Oct 23, 2014
stopcrazypp The way they put it does not make sense. The rated cell capacity should be higher than the 85kWh pack capacity, esp. given the Tesla limits both the top and lower end of the charge cycle.�
Oct 23, 2014
wk057 I've pulled over 81kWh out of my standalone pack in testing already and I could have pulled more (voltages were still safe) but I didn't want to fully discharge the pack. I figured 5% SoC was low enough. No idea where they got their 80kWh "actual" number...�
Oct 23, 2014
apacheguy AFAIK, nobody has ever pulled 81 kWh from a live Model S as evidenced by the energy dashboard on the instrument cluster. Most I recall is 79-80 kWh.�
Oct 23, 2014
palmer_md
These guys are far more conservative on their estimates for Tesla than I am. It seems they were paid to write this report by someone wanting to compete with Tesla. Like when I had my house appraised once by a buyer for my home and once by the seller. Very different results. Great information on what exists today, but their projections are what seem to be lacking. My estimates are much closer to what I've seen DaveT write in his megaposts and newsletter.�
Oct 24, 2014
wk057 Well, the Model S doesn't allow a full discharge on the pack for a variety of reasons. 5-6% safety margin seems reasonable.
In my standalone setup I have no such restrictions, so I could use the full capacity if I wanted to, but I think I'll stick with the same methodology as when it is in the Model S to help with longevity.�
Oct 24, 2014
JRP3 I assume by "actual" what they mean is "allowed". A 3.25 ah cell at 3.7V is 12.025Wh x 7104 = 85,425.6Wh�
Oct 24, 2014
wk057 This makes sense. They obviously are writing against Tesla, however. "Actual" to me implies that this is what the battery is actually capable of... which in there case dsying 80kWh is incorrect. Something like "Permitted" or even "Available" would be more accurate and less biased against the pack.�
Oct 24, 2014
kennybobby To what voltage did you take your pack down that you are calling "5%"? Panasonic uses 4.2 (403.2 pack) as the top and 2.5 (240 pack) as the cell bottom in their testing/data sheets, just curious what you are using...
Using 4.2 @ 3.25A-hr is the 'available' if 3.25 is the correct value, times 7104 is about 97 kWh. Allow margin at top and bottom and you have an 85 kWh pack. Of course the pack label indicates 85kWh, 400 VDC which implies a lower capacity cell than the reported 3.25 A-hr.�
Oct 24, 2014
rlang59 You use the nominal voltage (3.7V) when determining the capacity not the maximum rated voltage.�
Oct 24, 2014
tom66 Highlight the "Available upon purchase..." parts and copy-paste into Notepad to read under them. Lots of juicy information there.
$218 per kWh sounds interesting. Not sure what he means by 150kW EV powertrain costing more than 150kW ICE?
Tesla's IGBT cost for the PEM in the Roadster was less than $1,500 due again to the method of using multiple individual devices, like in the battery. Additional electronics doubled this, and the cost of the casing, cables and materials probably put it around $4,500. Motors are inexpensive, consisting primarily of wound copper, which is normally done by machine.
The Model S drivetrain is extremely well optimised, using less components and less control electronics. It probably costs under $6,000 to manufacture, including the electric motor.
This report smells of "what automakers want to hear"...�
Oct 24, 2014
rlang59 150kW is ~200hp so I assume that is what they are getting at.�
Oct 24, 2014
tom66 I'd really like to see Model 3 to have 250 hp base, and a 350 hp performance model.�
Oct 24, 2014
JRP3 Neat trick.
Tesla is charging less than $5K for the front drivetrain in the SD. Of course it is smaller than the standard RWD drivetrain.
Indeed, and what I'd expect from AAB.�
Oct 24, 2014
stopcrazypp The problem is all of Panasonic's NCA cells are 3.6V nominal, not 3.7V (there may be some third parties that claim 3.7V, but all of Panasonic's official datasheets say 3.6V).
A 3.35 Ah cell would work out (3.6V*3.35Ah*7104 = 85674.24Wh) and fit with an existing cell (the NCR18650B). So I suspect their numbers are wrong.�
Oct 25, 2014
kennybobby No maybe that's what YOU do, but i monitor voltage, current and time during charging and discharging to determine capacity. Then i can integrate the current-time curve to determine the cell capacity in A-hr, and i can multiply that times the voltage to determine the energy content of the cell in kWh. No percentages, SOC, ranges, miles, or # of turtles showing, just the basic measurements doing it the same way Panasonic does...�
Oct 25, 2014
scaesare I think rlang59 was using the "royal" you, in that he was stating that's what is standard in the industry, what will be stated on a datasheet, etc...
Here's an example: PANASONIC NCR18650 DATASHEET�
Oct 25, 2014
JRP3 Tesla is a third party, and they are the ones rating the pack. They may feel that each cell sees a low enough average C rate that the nominal voltage ends up being a bit higher than the rating from Panasonic. We also don't know what Panasonic is rating the specific Tesla cells at. Of course AAB could be wrong too.�
Oct 25, 2014
lolachampcar Tesla removing the safety features and having slightly tweaked chemistry (assumption on my part) for automotive use may give them better capacity than the commercial cell when used for a specific automotive application.�
Oct 25, 2014
magnet The panny nca data sheets say 3.65V nom
it is a 3.3Ah cell
pack is over 85kw but you can only pull about 80kw out (in the car). This is "brick insurance"�
Oct 25, 2014
stopcrazypp The third parties I'm referring to are less-than-honest sellers who wish to inflate their numbers and thus say it is 3.7V.
The Panasonic numbers are rated at 0.2C (~670mA, in 85kWh equivalent to 17kW discharge):
http://www.batteryspace.com/prod-specs/8678_specification.pdf
From Tesla's blog, at 55 mph, the Model S uses about 15kW of power, so it's about the same.
http://www.teslamotors.com/de_AT/blog/model-s-efficiency-and-range
Even at 200mA (~0.06C) discharge (5kW discharge for 85kWh pack), the boost in voltage is not enough for a 0.1V increase:
http://lygte-info.dk/pic/Batteries2012/Panasonic%20NCR18650B%203400mAh%20(Green)/Panasonic%20NCR18650B%203400mAh%20(Green)-Capacity.png�
Oct 25, 2014
rlang59 The industry standard way to rate a pack it to use the nominal voltage since the output voltage of the cells will decrease as they are discharged. So while everything you have written is correct, using the maximum rated voltage in your final step is not correct which will give you an incorrect capacity.
Yes that is what I was trying to convey.�
Oct 27, 2014
JRP3 I notice the "Typ.", (Typical?), capacity rating of that cell is 3.35ah, which would give 12.06Wh using 3.6V nominal, = 85.674kWh. Maybe that's where AAB was in error.�
Nov 11, 2014
wk057 Hackaday did an interview with me about my project, and came up with some pretty cool art work too.
![]()
http://hackaday.com/2014/11/11/draft-an-intverview-with-tesla-battery-hacker-wk057/�
Nov 11, 2014
JRP3 Great article
�
Nov 11, 2014
scaesare Indeed.... nice piece wk057...�
Dec 14, 2014
wk057 Well, anyone up for round two?
I have 85kWh pack #2 arriving tomorrow or Tuesday. :biggrin:
If there are any specific questions about the pack anyone would like me to try and answer while I tear down pack #2 let me know here and I'll do my best to oblige.�
Dec 14, 2014
apacheguy Comparison of the internals provided that it is a different Rev. would be useful.�
Dec 14, 2014
palmer_md what is your source for these packs. I'd like to do one of these projects for my home as well. Are you using copart or some salvage yard?�
Dec 14, 2014
wk057 They're from salvage vehicles. I've been getting them through a contact of a salvage yard in NYC. Not sure how shipping would work to you, though...�
Dec 15, 2014
kennybobby Maybe a heat gun would loosen up the adhesive for easier top removal...�
Dec 15, 2014
wk057 I'm going to try a long razor this time, now that I know there is nothing I can damage at that elevation in the pack by doing so. I'd rather not heat sections of the pack much honestly...�
Dec 15, 2014
JRP3 The cover looks thin enough to heat up quickly and soften the adhesive without heating the cells.�
Dec 15, 2014
mitch672 roughly what do you have to pay for one of these salvage packs? I am very curious.. I can't put solar on my roof (condo restrictions against modifying the exterior of the unit), but I can do a whole house UPS with a large pack and multiple 8KW inverter modules.�
Dec 15, 2014
wk057 They're roughly $20k. Comes out to about $235 per kWh, which is pretty cheap all things considered.�
Dec 15, 2014
rtz ![]()
Panel Separating Knife�
Dec 15, 2014
wk057 Maybe. It's actually just the stupid adhesive that holds the top on once I take all of the bolts out of the top.
I think I'm going to do a gopro time lapse this time of the tear down, although I'm not fully tearing this one down. Just enough to release the modules, then I'm reselling the casing and remaining components to the salvage yard.
But to do that I have to remove the top, remove the spacers, unbolt all of the modules' electrical connectivity, remove the coolant connections from each module, and get them out of there without damaging them. I won't have assistance this time either, unfortunately as they're on vacation. So, this solo tear down will likely take a bit longer.
Going at it in the garage, so, I could pin the gopro to a wall looking down at the scene probably. Should be fun.
�
Dec 15, 2014
tga That's an interesting idea. What inverters are you considering? Outback Radians or something else?
I have this hair-brained idea to build a Lotus 7 clone (ie, "locost") as an EV. The typical CALB cells are ~2x wk057's $235/kw figure (although I wouldn't need/have room for 85kWh; more like 25)�
Dec 15, 2014
rtz CALB 100Ah LiFePo4 Cell at .85 cents / Ah
http://store.evtv.me/proddetail.php?prod=SE100AHA�
Dec 15, 2014
wk057 Thats still $265.62 per kWh, doesn't have a liquid cooling loop, and would take up more volume per kWh also... salvage Tesla pack still wins
Edit: Oh, and those are old 3 years old and not even produced anymore...�
Dec 16, 2014
JRP3 They are also LiFePO4, don't need cooling, have long cycle lives, and are probably good as new. Plus you don't have to take anything apart :wink: But yeah, they do take up more space.�
Dec 16, 2014
mitch672 Yes, was talking specifically about Outback Radians, as multiple inverters can be synced together to get multiples of 8KW
most likely 2 would take care of my house, its natural gas heat, hot water and dryer. the largest load is the Oven, and Air Conditioner compressor, and the oven doesn't need to be on "backup power", the AC is also optional, but would be a "nice to have" on backup power.
other than that, its the HPWC @ 80A to charge the Model S, everything else is lights, PC's, furnace blower, washer/dryer motors etc�
Dec 16, 2014
wk057 I'm using the Radians... 8 of them for 64kW total. Enough power for my house as it stands with all electric HVAC, hot water, range, and a HPWC...
I do plan on improving efficiency however with solar hot water and space heating. I'm not 100% sure if I want to move anything to LP...�
Dec 16, 2014
wk057 ![]()
Let the games begin...�
Dec 16, 2014
mitch672 never mind the pack, how did you get a yellow Model S?
(8) Radians, really? 266 Amps, that's huge. I guess if you have an all electric house, does seem like overkill though.�
Dec 16, 2014
wk057 The yellow Model S is my fiance's. It is a wrap. Glossy Yellow Wrap Completed
The decision to do 8 Radians was basically due to the auxiliary heating in the HVAC setup. With the HPWC going and the HVAC aux heat, I'm already at 50kW draw before any other loads. During super cold days the aux heat runs for a few minutes at a time.
Eventually I can scale it down, but, as things stand that's what I need. I currently have 320 amp service to the house. (two 200A service panels fed from a 320A meter box)�
Dec 16, 2014
henderrj Pack two
Very interested. Keep up the good work - give us anomalies; anything different.
thanks,
�
Dec 16, 2014
Moonwick ...any "Hi, wk057 -- love, Elon" messages engraved in the aluminum. :biggrin:�
Dec 16, 2014
nwdiver Have you seen these?
http://www.geappliances.com/heat-pump-hot-water-heater/�
Dec 16, 2014
drees Many people disable the resistance coils on heat pumps to avoid those spikes in demand. If they only turn on for a few minutes at a time, you can probably live without them and save a decent amount of energy and reduce your peak loads, though you may get a bit of cold air during defrost cycles.
Looking forward to the tear down!�
Dec 16, 2014
wk057 Finished the tear down in record time since I knew what I was doing this time around. lol.
Compiling my time lapse video.
�
Dec 16, 2014
wk057 Tear down time lapse
�
Dec 16, 2014
apacheguy Congrats on doing it in one fell swoop. What was the total time, start to finish? Was there a reason you patched the enclosure back up after you were finished?�
Dec 17, 2014
spaceballs So awesome!�
Dec 17, 2014
J1mbo Awesome! Was it a D pack or something else?�
Dec 17, 2014
wk057 Total time of the video clocked in at 3 hours 11 minutes, plus some time during cuts where I gathered some things to use (like my air compressor).
I put the top back on with a few screws because the salvage yard was buying the casing back from me since I only needed the modules, fuse, and contactors. I have no use for it otherwise so, no point in keeping it. I'm going to probably build the crate again later also.
Was another D pack.
Pack voltage was sitting at 320.5V (3.34V per cell, 20V per module). You can see me take the voltage after I get the first part of the cover peeled back. Pretty dead, but not below 0 miles this time like the last one.�
Dec 17, 2014
ACDriveMotor I may have missed it but were the cells in your previous pack OK even though the pack was below 0 miles?�
Dec 17, 2014
wk057 Yes. They were fine. They were at something like 3.2V per cell, which is dead, but not destroyed. The 0 mile barrier in the car still leaves something like 5% capacity available IIRC.�
Dec 17, 2014
tezco Neat. Can Tesla access the contactors without having to peel back the main cover?�
Dec 17, 2014
tom66 Is the plan to extend your current battery system with this then?�
Dec 17, 2014
randompersonx Yeah,
I was wondering if you have any insight on how Tesla does this repair when the contactor fails. Especially interesting since apparently they are starting to do this at SC's.�
Dec 17, 2014
Zextraterrestrial 170kWhr of storage!! wow.
cool video�
Dec 17, 2014
mitch672 yes, but he's using (8) 8KW Outback Radian inverters, he'll need that for it to function.
64KW peak power...�
Dec 17, 2014
tga That's pretty impressive. When we have a power outage, I have to scale back to keep the 7kW generator happy (that still gives me well pump, heat, microwave, fridge, some lights, TV, internet, and laptops). But if I could run the oven and charge the car...
Anything worth doing is worth overdoing!�
Dec 17, 2014
wk057 Hi,
I am the supplier of both packs, anyone interested in such a pack, please fell free to contact me at firstpl@gmail.com�
Dec 19, 2014
rdrcrmatt I've tried to add additional information to my first post here in this thread, but the administration here has disabled the ability to do so as a bad solution, IMO, to a very small problem with a very small number of forum members.
While this policy is in place I will no longer be adding new information to this thread.
I will be self-hosting a page with all of the information and images I've taken through the process soon, which will have my updates.
If in the future I am able to add information here I will do so.�
Dec 19, 2014
pgiralt
Link to your site? These are some of the best posts on the site.�
Dec 19, 2014
wycolo Ask the Mods to turn the post into a wiki post - then you can update.�
Dec 19, 2014
wk057 Recently I've noticed that the EDIT option has been removed from my 'old' posts. So then just make a new post with heading to 'add to post dated such n such'.
--�
Dec 19, 2014
bonnie I dislike the wiki style on this forum. It is nothing like a normal thread.�
Dec 19, 2014
pgiralt I've wondered why that's not asked, too. The option was offered by doug, early on.
wk057, just report your first post (as doug suggested originally) & ask that it be made into a wiki so you can continue to edit. Others have done that. Very simple to do.
- - - Updated - - -
Really? What is it you don't like? It has worked really well for me in the past.�
Dec 19, 2014
NigelM You may be thinking about the Wiki section of the forum. I think the "wiki post" is different in that it just turns the first post into a wiki, but still shows up like any other thread - I may be wrong though.�
Dec 19, 2014
wycolo You're not wrong; that's exactly how the Wiki-post feature works.
Here's a couple of different examples:
Articles-megaposts-by-DaveT
Model-S-Delivery-Update
List-of-all-TSLA-quarter-reports�
Dec 19, 2014
NigelM So point to a Wiki-Post already!
--�
Dec 19, 2014
wk057 Just did, I was adding some example links in my post while you were typing.�
Dec 19, 2014
wycolo If it doesn't disrupt the flow of the thread (tabs are annoying) and I'm the only one who can edit it, then please do make the first post a wiki post.
This, however does not solve the issue of adding new unrelated content to the forum since users can not start threads like this without moderators... and if they could then I would see no reason to start a thread in any other fashion, thus defeating the whole edit time limit in the first place. Seems much more sane to just revoke the 1440 minute edit policy change.�
Dec 19, 2014
paulwesterberg Thanx! One really has to stumble upon these; they can't be accessed as a group (type) somewhere specific.
--�
Dec 19, 2014
wk057 I agree. The pagination on this site is horrible. So many useless meto posts that add nothing to the discussion but display just as prominently as helpful posts. I mostly use the reddit forum because I find it much easier to read.�
Dec 19, 2014
NigelM I agree the pagination is pretty annoying, with no real way to change a setting to display more posts per page or anything. However, I find reddit to be a cesspool of trolls and definitely do not prefer it over... well, over anything. But that's not really what I was referring to. I was referring to the different tabs for the content vs discussion in the Wiki section.
This forum is by far the best Tesla Motors related forum by far, even much better than the company's official forum IMO. But it definitely is not perfect as these issues illustrate. The mods definitely do a good job overall, but I definitely think this policy change is a horrible one.
- - - Updated - - -
Wikis are useful for some things. But I don't think a publicly editable wiki is a solution to everything that needs editing past 24 hours...
I'll elaborate on why I don't like the Wiki section of this forum. First, it is not categorized. It is not associated with any of the existing and utilized categories in the forum. It does not show up under the "New Posts" section that I check regularly, and seems to have virtually no exposure whatsoever aside from a link to "Wiki" at the top of the page. The sum of all of the view counts of every wiki post in that section is less than the view count of this single thread. I think that alone should demonstrate that there is an issue with it.
Combine all of that with the lack of editing permissions, the unnecessary tabs to get to a thread-like discussion, lack of a signature showing for the OP, and other misc discrepancies between the wiki and normal posts... well, suffice it to say it should be obvious why I dislike them.
- - - Updated - - -
Looking at the other "wiki post" threads, seems the moderators are using a kludge of making a publicly editable wiki post owned by a moderator-run user named "Thread Summary." This is definitely not preferred.�
Dec 19, 2014
wk057 Actually you can customize a fair amount if you go to "Settings" (top right of this page) and then "General Settings" (in the left menu), you'll see a long list of options including how threads are displayed and how many posts per page etc.
You're right in that it's not perfect, but this is a free-to-use forum which exists on donations, very little advertising income, and volunteer moderators. When Doug(Admin) logs in later he can hopefully take a look at the Wiki-post addition for this thread.�
1/1/2015
guest What kind of donation do I need to make to reverse this policy change? Or be able to moderate my own posts...
- - - Updated - - -
And honestly, I had looked before and never saw the setting for posts-per-page. Set to 500 now and things feel much better on that front at least. Thanks for getting me to take a second look.
�
Dec 19, 2014
jerry33 I'd be happy if it just sent every post as an email the way the Yahoo groups do.
As far as donations go, I donated some time ago now and I thought that Doug was doing something as a yearly reminder. The Mods here do great work (even if they're often not appreciated) and I'm aware of how much time, effort, and cash it takes to keep things going.�
Dec 19, 2014
NigelM You're welcome! For folks that prefer the threaded type view (a little more like reddit) that option is also customizable from the "General Settings" page. There's also a help page describing individual options here--->faq_vb3_thread_display�
Dec 19, 2014
doug This useful side discussion will probably be moved to site feedback. Thanks for the input.
I'll work on a solution about post edits. In the meantime, for this type of content, the blog section might make more sense than the wiki. You could give that a try.
�
Feb 18, 2015
Kiers Curious...how many kWh's of energy does it take to fully charge this 85kWh battery pack?�
Feb 18, 2015
wk057 Depends on the efficiency of the charger. The grid-based one I have is about 90% efficiency, so about 93kWh if it were completely dead... not going to let it get that low though. The solar charge controllers I have are more efficient.�
Mar 20, 2015
SeattleMatt I'm trying to understand the wirebonded fuse links on the 18650 cells. From this thread we learn that the pack is 96S74P, and if 3.1AH cells this means that 1C is 229A.
The Model S at 70 mph has an average C rate of about 0.25C (since it can cruise that that speed for nearly 4 hours). The P85D can pump out 691 HP for 2 seconds, which on a full pack means that's about 5.5C. So, we know the average current on the cells is about 0.25C, and the peak is about 5.5C. A rigorous hill climb would be about double the flat cruising (about 0.5C), but overall, we're left with a peak to average current consumption of roughly 10:1.
Using Onderdonk's equation for fusing and assuming copper, a 0.5 mm dia wire could withstand 5.5C for about 11.2 seconds, and the impedance of 10 mm of 0.5mm wire is about 84 mOhm per meter, so 1 cm would be under 1 mOhm. The cell impedance is probably around 50 mOhm, so the wire bonded wire contribution is minuscule.
Thus, it seems roughly that the wire bonding wires are probably on the order of 0.5 mm in diameter. And the pictures at the beginning of this thread hint that roughly 18 to 26 of these wires could fit across the 18mm cell diamter. But I wonder if anyone has published an actual measurement on the wire diameter? And I assume they aren't pure copper, but an aluminium alloy such is used for wire bonding power semi conductors.
TIA�
Mar 20, 2015
wk057 I'm actually in the process of dissecting a damaged module (from a third pack.........) and I'll be doing a bit more tests on the cells and these fuses in particular when I get more time.�
Mar 24, 2015
llavalle I'm trying to wrap my head around the module configuration (basically how each cell is wired in a module).
Each module has 74x6 cells, right? I assume they are 6S74P, right? That means you should have 6 separate bus-bar type of backing connecting the negative terminal of the battery (one for each 74pack of cefor but from your picture I can only see 4.
Is there something I'm not seeing?
@SeattleMatt, I had to read the "96S74P" nomenclature a couple of times to realize what it meant...even though I'm very familiar with this (LiPO RC enthusiast here). I'm just not used to numbers that big! I run 4S2P packs in my drone
For those of you who don't know what it means : 96S = 96 cells in series. 74P = each series has 74cells in parallel. Since most modern lithium based cells have a max voltage of around 4.2 volts, you can calculate the max voltage of your battery pack by doing "number of S" x 4.2. In this case, 403.2 Volts.
Btw guys, do you know what's the max discharge and recharge rate of these cells? I was thinking of building a small battery back for my hexacopter using 18650A cells but I'm concerned with my amps draw. I alreay have IMR cells that can take way more but they are obviously a lot less dense (weight wise) and since this is a flying machine - every grams counts.�
Mar 24, 2015
peter_east Hey wk057,
I've designed large lithium ion packs and systems so might be able to help if you have questions. Great photos, btw. One thing I noticed is that you refer to the board on each module as a BMS but it's really just a monitoring and balancing board. How do I know? Because everyone does it that way and I can tell by looking at it. The board has a micro, a precision reference, and a set of resistors to drain and high VSOC cell groups. There is also an isolated CANbus transceiver, you can see the trace separation areas on the PCB. There's an inside pack CAN and the external CAN. The actual BMS is the big PCB near the contactors and I'd love to see a high res photo of it as well. Unless you want to do some time-consuming reverse engineering you're not likely to use their BMS. Among other things it wants to talk to other vehicle components and unless you have an internal spy in Telsa who is willing to risk their job you're not going to get the mapping of its registers on the bus. You're probably not going to figure out even the small balancers either, although that's at least a doable project in a reasonable amount of time if you're good at code and they haven't locked the chip.
As I said, everyone is basically doing the same thing, a small balancer and measurement board on each battery module, powered by the module, and an isolated CAN transceiver talking to the BMS which makes all the decisions and sends balancing commands (because it has to have knowledge of all series cell groups).
Cool project you've undertaken! Like I said, if you have any questions, please ask, and I'd love to see a nice photo of their BMS (just the component side) to compare to what I had done in my designs.�
Mar 24, 2015
wk057 Each module has six sets of 74 cells. These sets are wired in series using five bus plates that run on the top and bottom of the modules. Half of the cells are inverted. So the positive terminal connects to the positive of end of the first set of cells, then the negative of those cells on the opposite side is connected to a bus plate that connects those 74 negatives to the next set's 74 positives. Then the next set's negatives on the opposite side are connected to a bus plate that connects to those 74 and the next 74's positives. It goes up one side of the module and back down the other side of the module so that the ends of the series are on the same side of the module on the top. Pretty nice design.
Then the modules are all connected in series inside the full pack.�
Mar 24, 2015
llavalle Wow ok! Pretty neat design indeed. Very compact and lightweight.
One of the module would make an excellent battery source for my lipo charger while I'm on the go.
I usually use my car battery but the 12v batt in the S is scaring me a bit...unless the dc to dc converter is charging it...�
Mar 27, 2015
wk057 So, I have a module from a 3rd pack that is damaged and I decided to dismantle it to harvest the good cells. Honestly, I don't know what I've gotten myself into. My original assessment of the pack being built like a tank definitely applies.
Each cell is individually glued to the hard plastic framework that holds everything in place. This framework is glued to the aluminum rails on the sides. I butchered the rails off of the thing in hopes to be able to maybe torque the whole thing apart. No dice. I literally jumped up and down on it while having one end propped up and it was solid as concrete.
I managed to remove about 6 cells without damaging them through brute force efforts on the plastic on the edge row of cells, and 3 others I punctured in the process. I think the only way to safely remove them would be to somehow dissolve the glue, unless I'm missing something.
Oh well.�
Mar 27, 2015
Johan Pictures? Pretty please, with sugar on top...�
Mar 27, 2015
wk057 Yeah, was getting there.
![]()
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![]()
�
Mar 27, 2015
Johan Very cool. So it's pretty clear then that the Tesla engineers are treating the modules as the smallest functional piece of each pack.�
Mar 28, 2015
kennybobby Great photos! Maybe a low temperature heat gun could blow 200-300F air and help loosen the adhesives for you. My curiousity is awake and now i have questions.
Do you have a micrometer or calipers to measure the diameter of the fuse wire? Can you determine the material of the fuse wires--copper, silver, aluminum, steel...?
It looks like the copper cooling tube is covered with ?foam tape, and there is also some sort of cloth tape showing. Is the cloth tape only at the end turns or touching every cell?
The sheet of metal that connects the 74 cells in parallel appears like some sort of foil that rolled up--i always thought it would be solid copper or aluminum "plates". Can you determine the thickness and material of those?
Those modules are an amazing assembly of engineering excellence--and that battery pack is a game changer to make BEV transportation an economically-feasible reality.�
Mar 28, 2015
JRP3 Or maybe a hot wire knife to slice through the glue without heating the cells.�
Mar 28, 2015
doug Looks more like 3M thermal conductive tape.�
Mar 28, 2015
apacheguy Doesn't it have to be hollow on the inside to allow the coolant to flow?�
Mar 28, 2015
JRP3 The tape holds the hollow copper tubing to the cells, the coolant flows inside that tubing.�
Mar 28, 2015
cgiGuy I know these may be more valuable as good cells, but if you find a way to get them apart, I'd be willing to buy one just to use as a demo for people who ask about the battery. Bet a lot of others would, as well. I wish Tesla would give us a "keychain" with a fake battery on it with the car.�
Mar 28, 2015
Pollux I carry around a couple of 18650s that I often show people when they are looking at the car. I ordered them off of Amazon from somewhere in China. Yes, not identical to what's in the battery pack. But close enough for most people.
Having said that, if @wk57 goes into the "ship a few cells for customer demos" arena, then sign me up!
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Mar 28, 2015
hcsharp How did the punctured cells behave? Did they start smoking and/or catch fire like a laptop cell would? I wouldn't store those in your house.
So it sounds like this module is different from the previous packs that you got WRT the glue? Why do you have to separate the cells from the modules? Can't you just keep each module intact like you did with the previous packs? Thx for sharing your adventures with us!
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Mar 28, 2015
wk057 The punctured cells actually still work fine, surprisingly. Nothing catastrophic. I put them on charge out in the yard, just to see what would happen... and nothing. They charged normally.
This module is from a 3rd pack that I received 6 modules from. This particular one was damaged and not usable in my setup, so, I'm dismantling it.... for science!
As for demo cells... I'm not sure I'd feel comfortable with having these sit around destined to discharge. Without being used, eventually the voltage will drop to the point where it is unsafe, even if you insulate it and all. I wouldn't keep a loose one in my glove box, that's for sure.�
Mar 28, 2015
Johan Did you try to read the QR code on the cells? Would be interested to know what it says. Maybe it's a link to a secret data sheet? (one can dream right?).
Anyway I'm on a SurfacePro pad here and don't have and good image manipulating software installed so not able to process it well. Someone wanna try?
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Mar 28, 2015
wk057 I actually did a while back... seems to just be a serial number. Nothing useful.
Edit: Here is my post earlier:
I actually reconstructed the barcode by hand for that one, since it was impossible to get a good pic.�
Mar 28, 2015
Johan Impressive.
You've got an eye for detail�
Mar 28, 2015
wk057 so yeah... about that damaged module I was liberating cells from... done with that.
Somehow one shorted out while I was removing glue/plastic. Immediately went red hot, popped, flew off like a firework and of course, directly up into an open door to my basement ~15' away. (I was working on this outside by the pool, which is 3 steps down from the basement door and ~15' away.) Slid across the tile floor and landed in front of my fiance's PC another 25' away. Sat there for several seconds while I was chasing after it with a fire extinguisher in hand. Hit it a few times with the ABC chemical, and the chemical boiled on the shell. Seemed to cool is a bit, though, so hit it a few more times, grabbed it with a pair of pliers and leather gloves and threw it back outside in the dirt..... along with the entire rest of the module and the rest of the cells I removed previously.
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So, think I'm done with that project.�
Mar 28, 2015
patrick42h That's a little scary. I'm glad you're fine and no major harm was done. I guess this is just a reminder that if these cells store enough energy to move a 5-ton car around, they can be tricky if they get damaged.�
Mar 28, 2015
JRP3 Ouch, a little more exciting than you were expecting. :scared:�
Mar 28, 2015
lolachampcar wk,
you crack me up..... like a kid in a candy store. I only wish I was there next to you prying away
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Mar 28, 2015
jerry33 That description reminds me of one kind fireworks we had when I was a kid. The kind with the 40x2 mm metal "wings" on the side. I see they now have plastic wings.
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Mar 28, 2015
purplewalt I have been following this thread with interest for quite some time.
You have a lot more patience and tolerance than I would ever be able to muster.
Might be best to quit while you are still ahead (and in one piece).�
Mar 28, 2015
wk057 Definitely was having fun up until the rocket cell. lol.
And honestly, if it didn't fly inside the house (ie: if I didn't leave the door open) it probably would have been a little exciting instead of dangerous. lol. I figured if one went nuclear I would be able to just get it on the ground and hit it with the fire extinguisher and/or garden hose. I didn't expect it to literally take off like a rocket and fly that far all the way into the house :-\
Edit: Cleanup of the aftermath complete. Total permanent damage: None.
Well, this was a somewhat expected event. If you short the cell with no protection, it's going to go up in flames, no doubt about it. In this case my forensic analysis leads to me to conclude that I had accidentally hit the edge of the positive end and bent the negative casing into it. There was no stopping it after that. In hindsight the hit that caused that damage was probably almost a minute prior to what I initially thought caused the short, so the battery rocket didn't happen instantly like I had originally thought.
That said, I think the production setup I have in place is much safer. Cell level fuses are in place to prevent these types of shorts. Climate controlled area. BMS, fire protective measures, etc.�
Mar 28, 2015
kennybobby There is always interesting experiments in your lab...Don't stop the research.
So do you think maybe 73 cells were shorted thru the case of one cell? How many amps?�
Mar 28, 2015
wk057 I had removed the bus plates prior to this, so, it was only one cell at ~50% SoC. But looking at whats left of it (finally cooled off after a couple hours), I can see where the negative casing was shorted to the positive tip plate where the insulating ring there was smashed by my accidental whack on it. So it would have been a pretty high current direct short. Even if it were only the same amount of power the P85D uses at full power, that's still something like 18A.�
Mar 28, 2015
Danal I've tried to get bad behavior from fully discharged "bag" style LiPo cells (below about 2V) every way I can: I've shorted them, cut them, driven conductive things through them (nails, screwdrivers), shot them (with a .22), tossed them in big fires... and I couldn't get any hazardous behaviors.
As you discovered, charged cells are an entirely different matter.
But a "Demo" cell? Discharge it, then clamp copper braid around it with a "C" clamp for a couple of days. After that, its not going anywhere from its own energy.�
Mar 28, 2015
bxr140 If you haven't given up and you haven't already done so, use a hot knife to cut away the fillet and any other exposed epoxy. Then, as suggested already, use a heat gun to soften up the bondline. As soon as you get close to the transition temp you should be able to pop the bondline by twisting or prying the cell, or otherwise using whatever leverage is geometrically possible. (Twisting is usually the best)
Ideally you should keep direct heat off the cells, up to and including shielding the cells with a hunk of metal or something more exotic (if you have the means), like high temp blanketing or something. If you can heat from the backside that's even better.
I have no idea how hot is too hot for the cells, but you can tape a thermocouple to the cell on the part most exposed or closest to your heat source.�
Mar 28, 2015
wk057 I thought about this, and I took a piece of the framework that I had broken off to my heat gun to see what it would take to loosen it. The glue or whatever it was wouldn't melt. The plastic housing was burning and the glue was still solid. :-\
Plus, heat + these cells scares me a bit at this point. Data I've read suggests thermal issues possible beyond 150F.�
Mar 28, 2015
bxr140 It won't melt, but it doesn't need to. It just needs to soften enough to the point where you can pop the bondline. Where I work (we build satellites) we have to debond expoxied things all the time. Its all about being patient and controlling the heat. Not everyone has the right touch, but based on the practical/hands on competency shown in your threads, I suspect you won't have any problem keeping it under control.
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