Fuse-wire for individual cells, DIY Tesla style

Batteries, Chargers, and Battery Management Systems.
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spinningmagnets   100 GW

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Re: Fuse-wire for individual cells, DIY Tesla style

Post by spinningmagnets » Jan 12 2020 8:37pm

This video from 2018 has a pic of the Model-3 pack at 29:41, which shows they are still using individual cell fuses.

https://www.youtube.com/watch?v=CpCrkO1x-Qo


eMark   100 W

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Re: Fuse-wire for individual cells, DIY Tesla style

Post by eMark » Jan 13 2020 12:39pm

Another informative video on the future of Tesla batteries beginning with the Tesla Y and going forward with a new dry battery chemistry that looks to distance Tesla's need for Panasonic. Will Elon Musk eventually overtake all the other major auto companies with the best competitively priced electric car ??? ...



Assuming Tesla Style fuse~wiring remains an integral part of their new batteries is it because its always been more about less cost and reduced production time than safety ???

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fechter   100 GW

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Re: Fuse-wire for individual cells, DIY Tesla style

Post by fechter » Jan 14 2020 3:33pm

"One test is worth a thousand opinions"

john61ct   100 MW

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Re: Fuse-wire for individual cells, DIY Tesla style

Post by john61ct » Jan 14 2020 6:02pm

fechter wrote:Nice article about wire bonding:

https://chargedevs.com/features/a-close ... e-bonding/
Yes, excellent, thanks! I've seen friction welding of high tech plastics but not yet metal.

Odds are slim of any DIYer getting the same results.

I doubt if this methodology is in any way a compromise, very likely optimal for all three factors mentioned.

Tesla has a lot at stake, being the most valuable U.S. auto maker ever.

> The company closed Monday with a market value of $81.39 billion, surpassing Ford Motor Co. 's peak of $80.81 billion set in 1999.


john61ct   100 MW

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Re: Fuse-wire for individual cells, DIY Tesla style

Post by john61ct » Jan 14 2020 8:59pm

Tesla is now valued (insanely) higher than GM and Ford, **combined** !

What a world we live in.

SHTF one day for sure

eMark   100 W

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Re: Fuse-wire for individual cells, DIY Tesla style

Post by eMark » Jan 15 2020 10:30am

spinningmagnets wrote:
Jan 12 2020 7:55pm
Some builders are interested in individual cell fusing, and some are not. To each their own. I only started this thread so any accumulated info about this will be all in one place.

If you are arguing against cell-fusing, then dont cell-fuse when you build a pack.
Certainly NOT opposed to cell~fusing for DIY ebike performance packs, even moreso when not including a SMART BMS that will also balance the cells during the entire charging process as the pack ages.
spinningmagnets wrote:
Jan 03 2020 9:28pm
Fuses cost more, and the majority of customers are extremely price-sensitive.
John in CR wrote:
Jan 06 2020 6:22pm
I don't think our ebikes have a large enough parallel structure for individual cell fuses to provide an overall safety benefit, because they would make killing an entire parallel group more likely.
spinningmagnets wrote:
Jan 07 2020 11:22am
That's a good point, I agree.


Tesla's Total Battery SAFETY innovations (raw performance and longevity), including VERY SMART Battery Maintenance Systems were suspose to prevent a battery fire. After two Tesla's hit debris in the road, piercing the car's underbody and a Federal Safety investigation all Teslas now in production have a triple underbody shield. That includes a hollow aluminum bar, a titanium plate, and a solid aluminum extrusion. Even after the fires, Consumer Reports picked the Tesla Model S as the best car overall car in 2014.

Tesla's latest battery uses different lithium cells (21700), and its liquid battery cooling system differs significantly from the Model S and X cooling design. ... https://www.latimes.com/business/story/ ... tery-fires ... It's rumored that Tesla has also obtaned 21700 cells from Samsung as Panasonic Gigafactory isn't yet able to keep up with production demands. It's also rumored that they are high capacity Samsung cells. Currently Li-NiMnCoO2 (LNM 8-1-1) seems to be the industry preference for all around cost and performance.

john61ct   100 MW

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Re: Fuse-wire for individual cells, DIY Tesla style

Post by john61ct » Jan 15 2020 11:04am

Yes aka lithium nickel manganese cobalt oxide or NMC, certainly more powerful than, adding nickel to the "old spinel IMR" aka LMO.

I believe also used in:
Sony / Murata VTC6
LG INR18650M36T aka M36

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serious_sam   1 W

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Re: Fuse-wire for individual cells, DIY Tesla style

Post by serious_sam » Jan 19 2020 8:10am

For DIY spot welded packs, welding a fuse wire to a cell seems problematic. So cost and effort probably outweighs the reward in that case.

For packs that are soldered, since it really only involves sizing the cell connecting wire appropriately and soldering those wires to a larger common "bus" wire, cell level fusing seems more practical.

It still probably won't protect against full pack thermal runaway if one cell actually burns, since the majority of ebike packs don't have adequate cell-cell thermal protection to stop a chain reaction.

But, possibly it will remove a cell that is starting to go bad, and reduce the chance that it will continue to be (over)loaded until catastrophic failure.

As a rough example: Say you run a pack with cells in 5P, and say you want to pull up to 10A per cell, so each cell is fused at 20A, and these cells have an internal resistance of 20mOhm. In this scenario, say one cell starts to sag more under load due to increasing internal failure. Each cell needs to supply 20A/4=5A each back into the bad cell to blow the fuse. The voltage difference only needs to be about 20mOhms*5A = 100mV to the bad cell. This is rough figures, but gives an order-of-magnitude to work with.

It might add some value to do cell level fusing if you're soldering your packs. The possible downside will be for those pulling high amps, that are concerned about voltage drop through the thin fuse wires. That should be considered too.

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