18650 cells with tags

[Waynemarlow]

Is there any supplier of cells with tags attached, for the two small 14S2P packs I want to make it just seems not worth while to purchase a spot welder ?

Thanks

 

[petemarconi]

try:

https://eu.nkon.nl/

They take an extra couple of days to weld the tabs on and charge €0.40 per cell. I've used them a few times
and found them excellent, genuine cells and fast well packed delivery.
Not sure if they will weld them up into blocks, you could ask though..

 

[Waynemarlow]

Thanks, found a supplier in the Uk but quite a bit more expensive.

Got to be the way on these small packs ?

 

[petemarconi]

Well, I always solder all mine, made and used 15 packs of differing sizes (10s2p up to 10s9p) and never had a problem - all packs still working fine. However, someone will be along in a minute to tell you why you shouldn't do this, how dangerous it is and how you'll ruin your cells...

 

[Waynemarlow]

Mmm I'm pretty handy with a soldering iron and had really wondered just how much ill effect it has by soldering them, if say it had a 10% long term effect it would be far more cost effective, tell me more ?

 

[petemarconi]

unless you've soldered cells before I would get hold of a few scrap ones to practise on. The 'secret' to good soldering as you prob know is to have all the bits to be soldered clean and tinned, I tin both ends of the cell before before soldering up into packs. The main worry with soldering cells is overheating them, so use a decent sized iron (40w - 100w) and bit and aim to have the iron in contact with the cell or whatever you're joining them with for a max of a second or so, you can also cool the joint using compressed air or a damp sponge, but I've never bothered. I've used this method successfully for three years, the packs I made originally show no more than normal ageing degradation.

 

[Waynemarlow]

Done a lot of soldering of components over the years and yes good tinning and powerful flat tip irons are pretty effective, I think also with the cells its quite good to a braid the surface slightly.

Peter you are probably quite a good resource for the BMS, can you recommend any brands / dealers

 

[petemarconi]

Can't help you with the bms I'm afraid, I've never used one. I prefer to rely on myself and a cell log, or to quote a few other people on here: I'm the bms The bms 'to use or not to use' argument will go on for ever, I'm happy to charge my packs using a 0-60v 3a or 5a lab power supply which enables me to charge the cells to whatever voltage I like - usually about 4.10v/cell for longevity, the lab power supply also means you can charge single cells/cell banks (I always fit balance leads to each pack), I've found that if you're using new cells (or have carefully capacity and internal resistance checked used cells), then if you keep the cell voltages between around 3.5-4.10v / cell then balancing is rarely, if ever needed. The lower bound voltage will vary depending on the type/manufacturer of cells, modern ones having a lower allowable voltage than ones over say 3-4 years old. If I was making packs for anyone other than myself or someone with some knowledge and the ability to check cell level voltages I would recommend using a bms.

 

[999zip999]

With a bms or not I would have a set of sense wires for ez checking and balancing.

 

[petemarconi]

Yep, agree 100% - I did mention that in my last post

 

[Waynemarlow]

You charge the cells with a lab power supply, they are probably less money than a proper charger but most 18650 chargers tail off the power of charge in the last bit ? Are you charging up to the 80% mark only, as my intention is to build a small light weight pack, but use it hard and will need all the power I can get from the one battery meaning I need to charge it as best as I can to 100%. Any thoughts?

 

[petemarconi]

I use a lab power supply because of the voltage flexibility it offers, it charges using cccv and will charge all the way down to cutoff at 0 amps. Cell manufactures recommend a varying charge cutoff usually around 50-100ma which a normal lithium charger will be set up to do, I've never had a problem using the lab supply with the proviso that the pack you're charging doesn't have any 'leaky' or old cells which would allow the supply to sit at a constant current of say 100ma rather than reach 0a and be effectively cut off. I'm presuming that with your pack being 2p only you'll be using some make of 'power' cells - samsung 30q or sony vtc5 or some such ? - I wouldn't have a problem using the full voltage range of these (check the data sheet for the lower bound) - if you're happy not using a bms then 4.20v/cell is fine, most bms will balance initially at a higher voltage than this (up to 4.25?) before maybe settling back around the 4.20 level, so you would be doing your pack a favour by just setting the pack voltage to give 4.2v/cell.

 

[Hillhater]

..If you are comfortable with DIY electrical rigs....
Most of the cheap " Meanwell" or similar clone power supplies on Ebay have a CC/CV operating system.
IE , they run at a preset current until a preset voltage is reached , then they taper the current down to zero..
..Just like a "real" charger !
Just select on for the voltage to suit your pack....they all have a small adjustment range, and some are even fully adjustable (0-xx volts) if you need that.
Shouldnt cost more than $30 .
18650 soldering tip..
Careful on the base (-ve) end of the cell can. Try not to put heat or solder on the center of the base..ie solder near the edge if possible. Its hard to heat damage the +ve cap on the top of the cell...its a separate component so dont worry too much about that end.
..But ideally , buy your cells pre welded into paralel pairs, then just solder links onto the tabs between the cells to form any pack configuration you like.

 

[Waynemarlow]

Good common sense replies here guys and starting to think there is a bit of " myth " about battery packs and soldering.

I'll contact the Dutch supplier and see whether they could parallel the cells up for me but I guess their spot welding machines will be vast industrial types and set up for single tabs, one can only ask the question I guess.

Regards.

 

[Punx0r]

Individual tagged cells allow construction of a pack that is soldered together without the difficulty or danger or soldering directly to the cells. This is the route I went. It's not as neat as a spot-welded pack, and a little taller overall, due to the thickness of the copper bus wires rather than nickel strip, but it saves buying a spot-welder.

 

[mitchdes]

Interesting and helpful information from everyone.

Just looking at building my first pack 14S4P.
I intended to use the factory tagged 18650 cells from nkon as these seem a great option.

Would there be an issue using Z-tags and soldering up the 14 cells in series, and then bridging over between the parallels?
Probably not explained things too clearly. I've attached an image of what I was considering.

 

[999zip999]

I fine a Big tip 80watt weller solding iron works fast , plus flux.

 

[Waynemarlow]

Mitchdes have a read at https://endless-sphere.com/forums/viewtopic.php?f=14&t=84412 and you should be able to answer your own questions on design.

 

[Punx0r]

That layout should work as long as it's relatively low power (a few amps per cell) as you've got a lot of single nickel strip making all the series connections.

 

[mitchdes]

Hi Punx0r - maximum current draw will be circa 20A for a 1000W motor. If I've got my head around this correctly then I suppose that averages out to 5amps per tab. Roughly any idea what current can be drawn through the nickel strips?

 

[Punx0r]

Should be OK according to the table here (and intuition): https://endless-sphere.com/forums/viewtopic.php?f=14&t=68005

 

[Jestronix]

Individual tagged cells allow construction of a pack that is soldered together without the difficulty or danger or soldering directly to the cells. This is the route I went. It's not as neat as a spot-welded pack, and a little taller overall, due to the thickness of the copper bus wires rather than nickel strip, but it saves buying a spot-welder.

Tabbed cells are awesome, I built a 32s 3p pack out 80v tool packs and the tabs made soldering a breeze. I simply folded the tabs down and soldered without too much worry about the heat going into the cells. All 96 cells have held up well

 

[mitchdes]

I am trying to keep the number of soldering points on each cell to a minimum.
Is there any reason why connecting the 18650 cells in this zig-zag pattern won't work?
14s4p arrangement - connected with 4mm tinned copper braid rated at 30amps. Cells are all hot glued together.

 

[Hillhater]

I am trying to keep the number of soldering points on each cell to a minimum.
Is there any reason why connecting the 18650 cells in this zig-zag pattern won't work?
14s4p arrangement - connected with 4mm tinned copper braid rated at 30amps. Cells are all hot glued together.

It will work OK, but if you want to keep the soldering points on the cells to a minimum ( thats "zero") , then use the tagged cells that this thread is discussing !

 

[Waynemarlow]

The price and quality of service from nkon https://eu.nkon.nl/ is very good, ordered 48 with tags and 2 days later they were delivered. For 0.40 Euro for the tags I think it was a no brainer.

Now to work out how to squeeze them into a 75mm diameter water bottle, shall we be the true ship in a bottle scenario or do we just cut the end off ?