Main Traction Battery Upgrade i-MiEV

[mradtke]

See post #212

I ordered these cells:

https://www.alibaba.com/product-det...8.html?spm=a2700.wholesale.0.0.256e30b1jevR7c

I searched on alibaba.com today for cells with similar specifications, and found that there are other vendors selling these cells at about the same price, not "significantly higher."

Mike

 

[MickeyS70]

To keep this thread focused on NMC conversions, I have moved discussions regarding LFP cells to

https://myimiev.com/threads/the-aftermarket-cell-replacement-saga.4403/

 

[mradtke]

Hello,

Please note that piev is the organizer of the traction battery upgrade effort and has consulted with many folks to get to this point. My son and I are now benefiting from piev's efforts. Our car's upgrade is performing as expected and we are very pleased.

My son is working on some documentation on "Pack Removal, Module Rebuild, and Man in the Middle." The first version of "Module Rebuild" is complete and may be found at:

https://5by9.net/prune_batteries/moThe first version of "Module Rebuild" is complete and may be found at:dule_rebuild.html

I will post notice of the other sections when they are available.

Our thanks to piev and all the other people who have contributed.

Mike

Hello,

My son has completed the "Pack Removal" section of the documentation.



https://5by9.net/prune_batteries/module_rebuild.html

Hello,

Please note that piev is the organizer of the traction battery upgrade effort and has consulted with many folks to get to this point. My son and I are now benefiting from piev's efforts. Our car's upgrade is performing as expected and we are very pleased.

My son is working on some documentation on "Pack Removal, Module Rebuild, and Man in the Middle." The first version of "Module Rebuild" is complete and may be found at:

https://5by9.net/prune_batteries/module_rebuild.html

I will post notice of the other sections when they are available.

Our thanks to piev and all the other people who have contributed.

Mike

Hello,

My son has completed the "Pack Removal" section of the documentation. It may be found at:

https://5by9.net/prune_batteries/pack_removal.html

Thanks,
Michael

 

[Jiminy]

Hi Michael,

Nice write up! Thanks to you and your son for making this.

Would it be possible to PM me measurements of the jumper tab below by marking it up in MS Paint so that I can have it quoted at Send Cut Send? I've made ballpark guesses below. I will change the numbers and repost when I get the measurements. Also, what is the thickness of the jumper? Rule of thumb is that thread engagement (for the 3mm-.5 screw) should be 1.5x diameter of fastener but more if material is soft like copper. This isn't gonna happen but 3mm might work OK. PCB busbars would be better.

 

[piev]

Hi Michael,

Nice write up! Thanks to you and your son for making this.

Would it be possible to PM me measurements of the jumper tab below by marking it up in MS Paint so that I can have it quoted at Send Cut Send? I've made ballpark guesses below. I will change the numbers and repost when I get the measurements. Also, what is the thickness of the jumper?

View attachment 1224

These may be different than Mikes but these are the measurements I made.

 

[Jiminy]

Hi Piev,

OK, thank you. By getting accurate measurements for this cell I can create models and then assemblies and figure things out without having physical parts present. I will make the cell models available to anyone here.

Can you confirm the numbers circled below in red with one of the spare cells you have? If you could just give me the number for each letter. Some of the measurements on your sketch don't compute for the way my weird little brain works. Also, I know your terminal studs were 6mm but I'm putting 8mm since that's how most people will spec them.


Jim

 

[Jiminy]

Based on the loose dimensions shown in post #245 the jumpers tie it all together nicely.

 

[kiev]

i think they could be made only as wide as needed to match copper pad on the flex tab on the CMBs, i.e. 8mm

Use aluminum and round off or radius all the sharp edges and transitions to eliminate stress risers.

Like an oval shape tapered the entire length. 12mm at the bolt end tapered down to 8 mm at the CMB, less material waste and no sharp corners.

Slot the 8mm hole for the stud mount to allow adjust and alignment.

The aluminum is stiffer than copper.

Could use a pop-riveter for rivet nuts for the threads?

There is no current flow in the CMB tabs (voltage sense only) so no need for a big bulky copper piece.

Crude example, adjust as necessary or desired to get the job done.


These could be sheared or punched out of sheet metal as tapered rectangles, then stack a few and drill or mill out the holes. i don't like sharp edges or corners so the radius could be ground off on a disk or belt sander.

 

[Jiminy]

The only thing I would beg to differ on is that all of the current of the battery will be passing through these bus bars. I would prefer they make as much contact on the cell terminal below and stock bus bar above. The outside diameter on the terminal's 8mm flange nuts are likely 17.5mm so the bus bars would need to be that wide at minimum. But I would make them as wide as need be to make full contact with the OE Mitsubishi bus bars. Also, I'm not concerned about stress risers on the "little end" of the bus bar as it is mounted to a very small pcb held with three silicone dots. The CMU is held in place by the top web of the module case so I don't predict much differential movement.

The price of making laser-cut flat pieces is dictated by the outside dimensions, length and width. The cost difference is very small (pennies) between what you suggest and what I think should be done. Even the per piece cost of a custom pcb bus bar will not be affected significantly by trimming it down. Here is a ballpark at 3.2mm laser-cut copper but I think it would be goodly less as a pcb. I'd really much rather buy bus bars than make them.


Edit: I added obround 8.2mm holes at the terminal end. One millimeter.
Edit: I clarified my understanding of the relative position of bus bars.

 

[kiev]

i measured 17mm diameter for the flange nuts (smooth bottom not serrated) and 18 mm width of the buss bars, 2mm thick and 70.5 long. They appear to be punched out of copper with a dull silver-colored plating.[likely matte tin plating]

the pad on the CMB is 8mm square.

The bottom of the flange nuts seem to have a slight belleville spring shape, in that they cut thru the plating on the buss bar at the OD of the nut exposing copper.

 

[Jiminy]

Ahh, flange nuts with integrated belleville washers. Neat! I used to use those for a product I sold in my former life.

Thanks for the measurements! By CMB, do you mean the separate little temp sensor pcb attached to the CMU? I haven't quite caught on to all of the acronyms.

Stock Mitsubishi bus bar (please correct me if I have it wrong.):

Jim

 

[Jiminy]

Another bus option?

 

[kiev]

CMB is the Cell Monitoring Board, sometimes called CMU boards. The little flex tab pcb attached with 3 white blobs doesn't have a name that i know of.

There is not a washer on the flange nuts, just that the bottom flange surface seems to be dished or coned very slightly similar to a belleville washer. i could see no indication that the flange touched the buss bar anywhere except at the OD of the flange where it dug in to the plating.

Don't know if this was a design feature or due to the cad plating on the flange nut that left a burr on the OD surface.

 

[Jiminy]

Belleville nuts as I know them are one piece flange nuts with a convex contact face which acts as a lock washer or, at minimum, a locking feature when torqued. McMaster-Carr used to sell them. I bought quite a few. It's a nice detail in this application.

 

[mradtke]

Hi Michael,

Nice write up! Thanks to you and your son for making this.

Would it be possible to PM me measurements of the jumper tab below by marking it up in MS Paint so that I can have it quoted at Send Cut Send? I've made ballpark guesses below. I will change the numbers and repost when I get the measurements. Also, what is the thickness of the jumper? Rule of thumb is that thread engagement (for the 3mm-.5 screw) should be 1.5x diameter of fastener but more if material is soft like copper. This isn't gonna happen but 3mm might work OK. PCB busbars would be better.

View attachment 1256

Jim,

I'm posting here since others may be interested in my drawing as well.
It will also be added to the document at:

https://5by9.net/prune_batteries/module_rebuild.html

The bus bars were chosen to be cut into a jumper and the remaining
piece used as a spacer to allow the inter-cell jumpers to be level.
However, the M6 slots needed to be re-worked to M8 slots. The bus bars
were purchased on Amazon:

https://www.amazon.com/gp/product/B0BBDTQVYP/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

We were only doing one car, so the the effort to hand cut the jumpers
was less than doing precise measurements, getting samples, and perhaps
repeating until we got it right. Only a few of our jumpers needed
re-work.

Michael

 

[Jiminy]

Welcome back to the Jiminy show.

Here is a possible way to do all of the bus bars that eliminates the stock bus bars entirely. I have not modeled the daughter board to the CMU so this would require refinement when I do but you get the idea. Bus "C" requires your imagination as I have not added it into this assy. It forms a "U". Best guess is that the whole pack would take 24x A bus bars, ~66x B bus bars ($[email protected] Cu on SCS), and 10x C bus bars. Pricy? yes.

 

[Jiminy]

Jim,

I'm posting here since others may be interested in my drawing as well.
It will also be added to the document at:

https://5by9.net/prune_batteries/module_rebuild.html

The bus bars were chosen to be cut into a jumper and the remaining
piece used as a spacer to allow the inter-cell jumpers to be level.
However, the M6 slots needed to be re-worked to M8 slots. The bus bars
were purchased on Amazon:

https://www.amazon.com/gp/product/B0BBDTQVYP/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

We were only doing one car, so the the effort to hand cut the jumpers
was less than doing precise measurements, getting samples, and perhaps
repeating until we got it right. Only a few of our jumpers needed
re-work.

Michael

Very cool. Thank you. May I ask what the CTC distance is on the cells you used? Based on what you have here your cell's terminals have different centers than Piev's.

Jim

 

[MickeyS70]

Welcome back to the Jiminy show.

Here is a possible way to do all of the bus bars that eliminates the stock bus bars entirely. I have not modeled the daughter board to the CMU so this would require refinement when I do but you get the idea. Bus "C" requires your imagination as I have not added it into this assy. It forms a "U". Best guess is that the whole pack would take 24x A bus bars, ~66x B bus bars ($[email protected] Cu on SCS), and 10x C bus bars.

If you look at @phebbler ’s design back in post # 236 you’ll notice “C” is not required, it’s just another “B”…

 

[Jiminy]

Hi Mike,

I drew this if you wanna use it:

The 54mm measurement in your drawing would not work in Cad based on your other numbers. If you see a mistake here please let me know and I'll correct it.

Jim

 

[MickeyS70]

Pricy? yes.

At first glance definitely, but you can easily offset that expense if you sell your old cells for solar storage and charge extra to include the original bus bars..