Plan: Off grid solar with a Model S battery pack at the heart

[MassModel3]

Good point, forgot about that. I have some leftover Tesla stickers that will work. Or shrink wrap.

Isn't that why God created duct tape? Fixes everything, cures all woes, no job too big or too small. Duct tape and super glue -- world's two best inventions.

...and railguns. I still vote for WK using railguns to fend off the zombies. It's not like he won't have the power. Make a great garage project once this current one is finished.

 

[okashira]

I see about 7% or 8% here from 3.2V to 2.5V at C/3 is not worthed to go below 3.2V

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A single-cell flashlight probably isn't a problem... but multi-cell OTOH.

That said, I have a 2-cell light in which I occasionally use 16850B's (while my protected cells are recharging). Livin' life on the dangerous side!

That's an easy fix. Ill be making custom battery packs from Model S cells shortly. They are actually much safer then most 18650's. Protection PCB is un-necessary.

 

[wk057]

View attachment 76071

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That's an easy fix. Ill be making custom battery packs from Model S cells shortly. They are actually much safer then most 18650's. Protection PCB is un-necessary.

Oh, so you have the cells? And this graph is from is actual testing? If so that is excellent.

 

[electrodacus]

View attachment 76071

Looks to be the same just higher capacity still about 8% gain only if you go below 3.2V to 2.5V
Not worth the degradation for that 8% additional capacity.
The 1A discharge curve looks like about 2.8Ah at just below 3.2V vs 3.05Ah or so at 2.5V
Thanks for doing the tests seems to confirm is Panasonic NCR with a bit higher capacity. I'm sure cycle life will be the same as the original spec.

 

[Ampster]

........
Thanks for doing the tests seems to confirm is Panasonic NCR with a bit higher capacity. I'm sure cycle life will be the same as the original spec.

Well, not really. The discharge curves may be similair but, as others have said, the Tesla cells have a different chemistry and the life cycle is significantly above the 300 cycles in the NCR spec.

 

[wk057]

Test complete. 38 hours 25 minutes runtime. 75.1 kWh AC output.

 

[okashira]

Oh, so you have the cells? And this graph is from is actual testing? If so that is excellent.

you mean these?

Heat shrink-ed with protective washers, ready for use in any application.




I just got this 8-channel, programmable, 4-wire voltage sensing, datalogging, 10A max, battery cycle tester from China:

The test data I posted above is from my programmable DC load that required a-lot more baby-sitting.

 

[Tedkidd]

Well, my fiance is thrilled. I've reclaimed about 100 square feet of floor space.

View attachment 75891

191 kWh; 2,016 lbs of batteries; ~20 cubic feet.

That is a thing of beauty!


After looking at hundreds of utility bills it seem 10k per year is about average in my neck of the woods, assuming heat from other sources.

In NY NYSERDA has completely perverted the EE business, so I'm mostly working on big homes or small commercial rather than average Joe homes now. Thats not completely accurate, I'm also doing a fair amount of mentoring work in Ohio, so I do still see bills from average homes.

ANYWAY, two recent large local homes I've worked on use over 40,000 kWh per year,... Plus the 2-3000 therms of gas. I convinced one of these clients to get a p85d (he was going to wait for X), but this electric use is before EV.

So I don't think you should feel your usage is out of line.

Can't imagine your brand new Heat Pumps are bad. If you are thinking the house needs improvement, one good "tell" about efficiency is your CFM50 leakage number. Have you had a blower door test?

 

[electrodacus]

Well, not really. The discharge curves may be similair but, as others have said, the Tesla cells have a different chemistry and the life cycle is significantly above the 300 cycles in the NCR spec.

Do you have any proof the cells use different chemistry and if so what is the chemistry?
As I mentioned in earlier comments that 300 cycles done by Panasonic are 100% DOD
If you charge the cells mostly to 80% SOC and then discharge them to 10 or 20% SOC even better most of the time then life cycle will be much larger with the same battery.
If you use the cell most of the time in the 20% SOC to 80% SOC it may last about 4x cycles so even if that is just 60% usable that is still about 240km for model S.
240km x 1200 = 288000km before battery is at 80% of original capacity.

 

[wk057]

you mean these?

View attachment 76096

View attachment 76094
Heat shrink-ed with protective washers, ready for use in any application.




I just got this 8-channel, programmable, 4-wire voltage sensing, datalogging, 10A max, battery cycle tester from China:

View attachment 76095

The test data I posted above is from my programmable DC load that required a-lot more baby-sitting.

Impressive. Just one question: How the heck did you liberate them from the module? I fought with the one I'm breaking apart for a while just to remove a few cells... there a trick to this? hehe

 

[Ampster]

Do you have any proof the cells use different chemistry and if so what is the chemistry?
........

How an Upgraded Tesla Travels 400 Miles on a Charge | MIT Technology Review

BU-808b: What causes Li-ion to die? Battery University

The Chemistry is NCA (Lithium Nickel Cobalt Aluminum Oxide)
Types of Lithium-ion Batteries – Battery University

 

[adiggs]

Electric lawn mowers.

Electric fences.

Neighbors.

Tesla coils.

Electric catapults.

Make your own aluminum.

Lasers (with or without cats and/or sharks).

Not that I'm anywhere close to needing to solve the problem, but I was thinking that if you had the right electrical equipment to chip / shred / compress / create wood pellets, then you can use summertime excess energy to convert raw logs into wood pellets, and store that excess energy as burnable pellets for winter.

Come winter, you can burn the pellets directly for heat. In the really extreme version, at least in theory, you get a generator that will take steam / heat from burning pellets and generate electricity from that. Now you can recover some of the energy (with lots of waste heat to keep the house toasty) over the winter, thereby transferring excess energy from summer time into winter.

 

[wk057]

Was on topic here earlier:

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.

 

[electrodacus]

How an Upgraded Tesla Travels 400 Miles on a Charge | MIT Technology Review

BU-808b: What causes Li-ion to die? Battery University

The Chemistry is NCA (Lithium Nickel Cobalt Aluminum Oxide)
Types of Lithium-ion Batteries – Battery University

Do you have any spec for the NCA. I doubt is any better than NCR in therms or cycle life. They are mostly interested in energy density for cars and it makes sense.

 

[Ampster]

Did you read the articles? ....and your doubts are based on what facts? Is it possible that Tesla was also interested in a longer battery life?

 

[electrodacus]

Did you read the articles? ....and your doubts are based on what facts? Is it possible that Tesla was also interested in a longer battery life?

I have good enough knowledge about Lithium batteries. For Laptops and EV normally you prefer energy density over cycle life.
Do you find about 300000km insufficient for a car? Currently in average cars are driven around 25000km/year that is about 12 year for that battery to get to 80% and seems as a good enough number.
The alternative like LiFePO4 can last 25 years but the down side is that range will be reduce to half do to lower energy density.
For OffGrid energy storage price for each unit stored should be more important and then LiFePO4 makes more sense. Not to mention LiFePO4 is much safer compared to any Li Cobalt variant.
Energy density is realy not important in OffGrid.

 

[oneday]

Energy density is realy not important in OffGrid.

You keep saying this but clearly it is, wk's setup does indeed seems pretty packed. And space is finite no matter how big your house is, you're starting to sound like a salesman. You know he is using salvaged cells, right? Ones that fit within his space, budget, use restrictions.

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Everyone doing this kind of system must work within those same constraints. To say space isn't a consideration is just silly.

 

[wk057]

Energy density is realy not important in OffGrid.

Pretty sure I debunked this a few posts ago...

I've found some comments about my project over the past ~7 months to be peculiar, especially when it comes to the energy density in stationary storage argument. (Lots of those on Youtube)

Energy density is most definitely a factor. I don't have infinite space to allocate to this project. I doubt anyone else does either. Using the Tesla battery modules in the space I have I'm going to be getting a floor footprint of roughly 14 square feet (and about 7' tall) for about 200 kWh worth of battery storage. That's pretty amazing. Completely impossible with lead acid or even other lithium ion solutions like LiFePO4. Other tech for stationary storage is exponentially larger, and as mentioned this space isn't free. Other people who would be building more modest setups will likely have even larger space constraints making energy density even more valuable.

As for cost point, my battery costs using the salvaged Tesla modules are on par with lead acid costs per kWh, and orders of magnitude less expensive than other lithium based solutions. Not to mention the other advantages of the modules I'm using besides density, such as possible high discharge and high charge rates (not utilizing these, but the potential is there) along with a liquid cooling loop, cell level fuses, etc.

 

[electrodacus]

You keep saying this but clearly it is, wk's setup does indeed seems pretty packed. And space is finite no matter how big your house is, you're starting to sound like a salesman. You know he is using salvaged cells, right? Ones that fit within his space, budget, use restrictions.

Look wk's house size and power consumption is well above average so that is why that pack looks large. My 2.5kWh pack house size and power consumption is on the other end of extreme My battery pack is about the same size as the inverter and about the volume of a desktop computer. And I use LiFePO4 so about 2x lower in energy density than Tesla cells still 3x higher energy density than Lead Acid.
I chose LiFePO4 since I was interested in reliability satiety and cost of storing energy. Tesla batteries where not available when I made the investment about 3 years ago but I will still use LiFePO4 today is not just a small difference the life cycle for LiFePO4 is a few times higher.

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Pretty sure I debunked this a few posts ago...
As for cost point, my battery costs using the salvaged Tesla modules are on par with lead acid costs per kWh, and orders of magnitude less expensive than other lithium based solutions. Not to mention the other advantages of the modules I'm using besides density, such as possible high discharge and high charge rates (not utilizing these, but the potential is there) along with a liquid cooling loop, cell level fuses, etc.

You have a house that is above average in both size and energy consumption. The volume used by those batteries as rapport to the house size in nothing. I'm sure on the other extreme with my set-up and 2.5kWh battery and average will be somewhere in the middle.
New LiFePO4 can be had at about 300 to 400$/kWh of storage capacity not sure how that is an order of magnitude. And that cost is not important you need to consider how much energy you can store during the life of the battery.
Look at this http://download.solarshop.net/english/uploads/FS-UK-Sony-Storage-system-data-sheet-10-08-2012.pdf Sony LiFePO4 datasheet (their complete solution is a bit expensive but nice) see the last page 6000 cycles of 100% DOD that is more than an order of magnitude compare to spec on the NCR with just 300 cycles the NCA will probably be very close to NCR but if you have a dtasheet for the NCA with cycle life I will love to see.

 

[ItsNotAboutTheMoney]

Look wk's house size and power consumption is well above average so that is why that pack looks large. My 2.5kWh pack house size and power consumption is on the other end of extreme My battery pack is about the same size as the inverter and about the volume of a desktop computer. And I use LiFePO4 so about 2x lower in energy density than Tesla cells still 3x higher energy density than Lead Acid.
I chose LiFePO4 since I was interested in reliability satiety and cost of storing energy. Tesla batteries where not available when I made the investment about 3 years ago but I will still use LiFePO4 today is not just a small difference the life cycle for LiFePO4 is a few times higher.

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You have a house that is above average in both size and energy consumption. The volume used by those batteries as rapport to the house size in nothing. I'm sure on the other extreme with my set-up and 2.5kWh battery and average will be somewhere in the middle.
New LiFePO4 can be had at about 300 to 400$/kWh of storage capacity not sure how that is an order of magnitude. And that cost is not important you need to consider how much energy you can store during the life of the battery.
Look at this http://download.solarshop.net/english/uploads/FS-UK-Sony-Storage-system-data-sheet-10-08-2012.pdf Sony LiFePO4 datasheet (their complete solution is a bit expensive but nice) see the last page 6000 cycles of 100% DOD that is more than an order of magnitude compare to spec on the NCR with just 300 cycles the NCA will probably be very close to NCR but if you have a dtasheet for the NCA with cycle life I will love to see.

No, we don't because Tesla isn't telling. You'd need to find an analysis by someone that's picked one apart and done a chemical analysis. Tesla uses their own NCA mix designed to their requirements, which includes sufficient durability for a 10 year life. Tesla's TMS manages for the car, with C rate up to 3.5 or 4. But for storage they're limiting to a C-rate of 0.5 and they're still not deep cycling. You need to stop being hung up on the 300 cycle life of a generic cycle based on full cycles at a higher C rate, especially given that real-world experience of Tesla cars says that degradation is very much under control and they should have no problem lasting 10 years.