Replacing LEV50 modules with 18650s

Started thinking about upgrading the battery capacity of a i-MiEV/C-Zero/iOn. First looked up the specs on the LEV50 cells:

https://www.dropbox.com/s/f3i6g7vmz6ktnjx/Screenshot%202015-11-03%2013.22.57.JPG?dl=0

The LEV50 cell is 113.5x43.8x171 mm, so there should be no problem to fit 24 or 6x2x2 18650 cells in that space (18650s would only be 108x36x130mm).

If you'd use 2.85 Ah cells that would be 88x24x3.7x2.8 or about 22 kWh, with 3.45 Ah cells 27 kWh. Not bad, I think!

Any objections on why this might not work, if one was able to enclose those 18650 cells into LEV50 size modules?

Price of 88*24=2112pcs of Samsung INR18650-29E 18650s would about 6000€ (the 22 kWh pack) at 2.80€ per cell.

If you're willing to do it, it would be a learning experience for all of us, as we are not sure how the car would respond to the main battery suddenly being higher capacity. At the worst, you would still have the same range as before due to the car's capacity calculation methods.

Looks like my account balance is closer to 600€ than 6000€ so it might take while. But, with battery gigafactories popping up around the world, at least some producing 18650s specifically, and LG already willing to sell their cells to GM for $145/kWh, it might get quite a bit cheaper in the future, making this a possibility. Ideally a LEV50 module would be good to have for inspection first.

Sometimes I've thought, but to replace a single defective cell in a battery out of warranty, if the LEV-50 is difficult to find.

Indeed, 18pcs of 2,85 Ah 18650 cells would be more than enough to replace a new LEV50 cell, not to mention a used one, and the cost would only be about 60€

One thought that also occurred to me at some point was that if one would be interested in replacing the whole battery pack with cells from a different chemistry, one could use 88pcs of 18650 cells to replace each LEV50 module with a single 18650 cell to keep the BMS happy and thinking that the battery is perpetually full.

jsantala said:

One thought that also occurred to me at some point was that if one would be interested in replacing the whole battery pack with cells from a different chemistry, one could use 88pcs of 18650 cells to replace each LEV50 module with a single 18650 cell to keep the BMS happy and thinking that the battery is perpetually full.

Click to expand...

jsantala, I like your concept, as well as your workaround plan, but the work involved in connecting 2112 cells without automation boggles the mind! A good mid-winter project. I would like to hope that the existing BMS would function unchanged but, like PV1, I would be fearful that coulomb-counting would tell the BMS that there's a capacity inconsistency and it would then shut everything down - and then what? Sadly, the world is now controlled by software and hacking it for even something as straightforward as this could prove challenging.

Ah, life was so much simpler when we just played with our EV Conversions and could do whatever we pleased … I recently got the old '65 Saab running again, on Enerdel Lithium (NMC), three lightweight series packs of 2P14S instead of 24 monsterous and heavy 6v golf-cart batteries.

Incidentally, I was looking at the Australian i-MiEV site recently and came across some postings that delved further into this arena … but I can't find it again. Actually, that would belong in the battery-extending thread. In case anyone is interested, here's the Aussie website: http://forums.aeva.asn.au/forums/mitsubishi_forum49.html

Edit: Found this specifically about range extending on the Aussie website:
http://forums.aeva.asn.au/i-miev-range-extender_topic4383.html

Actually, Joe, I wasn't hinting at a tamper-device like programming, just that going through all this work would yield nothing as the BMS would only allow the same amount of energy as the original LEV50 cells. It's possible, like one of my cell phones that I bought a very large battery for, that the car will re-calculate SoC each time it is power cycled. I would fully charge the battery in the phone, unplug it and watch the charge drop from 100% to about 60% charge, then plug it back and it would then truly fully charge. The phone adjusted SoC to match the voltage profile of the battery. The only problem with the phone was that the SoC calculation would run out before the phone corrected for the voltage, or it would sit at 8% for a very long time.

Koorz has actually done this a few times. I drove a few miles, parked at the store with 14 bars, and came back out to find 15 bars of charge that took 3 miles to drop back to 14 bars. The SoC could jump around based on pack voltage, so it is possible that after so much time of constant SoC corrections, the car will do a re-calibration and open up to the full capacity. Sorry, I wasn't running CaniOn so I don't have SoC values. And, no, I didn't do much regen in the last couple of miles .

I noticed when the pack in Bear was failing, that it would charge at full speed until one cell hit 4.11 volts, then it would switch to constant voltage mode and hold the cells at 4.105 volts. With the new pack and lower resistance of the cells, Bear now charges faster in the top 10% of charge than before. It used to slow down around 94%, but now goes to around 98% before slowing down.

Maybe it's possible to force the car to open up to the full capacity if you run the LEV50 cells down to about 1 bar, do the cell swap (dis/charging the new cells to the same SoC as the discharged LEV50s), then charge the whole pack with the car. If my theory's correct. Even as the car gets near 100%, the voltage won't be there yet, so it may continue charging until the cells hit 4.105 volts, regardless of the SoC calculation.

After a quick read through of the Australian i-MiEV forum, many of their questions and unknowns are already answered here.

Indeed, dealing with 2112 of 18650 cells would be a pain, even with just 24 at a time. Especially since you couldn't put two of them in a series, but all 24 in parallel. Might be a tall order. I've just gotten some real life experience with these 18650 cells since I swapped the cells in my electric cargo tricycle. It now has 30 cells in 3p10s configuration and just getting those connected has been an ordeal. Suffice to say sparks have not been avoided.

It would be really cool if someone could step up and produce some custom NMC cells in the LEV50 format. I wonder how much a chinese supplier would ask for some custom made?

When we push on the accelerator we have something like 3C in the LEV-50; 3C is very close to the limit of some 18650's. I wonder if, putting 24 or so in parallel, possible imbalances do work some cells at 4C and others at 2C, causing a rapid deterioration.

Just thinking, I have none experience with that cells.

We touched on this topic a little bit here:

http://myimiev.com/forum/viewtopic.php?f=23&t=2124&start=50

Don......