Battery cell technical information???

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triangles

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Aug 16, 2011
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Location
Toledo, Ohio
I'm looking for information on the cells used in the FFE with the intent of evaluating the feasibility of rebuilding a FFE battery, possibly with higher energy density cells. If anyone knows where I can find information on the LG cell models used in the FFE packs and/or similar sized cells from other EVs that would be very helpful. I've also contemplated a LiFePO4 pack but I would imagine getting that to play nice with the onboard charger and other systems is probably more of a hassle than it is worth.

If anyone knows where I can get an old FFE battery preferably near northern Ohio, for dirt cheap. I'd love to get my hands on one to learn how these are put together.
 
At one point I had found one of the LG chem cells that had to be what they were using in the 5P modules. It was long ago and don't have info to offer, just the hope it can be found again.
 
Okay, so here's what we have to work with.

We know the car uses 430 cells in an 86-Series/5-Parallel arrangement for a nominal 318V

23kWh or 33.5kWh gives us ~266Wh or 400Wh per 5P group.

That works out to around 72Ah or 105Ah per cell with the 3.7V nominal voltage.

Inside the pack we see cells grouped like this:



Seeing them 5 or 10 units wide suggests that is the parallel orientation and the dual ATX type connectors suggest those are stacked 2 high, making the larger blocks 20 cells and the smaller ones 10.

5 20s and a 10 gives you 110 cells. 3 of those on the bottom for 330 and 5 more 20s on the top to get 430. That all seems to line up with the exterior dimensions of the pack.

So you're looking for an LG Chem pouch cell rated for 72 or 105Ah that is ~4" wide, ~9" long and an inch or less deep. Give or take a little.

Just having the cell capacities narrows it down a TON.

Hitting google for lg-chem 70..75-ah gets me a discussion page noting the Mach E is using LGX E71a pouch cells which are officially a 71Ah cell but suspiciously close to the 72 we'd see on the Focus. Getting pictures of the bare cells seems difficult, but I think that gets us in the neighborhood.

Aside from the possible Mach E connection, I think this same cell/group format is used in several other EV packs but with different parallel groupings. But I'm sure you can tell that those stacked "plates" make for pretty easy modular construction.

Another page I found showed pinouts for modules with larger parallel groups like 7 and 9 and they basically offer cell level taps to monitor voltage along with thermistor feeds.

Some of their other module internals: https://www.diyelectriccar.com/threads/lg-chem-battery-dissection.204331/

The E48 and the NCM811 seem to have a form factor that is about 4" wide, 12" long with the tabs folded out and about a half inch thick. Which seems to generally fit to the range we're looking at here. Seems they are focusing on OEM integration though, so bare cells and spec sheets are really hard to pin down.

If you have any leads for that, let me know.
 
Old thread I know, but since google has picked it up it's worth pointing out that math is incorrect. There are indeed 20 cells in the larger modules and 10 in the smaller ones. However, each group of 5 cells are connected in parallel; the large modules are 4s5p and the smaller ones 2s5p.

The upper pack consists of 2 layers: 3 large + 1 small modules on the bottom, and 6 large + 1 small on the top. The lower pack consists of 2 side-by-side stacks: 5 large + 1 small in the rear, and 6 large in the front. All modules are connected in series, so we have:
3×4s5p + 2s5p + 6×4s5p + 2s5p + 5×4s5p + 2s5p + 6×4s5p =
12s5p +2s5p + 24s5p + 2s5p + 20s5p + 2s5p + 24s5p = 86s5p (430 cells total)

Assuming the cells are 3.6v nominal, that equates to a nominal pack voltage of 86×3.6 = 309.6V
Dividing nominal pack capacity by the nominal pack voltage yields a nominal "cell" capacity of 23,000Wh ÷ 309.6V = 74.29Ah
However, since each "cell" is actually 5 cells in parallel, the capacity of the individual cells is 74.29Ah ÷ 5 = 14.86Ah
or 14.45Ah if you assume a nominal cell voltage of 3.7V

I also measured one of the cells when I had my FFE battery apart. The pouch was 225mm long x 164mm wide x 5.65mm thick
Though the jelly roll (the portion of the cell that was 5.65mm thick) was only ~200mm long x ~150mm wide
The tabs were 45mm wide.
 
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