What else can we learn from Tesla battery pack design

Here is a pic inside the Powerwall itself, or a 1/16th of Powerpack, much the same really.



This is from the Tesla Gigafactory tour, so heaps of photos like this. Nothing more detailed than that however.
But people have pulled to bits Tesla cars, including the HV battery, and the design aspects are just as useful.

Tesla battery module, common to Powerwall/Powerpack v1.0 and Model S/X EV.



Typically 444 Panasonic 18650 cells, 6s74p ~24V per module.
Exact capacity depends on cells fitted.



1. Cell level fuses.
Every cell within a module has it's own fuse. Should a cell fail the high current flowing into it will cause the cell fuse to blow.




2. Module coolant loops
Each module has internal copper coolant loops between rows of cells. With silpad material for insulated heat transfer from cell casing to coolant tube
2_1_coolant_loops.jpg





3. Module containment
Each module contained in metal compartment within battery pack casing. Bottom and top sides covered with mica sheets to provide additional electrical isolation to each module.






4. Module Venting
Safely release pressure build up within module comparements, allowing the gasses to escape safely.

5. BMS
Each module has a dedicated BMS with cell balance and monitoring.
Monitors cells voltages, and balances them, also has two temperature sensors.
A master BMS communicates with the battery modules, and the car's main systems.






6. Main Contactors
The battery pack contains two inbuilt HV contactors, which disconnect the battery from external HV cables.
Also has a main HRC fuse.
6_1_main_contactors.jpg



7. HV current shunt
Detect incoming/outgoing current flow to external HV.
7_1_current_sensor.jpg

8. External coolant system
Radiator and pump circulate coolant through battery pack and hence into individual modules
Also coolant is monitored for stray voltages that indicate problems within the battery pack.






9. Insulation of busbars.
Modules linked together by busbars, have heatshrink materials over most of the copper to prevent short circuits.

10. Double insulated HV cables.
HV cabling has the usual layer of insulation over the copper wires, and a second flexable conduit over each cable. So positive
and negative cables are in seperate conduits.
Insulated plastic caps over and around bolt connections where high current/voltage connections are made.

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1 Prevent individual cell failures from creating cascade failures/fires.
The fuses Tesla use are 0.3mm aluminium (alloy ?) and blow at 25A or over 80 degrees C.

2 & 8 Prevent cells from oveheating, also buys time to escape car if run away battery failure is in progress.

3 Cell failure/fire containment, also prevent external forces from damaging cells. Cabling/busbars between modules are potted in some form of RTV rubber compound to seal any gaps.

5 Prevent major pack failure due to overcharging or unbalanced cells/modules and detect problems.

6 & 7 Prevent battery pack problems caused by the HV system in the car. For example overcharging, motors drawing too much current, or HV faults.

8 Detect coolent leaks, or short circuits within the battery modules

9 & 10 Prevent short circuits and reduce accidental contact with battery cables.

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Apologises for missing images, many of the photos I wanted to use need permission from someone who doesn't read his email.

Neato! I want to go check out the GigaFactory! Thanks for sharing!

I just want to add a quick point.

I compare tesla battery design and execution to NASA going to space.
Both tesla and NASA being pioneers have to ensure more standards are met for indemnity reasons as apposed to safety.

Think of it like this, NASA when going to space HAD to do everything as well as you could, perfectly in fact, as when something did invariably go wrong, they needed to be able to answer for any error or short sight by definitively saying they took every step and made every effort to ensure safety and materials were up to the highest standard.

This is why there are so many different levels of safety in tesla's design. Not because they are necessarily needed, its to ensure that no one can point the finger at some lack of design or foresight. While I agree this is the best design out there, I disagree that any and all measures are not only necessary, but that not adhering to such a high standard is wrong, or less right.

In short what Im asserting here is that we can put the tesla design up as the best, but remember when designing your own packs, its not necessary to adhere to all of their standards in order for your pack to be safe.

Stay safe through learning more, not by indemnifying yourself relying on a specific measure to alleviate responsibility and / or giving yourself a false sense of safety.

Thanks for sharing all the info station240, most informative.

Some of their design looks complex, but it's not.
Take the barriers between the modules, it's just a U shaped piece of sheet metal held in place by a few welds, not welded all the way down. Nothing that couldn't be made at home with a stick welder.

I doubt most of use need the cooling system, I just added it for interest/completeness.

The self contained electronics within the battery pack is interesting. The basic 12V contactor set used to isolate the big battery, which is driven off an external battery is a cheapish safety feature. The Electric car conversion shops have the contactors, everything else can be made. If the 12V battery lived next to the inverter, and the contactors next to the main battery, then a switch next to either can shut it down.

Any idea whats the "busbars" or sheets (that connect to the cells through the fuses) material?