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Connect nickel strips to bus bar?
#1
I am building a powerwall with 760 fullriver lifepo4 cells arranged in ten 12v modules of 4S19P to be used on a 24v pure sine wave inverter. I am spot welding nickel strips to the cells to do both the series and parallel connections. The parallel nickel strips extend past the modules to provide a positive connection on one end of each battery module and a negative connection on the opposite end of the battery module.
2 modules will need to be series connected to make 24v and then five of these pairs (10 total) will be connected in parallel to provide the 24v to the inverter. 

How do I connect the nickel strips to a bus bar? I read that spot welding nickel to copper does not work.
I am considering drilling the nickel strips so I can use small screws but the strips are thin and not very wide. 
What other options are there? 


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#2
Solder them. There's really no other way to do it. Based on your pack design, you could just use a piece of copper that overlaps a few cells and wrap the nickel around the wire a little bit and solder to it. It'll be difficult to do as there'll be a lot of heat wicking involved. I would screw them either, it'd tear under stress. I suppose you could use small screws with large washers, tho. That might work too. Especially since it looks like you have doubled up the nickel strips.

So your overall string will with 8s to your inverter. Just making sure of the voltages so no possible magic smoke is released. The inverter can handle a voltage range of 24V - 33.6V (3V - 4.2V per series) without any issues, correct?
I suppose if you go to 4V top end, or 32V for the string, that would be the top end. If your inverter can't handle that high voltage, you will potentially damage the inverter.
Proceed with caution. Knowledge is Power! Literally! Cool 
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#3
(08-12-2018, 12:18 PM)Korishan Wrote: So your overall string will with 8s to your inverter. Just making sure of the voltages so no possible magic smoke is released. The inverter can handle a voltage range of 24V - 33.6V (3V - 4.2V per series) without any issues, correct?
I suppose if you go to 4V top end, or 32V for the string, that would be the top end. If your inverter can't handle that high voltage, you will potentially damage the inverter.
I think you missed or forgot that he has LiFePo cells.
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#4
Oh yeah, i missed that portion Tongue

It's not slipping as much as it to, tho Wink
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at https://discord.gg/c7gJ5uA
(this chat is not directly affiliated with SecondLifeStorage)
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#5
Solder a copper lug/eyelet to the strips? Maybe partly flatten the "wire entry" end of the lug first, insert strips, hammer flat, then solder. Maybe fold the strip either length wise (long triangle) to fit lug or just doubled up for strength?

You will probably need balancing within those packs & should probably have the middle strips all paralleled as well.
Running off solar, DIY & electronics fan :-)
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