The weld times seem excessively long. This probably indicates the current is too low. Your battery sounds like it should work but possibly it's deteriorated or not adequately charged. Or there could be too much resistance in the circuit. With my graphene battery I'm welding .2mm nickel with a 8ms pulse.ChicagoJohn wrote: ↑Dec 23, 2017 6:24 pmHello. I'm new to ES and pretty new to 18650 technology. I'd appreciate any feedback on a project I'm working on. I am trying to spot weld 18650 cells using a 12V car battery (45Ah, 325CCA) as a current source. I have a Nano controlling pulse length and have verified accuracy with my oscilloscope. I'm using 0.1 X 8 mm pure Ni strip. I'm using 3 mm dia copper welding electrodes with rounded tips, 1 mm flats. After several trials, I think a dual pulse of 50 ms / 100 ms separated by 0.5 s works well. I've been putting considerable downward force (~10 lb) on the electrodes. Does any of this raise a red flag?
Until I have something I consider sufficiently reliable, I've been working with a piece of 30 gauge nickel plated steel to simulate an 18650 can. A problem I've had, and the main reason I'm posting, is that occasionally I get a dramatic result in which sparks of molten metal are thrown out six feet in any direction and I have a hole punched in the Ni / substrate. Inspecting the electrodes, I find a piece of Ni/substrate welded to one. Do you think this could be due to uneven force / inadequate force? Are there any tips or techniques that can be used to reduce the risk of this happening on an 18650 cell?
Finally, I am using a wood support under my metal substrate, and I note significant burns on it -- trying to replicate this effect by placing my soldering station tip on the wood for a second requires a tip temperature in the range of 700 - 800°F. Does this sound normal? I'm somewhat concerned about attempting this on an 18650 cell as things stand.
These are Turnigy RC Lipo batteries, mine is a pair of 2.2Ahr in parallel. It is 3s. These don't have CCA rating, but are rated for 130C discharge rate. Not cheap, but very lightweight and small.
Not being very familiar with these, would you share an item number? I didn't find any 130C Graphene in my search. I have a 800CCA SLA but it's getting tired.
Wow.. Amazing 570A. Will definitely look into. 600CCA lead acid ain't cheap either, and the form factor and weight advantage is awesome. I think I can find other uses for this battery too. Roughly how many welds do you do before recharging?fechter wrote: ↑Dec 25, 2017 9:50 pmThese are Turnigy RC Lipo batteries, mine is a pair of 2.2Ahr in parallel. It is 3s. These don't have CCA rating, but are rated for 130C discharge rate. Not cheap, but very lightweight and small.
My electrodes are semi-rounded and have about a 2mm dia contact area.
HALF as much as a lot of lead acid!
Can you do the same for nickel strip?DasDouble wrote: ↑Dec 27, 2017 9:57 amOK guys, so just here relly random the math formula to calculate the maximum amperage for your cable with a given cross-section in mm²:
Cross-Section of given cable (mm²) / 0,812(AWG20) * 11 (optimal °C) or * 16 (acceptable °C) or * 22 (poor/hot °C) => maximum amperage for your given cable.
For example I want to know how many amps I can push trough my AWG 10 cable so it becomes acceptable warm:
AWG 10: mm²: 5,26
-> 5,26 / 0,812 * 16 => 103,64 Amps.
How big is the cross-section of AWG x cable: https://de.wikipedia.org/wiki/American_Wire_Gauge
Source for the "0,812 value of a AWG20 cable": https://endless-sphere.com/forums/viewt ... 14&t=68005
(for questions or answer, please contact me via pm as I don´t look too often into this topic right here).
Shorter thicker leads from the welder and slots in the nickel will help. I have tig welding electrodes in the ends of the copper rod - which I highly recommend over using the copper alone. Clean 'pinpoint' welds and no electrodes sticking to the material.jonescg wrote: ↑Jan 04, 2018 7:50 pmThanks for the tips guys - I normally work on pouch cells so this is all new to me.
I'm only using 0.3 mm nickel because that's what we happened to buy for a different (non battery application).
I'm 100% confident we have pure nickel, it's just too much metal for this spot welder. I'm going to order some 0.2 mm stuff from the USA and try that.