copper terminals spot welding

Hi!

First i would like to explain i have 6x modules of 12s Panasonic/Sanyo NMC 25ah prismatic cells removed from an Audi A3 hybrid vehicle = 72 cells

I'm looking at battery building options to meet my future ambitions (get solar and a hybrid inverter to help power the home)

Option 1:Keep the 6 modules in their 12sconfig and put the rest modules in parallel, i feel this will have drawbacks as each module will need a 12s bms .

Option 2: split the 12s modules up into 12S6P and just have one bms .


So i have split 1 module up and tried to test spotweld 0.1 + 0.15 pure nickel stripsonto the cells terminals with no luck. I believe this to be because the cell terminals are coated with copper underneath.


I'm using malectrics spot spot welder with aTurnigy nano-tech 3S/5000mAh/130C Lithium Polymer battery as the power supply. This is achieving really good spot welds with the nickel strips and 18650 cells pulling around 450 amps


As i believe option 2 is the way to go i cannot progress if i cannot configure properly, so I'mlooking for some suggestions on how i can attach to the cells? keeping the original spot welds in the 12s modules would be easier but no ideal.

Thanks !!

Is soldering an option youre ok with?

Jon said:

Is soldering an option youre ok with?

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Hi Jon,

Soldering could be an option , however I tried with a fine tip and it didn't work that well. I will maybe next try with a different bigger tip .

I have been thinking about carefully dis- asembling 1 cell to see how big the terminals and how the prismatic cell is formed. This way if I find the terminals thickness, I can maybe look at somehow fixing to them.
Theres not much info on these cells on the web but the ones i have seen in Fords s- max in the states comes with bolt on terminals.
I obviously know this comes with dangers so I would be very careful and take precautions.

Matt

Are you able to cut the bridges 1/2 way between the cells to separated them and solder to the longer tag of bridges rather than removing the bridges back to the size of the cell terminals?

May be a bit easier working with the a longer tag of bridge material rather than the terminal, less heat will get away from the soldering point.

And as you say, use a big soldering iron that can give a lot of heat quickly, a fine tip will struggle.

Jon said:

Are you able to cut the bridges 1/2 way between the cells to separated them and solder to the longer tag of bridges rather than removing the bridges back to the size of the cell terminals?

May be a bit easier working with the a longer tag of bridge material rather than the terminal, less heat will get away from the soldering point.

And as you say, use a big soldering iron that can give a lot of heat quickly, a fine tip will struggle.

Click to expand...

Even with a big iron, you may not have any luck. Copper is an excellent conductor of heat, and will draw it away very quickly. I agree, save as much of the original material as possible, and use the biggest soldering iron you can find.

Best option, keep all modules complete, and solder bridges so they are all in parallel. Once they are all manually balanced at the same voltage, just solder thin wires to the bridges, and connect each 1s to the next 1s on each module.

Cheers for your feedback Jon & Geek!

Keeping as much as the already spot welded bridge material is a good shout.
I start work on my pack in the next couple of weeks so will keep you updated.

Matt