One problem I've had before was if one cell in a pack is damaged and replaced, the BMS balance current would take forever to flatten the pack.
Do you know if Tesla has any way of improving or making this faster?
Inside a Tesla Model S Battery Pack
11–20 of 83 posts
Re: Inside a Tesla Model S Battery Pack
#12From 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?
Yes, of course 18650 is the form factor.
From what I understand these are stock Panasonic NCR-18650 3100 mAH batteries though.
Any ideas on what "special chemistry" they are using?
Re: Inside a Tesla Model S Battery Pack
#13Earlier quoted context omitted.
18650 is the form factor. These cells don't use the usual chemistry. Do you really think that the form factor is dangerous?
Yes, of course 18650 is the form factor. From what I understand these are stock Panasonic NCR-18650 3100 mAH batteries though. Any ideas on what "special chemistry" they are using?
Every article I've seen about the battery says that it doesn't use the usual chemistry, and that only the form factor is standard. I figured you would have something factual to say, given that you're saying you know it's dangerous.
Re: Inside a Tesla Model S Battery Pack
#14Earlier quoted context omitted.
18650 is the form factor. These cells don't use the usual chemistry. Do you really think that the form factor is dangerous?
Yes, of course 18650 is the form factor. From what I understand these are stock Panasonic NCR-18650 3100 mAH batteries though. Any ideas on what "special chemistry" they are using?
Model S is using NCA (Nickel Cobalt Aluminum). It's not clear if the stock Panasonic batteries have the same battery chemistry (they might but Panasonic doesn't share their battery chemistry), but we do know that the Tesla batteries are not exactly stock Panasonic batteries. They have casing modifications made to them for Tesla's purposes.
Re: Inside a Tesla Model S Battery Pack
#15Earlier quoted context omitted.
Yes, of course 18650 is the form factor. From what I understand these are stock Panasonic NCR-18650 3100 mAH batteries though. Any ideas on what "special chemistry" they are using?
Every article I've seen about the battery says that it doesn't use the usual chemistry, and that only the form factor is standard. I figured you would have something factual to say, given that you're saying you know it's dangerous.
All the information I've seen says they use stock Panasonic NCR-18650A lithium ion batteries just like clumsysmurf said. (The "A" just means that it's the 3100mAH nominal capacity version - there are several NCR-18650 batteries with different capacities.)
It's a fairly common 18650 battery, lots of laptops use this specific model.
Re: Inside a Tesla Model S Battery Pack
#16Earlier quoted context omitted.
Yes, of course 18650 is the form factor. From what I understand these are stock Panasonic NCR-18650 3100 mAH batteries though. Any ideas on what "special chemistry" they are using?
Every article I've seen about the battery says that it doesn't use the usual chemistry, and that only the form factor is standard. I figured you would have something factual to say, given that you're saying you know it's dangerous.
I'm not sure what you are trying to do - but I almost fell for it.
First, I specifically stated "3100mAH NCR-18650s" which is a specific part, not a form factor which anyone who handles these batteries would know - which was your first (confused) reply.
Second, from everywhere I have read, like (1) these are just standard cells.
Lastly, I was originally stating that I would feel unsafe being around this technology. I did not say "the technology is unsafe."
If it makes you feel better, Tesla as a company gives me great hope and I am rooting for them. I do not have ties to anyone at all.
It would have been nice if you could have simply pointed to some factual reason (like breser did above) why I shouldn't be worried.
(1) http://www.greencarreports.com/news/1084682_what-goes-into-a...
Re: Inside a Tesla Model S Battery Pack
#17Earlier quoted context omitted.
Yes, of course 18650 is the form factor. From what I understand these are stock Panasonic NCR-18650 3100 mAH batteries though. Any ideas on what "special chemistry" they are using?
Model S is using NCA (Nickel Cobalt Aluminum). It's not clear if the stock Panasonic batteries have the same battery chemistry (they might but Panasonic doesn't share their battery chemistry), but we do know that the Tesla batteries are not exactly stock Panasonic batteries. They have casing modifications made to them for Tesla's purposes.
Thank you for the clarification.
Re: Inside a Tesla Model S Battery Pack
#18Seems like there is a lot of room for improvement?
Reducing the sheer number of casings on individual cells would radically reduce weight/volume.
Then with less groups of cells you could actually have the BMS monitor them like my lifepo lithium battery for bicycle.
Re: Inside a Tesla Model S Battery Pack
#19Interesting 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
That almost looks like it was built by a mechanical engineer, not an electrical engineer. All the effort seems to be focused on building a sturdy case for the batteries, and the actual electrical connections are all steel screw terminals and crimping, without any spot welding anywhere.
I'd be worried about the electrical resistance of all those contacts, and the heat it produces. Tesla's battery pack seems like a more intelligent electrical design, with a barebones mechanical design to back it up.
Re: Inside a Tesla Model S Battery Pack
#20I 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 i…
Here is the spec sheet for the main square chip on that board.
http://www.ti.com/lit/ds/symlink/bq76pl536a-q1.pdf
You're right. It does have a cell balancing feature.