For his next Teardown Tuesday I request Dave tear down a Tesla 85KWh battery pac - Page 1
Forum section: electronics / general

author: JoeN
author_rank: Frequent Contributor
timestamp: September 11, 2014, 09:26:03 pm
content: Just kidding, this guy already has. I doubt it will fit in Dave's lab. What a monster.http://www.teslamotorsclub.com/showthread.php/34934-Pics-Info-Inside-the-battery-packI only post this because I think maybe some of you will be interested and I don't see it posted already. This guy is saying that 318V on the pack is considered lower than totally discharged. I wonder what fully charged is. 318V is already a dangerous voltage. (edit: I see now it is rated for 400V)

author: calexanian
author_rank: Super Contributor
timestamp: September 12, 2014, 04:38:26 am
content: Crazy.... I still think it would be easier to make 100 larger cells in series and monitor those individually rather than buss up thousands like that!

author: EEVblog
author_rank: Unknown
timestamp: September 12, 2014, 05:20:08 am
content: Quote from: JoeN on September 11, 2014, 09:26:03 pmIt would fit in the lab if I clear out everything including my new bench, but not in the lift, nor the door

author: EEVblog
author_rank: Unknown
timestamp: September 12, 2014, 05:21:34 am
content: Quote from: calexanian on September 12, 2014, 04:38:26 amIt would be very interesting to know the engineering considerations, compromises and showstoppers etc that went into the design.I'm sure there are countless things to consider here!

author: mtdoc
author_rank: Super Contributor
timestamp: September 12, 2014, 05:38:12 am
content: Interesting teardown and design analysis of the Volt's battery here.

author: ejeffrey
author_rank: Super Contributor
timestamp: September 12, 2014, 06:09:45 am
content: Quote from: calexanian on September 12, 2014, 04:38:26 amI doubt it is really harder easier to manufacture a pack with 100 vs. 10000 cells. There are also some reasons you might not want to use larger cells. Cooling the pack is a major concern, especially when charging. It is a lot easier to cool lots of little cells than a few big ones. It also possibly makes it easier to do the flat pack under the car which gives you the absurdly low center of gravity and makes ideas like the fast battery change easier to implement.Of course, off-the-shelf is always a huge advantage. Of course for a high volume customer, Panasonic would have been willing to build a custom cell, but they already had the equipment to manufacture huge, huge quantities of 16850 cells that are already used in everything else. You go the custom route, and you are tied to their capacity for producing that part. Some equipment goes down and you can't sell cars. This way, as you grow, you can just take over more of their overall capacity, rather than requiring expansion of the custom production line.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 12, 2014, 10:19:57 am
content: Quote from: EEVblog on September 12, 2014, 05:21:34 amAn entire pack would be pretty crazy (and perhaps not as illuminating as one would hope), but a few control / conversion modules, now there's something, y'think?Tim

author: amyk
author_rank: Super Contributor
timestamp: September 12, 2014, 12:52:34 pm
content: That would be a 96s74ppack, with a fully-charged voltage of ~403.2VThe connections to each cell look like a scaled-up version of a wirebond.

author: coppice
author_rank: Super Contributor
timestamp: September 12, 2014, 01:14:22 pm
content: Tesla say the battery pack is part of the car's structure. They also say it can be swapped in 90s. Does anyone know how they achieve those simultaneously?

author: TerraHertz
author_rank: Super Contributor
timestamp: September 12, 2014, 02:19:17 pm
content: Fascinating that it appears to be made of hundreds of 18650s, with each one individually fused within the blocks that are in parallel.The other thing I noticed is that although the writer thinks the BMS boards don't play any direct part in charge leveling, looking at the hi-res photo of a BMS board he provides, I'd say he's wrong. Looks to me like the BMS boards have the ability to shunt some charging current past each individual block of cells. Which means they can level the cells.If the BMS boards were only monitoring voltage, why are there a bunch of paralleled higher power resistors and at least one transistor associated with each cell sense line?Seehttp://files.wizkid057.com/teslapack/update2/Tesla%20BMS%20Module%20-%20Front.jpg

author: coppice
author_rank: Super Contributor
timestamp: September 12, 2014, 02:24:26 pm
content: Quote from: calexanian on September 12, 2014, 04:38:26 amI can see how it looks that way, but consider other applications of lithium batteries. If a notebook has optional battery capacities they aren't 3 small cells, 3 medium cells or 3 big cells. They are 3, 6 and 9 cells. The use of numerous small cells seems to be commonplace.

author: GreyWoolfe
author_rank: Unknown
timestamp: September 12, 2014, 03:24:23 pm
content: Forget the battery pack, I want Dave to tear down a whole Tessla!

author: wraper
author_rank: Unknown
timestamp: September 12, 2014, 09:35:30 pm
content: Quote from: calexanian on September 12, 2014, 04:38:26 amAnd get Dreamliner fire problem (uses large cells)... AFAIK this is made for safety and cooling reasons. If one cell fails nothing extraordinary happens. Imagine large lithium cell getting short.

author: tom66
author_rank: Super Contributor
timestamp: September 12, 2014, 11:16:00 pm
content: The Nissan Leaf uses large-format cells, and air cooling only (it's difficult to liquid cool large format cells.) The range degradation in hot climates on those vehicles is terrible - many owners have lost 30% in 3 years. Whereas most Tesla owners report less than 3% loss in 2 years.The 18650 that Tesla use is optimised for them. You can't buy it anywhere. It's a variant of the NCR18650B, approx 3.2Ah capacity but supports 4C discharge and almost 2C charge rates. Tesla only work from 3.3V~4.15V (normally 4.05V in normal range mode) to extend longevity.

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: September 13, 2014, 03:36:45 pm
content: Quote from: tom66 on September 12, 2014, 11:16:00 pmA little on the pricy side...http://www.fasttech.com/product/1141104-panasonic-ncr18650b-protected-rechargeableI don't know if you'd want to run them at 4C, their specs don't look good past 0.5C (2A).http://lygte-info.dk/review/batteries2012/Panasonic%20NCR18650B%203400mAh%20%28Green%29%20UK.htmlhttp://www.dampfakkus.de/akkutest.php?id=141

author: JoeN
author_rank: Frequent Contributor
timestamp: September 13, 2014, 08:15:51 pm
content: Quote from: justanothercanuck on September 13, 2014, 03:36:45 pmMaybe that is why they are now building their own factory. I wonder if they have commodities contracts on the lithium they are going to need to produce so many batteries.http://www.bloomberg.com/news/2014-09-11/why-musk-is-building-batteries-in-a-desert-when-no-one-is-buying.html

author: tom66
author_rank: Super Contributor
timestamp: September 13, 2014, 10:15:45 pm
content: Quote from: justanothercanuck on September 13, 2014, 03:36:45 pmIt's a modified version of that cell intended to support fast charge and discharge rates. It cannot maintain 400kW continuously, as it begins to power limit (Tesla could have gone with a cell which supported continuous discharge, but that would make more sense in a track car.)