LTO Battery question


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Tim Dale

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I had a quick question for you guys

I'm in the designing stage of a DIY powerwall for my off grid property in E. Texas

I know I want around 45KWHrs of storage

So far I've been looking at using the Liito Kala NCR18650B batteries , They will cost approximately $187 KW/Hr shipped, that's just the cost of the batteries, it doesn't include the cost to assemble them into packs (total cost for these batteries will be around $8400)

But then I ran across these LTO cells , they claim 20,000 to 30,000 cycles, while the increase cycle life is certainly a benefit, they are even lower cost than the Liito Kala NCR18650b cells. The proce quoted to me with delevery comes out to $160 KW/Hr for the LTO Cells (Total cost for these cells will be about $7200)

they seem to have many advantages like cycle life, and reduced cell count, which shouldmake assemblingthe packs much easier and quicker. really the only downside I can find is the lower energy density, but this will be for a stationary powerwall, not an EV, so energy density is less of a concern for me.

I have ordered 10 of the LTO cells to test out, to see if they live up to the hype,but I can't just pop them into my 18650 cell tester.

Do you guys have any suggestions on how to give these cells a good test over the course of a few months, I'd like to build a battery tester for them, but really have no idea where to begin other than assembling a battery pack and then doing constant charge/discharge cycles on it, but I was hoping for something a little more automated

Any suggestions or ideas on how to properly test out these LTO cells would be greatly appreciated, also looking for BMS suggestions for this test pack

TIA,
Tim
 

Tim Dale

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As a follow up I was thinking about assembling the 10 batteries into a 5s2p pack

Should have around 900 W/hrs of storage so I'm gonna need a pretty big load to test this out, and doing multiple daily cycles will consume over 10KW a day, soI was thinking about using a cheap micro grid tied inverter for the load, I can find them on ebay for about $100

If I can find an automated way to initiate a charge discharge cycle, while monitoring the performance of the battery I should be able to get over 10 cycles a day, and wasting 10kWh a daydoesn't seem like a good idea if I can use a micro grid tied inverter for my load testing, that way the battery power will not go to waste

So I need to figure outa BMS and a charger and then a way to automate this testing process so that I can gather some useful data on these cells, Perhaps a raspberry pi could be used for the control and data logging

Any ideas are welcome
 

completelycharged

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jdeadman

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for testing cells of that capacity I'd be looking at a bigger charger like the Icharger or Duo that can charge and discharge at higher rates
 

Tim Dale

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completelycharged said:
Guessing these are 30Ah cells - clear wrapper with no logo on... do they have the smaller test sticker on ?

I'll have to check when they get here, but they better not be 30A cells, the seller had the 30A cells as well and they were only $8.90 a cell,https://www.alibaba.com/product-det...l?spm=a2700.7724838.2017115.87.5911474cGhsFpi

They were even less expensive per KW than the 40A cells, but I figured the 30A cells were probably the rejected 40A cells that didn't make the cutso I went with the 40A ones found here https://www.alibaba.com/product-det...l?spm=a2700.7724838.2017115.12.5911474cy22mlc

I found your post on your LTO powerwall, did you run into any importation issues on your order?
 

completelycharged

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Tim Dale

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I appreciate you reply and the info

I'll be sure to post pictures

My main concern is the quality of the LTO cells being sold, I figured it best to order 10 of themto test out before placing a larger order.

I'm trying to decide between these LTO cells and the Liito Kala NCR18650B batteries, I can get the the Liito Kala cells from Aliexpress for $187 per kWh shipped to my door ($2.34 each ifpurchased with the aliexppress androidapp)https://www.aliexpress.com/item/5pc...615.html?spm=a2g0s.9042311.0.0.199f4c4dwEXDnv

No customs or import issues with aliexpress, at least I've never had issues ordering from there before

The Liito Kala cells are supposed to be as good as the Panasonic NCR18560B, I have 10 of them also on the way for testing.

I really want these LTO cells to pan out, but first I want to do some testing before I make a decision on which battery to use for this project

Thanks again
Tim
 

completelycharged

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Tim Dale

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I really appreciate your reply

The goal is to provide power to an off grid cabin in East Texas, I have some property out there and I want to keep the cabin off grid

I use no more than 20KW a day, and that's during the summer with a window AC unit, but I hate running a generator

So the plan is a Solar array and a Powerwall, I was able to buy a lot of Jinko 325 watt solar panels for $75/ea ($0.23/Watt), I'll put up an 8kW array, this will make way more power than I need, PVWatts shows it should make about 12,000 kW a year

I figured a 45kWh battery pack would be a good size, 1st) de-rate it by 20% for extended cycle life. That gives me 36kWh, with a daily use in summer of 20kWh that should give me some spare capacity for a couple of bad solar days before having to run the generator to charge the battery pack

I am definitely concerned about cycle life, as you point out it's all about maximizing the return on investment

I am still trying to get hard data on the cycle life of the NCR18650B, there is information out there claiming over 7,500 cycle by de-rating the battery, http://blog.evandmore.com/lets-talk-about-the-panasonic-ncr18650b/ but I'm very skeptical of these claims

I'd much prefer the LTO for it's proven cycle life and for the reduced part count, I really don't want to solder up 3600 batteries

My only concern with LTO cells is that I really have no idea what I'm gonna get. Spending a bit on these test cells is no big deal, but dropping $7,000 is another story all together

Thanks again, I really appreciate you post
 

completelycharged

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Tim Dale

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completelycharged said:
My pack is 28kWh (one pack spare until I add nother to make it 32kWh total) and will use 90% range because using a more narrow range with LTO might mean 50,000 cycles but I won't live that long... unless the cells are at a high temperature. One thing to consider if your climate is 30C+ is that the cells have a very low internal reisstance so will give of very little heat when cycling them so putting them in a chilled space will extend the life far more than reducing the cycle range....

Forget the generator completely, if the majority of your use is AC, buy a couple of freezers, fill them with water bottles and then run them 24x7 when you have power and use the bottles (or glycol coollant loop through the freezer) for cooling on the days where solar is not making enough. Ice will store the electrical equivalent of around 100kWh per cubic meter and is far, far cheaper than batteries for cold storage... and can be a lot quicker to extract. Extremerly cheap option is just to take a bottle out and stand it in a tray to capture the condensation. Over time the bottle will thaw while it chills the room. Very unconventional but I think batteries are a bit of a waste for AC and deffinately not for space heating, but that is my view and distorted by the climate and setup in the UK.

The use of a freezer / cold store would allow the pack size to decrease by half or more. Plus, consider than during the times the sun is out and the heat is being generated, so is your power so the AC demand when the sun is shining and being produced will go directly into the AC system and not the batteries so you may end up with only 60% going into the batteries and 40% into the AC, depending on latitude/sunrise/sunset times, etc.

As a suggestion, consider the case of using a lot smaller LTO pack size and implementing a freezer/glycol loop.
https://www.homebrewtalk.com/forum/threads/temperature-controlled-fermentation.81596/
These are using the approach for cooling homebrew rather than storing cold.... same implementation and you just run the glycol through when you need the cool boost..

Then again, forget the lot and just implement the homebrew..

Oh, WOW!

I suddenly have a bunch of reading to do, This chilled glycol loop ideais not something I had ever thought of

As far as climate, Texas gets pretty hot, today it was 115F or 46C, It's not always this bad, but summers are generally over 100F or 38C soI plan to keep the batteries inside the climate protection of the cabin, I have read heat makes batteries degrade much faster, so keeping them inside a cabin at 74F or 23C should help slow down the degradation compared to outside storage. This isone more reason I like LTO, they are said to bemuch saferindoors.

Hmmmmm, so aheavily insulatedchilled thermal mass, this requires some reading, our summers can be pretty warm :)



Thanks again
Tim


Indecently the LTOcells they are claiming to have are listed as the 66160H 40Ah, So that's a tiny bit promising

I've attached the spec sheet they sent me

Thanks
Tim
 

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  • Kylin+power+LTO+2.3V+40Ah+Cell.pdf
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completelycharged

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Tim Dale

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completelycharged said:
Model "RACEPOW-LTO-66160H" - who or what is RACEPOW...

Cell pictures are standard from YinLong website

This may be closer to the actual cells delivered... depending on source and quality.


image_cijpgl.jpg


Notice on this cell test the capacity is just under 40Ah... and that is still at 1C... not bad for a used cell. This is closer to what is more likely to turn up...

If I can get cells that test out at 40Ah for $14.90a cell, I'll consider that a big win, Even if shipping andimport fees cost me $2000 for 500 cells, my total cost would be $205 a kWh for the cells to makea 46kWh packand I'd have a 10+ year life out of it, that's gotta be way more cost effective than 18650's and more than2X as efficient as lead acid

Also not much more expensive thanFLA batteries that aregoing to cost me around $170kWh, I'd stay away from golf cart batteries and useFLA Rolls Surrettebatteries if I was going to go the FLA route, Rollsshould also last 10 years, but I desperately want to avoid all the downsides ofFLA batteries, they have horrible charge efficiencies especially at the top of the battery, they have so many downsides.

Also to consider, once Ide-rate the FLA battery packby 50% it becomes more expensive than the LTO cells. FLA batteriesare never supposed to drop below 50%, the LTO cells are actually cheaper per usable kWhbecause I only plan to de-rate them by 80%
 

completelycharged

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Tim Dale

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First a quick update

The initial quote I received was not to my door, it was a FOB quote, I guess their was some confusion on what I was asking them

Also after making my sample order they reduced their quoted price to $14/cell for 400 batteries

I received some of the pictures I asked for and they answered all of my questions, but now I'm a little more concerned.

When I asked about the batteries history Iwas told they are brand new

I asked them to clarify, saying surly this is a mistake, that these must be high quality reclaimed cells that have been tested, no?

Their reply was no, these cells are brand new. But everything I read says these will be reclaimed cells, which I'm totally fine with as long as they are tested for remaining capacity, so I don't understand their need to claim that the cells are new

If I buy these cellsI'll insist upon a capacity guarantee in thecontract statingthat the cells will be tested upon arrival and that they guarantee every cell will still have 40Ah of capacity, if they screw me over I can get a refund from my credit card company for breach of contract

I'm really thinking about going a bit smaller, and instead of 500 batteries just using 400 for roughly 37kWh which will be around 30 kWh usable after I de-rate the pack

Total quoted cost for the batteries FOB is $6000 or $162 kWh, I still need to figure out the cost for a freight forwarder to complete the importation,I'm looking at an LTC shipment of 500 KG consisting of27 boxes each200*300*400 in size.

Even if this cost is $2000 my total cost per kWh will only be $216, and LTO cells should have a cycle life 10X that of NCR18650B cells, even if it's only 2X, these LTO cells will be more economical over time than 18650'sand much easier to construct battery packs with

So if the cell testing goes well I'm going to go with these LTO for my Powerwall

I'll post more updates after I get the sample batteries in, but I'm really concerned with their claim that these are all brand new, I'll have to address this concern in the purchase contract

In case anyone else is interested in the supplier that I'm talking to, their info can be found herehttps://feida-battery.en.alibaba.com/?spm=a2700.8443308.0.0.4e073e5fnGAeki

Any recommendations on the best way to test these cells would be appreciated


image_tniobu.jpgimage_ickppd.jpgimage_dwmtfu.jpgimage_nbogzg.jpgimage_wiubpx.jpgimage_mzhrvj.jpgimage_ggsvzi.jpgimage_zfgelj.jpg
 

Tech4U

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Tim Dale said:
So the plan is a Solar array and a Powerwall, I was able to buy a lot of Jinko 325 watt solar panels for $75/ea ($0.23/Watt), I'll put up an 8kW array, this will make way more power than I need, PVWatts shows it should make about 12,000 kW a year

May i ask where you got these as i am in need of a few more panels.. Im in north louisiana
 

Tim Dale

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masteryodajames said:
TimDale said:
So the plan is a Solar array and a Powerwall, I was able to buy a lot of Jinko 325 watt solar panels for $75/ea ($0.23/Watt), I'll put up an 8kW array, this will make way more power than I need, PVWatts shows it should make about 12,000 kW a year

May i ask where you got these as i am in need of a few more panels.. Im in north louisiana

There was a guy selling them on Craigslist in Odessa Tx. I'll PM you his #
 

completelycharged

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Tim Dale

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completelycharged said:
Interesting, especially why they try and sell them as new with images that prove they are not...

Cell + FOB pricing is what I would expect, beware of the FOB shipping sting....

Questions / points would be :
1. ICAO/IATA regulations limit the State of Charge (SOC) to 30% - 2.3V reading on the cell is over 60% SOC, would any manufacturer ship new cells at >60% SOC ?
2. Internal impediance in the spec sheet they sent and the official spaec sheet is sub 1mOhm, thier reading is 1.4 and 1.33mOhms... >30% above spec for "new" cells
3. Packaging with no cell holders, nice.... 20kg of cells in a carboard box with 5mm of packing.

Point 2 is the very reason they are "recycled" - try fast charging them at 10C at a bus stop.... 400A x 1.4 mOhm = 220W heat dissipation while charging.. from one cell !!!! Put another way 24% of the charge energy is lost as heat.... (400^2 x 0.0014) / (400A x 2.3V = 920 Watts) this is the impact of IR.... and why they are recycled...

Use them in a powerwall at 5A 0.28% heat loss.. no real issue. 40A, 2.3%, 80A 4.5%. 200A 11.3%.

From the images there are a few things, which raise issues for me, so beware.

I would need a lot lot more proof before sending them $x,000 before they release the goods... no seller will put them on a boat without full payment...

Max I'd ever be pushing or pulling from the pack would be when charging on a perfect day with the7.8KW array I'm going to be putting up, and it will never be that high in reality, on a perfect day(24) 235 watt solar panels will probably max out around 7KW (Just a guess)

I think my intended usewill be pretty easy on a 36kWh396 cell22S18P48V pack

The seller said they do guarantee every cell will load test 40Ah, they have clearly communicated this fact and they are now pretty much bound to it legally if there is a future dispute. I think their claim is BS, but I'm also no expert, just a random internet guy trying to build a diy powerwall to save come money :)

Is there a way to use the IR reading to tell how much life these cells would have in my specific application, estimate the Ah capacity left in them?

If I pay with my credit card I get purchase protection from fraud, as long as it's under $10,000, and this certainly will be. If the seller misrepresents what they are selling I can dispute the charges after I get the batteries and have them tested for capacity, I'll clear and confirm that with my credit card company before making the purchase

By the way, do you know if your supplier still has these batteries for sale and if they are a similar cost?

Thanks again for you help

Tim
 

completelycharged

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Good luck with the credit card.
 
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