible to build a power bank made only from six capacitors (one possible configuration is 3S X 2P for 8V). However, then you must find a power supply to keep the 8V Supercap bank charged. Some very large high-amp car battery chargers have a transformer with two coils on the output that can be configured by a simple switch to provide 12V at "X" amps, or 6V at "2X" amps.
We must find the best balance. Higher amps would cause more heat on the unit, but higher volts would cause more inductance? (I am still learning). If using a 4S Headway pack, the 12V car battery charger as a power supply could easily be found locally. However, adding super caps might make the jolts easier on the LiFePO4 cells.
I am open to any suggestions for a LiPo alternative that would work. The current default is to use one large new car lead-acid battery, or possibly two car batteries in parallel (still at 12V, but twice the amps).
edit, just ordered six Maxwell 350 Farad super caps (D cell size), 2.7V each, 3.2-mOhms...
I tested a 10Ahr, 6s Lithium Titanate pack but it was pretty weak.
The 20Ahr A123 prismatic cells might be something to try.
The 20Ahr A123 prismatic cells might be something to try.
tomjasz
1 GW
bigbore said:
While 12v LA batts are bulky, but I can pick them up for the core charge from battery sellers. When done return for money back. Married to a battery charger tender they last through a lot of welding, cheap.
It's not about the inductive kickback, that only depends on flowing current and conductor inductance (inductance is a pure geometrical/material relation). The reasons why I try to keep the battery (or ultracapacitor) voltage as low as possible are this:spinningmagnets said:
- to get higher voltage, you need add more cells in series, and this also causes their internal resistances to add up. But we ideally want to have a power source with "zero" resistance.
- the welder plus a typical weld spot have a combined resistance in the order of 5 milliOhms. If we want 1000A welding current, this means an ideal power source (no internal resistance) needs to have V = R*I = 0.005Ohms * 1000A = 5V. If that ideal battery would have 10V instead, then we would get too much current, 2000A. We don't want that much current, so in order to get back to the 1000A, we need to add another 5 milliOhm resistance. Like, I = V/R = 10V / (0.005Ohm + 0.005Ohm) = 1000A. But this resistance does not help us, it just dissipates unnecessary heat. Therefore, the rule: as little internal battery resistance as possible, and as little voltage as possible. It's in fact an optimization task.
spinningmagnets
100 TW
It's starting to look like the 12V car starter lead-acid battery truly is the best option for someone who does not want to use LiPo.
The 12V style is everywhere, but I recall there are 6V lead-acid starter batteries for older cars and golf carts (perhaps rare, and hard to find though...)
The 12V style is everywhere, but I recall there are 6V lead-acid starter batteries for older cars and golf carts (perhaps rare, and hard to find though...)
tomjasz
1 GW
spinningmagnets said:
Big and heavy, but with a battery tender they re an effective and very inexpensive alternative. I've found a couple of battery resellers. Crown Auto and such, that take batteries in and payout a core charge. I can buy a 12V LA for under $20. T9opping off with distilled water and sometime a bit of battery acid can make for a power source for hundreds of welds. And when they drop off, you can take back and either get the refund or another battery. Not all shops will do that but making good relationships. maybe offering your battery welding skills, can make for an effective barter. I've got a deep cycle marine sealed (troller) battery. It just rocks on and on 640CCA
