Making a custom battery pack for MiEV

[martinwinlow]

This is a bit of a thread hijack but I was wondering if any battery geek out there has thought of replacing the discrete LEV50's with a 'brick' of 18650's in parallel, 'Tesla-style'? And might this be a comparatively easy yet affordable way around all the problems of sourcing replacement cells that'll fit the original module packaging as well as be agreeable to the existing BMS? Even if we only had the original 16kWh you would still have a very capable city car and possibly at a much cheaper price-point than the larger format/capacity cells that feature in this thread...? Just a thought!

To answer my own Q... 2 rows of 9 (in parallel, obvs) would fit and 18 x 2.5Ah would give 45Ah but even at £2/cell that still the best part of £3k ... plus all the cell holders and not to mention the faff...

 

[MickeyS70]

This is a bit of a thread hijack but I was wondering if any battery geek out there has thought of replacing the discrete LEV50's with a 'brick' of 18650's in parallel, 'Tesla-style'?

See discussion below:
https://www.forums.aeva.asn.au/viewtopic.php?t=5515

 

[piev]

This is a bit of a thread hijack but I was wondering if any battery geek out there has thought of replacing the discrete LEV50's with a 'brick' of 18650's in parallel, 'Tesla-style'? And might this be a comparatively easy yet affordable way around all the problems of sourcing replacement cells that'll fit the original module packaging as well as be agreeable to the existing BMS? Even if we only had the original 16kWh you would still have a very capable city car and possibly at a much cheaper price-point than the larger format/capacity cells that feature in this thread...? Just a thought!

To answer my own Q... 2 rows of 9 (in parallel, obvs) would fit and 18 x 2.5Ah would give 45Ah but even at £2/cell that still the best part of £3k ... plus all the cell holders and not to mention the faff...

Sounds like a good idea. I believe you will discover that packaging a battery is harder than finding cells that fit the package.

Adapting the battery case is not a simple task.

 

[martinwinlow]

Sounds like a good idea. I believe you will discover that packaging a battery is harder than finding cells that fit the package.

Adapting the battery case is not a simple task.

Actually, I think that's one advantage of using 18650s in that there is a wealth of easy and cheap systems to hold cells together in pretty much any arrangement you desire. It would be joining them up electrically as well as providing appropriate terminal connections that will work with the existing BMS PCBs, etc, that may be problematic, I'd have thought. I think, short of a big price drop in 2.5 to 3Ah 18650's, if you were going to go to all that trouble to upgrade what is a fairly old and valueless car (not like they are collectable (yet) or something!) you would be better off spending a bit more and sticking with larger prismatic cells. Anyway, hijack over...

 

[Jiminy]

My son and I designed a replacement cell in CAD that held 14x 2170 Tesla cylindrical cells. They fit in the same space as a stock LEV50 and would require a custom PCB for the top voltage collector. You'd have to print 88x plastic shells. There would be little cooling due to having to hold the cells well. The capacity would be 70Ah assuming 5000 mah per cell. Cost would be attractive IF you bought a Model 3/Y battery module and salvaged all of the cells from one module. It would likely take 3-4 years to do so as the cells are entombed in an epoxy from the Tesla factory. You'd also have to perfect the process of welding wire to the cases of the Tesla cells. Daunting? why yes.

Prismatic I think is the answer but pouch could work. CMU connection details would be the biggest thing to work out.

 

[MickeyS70]

Prismatic I think is the answer but pouch could work. CMU connection details would be the biggest thing to work out.

What about AA cells?