tomjasz
1 GW
How about a half dozen layouts showing best practice and strip usage? 10s 12s 15s and 15s. Rather than w3 point out whats wrong we show whars best.
ChicagoJohn said:Hello. 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.
ChicagoJohn said:Could you tell me the CCA rating of your graphene battery and what the shape of your electrode tips is?
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.fechter said:These are Turnigy RC Lipo batteries, mine is a pair of 2.2Ahr in parallel. It is 3s
fechter said:ChicagoJohn said:Could you tell me the CCA rating of your graphene battery and what the shape of your electrode tips is?
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.
My electrodes are semi-rounded and have about a 2mm dia contact area.
ChicagoJohn said:I found a graphene 3S 5000 mAh Turnigy RC Lipo for ~$58 incl shipping (hobbyking) that should do the trick. It is rated for 65C continuous and 130C burst. Not cheap, but a heck of a lot less 600 CCA lead-acid. s.
Can you do the same for nickel strip?DasDouble said:OK 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/viewtopic.php?f=14&t=68005
(for questions or answer, please contact me via pm as I don´t look too often into this topic right here).
Cheers, Elias
jonescg said:Thanks 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.
Cheers,
Chris
I thought I'd follow up on my status with respect to fechter's method. My 3S graphene Turnigy 5000 mAh battery arrived and in preparation for a trial with my delivery system (based upon a small engine starter relay) I wanted to get an estimate of where my current would be at relative to the manufacturer's stated "burst" rating of 130C = 650A for a 5Ah pack. At 11.39VDC charge, I connected the pack to my delivery system using the XT90 connector supplied such that all connections and cabling remain the same as in the welding scenario, including the use if nickle strip as the electrode contact surface to the load. For a load I used a 3.2 Ohm 25 watt resistor.fechter said:ChicagoJohn said:Could you tell me the CCA rating of your graphene battery and what the shape of your electrode tips is?
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.
Img_0571.jpg
My electrodes are semi-rounded and have about a 2mm dia contact area.