Battery interior and Repair of Model S

[SCW-Greg]

This is the best one i have. I will take others when i go back there next week. TO be clear the number of cells should be the same. it is just that the connectors are in the opposite directions. View attachment 50637

Interesting in this picture, in that there looks to be hand drawn sharpie marks between the runs, and three different individual cells marked/encircled by a red "C". Was this done at the factory? Or since the wreck?

Are those three cells marked as deficient?

 

[JRP3]

This would be a perfect time to find out exactly what amp hour capacity the individual cells have. Pull some good ones out of the damaged module, fully charge them and then fully discharge them and measure the capacity. Unless there are markings on them already designating the capacity.

 

[freds]

Are any of the cells damaged or is it just damage to the cooling system feed lines?

Not advocating anything here but since the battery pack is arguably the most dangerous part of the car maybe Tesla should come up with a policy requiring it's replacement if damaged and restrict damaged packs from being supercharged, etc.

 

[spaceballs]

I had the same hand drawn sharpies on my battery sheet on my roadster. It's likely from QA when they do the wire spot weld, the ones I has circled in red were spot welded more than once (you can see the spot weld marks).
Interesting enough I had one wire spot weld had a loose small metal ring that accidentally looped through in the center of it (guessing it came from the spot welder). It could have been a liability issue if it ever eventually broke the fuse wire, and shorted itself between battery bricks (I ended up removing it for safety).

Interesting in this picture, in that there looks to be hand drawn sharpie marks between the runs, and three different individual cells marked/encircled by a red "C". Was this done at the factory? Or since the wreck?

Are those three cells marked as deficient?

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Think you can post photo of the other side of the module? curious what the BMS looks like.

This is the best one i have. I will take others when i go back there next week. TO be clear the number of cells should be the same. it is just that the connectors are in the opposite directions.

 

[TonyWilliams]

Ok, now I'm more motivated to open up the Rav4 EV pack !!! Where's a good place to buy rubber clothes and boots?

 

[islandbayy]

Ok, now I'm more motivated to open up the Rav4 EV pack !!! Where's a good place to buy rubber clothes and boots?

The "Adult" superstore just off the freeway in the middle of nowhere @_@

 

[daxz]

This one is perfect. I would imagine the number of cells should be the same too.

Edit: I just counted this one. It seems to be 444 cells, which if we break into 6 groups would be 74 cells per group (verifying the guess from before). Total cell count would be 444*16 modules = 7104 total cells, which matches the best guess we have had so far.

I count 32 on each row. 32 + 32 for each cell group = 64 and I also count 7 groups 64*7 = 448 * 16 = 7168 cells. I'm I looking at the right thing?


Outer rows only have 31 in each row.
Counting with rows it's 32 for each center row and 31 for outer 2 on each side (4 less) = 444 *16 = 7104 cells

 

[Saghost]

This one is perfect. I would imagine the number of cells should be the same too.

Edit: I just counted this one. It seems to be 444 cells, which if we break into 6 groups would be 74 cells per group (verifying the guess from before). Total cell count would be 444*16 modules = 7104 total cells, which matches the best guess we have had so far.

It looks to me like 444, too - three plates that each have 148 cells welded to them. It'd be nice to see the other side of this pack - presumably the plates are split in the opposite way (and the half of the cells upside down compared to the other half) to break the "groups of 148" that this seems to show into two 74s each, one above this plate and one below (electrically, I mean - the plate being the positive end of one stack and the negative end of the other stack.)

It looks like there's three sense lines running to an electronics pack (BMS?) on the opposite end (the one for the only sheet that doesn't reach the other end is clearly visible in the middle of the pack,) and a pair of tube ends (for coolant, I assume?) on this end.
Walter

 

[stopcrazypp]

It looks to me like 444, too - three plates that each have 148 cells welded to them. It'd be nice to see the other side of this pack - presumably the plates are split in the opposite way (and the half of the cells upside down compared to the other half) to break the "groups of 148" that this seems to show into two 74s each, one above this plate and one below (electrically, I mean - the plate being the positive end of one stack and the negative end of the other stack.)

Yes, the split is kind of unusually shaped (and on at least this side it seems to be 3 groups instead of six). Your guess seems to make sense electrically.

 

[qwk]

Ok, now I'm more motivated to open up the Rav4 EV pack !!! Where's a good place to buy rubber clothes and boots?

The rav4 pack uses the same modules as the model S, and most likely have the same exact cells in them.

 

[SCW-Greg]

I count 32 on each row. 32 + 32 for each cell group = 64 and I also count 7 groups 64*7 = 448 * 16 = 7168 cells. I'm I looking at the right thing?

Yep, as daxz, notes, if you look closely, the outer two rows are short two cells each. -4

 

[scaesare]

Thanks for posting these pics, nir... very interesting.

May I request a rather close-up picture of the "terminal end" of the sheet? I'd like to see what the electrical connectors look like...

Thanks.

 

[nir]

I will ask martin to do that, and i will report back.

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So the latest, is that we have found a used complete battery pack, but i only need the 1 module. Anyone need an almost complete battery pack - 1 module?

 

[Cottonwood]

So the latest, is that we have found a used complete battery pack, but i only need the 1 module. Anyone need an almost complete battery pack - 1 module?

In the mean time, figure out how to do a slow, manual charge to say 60%, perhaps module by module, then check month to month to see what the self discharge rate is so that you can come up with a schedule to recharge from 40-50% to 60%. Keeping the modules at ~50% charge is most likely the best storage method.

Great reporting! Thanks and Good Luck!

 

[stopcrazypp]

I will ask martin to do that, and i will report back.

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So the latest, is that we have found a used complete battery pack, but i only need the 1 module. Anyone need an almost complete battery pack - 1 module?

Wouldn't it be better to just use the used pack as a whole? The cells would likely be better balanced this way and you wouldn't have to do repairs to the damaged pack. Or is that used pack only 60kWh?

 

[JRP3]

In the mean time, figure out how to do a slow, manual charge to say 60%, perhaps module by module, then check month to month to see what the self discharge rate is so that you can come up with a schedule to recharge from 40-50% to 60%. Keeping the modules at ~50% charge is most likely the best storage method.

I don't think that's necessary, just keep an eye on the charge level and don't let it drop below 10%-20% or so. A disconnected pack should show almost no self discharge. It's also a good way to check for issues, if one or more modules is showing excessive discharge that probably means it has bad cells or faulty management circuitry.

 

[trigga71]

Where did you find the battery pack? What size is it? and for how much?

 

[wk057]

I might actually be interested in it, depending on cost, even if it is down a module... or just whatever modules you don't need to use. Let me know a price and I'll see if I can consider it for my project.

 

[Lerxt]

Now a good project would be to salvage parts from the battery and make an add-on battery to increase range....

 

[nir]

Answers to questions above:

This would be a perfect time to find out exactly what amp hour capacity the individual cells have. Pull some good ones out of the damaged module, fully charge them and then fully discharge them and measure the capacity. Unless there are markings on them already designating the capacity.

If you take a picture straight down on a left "pack" and right "pack" (since you say they are different) such that we can count the amount of cells, you can finally be able to help us solve the mystery of how many cells the Model S contains. If I'm not mistaken, there are 16 modules (or as you call them "packs") in the 85kWh pack. You show 14 in the flat section (1 damaged one taken out). There should also be two more stacked on top of each other near the front of the car.

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Originally Posted by dm33
I think (but am not sure), that Tesla manages the battery charge at a much lower level than half a pack. It will try to balance the cells to maintain proper change. Not sure if its down to individual cells or a relatively small group of cells.
Yes, it's a much smaller level. From looking at pictures of the battery diagnostic screens, Tesla manages it at 6 groups per module. Given 16 modules in total (for 85kWh pack) that's 96 groups of cells. One group would have all the cells wired in parallel so that they self balance (however each group must be balanced individually).

Battery modules – all 16 of them – are divided into 6 sections and voltage is individually monitored on each of them. It is passive monitoring. Each section connects 74 cells in parallel, then all 6 sections are connected in series to complete one module. Battery does not have self-balancing capability, charging or discharging is being done at the same time with the same current on all battery modules / sections in whole battery pack. Smallest group of cells that can be charged / discharged is one module.

Tesla designed battery modules that are connected in mixed parallel and serial configurations for few simple reasons:

- small cells could not be connected all in series due to size and electrical properties. (if all connected in series voltage would be about 25.500 Volts)
- if few cells will deteriorate, whole battery pack will still be usable unless voltage difference between sections will be to great (then system will shut down battery pack).
- manufacturing is easier in that configuration as each cell is connected with hair thin short wire, then sections are connected with metal plates all at once.

Final charge is done once all modules are assembled all together into battery case. Once installed in battery pack, battery is charged during final charge using constant current method.

Martin