Nickel strip for 12V 90AH 32700 cells.

[Fahmula]

I’m thinking of making a 12V 90Ah battery pack using 32700 6000mAh battery cells from battery hookup. I have been doing some research to figure out the amp rating for 0.15x10mm nickel strips which seems to be about 6A.

This would be a 4s15p pack in a 5x12 configuration. The max current draw for the pack would be 100A and I was wondering if that would mean that each parallel pack would only be providing 25A?

 

[snoobler]

Confusing.

DO you have a single 15P4S battery? Four groups of 15 32700 in parallel with the groups in series?

If so, you only get to divide the current across the 15 parallel cells as each series group gets the whole 100A.

100A/15 = 6.7A per cell

Expect lots of blown "fuses".

If you have four 15P4S batteries, then 25A would be correct.

 

[Fahmula]

Confusing.

DO you have a single 15P4S battery? Four groups of 15 32700 in parallel with the groups in series?

If so, you only get to divide the current across the 15 parallel cells as each series group gets the whole 100A.

100A/15 = 6.7A per cell

Expect lots of blown "fuses".

If you have four 15P4S batteries, then 25A would be correct.

Yeah a single battery with 4 groups of 15 32700’s in parallel. I’m just trying to figure out how much nickel strip I’d need for each series connection.

 

[snoobler]

2

Generally speaking because of the less-than-catastrophic consequences of a shorted LFP cell (no boom or fire), they usually aren't fused. You're really just protecting your operability and financial interests in the pack's failure, repair or replacement.

 

[Fahmula]

2

Generally speaking because of the less-than-catastrophic consequences of a shorted LFP cell (no boom or fire), they usually aren't fused. You're really just protecting your operability and financial interests in the pack's failure, repair or replacement.

Why only 2? I’ll definitely be extremely careful if I make this battery.

 

[snoobler]

2 per cell to permit up to ~14A.

 

[Fahmula]

2 per cell to permit up to ~14A.

Sorry I’m a bit confused. Let’s say I have 4 groups of 15 cells already in parallel. I’d need enough nickel strips for 100A from group 1-2 and the same from 2-3 and 3-4?

 

[snoobler]

I think we're talking about 2 different things.

If the nickel strips are being used to join the parallel groups in series, then it need to be able to handle the 100A, so 100/6 = 16.7 strips.

It'd treat it like a fuse and apply 1.25 to it - 21 strips.

 

[Fahmula]

I think we're talking about 2 different things.

If the nickel strips are being used to join the parallel groups in series, then it need to be able to handle the 100A, so 100/6 = 16.7 strips.

It'd treat it like a fuse and apply 1.25 to it - 21 strips.

So I’d need 21 strips to attach each group of parallel cells which would be 84 in total?

 

[snoobler]

Cell -strip - cell -strip - cell - strip - cell

You only need three sets of strips between the four cells, so 63?

 

[Fahmula]

Cell -strip - cell -strip - cell - strip - cell

You only need three sets of strips between the four cells, so 63?

I’m starting to understand. Would it be something similar to what’s shown in this video.

 

[snoobler]

Yeah.

How do you plan to construct your 15P cell? I was assuming you're using nickel sheet.

Since you're dealing with 15 cells, assuming 3x5, you'd put 5 on each cell joining a cell in the next parallel group, so 25 each.
(+) and (-) are the end of a cell.
"5 " is 5 nickel strips joining to the adjacent + or -.

+ + + 5 - - - 5 + + + 5 - - -
+ + + 5 - - - 5 + + + 5 - - -
+ + + 5 - - - 5 + + + 5 - - -
+ + + 5 - - - 5 + + + 5 - - -
+ + + 5 - - - 5 + + + 5 - - -

 

[Fahmula]

Yeah.

How do you plan to construct your 15P cell? I was assuming you're using nickel sheet.

Since you're dealing with 15 cells, assuming 3x5, you'd put 5 on each cell joining a cell in the next parallel group, so 25 each.
(+) and (-) are the end of a cell.
"5 " is 5 nickel strips joining to the adjacent + or -.

+ + + 5 - - - 5 + + + 5 - - -
+ + + 5 - - - 5 + + + 5 - - -
+ + + 5 - - - 5 + + + 5 - - -
+ + + 5 - - - 5 + + + 5 - - -
+ + + 5 - - - 5 + + + 5 - - -

This is how I had it in mind. Just wasn’t sure of how many nickel strips I needed. Wouldn’t it be pretty hard to apply weld 5 nickel strips?

 

[snoobler]

It is a bit challenging. but slight offsets from the last weld work fine, and you'd want to spot one strip at a time.

If you're using sheet to parallel the cells, could you cut the sheet and use it to crossover to the next cell group?

 

[Fahmula]

It is a bit challenging. but slight offsets from the last weld work fine, and you'd want to spot one strip at a time.

If you're using sheet to parallel the cells, could you cut the sheet and use it to crossover to the next cell group?

What do you mean by sheets? You mean these? (Pic attached)
Also what if I use 5 1 inch 12awg wire going from the + of each pack to the - of the next. I’d solder the wire the nickel strips before I spot weld them.

 

[snoobler]

That would handle it.

 

[Fahmula]

That would handle it.

It wouldn’t be an issue soldering the wires to just one strip of nickel right? Thanks for all your help. You helped me understand this a lot more.

 

[snoobler]

As long as all your join points, welds or solder, are solid, no issue.

 

[snoobler]

One other thing. 100A out of 90Ah cells is > 1C discharge. Important to confirm the cells can handle this.

 

[Fahmula]

One other thing. 100A out of 90Ah cells is > 1C discharge. Important to confirm the cells can handle this.

These cells are capable of 3C so should be more than okay.
I found this reputable seller of nickel strips on eBay. I think this would work better for my build since is pure copper with nickel plating which should be good for 18A

Pure Nickel Plated Copper Strip Tab 0.15mm x 8mm 18650 US Sales | eBay

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