Does this bus configuration look acceptable?

[KiefRichards]

I’m about to weld up my battery pack and was hoping for some input before its too late to turn back.

0.15 copper series buses and .15 nickel parallel connections. Both buses are 10mm wide.
Its an 9p20s configuration to be used with an EM150 controller and qs138 motor.

My goal is to have a battery capable of 300A burst for a few seconds.

Any criticism would be welcomed. I’d like to do this right.
The batteries are sorted into parallel groups with matching IRs. Lowest IR cells of each P group are in the middle of the parallel strings.

Thanks!

 

[999zip999]

Have you tested how well you can spot weld a parallel strips to the cells our practice cells. What spot welder do you have ?

 

[KiefRichards]

Kweld welder. Yes, I spent time practicing on old cells for a while. I settled on 70 joules.

 

[spinningmagnets]

Looks very good to me. Are you using magnets to hold the buses in place for welding?

I am curious about the two end collector buses for attaching the positive and negative cables.

 

[Amperry417]

Looks great man. I'm currently building a very similar 20s9p battery except no cell holders and in a "W" pattern with Samsung 48X cells. Experimenting with .1 copper and .15 copper. I noticed for the welding tabs, that nickel plated steel works much better than pure nickel, as it creates more heat at the weld due to higher resistance than pure nickel. The slot in your nickel helps tremendously. I tried slotted pure nickel versus non-slotted plated steel and the plated steel still aided the weld quite a bit better.
It looks like your negative probe is welding great but in one of your pics, not quite so solid on the positive probe side (I assume since the negative side typically welds hotter). Not sure if nickel plated steel would suffice for your parallel connections but I bet it would help get the welds more consistent for you on both probes. Same thing was happening to me with the slotted pure nickel but as soon as I tried the plated steel tabs, both probes we're welding wonderfully.
I decided on .1 copper with .1 nickel plated steel tabs as welding aids because that's all my battery really needs. Your P42A cells (from the looks of them and the 300a burst statement) will require more than .1, especially with 10mm wide strips. Take a look at the ampacity chart. 10mm wide .15 copper looks to be safe for around 21a continuous. Have you thought about using solid copper plates for the series and parallel? And then just using a small nickel tab at each welding area? That would give you much more cross section than the 10mm wide copper strips. In your case a solid plate would simply be a rectangle shape but not sure if it would work over the cell holders since they stick up past the cell ends. Maybe a dimple would help with this.
Everything looks great though, just throwing out some suggestions to think about since I've been researching and experimenting with very similar ideas to yours. I like the idea of the magnets holding things in place while welding, I might steal that idea LoL.
Again, your setup looks great. Just some food for thought :wink: