EV batteries for energy storage

[Ampster]

Why do powerwall's cost $460 a kWh, while the batteries themselves only cost $125 per kWh?

If you are talking about a Tesla Powerwall there are a number of reasons. First you are getting a Gateway and an inverter that manages your power and can AC couple to a GT inverter. You are also getting a BMS and a thermal management system which allows Tesla to give you a warranty. Finally you are getting software that allows you several modes to best manage your energy use.

In summary, there is a lot of difference between a dumb battery and an integrated system like a Powerall or a properly installed hybrid inverter and batteries.

[solar_future]

Great description of your project.
You are correct using packs out of used cars is definitely a do it yourself category job that requires some skills.

The only thing I would mention is that the price of new Lithium batteries have come down. I just purchased 28 kWh of new LFP batteries delivered to my door for less than $125 per kWh. That replaces a Nissan Leaf pack that was getting a little old and did not have enough capacity. I hope to sell it in and recoup some of the investment. As you mention there is still a market for used EV packs. The price I paid for new cells from China makes Lithium the the more economical long term choice. I am a minority in that view on this forum but this is not the largest or most active forum on the internet when it comes down to this subject matter.

Thanks for reviving this thread. It reminded me that I had promised to take down a comment I made about one of Sunking's errors and now I have done that.

Why do powerwall's cost $460 a kWh, while the batteries themselves only cost $125 per kWh?

[Salts]

Looks quite professional, in the metal cabinet I would consider required. Bruce Roe

14ga 36x48x20 Hoffman Enclosure. I figure if there's a fire, that should be enough to contain it.

[bcroe]

. Here's mine...

Looks quite professional, in the metal cabinet I would consider required. Bruce Roe

[Ampster]

I have experience with solar storage using both Lead Acid, Chevy Volt, and now, Chevy BOLT batteries.

While Sunking isn't wrong, he's leaving out some details. Some of these details matter, some only matter to some folks.

For example, per his statements on DOD and cycle life in lithium, he is absolutely correct. Charge a quality lithium EV battery to 4.2 volts and discharge to 3.0, and your cycle life will probably end up being in the 300 to 500 range. But who does that? I guess a few folks do. Some of the cheap Chinese BMS's on the market aren't programmable and they pretty much do exactly that.
The secret is to stay between the discharge curve "knees". For most Lithium EV batteries, these knees start at around 4.05 volts at the top and 3.45 at the bottom. You basically loose 20% of your battery capacity.. maybe a bit less depending on how one chooses to run the math. And your cycle life will jump from 300-500 to 1500 to 2000 or more. There are other factors that can increase and decrease those numbers by about 30% as well. Rate of charge and discharge and temperature all play huge roles in battery degradation. For us using them for solar storage, we mostly see increases in cycle life because our homes don't accelerate down the road at 70mph on a 90 degree day.

But one of the things Sunking left out is that Lead Acid batteries have the same DOD issues. Most quality lead acid batteries (Rolls, Trojan SIND, etc), only last for a long time if you limit their discharges to 50%... and if you want them to really last a long time, only dip down to 70% SOC. So the FLA batteries are also de-rated and have to hold back some capacity.

........
Lead Acid is grade school simple to use.. They are mintenance heavy, they exhaust dangerous fumes when charging, and they don't do well when they're cold.. they really don't do well when cold.. Think a lithium battery needs to be derated? a FLA loses most of its capacity at just 40 degrees... But FLA are work horses... not much to go wrong with them so long as you don't do something colossally stupid.

In a solar storage application, from my perspective, the biggest drawback to lead acid is that they MUST be kept fully charged as much as possible.. so if you have a few bad solar days in a row, your battery is basically dying while not being maintained at full charge. And lead acid doesn't store very well like lithium does.. Lithium is perfectly happy just sitting there doing nothing for months and months.. whereas Lead Acid is more needy of attention.. they need to be cycled or they sulfate.. They need a periodic discharge and a quick charge up to blow the soft sulfates off the plates before they become hard sulfates and permanent.

If I had to choose between buying new and quality FLA batteries or new Lithium, the FLA is hands down the winner. Thing is, and Sunking left this part out, we don't have to buy new lithium batteries.. the market is starting to flood with good used cells that still have 90% of their life left. Entire businesses are popping up to sell these "slightly used" lithium batteries that still have most of their capacity left..

I bought my Chevy Volt battery pack last year.. 2014 with 30k miles on it.. paid $1300. It tested at 16.59kw. Then I came across Chevy BOLT cells that were never cycled.. LG Chem, same as Chevy Volt, brand spanking new.. Sold my 16.5kw Volt pack modules for $3200 and paid $2200 for 25kw of Chevy BOLT cells.... They allow my inverter to access more of their capacity because of the bottom end limitations.

Its easy to find BMW packs, Nissan Packs, etc now. This isn't 2015-17 anymore where finding lithium ion EV batteries for sale was like seeing a Unicorn. EV batteries are everywhere and selling for about $100 per kilowatt.. although, in the interest of full disclosure, you'll also need to spend $500 to $1000 for a quality BMS, contactor, etc. And they usually require your labor.

Biggest drawback to the EV Batteries is that you better damn well know what you're doing with them. They have built-in idiot detectors that do spectacular and catastrophic things when someone who doesn't know what they are doing starts playing with them. With Lead Acid, you simply buy new batteries.. with lithium, you buy a new house or garage...

.....

Great description of your project.
You are correct using packs out of used cars is definitely a do it yourself category job that requires some skills.

The only thing I would mention is that the price of new Lithium batteries have come down. I just purchased 28 kWh of new LFP batteries delivered to my door for less than $125 per kWh. That replaces a Nissan Leaf pack that was getting a little old and did not have enough capacity. I hope to sell it in and recoup some of the investment. As you mention there is still a market for used EV packs. The price I paid for new cells from China makes Lithium the the more economical long term choice. I am a minority in that view on this forum but this is not the largest or most active forum on the internet when it comes down to this subject matter.

Thanks for reviving this thread. It reminded me that I had promised to take down a comment I made about one of Sunking's errors and now I have done that.

[Salts]

I have experience with solar storage using both Lead Acid, Chevy Volt, and now, Chevy BOLT batteries.

While Sunking isn't wrong, he's leaving out some details. Some of these details matter, some only matter to some folks.

For example, per his statements on DOD and cycle life in lithium, he is absolutely correct. Charge a quality lithium EV battery to 4.2 volts and discharge to 3.0, and your cycle life will probably end up being in the 300 to 500 range. But who does that? I guess a few folks do. Some of the cheap Chinese BMS's on the market aren't programmable and they pretty much do exactly that.
The secret is to stay between the discharge curve "knees". For most Lithium EV batteries, these knees start at around 4.05 volts at the top and 3.45 at the bottom. You basically loose 20% of your battery capacity.. maybe a bit less depending on how one chooses to run the math. And your cycle life will jump from 300-500 to 1500 to 2000 or more. There are other factors that can increase and decrease those numbers by about 30% as well. Rate of charge and discharge and temperature all play huge roles in battery degradation. For us using them for solar storage, we mostly see increases in cycle life because our homes don't accelerate down the road at 70mph on a 90 degree day.

But one of the things Sunking left out is that Lead Acid batteries have the same DOD issues. Most quality lead acid batteries (Rolls, Trojan SIND, etc), only last for a long time if you limit their discharges to 50%... and if you want them to really last a long time, only dip down to 70% SOC. So the FLA batteries are also de-rated and have to hold back some capacity.

In fact, the only two chemistries I'm aware of that don't mind being run down to almost nothing are NiCad's and LTO (Lithium Titanate Oxide).. NiCads are big, bulky, horrible for the environment, and don't last long, and make sure you're sitting down if you check the price on LTO batteries.

Lead Acid is grade school simple to use.. They are mintenance heavy, they exhaust dangerous fumes when charging, and they don't do well when they're cold.. they really don't do well when cold.. Think a lithium battery needs to be derated? a FLA loses most of its capacity at just 40 degrees... But FLA are work horses... not much to go wrong with them so long as you don't do something colossally stupid.

In a solar storage application, from my perspective, the biggest drawback to lead acid is that they MUST be kept fully charged as much as possible.. so if you have a few bad solar days in a row, your battery is basically dying while not being maintained at full charge. And lead acid doesn't store very well like lithium does.. Lithium is perfectly happy just sitting there doing nothing for months and months.. whereas Lead Acid is more needy of attention.. they need to be cycled or they sulfate.. They need a periodic discharge and a quick charge up to blow the soft sulfates off the plates before they become hard sulfates and permanent.

If I had to choose between buying new and quality FLA batteries or new Lithium, the FLA is hands down the winner. Thing is, and Sunking left this part out, we don't have to buy new lithium batteries.. the market is starting to flood with good used cells that still have 90% of their life left. Entire businesses are popping up to sell these "slightly used" lithium batteries that still have most of their capacity left..

I bought my Chevy Volt battery pack last year.. 2014 with 30k miles on it.. paid $1300. It tested at 16.59kw. Then I came across Chevy BOLT cells that were never cycled.. LG Chem, same as Chevy Volt, brand spanking new.. Sold my 16.5kw Volt pack modules for $3200 and paid $2200 for 25kw of Chevy BOLT cells.... They allow my inverter to access more of their capacity because of the bottom end limitations.

Its easy to find BMW packs, Nissan Packs, etc now. This isn't 2015-17 anymore where finding lithium ion EV batteries for sale was like seeing a Unicorn. EV batteries are everywhere and selling for about $100 per kilowatt.. although, in the interest of full disclosure, you'll also need to spend $500 to $1000 for a quality BMS, contactor, etc. And they usually require your labor.

Biggest drawback to the EV Batteries is that you better damn well know what you're doing with them. They have built-in idiot detectors that do spectacular and catastrophic things when someone who doesn't know what they are doing starts playing with them. With Lead Acid, you simply buy new batteries.. with lithium, you buy a new house or garage...

Here's mine... Post3.jpg

[Ampster]

i appreciate the input. I can tolerate being called names but being called a liar, then offering to correct any factual errors and getting no response rubs on me. i will take this down after a few days. I think he knows he was wrong about the Panasonics anyway. Are there any terms of service that would serve to guide me?

[Mike90250]

Ampster, I don't care about past history, digging through old threads, picking scabs off year old stuff.

And for the site ToS, a lot is left up to the moderators, who see your name and sunking in a lot of moderation requests. Sunking has a lot of common sense, and posted much useful stuff, which is to his credit. Your posts, IMHO, not so much.

[Tecnodave]

I have these batteries alledegably from Tesla's battery plant, they are 21mm by 70 mm, I think that they call them 2170 cells, much like a 18650 Panasonic, but not the same at all. It's evolution

pnjunction,
my main battery battery bank are Rolls Surette S-530 L-16 I salvaged on the way to Kragan auto to be recycled, they were "dead", now at 1.265 s.g. across all cells, shipped out the door June 26,2005, youngsters at 14 y.o. Not bad for $20.00?
just tinkering....I'm willing to share how I did that

[PNjunction]

The sad thing is that most lithium threads are totally devoid of what we used to do in these forums *FIRST* - that is figuring out what capacity of battery bank you need to support your typical household needs for DAYS at a time - kind of serious stuff.

Now most (not just here) are only concerned about how to power a tablet or perhaps maker gadgetry, when the lights go out. Heck, I can shoehorn a sack of potatoes, copper nails and zinc-strips to make that happen - nevermind using an EV battery, which is not designed for day-in-day out, days at a time outages.

Do that with a typical non-lifepo4 EV battery, every day, and then pay for it over and over again - you'll come screaming back to lead.

Over the years we read a lot of noise about EV batts for these uses - and guess what ? NONE of them start out with FACTORY FRESH cells, but with some JUNK.

Dunno - guess I'm on a soapbox again imagining how it would go before lithium was a thing:

"I found these Rolls batteries at the dump, and now I want to .... :
"A hardware store has gone out of business and wants to give me 5000 old AA-sized nimh rechargeables and ...."
"Friend of mine has 70 sla batteries from his old UPS alarm business and my speaker-wire connections melted..."

Heh, gotta stop before I get into trouble. ..

[Ampster]

I also read recently that they are reducing the Cobalt in their batteries.

[motorcyclemikie]

opps, I used the posted Tesla link and got shot. anyway the link to Tesla's information about their batteries and material was very interesting. I can understand why Tesla is using the 2170(0) battery in their new Tesla 3. They claim that the 2170 has about 30% more power than the 18650 battery does, very interesting although the 2170 battery is about 30% larger than the 18650 battery, probably has something to do with it.

[motorcyclemikie]

Actually the new Tesla Model 3 battery uses their newly developed 2170 cells

https://evannex.com/blogs/news/tesla-s-battery-pack-is-both-mysterious-and-alluring-work-in-progress

https://www.teslarati.com/inside-tesla-model-3-2170-lithium-ion-battery/

https://www.reddit.com/r/teslamotors...ns_calculated/

Great information on the batteries and their materials, very interesting how the Tesla 3 uses the 2170(0) battery and gets 30% more power than the 18650. Might have something to do with the approximate 30% increase in size? Naw, couldn't be that simple of an explaination,

[jflorey2]

Tesla also hired as a consultant, Professor Jeff Dahn from Dalhousi University who has done some work on predicting cycle life of Lithium batteries. He is one of the consulting partners mentioned above.

Jeff gave one of the keynote talks at the International Battery Conference I was at last week. Very capable guy.

[Ampster]

............

Tesla has a chemistry RD department that parents over the multiple subsidiaries and contracts with other international entities. This is headed by Green Bay Wisconsin raised, JB Straubel. Think of it more as a hybrid between traditional chemistry R&D and contractual outsourcing. About 2/3 of the department budgetary goes to a fluctuating, currently, 19 different partnerships and contracted engineering organizations that focuses explicitly on battery chemistry and process."

In other words, it's not a Panasonic NCR18650B.

Most of what I have said on this forum about the future of Energy storage, I have learned from watching videos of JB Strauble's speeches and presentations. I have also picked up some information from technical publications. I think he has done a lot to improve the performance of the batteries in those cars. I am sure he also collaborated in leveraging the battery technology into energy storage via the Powerwall and the Powerpacks.The Powerpacks are used in commercial and industrial as well as grid scale implementations.

JB Straubel started at Tesla before Elon Musk made an investment and took control of the company from some of the original founders. JB actually built an EV when in college..

Tesla also hired as a consultant, Professor Jeff Dahn from Dalhousi University who has done some work on predicting cycle life of Lithium batteries. He is one of the consulting partners mentioned above. I think it was one of the videos of his lectures and TEDX talks that clued me into the subtle change in the ectrolyte that has contributed to the long life of those batteries.

Thanks jflorey2 for the above and for starting this thread in the first place.