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Author Topic: 18650 Cells  (Read 6113 times)

Offline Howard Rush

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18650 Cells
« on: November 11, 2022, 02:13:20 PM »
I see Molicel P28B 2800 mAhr 40-Amp Li ion cells for sale.  Are these the ones to use now?
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Online Brent Williams

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Re: 18650 Cells
« Reply #1 on: November 11, 2022, 04:42:47 PM »
The Molicel P26A 2600mah is the cell that has been used the past few years.  The P26A has been superseded by the newer Molicel P28A 2800mah.  These are both rated for a 35amp continuous discharge rate.

The Molicel P28B 2800mah is a really great choice as well.  The P28B is rated a bit higher, at 40amps continuous discharge and has lower resistance overall. 

The P28B does seem harder to obtain and more expensive than the P28A.  Do you have a good source for the P28B? 

From the data online, NASA seems to be quite fond of the P28B battery.

« Last Edit: November 12, 2022, 01:07:29 PM by Brent Williams »
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Online Crist Rigotti

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Re: 18650 Cells
« Reply #2 on: November 11, 2022, 08:47:18 PM »
I see Molicel P28B 2800 mAhr 40-Amp Li ion cells for sale.  Are these the ones to use now?

Where are they on sale?
Crist
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Offline Howard Rush

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Re: 18650 Cells
« Reply #3 on: November 12, 2022, 04:27:31 PM »
Looking at the fine print on Web pages, I see that the P28B isn't available retail yet.  Fred sent me this: https://budgetlightforum.com/node/83309 .
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Online Crist Rigotti

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Re: 18650 Cells
« Reply #4 on: November 12, 2022, 05:40:49 PM »
Looking at the fine print on Web pages, I see that the P28B isn't available retail yet.  Fred sent me this: https://budgetlightforum.com/node/83309 .

Thanks Howard
Crist
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Online Brent Williams

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Re: 18650 Cells
« Reply #5 on: November 12, 2022, 05:42:44 PM »
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Re: 18650 Cells
« Reply #6 on: November 13, 2022, 12:43:48 PM »
Howard,
The Epoch p28b grade A cells are available:  https://www.18650batterystore.com/products/epoch-18650-2800mah-40a-battery-p28b
I ordered some last week and are supposed to arrive on Tuesday. 

Rick

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Re: 18650 Cells
« Reply #7 on: November 13, 2022, 02:13:21 PM »
Howard,
The Epoch p28b grade A cells are available:  https://www.18650batterystore.com/products/epoch-18650-2800mah-40a-battery-p28b
I ordered some last week and are supposed to arrive on Tuesday. 

Rick

Are the Epoch a re-wrapped Molicel?
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Offline Fred Underwood

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Re: 18650 Cells
« Reply #8 on: November 13, 2022, 03:00:30 PM »
If this is correct, Epoch is rewrapped Molicell

https://budgetlightforum.com/node/83309

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Re: 18650 Cells
« Reply #9 on: November 16, 2022, 09:51:02 AM »
I received the Epoch P28b cells today.  The weight of 6 cells is 0.2 oz more than the weight of 6 P28a cells, so if you're a weight weenie, you might want to stay with the P28a cells.  Also, the P28a cells are almost half the cost of a P28b. 

Rick

Online Brent Williams

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Re: 18650 Cells
« Reply #10 on: November 16, 2022, 10:36:58 AM »
I received the Epoch P28b cells today.  The weight of 6 cells is 0.2 oz more than the weight of 6 P28a cells, so if you're a weight weenie, you might want to stay with the P28a cells.  Also, the P28a cells are almost half the cost of a P28b. 

Rick

Good data, Rick.  I'm not sure if the added cost of the P28B is worth it for me.  With my current P28A packs, I am landing at 3.6v per cell which means I'm not really taking the battery that deep.  That's basically nominal voltage for the Li-ion cells.  My batteries are warm after the flight, but not what i would consider hot.
63.5oz plane, 12x6 wood 2-blade prop, Badass 3515/580kv.
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Offline AMV

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Re: 18650 Cells
« Reply #11 on: November 16, 2022, 12:58:45 PM »
63.5oz plane, 12x6 wood 2-blade prop, Badass 3515/580kv.

Say again, please? There's no such motor.

 H^^
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Online Brent Williams

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Re: 18650 Cells
« Reply #12 on: November 16, 2022, 02:05:24 PM »
Say again, please? There's no such motor.

 H^^
-Andrey

The Badass 3515/580kv was originally an unadvertised special run that wasn't shown on the website. 
- They are now available for order on the website.
https://innov8tivedesigns.com/badass-3515-580kv-brushless-motor.html
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Online Ken Culbertson

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Re: 18650 Cells
« Reply #13 on: November 16, 2022, 02:16:17 PM »
The Badass 3515/580kv was a special run wasn't advertised on the website.  They will be available for order on the website in the future, I believe.
Brent, what advantage do you get from the 580 vs the std 710?  I get headroom of 32% on a TP 5s 2800 battery with my BA 710's pulling a 65oz plane with plenty of power.  More than I can use.  How much extra battery with the 580 and is the power that much better?

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Online Brent Williams

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Re: 18650 Cells
« Reply #14 on: November 16, 2022, 02:56:57 PM »
Brent, what advantage do you get from the 580 vs the std 710?  I get headroom of 32% on a TP 5s 2800 battery with my BA 710's pulling a 65oz plane with plenty of power.  More than I can use.  How much extra battery with the 580 and is the power that much better?

Ken

The 580kv motor on 6s operates in a very similar manner as the 710kv motor on 5s.  The prop that you would use for the 710kv/5S setup would work for the 580kv/6S setup about the same.  The flatter pitch, 3-blade props that are being used with the active timers are generally being run at a higher RPM range than the Badass wood 12x6 2-blade that I am running at 9624rpm.
710kv x 18.5v = 13135 x .75 = 9851rpm
580kv x 22.2v = 12876 x .75 = 9657rpm
710kv x 22.2v = 15762 x .75 = 11821rpm

75% of peak was used in this example as a general starting number of where to operate a given motor kv/battery voltage combo for good ESC governing headroom.  Select prop for the rpm range that works for your own timer run characteristic preference and the motor KV/battery cell count.
« Last Edit: November 16, 2022, 03:48:40 PM by Brent Williams »
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Online Crist Rigotti

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Re: 18650 Cells
« Reply #15 on: November 16, 2022, 04:22:33 PM »
The Badass 3515/580kv was a special run wasn't advertised on the website.  They will be available for order on the website in the future, I believe.

I just got an email saying there are in stock!
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Online Brent Williams

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Re: 18650 Cells
« Reply #16 on: November 16, 2022, 08:47:42 PM »
Brent, what advantage do you get from the 580 vs the std 710?  I get headroom of 32% on a TP 5s 2800 battery with my BA 710's pulling a 65oz plane with plenty of power.  More than I can use.  How much extra battery with the 580 and is the power that much better?

Ken

Here is a little info on the topic of advantages and challenges of the Li-ion 6S 2600/2800 versus the Thunder Power 5s LiPo 2800 battery.  This is info from my reading on the topic and pestering of battery makers like Dane, and inquiring with the vanguard of guys using these in stunt, ie Paul Walker, Chris Cox, Joe Daly, ect 

Advantages:
  - 6S punch
  -  Weight is about the same +/- 10g or so
  -   You get, potentially, a thousand charge cycles per pack.
  -    You can discharge much deeper without damage.
  -     Discharge curve is flatter and longer than Lipo.
  -     Somewhat lower chance of burning your house down vs LiPo.

Li-ion Disadvantages:
 - Packs harder to source
 -  DIY may be required.
 -   Limited to fewer mAh options.  2600,2800 in 18650 Molicell or 4200,4500 in 21700.
 -    Li-ion runs a bit warm, so adequate cooling must be part of the design.
 -     Li-ion has higher internal resistance, which may or may not matter all that much.
 -      Li-ion is not for ultra high amp draw use like FPV racing.  Control line stunt really doesn't tax these very much, especially at 6S.
 -       Li-ion charges at a slower rate than LiPo. 1C charge rate (-ish)
« Last Edit: November 16, 2022, 10:36:54 PM by Brent Williams »
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Offline AMV

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Re: 18650 Cells
« Reply #17 on: November 17, 2022, 06:29:09 AM »
I just got an email saying there are in stock!

What a coincidence, me too ;D
Spice is the variety of life.

Offline Dennis Pedersen

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Re: 18650 Cells
« Reply #18 on: November 18, 2022, 06:46:44 PM »
  Can you fellows please tell me what you are using for nickel strap size and are you spot welding. Basically would like to know how you are assembling your 18650 packs.
      Thanks  ;D
Dennis Pedersen
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Online Brent Williams

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Re: 18650 Cells
« Reply #19 on: November 18, 2022, 07:40:49 PM »
  Can you fellows please tell me what you are using for nickel strap size and are you spot welding. Basically would like to know how you are assembling your 18650 packs.
      Thanks  ;D

.15 mm nickel is good.
.2mm is really good, but you need a sufficiently powerful spot welder for the thicker material.

Here's a link to building a 6s pack.  This shows how the packs are assembled.  That said, the battery pack would be better, safer and last longer if it used fish paper on the ends of the cells and in between the cells. Be safe.  It is only a few cents to implement some safety measures.
- http://everythingfpv.com/how-to-make-a-6s-4000mah-li-ion-battery-pack/
 
Dane Martin discusses important building practices and gives some great safety and longevity tips in assembling Li-Ion packs in these 3 videos:





« Last Edit: November 18, 2022, 08:15:29 PM by Brent Williams »
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Offline Dennis Pedersen

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Re: 18650 Cells
« Reply #20 on: November 18, 2022, 10:04:16 PM »
  Thanks Brent. The big ones where what size of nickel straps and what where people using for spot welders. The videos and your info pretty much answered it all.
    Thanks and Take care
Dennis Pedersen
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Online Brent Williams

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Re: 18650 Cells
« Reply #21 on: November 18, 2022, 10:40:04 PM »
  Thanks Brent. The big ones where what size of nickel straps and what where people using for spot welders. The videos and your info pretty much answered it all.
    Thanks and Take care

.15mm x 8mm Pure Nickel strip is what I sourced for my packs. 
Thicker and wider material is probably better.  I would use as wide of material as you can fit, and as thick as your spot welder can handle.

I recently bought a complete K-weld setup which I will use for spot welding.  They are a couple hundred bucks.  (...its a hobby...right?...)
(I previously picked up a Sunkko 737DH spot welder unit, but never used it due to a part number selection snafu. Wrong voltage for USA. A pricey error on my part...)
If you are handy, you can DIY a very powerful spot welder from online tutorials using repurposed microwave oven transformers.
« Last Edit: February 26, 2023, 07:56:56 PM by Brent Williams »
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Re: 18650 Cells
« Reply #22 on: November 20, 2022, 09:05:55 AM »
I built up a 6 cell pack with the new P28B cells.  The all up weight is 10.55 oz, which is a little more than the P28A cells.  Part of my routine is to charge up the battery and then discharge it on the bench.  I discharge the battery to 3.0 volts/cell (under load) which takes 5 1/2 minutes.  The P28A cell batteries are qualitively hot after discharge (the first time, then not as hot on subsequent cycles).  The P28B cell battery was no where near as hot after it's first cycle. 

I've been using .2mm x 8mm pure nickel strip and a Sunkko welder.  I've been using 3-4 welds (6-8 weld points) to attach the strip to the battery.  Does anyone have insight as how many welds are desired?

Rick

Online Brent Williams

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Re: 18650 Cells
« Reply #23 on: November 20, 2022, 02:34:41 PM »

I've been using .2mm x 8mm pure nickel strip and a Sunkko welder.  I've been using 3-4 welds (6-8 weld points) to attach the strip to the battery.  Does anyone have insight as how many welds are desired?

Rick

From what I have read and observed, your practice of 6-8 weld points is an adequate number of spot welds per strip. 

Which model of Sunkko are you using?  I have read that .2mm nickel can be at the upper end of what is possible for some types of spot welders. 
Glad to hear that your Sunkko is up to the task.
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Offline Dennis Pedersen

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Re: 18650 Cells
« Reply #25 on: November 20, 2022, 03:59:41 PM »
I haven't yet assembled any packs, but found an interesting reference explaining make up of18650 cells.  It helps to understand why spot welding is preferred to soldering.  Soldering is still used to attach the wire battery leads.


Here's what you should know about internals of 18650 cells | ELECTRICBIKE.COM

https://www.electricbike.com/inside-18650-cell/#:~:text=The%20positive%20and%20negative%20electrodes%20of%20an%2018650,conductive%20metal%20shell%2C%20which%20forms%20the%20negative%20electrode
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Re: 18650 Cells
« Reply #26 on: November 20, 2022, 04:36:30 PM »
Brent,
I'm using a Sunkko 709A spot welder.  I set the power dial to "full" and use 6 pulses, which makes a strong weld with the 0.2mm Ni. 
Rick

Offline Dennis Pedersen

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Re: 18650 Cells
« Reply #27 on: November 24, 2022, 06:01:56 PM »
   Well as the old saying go (time will tell) if I made the right choice. I found several reviews about spot welders and they kept talking up the kWeld unit. I then found we have a dealer in Canada which really added more value to the unit for myself. I have one on the way now so I guess I shall see how we get along  n~ . Now to find somewhere that has the .2x8mm nickel strips in stock!     https://cellsaviors.com/blog/best-spot-welders
https://gridrewired.com/products/kweld-spot-welder-kit
Dennis Pedersen
Alberta Canada

Offline Dennis Pedersen

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Re: 18650 Cells
« Reply #28 on: December 02, 2022, 10:30:05 PM »
   I received my P28A cells along with some 21700 cells,  fish paper and terminal insulators from 18650 Battery Store. My K Weld unit also arrived from Grid Rewired. I did some test welds on some old 18650 cells and got things working well. I just finished up a 4 cell pack and doubled up the .15x8mm nickel straps, welding the first on then the second overtop, it worked well. The photo with 2 straps on is the first ones and the photo with just one strap actually has the second one welded on top. Just wondering are people running double or tripled up straps or just singles?  Thanks  :)
« Last Edit: December 08, 2022, 08:32:03 PM by Dennis Pedersen »
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Offline AMV

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Re: 18650 Cells
« Reply #29 on: December 08, 2022, 11:55:48 AM »
Dane Martin discusses important building practices and gives some great safety and longevity tips in assembling Li-Ion packs in these 3 videos...

He makes it look soooo easy.  Makes me want to try it myself  #^ #^ #^

Cheers H^^
-Andrey
Spice is the variety of life.

Offline Matt Brown

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Re: 18650 Cells
« Reply #30 on: December 18, 2022, 12:38:51 PM »
I just found this thread. I知 looking at a new Pathfinder profile electric. Was curious about maybe going to LiIon. I was originally thinking a 4S Lipo. Would I be smart to think 5S LiIon or would 4S still be decent? I was thinking Cobra 2826/10 930KV motor and I will be using a Fiorotti timer as I love it on my SV11. I have this same motor on my Twister but it is overkill but I needed the nose weight. I知 pretty sure a 4S 2700 Lipo would be sufficient but not sure if these 2800 LiIons would be enough on 4S. I知 thinking I壇 have to use a lower KV motor if I went up to 5S LiIons.
Any flaws you see in my thinking? Recommendations?

Thanks, Matt

Offline AMV

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Re: 18650 Cells
« Reply #31 on: December 20, 2022, 09:03:29 AM »
I just found this thread. I知 looking at a new Pathfinder profile electric. Was curious about maybe going to LiIon. I was originally thinking a 4S Lipo. Would I be smart to think 5S LiIon or would 4S still be decent? I was thinking Cobra 2826/10 930KV motor and I will be using a Fiorotti timer as I love it on my SV11. I have this same motor on my Twister but it is overkill but I needed the nose weight. I知 pretty sure a 4S 2700 Lipo would be sufficient but not sure if these 2800 LiIons would be enough on 4S. I知 thinking I壇 have to use a lower KV motor if I went up to 5S LiIons.
Any flaws you see in my thinking? Recommendations?

Thanks, Matt

Hi Matt,

Assuming the Pathfinder's weight will be around 63 oz (correct me if I'm wrong, I'm just estimating based on 14oz per sq-ft on 640 sq in), you will want around 590 Watts of power (using 150 W per lb for a stunter).  I'm also assuming 320 seconds of "motor-on" time (05:20) and figuring that you'll want about 20% of full charge remaining when you land, to be safe.

With a 4S, your choices of motor and prop are something like these:


Here you can see that the motor you're considering will give you decent performance with a 11x5.5 prop, and a 4S 2700 LiPo will give you more than enough flight time.  The same should apply to a LiIon as the voltages under load are very similar between the chemistries.  However, consider that in this 4S scenario you could instead get the much lighter BA-2814-980, save yourself almost 2 oz of weight, consume a little more juice, yet stay within the same speed and RPM neighborhood.  Not to mention that a 4S LiIon will weigh less than a 4S LiPo for the same capacity.

With a 5S, your choices are these:


Here, the possibilities are even more interesting.  The extra S in your pack will make it heavier, but using LiIon will offset that in your favor.  The more interesting thing here is the choice of motor.  You could go with one of the motors labeled 2 through 4 on the list there, which are lighter by about an ounce vs. your considered one, stay within your desired flight envelope, AND consume far less power, in the 2000-2300 mAh range.  I think that combo is a nice win-win, all things considered.

Inspiration for my musings:


Cheers H^^
-Andrey
« Last Edit: December 20, 2022, 10:24:06 AM by AMV »
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Online Ken Culbertson

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Re: 18650 Cells
« Reply #32 on: December 20, 2022, 09:25:21 AM »
I just found this thread. I知 looking at a new Pathfinder profile electric. Was curious about maybe going to LiIon. I was originally thinking a 4S Lipo. Would I be smart to think 5S LiIon or would 4S still be decent? I was thinking Cobra 2826/10 930KV motor and I will be using a Fiorotti timer as I love it on my SV11. I have this same motor on my Twister but it is overkill but I needed the nose weight. I知 pretty sure a 4S 2700 Lipo would be sufficient but not sure if these 2800 LiIons would be enough on 4S. I知 thinking I壇 have to use a lower KV motor if I went up to 5S LiIons.
Any flaws you see in my thinking? Recommendations?

Thanks, Matt
Matt:  You might want to PM Crist Rigotti about his setup and recommendations.  His Pathfinder is an exceptional performer (I have flown it) and electric.  I will not quote his configuration since I might get it wrong, and he may have changed it since switching to the Fiorotti timer but I do know that he is using Li-ion batteries.

Ken
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Offline Matt Brown

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Re: 18650 Cells
« Reply #33 on: December 20, 2022, 10:10:26 AM »
Some great info AMV. Several good possibilities. I usually decide on motor and battery sizes after the plane is built to get balance right. Not much sense in going for the light motor and battery setup then having to add a chunk of dead weight to get the CG right.

Ken, I値l check the setups thread. I think I saw Crist痴 Pathfinder listed in there. If not, I値l message him.

Thank you!
Matt

Offline AMV

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Re: 18650 Cells
« Reply #34 on: February 23, 2023, 02:20:05 PM »
   I received my P28A cells along with some 21700 cells,  fish paper and terminal insulators from 18650 Battery Store. My K Weld unit also arrived from Grid Rewired. I did some test welds on some old 18650 cells and got things working well. I just finished up a 4 cell pack and doubled up the .15x8mm nickel straps, welding the first on then the second overtop, it worked well. The photo with 2 straps on is the first ones and the photo with just one strap actually has the second one welded on top. Just wondering are people running double or tripled up straps or just singles?  Thanks  :)

Hi Dennis,
I have the kWeld too.  I'm working with 0.2mm nickel, dialing in the energy on some practice cells.  Is 32 Joules about right?  Do you recall how much weld current you've been getting out of that 45C power supply at that energy setting?

-Andrey
Spice is the variety of life.

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Re: 18650 Cells
« Reply #35 on: February 23, 2023, 02:45:54 PM »
This big pack was done (not by me) with a K-Weld using a sandwich of .15mm copper and .1mm nickel plated steel.
K-Weld settings - 84 Joules powered with a 3S 6000mah 75c Lipo pack.
The .1mm nickel plated steel is used for resistance to aid in penetration of the spot weld.
Laser-cut, "Ted Fancher Precision-Pro" Hard Point Handle Kits are available again.  PM for info.
https://stunthanger.com/smf/brent-williams'-fancher-handles-and-cl-parts/ted-fancher's-precision-pro-handle-kit-by-brent-williams-information/

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Re: 18650 Cells
« Reply #36 on: February 24, 2023, 08:52:21 AM »
Brent, that's neat.  Thanks for the info.

 H^^
-Andrey
Spice is the variety of life.


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