18650 spot welding -how to- ULTIMATE REPOSITORY

Batteries, Chargers, and Battery Management Systems.
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Offroader   10 MW

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Post by Offroader » May 30 2016 11:32pm

agreed, you can pulse them at 20A for 5 seconds, but anything long will raise the battery temp very quickly.

I find my 10 amp rated cells increase in temp very quickly if I push them at 7 amps on the street for more than 20 seconds. However, if I pulse them with off-road riding for lots of short bursts, they don't get nearly as hot.

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Post by Ballistrophobia » May 30 2016 11:56pm

Thanks for the replies. I'm wanting to power a single brushless outrunner motor, it's rated for up to 80A max, but I don't expect it to pull much more than 20A or so under normal conditions ('it's very flat where I live). Even if I got 10A out of each 25r cell, I think I'll be ok with 4p.

With this new information, would you guys suggest just using nickel? Or a nickel and copper combo?

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Post by Tats » May 31 2016 12:00am

This question relates to the layout/design of a pack to minimise materials, ease of repair if required and safety. I see a lot of packs with every cell pretty much connected to every other cell in the parallel configuration and I'm wondering on the value of this vs just running the cell series connections within the pack and having external bus-bars to take the majority of the current and therefore make the parallel connections external to the pack.

e.g. Using basic Ohms law If I want say 25A current draw from the 10P battery - the bus-bars need to carry the total 25A current but each of the 10 series group of cells only draw 2.5A each. So I make 10-14s connections with nickel/whatever and on the final cell I solder or fuse this set of series cells to a busbar that can be insulated from the rest of the pack. Therefore I know that on any single piece of nickel within the pack it only has 2.5A on it. If I want to test the pack then I can isolate/check at the bus-bar each series connection easily. If I want to add additional capacity its just another 2 connections onto the bus-bar for each additional series group. To ensure a good connection to the bus-bar I drill a few holes in it and route the main leads through these and solder getting good stress-relieved connections across a large area.

Am I missing something with this approach? Note: my high school physics is very rusty....

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Post by oatnet » May 31 2016 1:39am

Tats wrote:Am I missing something with this approach? Note: my high school physics is very rusty....
Research parallel before series vs series before parallel, there have been many discussions here.

In series before parallel, you will need a separate BMS for each series string. Even with a BMS alert, problems happen when you lose a single cell; all of the high v strings dump current into the low serial string trying to bring it up to their voltage. This can result in very high-amp transfers that exceed the capacity of your bus bar, at full pack voltage. Depending what the charge status is of the pack, this can drain the high strings below a safe LVC, or overcharge the cells in the low string at too high a c-rate or beyond safe HVC, or simply charge up a dead cell which is usually a bad idea.

Conventional wisdom here is to parallel before series - in the worst case one of the parallel strings drops voltage, and triggers the BMS, or kills the whole parallel row - but this failure happens at cell voltage, not pack voltage. A parallel row will drain itself propping up a failed cell, but cannot over volt the cell like a series-imbalance would.

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Post by Ozzzz » May 31 2016 9:39am

Great thread, thanks. Nicely explained and good follow up comments!
I don't expect many AU cell buyers from that link?
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Post by Ballistrophobia » May 31 2016 8:12pm

Looking for different Nickel and Copper options online and came across this: http://www.ebay.com/itm/221895723691?_t ... EBIDX%3AIT

Would this be a good option? It's 0.1x200x1000mm, which I could easily cut down into 100- 0.1x10mm strips for spot welding. Thoughts?

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Post by parabellum » May 31 2016 8:59pm

Ballistrophobia wrote:Looking for different Nickel and Copper options online and came across this: http://www.ebay.com/itm/221895723691?_t ... EBIDX%3AIT

Would this be a good option? It's 0.1x200x1000mm, which I could easily cut down into 100- 0.1x10mm strips for spot welding. Thoughts?
If you know what you are getting. Reading description it is 99...% Copper, Aluminum paper and Copper Foil Shielding Tape with Double-sided conductive adhesive all at same time. Hilarious! :D

P.S. 0.1mm is nice gauge, it is easy to cut with Manual Guillotine Paper Cutter, any thicker and it gets difficult. Also note, copper oxidises and it can be randomly triggered, moisture, contamination, galvanic reaction.

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Post by ridethelightning » Jun 01 2016 3:01am

Ballistrophobia wrote:Looking for different Nickel and Copper options online and came across this: http://www.ebay.com/itm/221895723691?_t ... EBIDX%3AIT

Would this be a good option? It's 0.1x200x1000mm, which I could easily cut down into 100- 0.1x10mm strips for spot welding. Thoughts?
thats the exact stuff i used, well actually it was this one-
http://www.ebay.com.au/itm/141516612693 ... EBIDX%3AIT
its not sticky and looks like pretty pure copper to me.

after spotwelding my pack, i clean any grease etc off with isopropyl alcohol and seal the whole pack up in adhesive foam, then heatshrink to stop any moisture getting in.

so far so good. id say the corrosion would only be an issue if salt or water got in there, or perhaps ZnCl solder flux residue.

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Post by Tats » Jun 01 2016 5:52am

Thanks oatnet for the clear simple explanation-nice one

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Post by oatnet » Jun 01 2016 6:42am

Tats wrote:Thanks oatnet for the clear simple explanation-nice one
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Post by Wakkabu » Jun 15 2016 7:01am

parabellum wrote:
Ballistrophobia wrote:Looking for different Nickel and Copper options online and came across this: http://www.ebay.com/itm/221895723691?_t ... EBIDX%3AIT

Would this be a good option? It's 0.1x200x1000mm, which I could easily cut down into 100- 0.1x10mm strips for spot welding. Thoughts?
If you know what you are getting. Reading description it is 99...% Copper, Aluminum paper and Copper Foil Shielding Tape with Double-sided conductive adhesive all at same time. Hilarious! :D

P.S. 0.1mm is nice gauge, it is easy to cut with Manual Guillotine Paper Cutter, any thicker and it gets difficult. Also note, copper oxidises and it can be randomly triggered, moisture, contamination, galvanic reaction.

That last bit is why I never considered copper plate in my battery pack. Bike battery sees a lot of high humidity levels. Especially when biking in rain. Oxidation is going to happen.
There are some pictures on here of packs made with copper sheets and all of them show the tell tale green spots.

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Post by bigbore » Jun 29 2016 2:43pm

Anybody already bought this nickel strip 0.2mm x 10mm?
http://it.aliexpress.com/item/20m-0-2-1 ... Title=true

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Post by irq » Jul 02 2016 5:14pm

if one really feels to be forced using copper, i whould clean it like your mum whould clean your room/flat/house until it really shines. after that, give it a nice shower of plastic spray. this will prevent any further oxidation and all the other nice things copper tends to do.

i dont know a matching product in the us uk or so, this one is a popular one in germany mostly used by electronic repair shops, industry and so on. smells really awful, but sticks forever. but you still will be able to solder through it, the heat is enaugh to burn it away.

http://www.voelkner.de/products/19467/P ... oCaa3w_wcB

i dont use copper, but i give my packs also a shower of that spray incl. the bms (pcb is the main target anyway of that stuff). imho its based up on some kind of transparent acrylic resin.
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Post by Samd » Jul 03 2016 8:26am

Yep thanks for the summary oatnet.

Gotta admit allex recently gave me a pointer to series the strings first and it didn't sit well. Now I am clear.


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Post by pguk » Jul 04 2016 7:01am

Here's a video where the guy does a fast corrosion test for 2 batches of nickel he bought from china. One rusted immediately in vinegar + hydrogen peroxide + salt solution, one didn't. He shows who the sellers are.
https://www.youtube.com/watch?v=1r2tkwUnNv4

Here's the link to the shop of the good nickel on aliexpress, called Bring Good Things To Life:
http://www.aliexpress.com/store/1315530

I was stung twice before I came across this. I ordered some and can confirm its the good stuff - no corrosion at all.
If you leave a roughed up piece of nickel plated steel in this solution, the steel is eaten away completely after about an hour and you're left with a wafer thin strip of nickel.

Edit: Just seen that this was made and posted by Joss on pg 8 here.
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Post by Invisionelite » Jul 05 2016 2:45pm

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Post by Nobuo » Jul 05 2016 5:21pm

okashira wrote:I made this calculator for a mosfet type welder and for batteries (specifically JP welder + battery source)
I put a good amount of work into it, so please give credit and keep my contact on there if you modify it. And distribute this read only link.
https://onedrive.live.com/redir?resid=6 ... ile%2cxlsx

Make sure you update the blue values to match your setup. Green values i carefully tweaked based on lots of testing and data... but if your setup is different keep that in mind

One could tweak it to work with a cap welder (hint, major change in the % peak current column is needed - you need to account for the falling voltage of the capacitors based on coulombs discharged) let me know if you need help with that. I spent about 15 minutes giving it a start... added calculated voltage drop @ the cap, now you need to use this to compensate for new voltage and how it will affect the current slew rate and peak current ...

Nobuo can you put in OP?
Would like to see someone develop it more for a cap welder.
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Post by mudflap5 » Jul 12 2016 3:22pm

Time for a new spot welder. Had a 788H and it has been repaired one too many times. Kicked it to the curb! Posted in the "Wanted" section for a JB spot welder, and it looks like Riba will be out for an extended time. Aside from the cheap ebay welders, is there anything else available that is somewhat reliable for under $1k? I would like to start a new pack build in about 3 weeks, and need to get a new welder.

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Post by tomjasz » Jul 12 2016 3:46pm

I have a new welder that failed on the first run and the vendor sent a new PCB. Beyond my skill level to repair, It's the model with the POS solder station.
Thanks Justin_le we're here thanks to you. All the best to the mods for their tireless work keeping it on an even keel.

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Post by mudflap5 » Jul 12 2016 4:02pm

tomjasz wrote:I have a new welder that failed on the first run and the vendor sent a new PCB. Beyond my skill level to repair, It's the model with the POS solder station.

Which model # welder are you using?

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Post by tomjasz » Jul 12 2016 5:47pm

I use a JP now but I bought this POS.

https://endless-sphere.com/forums/viewt ... o#p1082569
Thanks Justin_le we're here thanks to you. All the best to the mods for their tireless work keeping it on an even keel.

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Post by zzoing » Jul 18 2016 9:16am

Should the link in between every parallel group of batteries be equals to the total max amperage of the battery?

for example, the middle group of cells in a battery, halway between + and -, which is rated at 40 amps, should be able to transmit 40 amps through it?

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Post by flippy » Jul 19 2016 12:17am

it is highly advised to have the highest current capacity where possible and every interconnect between each group will see the same current. 40A on the output means 40A on the interconnect.

more never is a problem, less however....
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Post by BlueBand » Jul 23 2016 4:57am

Hi mistercrash, another question or is it what you are asking is the lower resistance of zinc compatible with resistance spot,

I think it will require a much higher currant (More Toxic fumes + accelerated and prolonged heat) to produce a quality spot weld. I have not yet committed a crime but as soon as my 788H+ is modified (47R Ceramic bridging a SPST with Missile Cover), I will be rebuilding a lot of Snap-On and Bluepoint 14.4v & 18v packs. So power tools for me with 1.8 x 8 x 30mm Nickle Guys/Girls.

Please someone with some knowledge on these subjects (Resistance Welding and Metallurgy) give any credence to this brilliant Idea or pile of crud.

I also require some Ni-Cd SC 2500mAh paper jacket no tab batteries I have just purchased 45 @ £((.00, ouch there must be a cheaper supplier that is reliable and honest in what the batteries real mAh is I hope that these work out at 2200-2500mAh. I have also just received 12 x 2800mAh SC Ni-Cd's ()Plastic coat and Tabs from China Wow what kind of mAh will they push
(I am hoping 1700mAh but alas expect 1300mAh) so at half the price I would not expect any more than half the quality.

David

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