LiFEPO4 Scooter Battery welding

[NickF]

Hi All,
I recently purchased 16 LiFEPO4 15amh Scooter batteries with a view to make a 48v battery for a rackmount UPS. I went with these types of batteries specifically for the space constraints of the UPS.

Unfortunately, I am currently unable to spot weld 0.12mm Nickel strips to the copper terminals using a Wise Mable DIY spot welder, even on 30ms (full power).

They did come with nickel covering spot welded to the copper bars (as picture below), but I removed them thinking these were second hand and I would weld new pieces to make better connections between cells. Annoyingly my diy welder is not man enough for the job.
I have prepared the copper terminals by finely filling\sanding them, but this has made no difference.

Any suggestions on how to either weld, or join by some other means, these cells together would be most welcomed?

Anyone in the UK, with professional welder available to weld them for me please get in touch?

 

[nc73]

you can solder it if you're decent with a soldering iron, don't heat it for long. At least that's what I did once.

 

[NickF]

you can solder it if you're decent with a soldering iron, don't heat it for long. At least that's what I did once.

Will give that a go thanks. Just ordered 15mm wide and 2mm thick copper bar. As I think it will be better to solder than several strips of nickel

 

[Risky Rob]

you can solder it if you're decent with a soldering iron, don't heat it for long. At least that's what I did once.

I wonder if solder will hold together cells of a jiggling scooter battery? Has anybody built their own spot welder. I see videos on that.

 

[nc73]

I wonder if solder will hold together cells of a jiggling scooter battery? Has anybody built their own spot welder. I see videos on that.

No, I've done it before.

 

[Risky Rob]

No, I've done it before.

OK, thanks.

 

[justgary]

you can solder it if you're decent with a soldering iron, don't heat it for long. At least that's what I did once.

Will give that a go thanks. Just ordered 15mm wide and 2mm thick copper bar. As I think it will be better to solder than several strips of nickel

You will need a huge soldering iron to get heat into the copper bar and the battery lug at the same time without overheating them. Even then it will be tricky if your copper bar is very long at all. This 550W iron might be a good choice.

https://americanbeautytools.com/Soldering-Irons/19

Asking around among some Ham radio friends might get you the use of one, including a free helper. I have found them at flea markets as well.

 

[NickF]

You will need a huge soldering iron to get heat into the copper bar and the battery lug at the same time without overheating them. Even then it will be tricky if your copper bar is very long at all. This 550W iron might be a good choice.

https://americanbeautytools.com/Soldering-Irons/19

Asking around among some Ham radio friends might get you the use of one, including a free helper. I have found them at flea markets as well.

Thanks for the advice. The length of busbars should be quite short, ~47mm. I will use a heat plate though to heat the busbar and battery terminals up to 100c first before starting. I have a powerful iron that can do 500 degrees so will give that a go. My only concern with soldering is will I get sufficient bond as to prevent excess heating of the terminals.
I have filled the copper terminals will a 4000 grit sanding block, so I hope I get a good contact. I will also file the busbars as well.
Hopefully, I won't be drawing lots of current through them, so I am hoping this will be ok!

Ok, that is a pretty heavy duty iron, mine is nothing like that!

 

[NickF]

Thanks for the advice. The length of busbars should be quite short, ~47mm. I will use a heat plate though to heat the busbar and battery terminals up to 100c first before starting. I have a powerful iron that can do 500 degrees so will give that a go. My only concern with soldering is will I get sufficient bond as to prevent excess heating of the terminals.
I have filled the copper terminals will a 4000 grit sanding block, so I hope I get a good contact. I will also file the busbars as well.

 

[Risky Rob]

Thanks for the advice. The length of busbars should be quite short, ~47mm. I will use a heat plate though to heat the busbar and battery terminals up to 100c first before starting. I have a powerful iron that can do 500 degrees so will give that a go. My only concern with soldering is will I get sufficient bond as to prevent excess heating of the terminals.
I have filled the copper terminals will a 4000 grit sanding block, so I hope I get a good contact. I will also file the busbars as well.
Hopefully, I won't be drawing lots of current through them, so I am hoping this will be ok!

I've read where people use 2 irons at once to heat the fitting.

 

[justgary]

a powerful iron

Your 80 Watt pencil iron for electronics probably won't cut it.

It might be better to keep focusing on a way to weld tabs back on. Also, I don't think each cell needs anything nearly as big as the copper bars you plan to use.

 

[NickF]

I've read where people use 2 irons at once to heat the fitting.

Can I just check in terms of soldering, should I be just soldering around the edge of the bus bars onto the terminals i.e. no solder underneath the bus bar and the terminal, or should I have solder between the bus bar and the terminals? Hope this makes sense...

 

[NickF]

Alternatively, I do have an arc welder but the thought of that scares me!

 

[Risky Rob]

Alternatively, I do have an arc welder but the thought of that scares me!

Isn't a common method to spot weld with nickel strips?

 

[NickF]

Isn't a common method to spot weld with nickel strips?

my DIY Spot welder is not man enough for the job. I have a Wise Maple running with 3S LiPO battery. Even on max duration it does not weld 0.12mm Nickel to the copper terminals.

 

[Risky Rob]

my DIY Spot welder is not man enough for the job. I have a Wise Maple running with 3S LiPO battery. Even on max duration it does not weld 0.12mm Nickel to the copper terminals.

I am mulling over how I will build a battery from 18650 cells, and have .15 nickel strips.

 

[justgary]

Can I just check in terms of soldering, should I be just soldering around the edge of the bus bars onto the terminals i.e. no solder underneath the bus bar and the terminal, or should I have solder between the bus bar and the terminals? Hope this makes sense...

It would be best to get solder under the bars as well.

What about not bothering with welding or soldering? Can you just clamp them into a frame that keeps pressure on the terminals, just like a small battery holder does? A little grease to keep oxygen out would make the connections last a long time.

 

[NickF]

It would be best to get solder under the bars as well.

What about not bothering with welding or soldering? Can you just clamp them into a frame that keeps pressure on the terminals, just like a small battery holder does? A little grease to keep oxygen out would make the connections last a long time.

I have to fit this within an APC UBS draw (RBC43) so there is not much room to build an external frame. Think it would be pretty complex considering this is 16S1P

 

[TomC4306]

Have you considered soldering wire?

 

[TomC4306]

Or maybe you can spot weld the nickel strips to a tinned terminal.
Dunno