Inside the Tesla pack

Batteries, Chargers, and Battery Management Systems.
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flathill   100 kW

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Inside the Tesla pack

Post by flathill » Feb 01 2013 2:49am

Tesla rav4ev pack
same arch for model s
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Last edited by amberwolf on Feb 01 2013 3:02am, edited 1 time in total.
Reason: corrected spelling of "Tesla" (from Tezla) in title so people can find it in a search

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jonescg   1 GW

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Re: Inside the Tesla pack

Post by jonescg » Feb 01 2013 4:30am

Interesting. Kapton tape around groups of paralleled cells? Individual fuses for each cell in the paralleled group? Or are they just springs to hold it in place?

flathill   100 kW

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Re: Inside the Tesla pack

Post by flathill » Feb 01 2013 5:05am

Kapton wrapped coolant pipes
Those wires are fuses
One on each terminal
Plus two more in cell
Plus fuse separator
Plus one on each bank
Plus two main
Plus two contactors
Plus one independent (of bms) shorter triggered by total pack voltage overcharge to blow fuses as last resort if contactors weld closed
(the only fire risk is if all cells overcharge at same time due to charger/bms sabotage)

SamTexas   100 MW

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Re: Inside the Tesla pack

Post by SamTexas » Feb 01 2013 6:52am

I don't understand everything, but it looks like a very safe setup. Thanks for the pictures. Where did you get them? Links?

One thing I noticed is that cells are quite far apart from each other. So cooling/ventilation should be every efficient. And heat propagation (in case of thermal runaway) should be well contained. Good design at the cost of much larger required space.

flathill   100 kW

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Re: Inside the Tesla pack

Post by flathill » Feb 01 2013 3:07pm

The cells are quite far apart to withstand crashes/impacts. With a skateboard battery you are not too limited in volume anyway. Space is just air. Note there is a super thick layer of heavy air between the belly and the battery. The Model S has a ballistic shield belly protecting the batt :mrgreen:

This is what happens with close packed large format prismatics in a crash. This BYD got rear ended. Note it uses "ultra safe" lithium iron grandma cells
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Don't think they made it out alive

Hillhater   100 GW

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Re: Inside the Tesla pack

Post by Hillhater » Feb 01 2013 7:28pm

flathill wrote: (the only fire risk is if all cells overcharge at same time due to charger/bms sabotage)
don't each of those cells have a built in over/under voltage protection circuit also ?
http://www.lygte-info.dk/info/battery%2 ... %20UK.html
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liveforphysics   100 GW

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Re: Inside the Tesla pack

Post by liveforphysics » Feb 01 2013 8:42pm

That is a sick pack.

NCA chemistry cells so they have a few thousands cycles in them and good cold weather performance and a more reasonable C-rate (like 5C bursts).

A thermal transport medium contacting each cell through a thermal pad to a flattened aluminum hydro-formed (I'm guessing) pipe wrapped in Kapton to prevent shorting potentials between cell group cases at different potentials. Flow the liquid in, it flows out either with less energy left in it if you're heating the pack on a cold day, or flow out with more energy in it to get transferred to the air through radiator if you're flogging the pack.

They fixed my biggest issue with tab welds on round cells, which is fatigue from minimal compliance distance and the inherent stress-focusing/riser action of two surfaces being bonded by little connection spots. Those long bond-wire looking interconnects are brilliant. Things can flex and vibrate and wiggle for a very long time, and it's wiggling over a long distance of material, so everything stays well inside it's non-fatiguing range of its stress curve.

I love that it functions in a way that any cell can have any type of cell failure and it's ultimately a non-event, the pack just reduces in capacity by a percent or something the user likely would never even notice.

That is the best method to do an 18650 pack that I've ever seen.

Kudo's to you Tesla, and Kudo's to you Elan Musk, you've made some awesome things happen in the world. Big respect.

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grindz145   100 MW

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Re: Inside the Tesla pack

Post by grindz145 » Feb 01 2013 9:32pm

Awesome photos! Individual fuse lines are amazing. I wonder how these things are assembled? I wonder how much automation they have. There is otherwise a whole lot of labor involved in assembling these.

flathill   100 kW

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Re: Inside the Tesla pack

Post by flathill » Feb 01 2013 11:05pm

even their cooling/heating system is tight
two independent circuits
one for motor/controller
one for battery
the two circuits can be run in series parallel or independent
excess heat from motor controller to heat the cells in cold climates
but not when u dont want it
(anything in between
also redundancy to get you home

the terminals bond wire fuses that connect to the main "tabs" ... run away from the terms
the biggest problem with normal cell tabs in addition to flexure failure is they run over the top of the cells
it is only a matter of time until the tabs short to cell case
also notice the large flat wire busbar is a actually thin laminations of copper
flexure resistant
Last edited by flathill on Feb 01 2013 11:09pm, edited 1 time in total.

Hillhater   100 GW

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Re: Inside the Tesla pack

Post by Hillhater » Feb 01 2013 11:08pm

grindz145 wrote: I wonder how these things are assembled? I wonder how much automation they have. There is otherwise a whole lot of labor involved in assembling these.
22.00 mins into this , gives a hint...
http://www.youtube.com/watch?v=VVktbM6j ... r_embedded#!
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grindz145   100 MW

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Re: Inside the Tesla pack

Post by grindz145 » Feb 02 2013 8:05am

Hillhater wrote:
grindz145 wrote: I wonder how these things are assembled? I wonder how much automation they have. There is otherwise a whole lot of labor involved in assembling these.
22.00 mins into this , gives a hint...
http://www.youtube.com/watch?v=VVktbM6j ... r_embedded#!

Wow! Yeah even that little robotic cell picking machine is awesome! More automation than I've ever seen in a US battery manufacturing environment. Thanks for that.

edit: after watching the rest of the video... they are not messing around with automation.... it's world class.

flathill   100 kW

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Re: Inside the Tesla pack

Post by flathill » Feb 08 2013 4:07pm

I found the missing link!
the wire bonds allow fully automated assembly
also act as fusible link
also act as breakable link in case of cell venting
note the new NCR18650PB has a new vent design on the negative terminal (C shape):
ncr18650pd.jpg
ncr18650pd.jpg (30.5 KiB) Viewed 464 times
Now look at this ingenious Telsa patent
tesla.gif
tesla.gif (58.38 KiB) Viewed 464 times
I guess it was true Tesla and Panasonic had a true partnership

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