High current weld strips

jvens · Jan 8, 2019

Hi all,

I want to build a battery pack that will be used as starterbattery in a vehicle.
something like this, but 4S4P.

https://goo.gl/images/n8aPWZ

For the requested currents, there must be very decent strips inside this battery. The current will be 350A for a few seconds.
But:
A. I don't know where to find them
B. I don't know how I should calculate the requested thickness

Could you pls advise? Thanks!

fechter · Jan 8, 2019

What kind of cells are you planning on using? Something like 8ga copper will take that much current for several seconds.

jvens · Jan 8, 2019

The cells just like the one that example is made of: ANR26650M1-B

fechter · Jan 8, 2019

I'd go with the thickest nickel your welder can handle to place a short tab on the cells and solder that tab to some 8ga copper. As long as the path length through the nickel is short, it won't heat up very much.

The A123 cells may be aluminum on one end and very difficult to weld to.

jvens · Jan 9, 2019

So that is not very easely..

Could I better choose another cell?

I want to have a professional design with a very good connection between the cells..

fechter · Jan 9, 2019

I'm sure there are better cells out there but I can't give a specific recommendation. Anything with bolted connections will be easy. Prismatic cells with tabs can be bolted also with some DIY hardware. The cells have to be able to supply the required current without the voltage dropping too much.

Overclocker · Jan 9, 2019

4s2p anr26650m1a. sufficient to jump my cars a honda fit and a ford ecosport, both 1.5L engines

.15mm nickel tabs spot welded to the A123. then 10ga stranded copper wire soldered on top. i guess the little spot welds create a bottleneck. but right now i can't think of a better way, without soldering directly onto the A123

fechter · Jan 9, 2019

Overclocker said:
.15mm nickel tabs spot welded to the A123. then 10ga stranded copper wire soldered on top. i guess the little spot welds create a bottleneck. but right now i can't think of a better way, without soldering directly onto the A123

That looks like what I was thinking originally. Obviously you were able to spot weld tabs to the bottom of the cells.

atarijedi · Jan 9, 2019

I would do what Tesla does, have individual fuse wires going from each cell to a bus bar.

https://endless-sphere.com/forums/viewtopic.php?t=79950

https://endless-sphere.com/forums/viewtopic.php?t=88039

You will be able to size the wire better, and get much higher currents, than if you use nickel strips.

Overclocker · Jan 11, 2019

fechter said:
Overclocker said:

.15mm nickel tabs spot welded to the A123. then 10ga stranded copper wire soldered on top. i guess the little spot welds create a bottleneck. but right now i can't think of a better way, without soldering directly onto the A123

Click to expand...

That looks like what I was thinking originally. Obviously you were able to spot weld tabs to the bottom of the cells.

yes the metal can is aluminum but there's a circular steel piece at the bottom

High current weld strips

jvens

10 µW

fechter

Administrator

jvens

10 µW

fechter

Administrator

jvens

10 µW

fechter

Administrator

Overclocker

10 kW

fechter

Administrator

atarijedi

100 W

Overclocker

10 kW

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