Pics/Info: Inside the battery pack

[rlang59]

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...

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.

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

Yes that is what I was trying to convey.

 

[JRP3]

The Panasonic numbers are rated at 0.2C (~670mA, in 85kWh equivalent to 17kW discharge):
http://www.batteryspace.com/prod-specs/8678_specification.pdf

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.

 

[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/

 

[JRP3]

Great article

 

[scaesare]

Indeed.... nice piece wk057...

 

[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.

 

[apacheguy]

Comparison of the internals provided that it is a different Rev. would be useful.

 

[palmer_md]

Well, anyone up for round two?

I have 85kWh pack #2 arriving tomorrow or Tuesday. :biggrin:

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?

 

[wk057]

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?

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...

 

[kennybobby]

Maybe a heat gun would loosen up the adhesive for easier top removal...

 

[wk057]

Maybe a heat gun would loosen up the adhesive for easier top removal...

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...

 

[JRP3]

The cover looks thin enough to heat up quickly and soften the adhesive without heating the cells.

 

[mitch672]

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...

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.

 

[wk057]

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.

They're roughly $20k. Comes out to about $235 per kWh, which is pretty cheap all things considered.

 

[rtz]

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...

Panel Separating Knife

 

[wk057]

View attachment 66086
Panel Separating Knife

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.

 

[tga]

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.

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)

 

[rtz]

CALB 100Ah LiFePo4 Cell at .85 cents / Ah

http://store.evtv.me/proddetail.php?prod=SE100AHA

 

[wk057]

CALB 100Ah LiFePo4 Cell at .85 cents / Ah

http://store.evtv.me/proddetail.php?prod=SE100AHA

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...

 

[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.