Inside a Tesla Model S Battery Pack

I think he's wrong about one thing. A good BMS not only monitors cell voltages, it has the ability to bypass some charging current around individual cells. Not a lot, but enough to balance the charge of all cells over a cycle. That capability can do wonders for the reliability and life of a pack.

While I worked in EVs for 6 years, I have no knowledge of the Tesla BMS - they were not our customer and I worked mostly in motor control anyway.

Re: Inside a Tesla Model S Battery Pack

#6

Post by aresant » Thu, Sep 11, 2014, 8:34 PM UTC

I had a similar appreciation reading this that I felt for the original iPhone tear-aparts by ifixit and their brethren.

EG - looking at a truly innovative use of existing technologies pushed to their limit and engineered to a sum greater than their individual parts.

Makes me want a Tesla even more.

Re: Inside a Tesla Model S Battery Pack

#7

Post by Gracana » Thu, Sep 11, 2014, 8:57 PM UTC

Interesting to compare this to the ford fusion battery[1], which uses clever construction to prevent a technician from being exposed to high voltages during construction and teardown.

[1] http://www.etotheipiplusone.net/?p=3109

Re: Inside a Tesla Model S Battery Pack

#8

Post by clumsysmurf » Thu, Sep 11, 2014, 9:03 PM UTC

From what I've read these packs have around 7000 3100mAH NCR-18650s. Over the years I've used these NCRs (or lower mAH versions) individually in special flashlights - and while they seem to have good reliability overall, one did fail on me while charging. Thats why often hobbyists charge these outside in fireproof bags.

I would be terrified to drive a car with this technology.

Re: Inside a Tesla Model S Battery Pack

#9

Post by greglindahl » Thu, Sep 11, 2014, 9:08 PM UTC

clumsysmurf wrote: post #8

From what I've read these packs have around 7000 3100mAH NCR-18650s. Over the years I've used these NCRs (or lower mAH versions) individually in special flashlights - and while they seem to have good reliability overall, one did fail on me while charging. Thats why often hobbyists charge these outside in fireproof bags. I would be terrified to drive a car with this technology.

18650 is the form factor. These cells don't use the usual chemistry. Do you really think that the form factor is dangerous?

Re: Inside a Tesla Model S Battery Pack

#10

Post by [deleted] » Thu, Sep 11, 2014, 9:09 PM UTC

clumsysmurf wrote: post #8

From what I've read these packs have around 7000 3100mAH NCR-18650s. Over the years I've used these NCRs (or lower mAH versions) individually in special flashlights - and while they seem to have good reliability overall, one did fail on me while charging. Thats why often hobbyists charge these outside in fireproof bags. I would be terrified to drive a car with this technology.

[deleted]