Spot Weld and solder or whatnot ? LiFePo4

[suprted1]

I bought 30 LiFePo4 cells for my E-Bike project.
But this battery has been nothing but trouble. There is no tabs on these cells.

Is there any good ideas out there how to connect these cells rock solid ?

I also started to build my own spot welder, but 800Amps, works more like a vaporizer then a spot welder.
Spot welder is built on the modified trafo style. If I modify it to deliver 400Amps, which seems to be the level of other working DIY spot welder projects.
Then this might work.

But all ideas will be much appreciated, about solutions to connect these batteries.

Cheers folks
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The Solution :

A trafo from a microwawe, a simple relay on the coli, primary side.
A control signal to the relay from a foot pedal, to keep both hands available. electrodes made of copper pins from a 380V cable plug.
Some wood to make the parts move accordingly to my needs.
50 square mm wire to make the secondary coil. ( probably 20 square mm is better)
Modified primary coil, to adjust output current with 8ohm 100Watt resistors in series with primary coil.
Plug and play, and have fun.
800Amps works like a vaporizer on thin nickle battery tabs. Which was the result with no 8 ohm resistor in series.
Works like a charm.
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[suprted1]

Isnt there anyone who has built battery packs with theis kind of batteries ?

 

[cal3thousand]

If you don't have a suitable battery tab welder, take the cells to Batteris Plus or some other battery store and have them do it for you. Shouldn't cost much.

 

[Animalector]

Just out of interest... what sort of batteries are these? where did you get them?

Andy

 

[suprted1]

Just out of interest... what sort of batteries are these? where did you get them?

Andy

I bought them from Goldenmotor.
But stupid me forgot to mention I needed tabs on them.
12Ah batterys. And I thought I would get more capacity on the same space with rectangular cells.


I have spoken with all hobby (RC) stores in the area, but none of them has any idea where to have the batteries spot welded or similar.
I dont think its available anywhere here in Norway....
If any specific suggestions, please let me know.

 

[suprted1]

Finally I found a proper level to spot weld at. 450Amps, and its working.
Just added a 8 ohm resistor, max 100W. To the primary coil on the transformer. And Amps went from 800 to 450.
If i add more resistors in series, i have the option to adjust down to 225Amps with 6 of these .

 

[dnmun]

what is the piece of black metal that has the studs from the ends of the electrodes riveted into it?

if that is copper you could try soldering to it. if it is nickel plate it should take solder too.

 

[SamTexas]

I bought 30 LiFePo4 cells for my E-Bike project.
But this battery has been nothing but trouble. There is no tabs on these cells.

The picture you posted is too small. However the terminal posts appear to be copper and lead. If that's true, then soldering should be very easy.

 

[suprted1]

I bought 30 LiFePo4 cells for my E-Bike project.
But this battery has been nothing but trouble. There is no tabs on these cells.

The picture you posted is too small. However the terminal posts appear to be copper and lead. If that's true, then soldering should be very easy.

I have soldered a few kilos of solder the last years, so I am not too unfamiliar with soldering.
I also tried Alu-Sol which is a prefered solder on metals not binding with the solder, but no success.
Tried soldering with oil on the surface while brushing away the outer layer on the tabs. No success.
But finally i got my spot welder working, so I think its gone be all right now.

 

[suprted1]

what is the piece of black metal that has the studs from the ends of the electrodes riveted into it?

if that is copper you could try soldering to it. if it is nickel plate it should take solder too.

I dont know which metal it is, but its actually shining like chrome. Its not black, just seems a bit black on the picture.
Maybe nickel or something.