MAKING A CHEAP BATTERY PACK WITH CHINESE CLONES? IMR AKA LMO BATTERIES 18650

flippy said:

lay them in a brick formation. you need to cut the exess off but they are so cheap it does not matter.

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Also a couple cells that i disassembled the hot glue tore some of the battery wrap on a couple i tossed them tho probably best bet?

if you use cell holders wrapping is not needed. just put a disk on the top so the top edge does not touch the strip.

All a learning curve although the risks are very serious.

I got my introduction into 18650 cell danager from a puncture of one cell and watched in amazement a jet of fire leap out of the cell and then onto the next. Black smoke, mini fire ball, the odd explosion it was all there.

Set in motion a fire fighting plan and was very glad to have carried out this experiment. I discovered powered fire extinguishers although put the fire out these extinguishers don’t cool the cells, soon the fire returned from a cell that had went thermal.

Water did the final task of acting as a coolant. Do not use water if are in any way connected to mains electricity. If a pack is charging and starts a fire leave the area. Call the professionals. Your life is more valuable than any home.

NB. All carried out in a garden.

if you want a fire extinguisher you need a foam based one. powder wont do anything apart from destroying anything copper or aluminium (basically everything) in the area.

get a certified fire blanket. that is the best way to prevent a workbench fire from lighting the whole place on fire. blanket over the battery and then grab the foam and keep any fire under the blanket with it. let the battery burn itself out and concentrate on keeping it under the blanket, the battery is impossible to put out.

Well I have all stuff ordered that I need could only find 8x.15mm nickel strips. I disassembled the packs I had carefully came out with 41 18650s that I deemed acceptable shape others I tossed. All 41 cells tested 4.15-4.18v 90% were 4.16-4.17v.

flippy said:

if you use cell holders wrapping is not needed. just put a disk on the top so the top edge does not touch the strip.

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Am I getting safer? I got l thicker nickel strips. Added in battery spacers and top insulation.

Btw I had a very hard time getting the strips to stick to the battery with my welder. I had current maxed out with 4p 6p and 8p enabled the handle got very hot and it wouldn't stick well for me drove me nuts. Any idea what I am doing wrong?

Better. But use a dremel to get rid of the weld spots on the cells before putting on new strips next time you reuse cells.

You are at the limit of the welder. I had the same issues and when the second one blew up (again) i got a different type of welder.

mightbaal said:

Any idea what I am doing wrong?

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Getting better!
Only remark: You do not need 2 paralleling strips, on 1 serial connection. It does not harm but no added benefit.

bonus tip: also make sure you cover the entire cell with strip. it should not be possible to see the positive end of the cell. you can see you only cover half of the left bottom cell for example. also make the parralel strips longer so it goes over the side by about an inch. that way you can attach the balance wires on the side.

flippy said:

bonus tip: also make sure you cover the entire cell with strip. it should not be possible to see the positive end of the cell. you can see you only cover half of the left bottom cell for example. also make the parralel strips longer so it goes over the side by about an inch. that way you can attach the balance wires on the side.

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Yea I replaced that. So here is something i dont get.... these Chinese cells! I max my welder out and they wouldn't stick but it's not the basic Chinese welder it's actually a good one they say. The 709A. The basic (forget model number) puts out 220A on the highest setting the 709A (mine) puts out 650A on the highest setting (obviously low voltage).

So my problem and fix (this is odd to me). When I went to thicker and wider tabs they would never stick to the tabs and if they did it was weak. I couldn't figure it out so here is how I solved it. I took a dremel with a 240 grit sand paper on it and scuffed up the terminals lightly. That's it!!!! Now literally I make a weld on that and try to remove it and it rips 2 nickel spots off on the battery and 2 decent holes in the strip! I even tried to use a wire brush on the dremel instead of the cone sandpaper and that didn't even work! Not sure if this is specific to Chinese clones or not but the batteries works great!

i have destroyed 2 of those 709's. never again.

i modded them quite to the extreme (lots of cooling on the transformer and much better connections and wire) but they still blew.

use a dremel 85422 or 8215, those work best and really fast.
dont forget to blow out any metal dust from the inside edge of the cell.

mightbaal said:

709A (mine) puts out 650A on the highest setting

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That is not optimal, in KWeld tread they work around 1200A pulses for .15-.2 tabs and striving for up to 2000A for thicker Nickel. They are shorter but results are better then long low current discharges.

parabellum said:

mightbaal said:

709A (mine) puts out 650A on the highest setting

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That is not optimal, in KWeld tread they work around 1200A pulses for .15-.2 tabs and striving for up to 2000A for thicker Nickel. They are shorter but results are better then long low current discharges.

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That's gotta have some thick stuff! I know when I do 3 welds the bottom of the battery gets pretty hot at 6xx amps...

mightbaal said:

That's gotta have some thick stuff! I know when I do 3 welds the bottom of the battery gets pretty hot at 6xx amps...

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That is the interesting part, with higher Amps less energy is used to make better weld. K-weld is energy based spotwelder, you adjust the Joules you want in a weld, and pulse is reduced in time at for given current/resistance condition. Pulse is much shorter, giving no time to heat dissipation.
At same weld quality, high Amp pulse needs less Joules then low Amp pulse. So less heat.