Need help buying cylidrical LTO cells

flint

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Oct 24, 2019
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Hey everyone, I'm new here. I'm building a small power pack and hope to share my project with everyone. But right now I'm having trouble buying cells.

I specifically need cylindrical Lithium Titanate (LTO) cells, either 18650 or 26650. The Yinlong ones are way too big for my project.

So far I scoured the Internet and I found only one company, Tiankang, that makes 18650 cells. The PN is TK18650 NT35.

Does anyone have experience with Tiankang cells? Or know where can I buy authentic new cells?

Are there any other 18650 or 26650 LTO cells out there, available in small quantities (<1000 pcs)?

I see that KOK Power (KOK Battery) sells the Tiankang batteries for $2-$3 a cell (about $1/Wh). Are they are a reliable supplier?

Thanks everyone for all your help, especially because I'm the new guy here. Hopefully I can help others out in the future, once I get going.

Flint
 

100kwh-hunter

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lifepo4 is not a option?, cous i think it is not existing the way you want?
Most china is nice to play with and get your feet wet, in my opinion.
But serious play....sorry i am not convinced

With best regards,
 

flint

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100kwh-hunter said:
lifepo4 is not a option?, cous i think it is not existing the way you want?
Most china is nice to play with and get your feet wet, in my opinion.
But serious play....sorry i am not convinced

With best regards,

Thank you for the reply, 100kwh-hunter.

I need LTO for the low-temperature charging capability and for the high current delivery. LiFePO4 would be my first choice otherwise.

Do you or anyone else have experience with KOK Power? Are they a reputable reseller for selling batteries which are really new and authentic?

I can risk choosing a bad brand, and then having to change direction later, but I do need to know that the product I'm getting is new and authentic. Otherwise if things don't work I won't know why.

Flint
 

OffGridInTheCity

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flint said:
I can risk choosing a bad brand, and then having to change direction later, but I do need to know that the product I'm getting is new and authentic.
Yes sir, that's the issue with battery purchases. Can only suggest you begin with small purchase(s) and establish trusted source(s).
 

Korishan

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Oz18650 said:
Can you describe your project?
People might have some other suggestions.

Agreed. It's kinda hard to make suggestions and/or ideas when the requirements are vague and the project is shrouded in mystery.

flint said:
I need LTO for the low-temperature charging capability and for the high current delivery. LiFePO4 would be my first choice otherwise.

Why LTO specifically? Other than temps and current. I don't understand why LiFePO4 wouldn't work just the same. How much current do you plan on dumping into these poor things?!?!?
 

100kwh-hunter

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Like offgrid was stating, you can get small batches, it is known to be good, but i also read stories that the second or third purchase was really bad.
It really hard to tell, maybe you are lucky, maybe not.

Oz18650 Wrote:
Can you describe your project?
People might have some other suggestions.

Korisahn wrote:
Agreed. It's kinda hard to make suggestions and/or ideas when the requirements are vague and the project is shrouded in mystery.

My question is similar ,sorry butt. We want to help you but we need more data.
 

completelycharged

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If your considering (about $1/Wh) pricing level then this is quite expensive and guessing your looking for new LTO and not recycled ?

Commercial project ?
 

flint

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Oz18650 said:
Can you describe your project?
People might have some other suggestions.

Hi Oz18650,

I am building a small power pack which can be recharged via solar and can power equipment in a remote wilderness location for a decade or more without maintenance.

My goal is to use enough cells that the power pack has extra capacity, and then if some cells fail they can be disabled and the equipment can run off of the remaining cells. That is why high power output is important. Less runtime is fine, but not having enough output watt capacity is not. I need to be able to draw 5-10 C from the batteries.

The extra safety of LTO, not needing to worry about fires if the cells get damaged, is a big bonus too. I like that LTO is pretty worry free, even in rugged wilderness environments.

Flint


OffGidInTheCity and 100kwh-hunter, thank you for the tips on establishing quality with a manufacturer or vendor by testing things out and then being careful. I wish there were established LTO cell manufacturers with distributors. I will take your advice and start out with a small order.

completelycharged, yes unfortunately I'm probably looking at new cells since I have not found any used LTO 18650/26650 cells on the market yet. This project is for a residential property, but if it works out maybe someone would find the project useful for commercial too (where the price probably isn't such a huge concern).

I wasn't expecting so many replies from you all. Wow, what a cool community. I'm excited to be here.

Flint
 

Oz18650

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Will the pack be used in multiple locations? Ie how moveable does it need to be?
If it is being used for 10 years or more in one remote location, would a larger number of cells being used at lower currents work for you? Ie a more typical powerwall like most people here are building?
You mentioned low temperatures. Would a solar based heater work for temperature control for the cells - vacuum tube water heaters work in very low temperatures as long as there is sunlight on the tubes.
Just some ideas to consider.
 

Korishan

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flint said:
I am building a small power pack which can be recharged via solar and can power equipment in a remote wilderness location for a decade or more without maintenance.

My goal is to use enough cells that the power pack has extra capacity, and then if some cells fail they can be disabled and the equipment can run off of the remaining cells. That is why high power output is important. Less runtime is fine, but not having enough output watt capacity is not. I need to be able to draw 5-10 C from the batteries.

The extra safety of LTO, not needing to worry about fires if the cells get damaged, is a big bonus too. I like that LTO is pretty worry free, even in rugged wilderness environments.

With those requirements, why won't LiFePO4 work? Not trying to dissuade you away from LTO, just curious as to your reasoning. LiFePO4 cells also have an extremely hard time catching fire or causing issues and can discharge at high C ratings as well. And they come in very different form factors, more than LTO and probably even more than Lithium Ions.
 

flint

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Oct 24, 2019
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Oz18650 said:
Will the pack be used in multiple locations? Ie how moveable does it need to be?
If it is being used for 10 years or more in one remote location, would a larger number of cells being used at lower currents work for you? Ie a more typical powerwall like most people here are building?
You mentioned low temperatures. Would a solar based heater work for temperature control for the cells - vacuum tube water heaters work in very low temperatures as long as there is sunlight on the tubes.
Just some ideas to consider.

Hi Oz18650,

A solar-based heater would be pretty cool! Direct solar heating would be even cooler than electric heating.

For this particular battery pack though I need to keep things as simple and reliable as possible. A solar-based heater might be a good way to extend range short-term or extend life long-term. But if it failed I would still need the battery pack to work fine (i.e. "gracefully degrade").

I have an idea for a second residential installation though, if this first one works out well, and your solar-based heater idea could be awesome for that one. Plus fun to play with. :)

Flint

For the current battery pack, I'm also going to have to find an inverter and charge controllers which can last a very, very long time without maintenance. That's coming up on my list after I sort out the cells.
 

completelycharged

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Dig a hole 1.5 to 2m deep and put your battery pack there, any chemistry will work fine and temperature stabilized.
Theft not an issue.
With the relatively small sized pack, use a post hole borer, 6in - 8in in diameter. Get some underground waste pipe, put an end cap on the end in the ground (waterproof seal) and then use the pipe as a liner. Follow through with insulation cap at the top (6in thick polystyrene).

Cost of hole is less than the premium of LTO ?

The odd requirement to have a massively undersized battery pack (peak loading 10C) and seemingly quite small Wh is curious as to what over a 10 year time frame is being powered (electric gate ?)
 

100kwh-hunter

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Somethingmust be taking in consideration:
Polystyrene is moist sensitive, it will attract and store moist, very hard to get rid of.
Insulation value drops to near zero when its 40-50% saturated.
Pir sheets are less sensitive but in the long run(3 years) the value can drop to half it original R number
I would go for xps or such, moist does not have a chance to get in, and thus will keep its insulation value.

With pir sheets i would do 3 or 4 inch, xpm 1,5-2 inch.
Besides the ground is at a stable temperature, make a u bend at the upper end no need for a insulation cap.
Heat will stay below, how strange it my sound, people that have a fireplace with chimney will understand :angel:
In deep ponds also, surface will freeze over and below it can be 10C.
Electric gate to keep people out or keep the cows inside, big difference between those two :D :exclamation:

Best
 

Araknid

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I can help you out a little ... I’ve tested about 4 types of 18650 lto cells and found a winner. 1500mah 18650 2.7v to 2.5v and about 3.75Wh
 

Araknid

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I’ve got 18650 type and 18650 but as a capacitor.

avoid the blue ones, rubbish at 1100mah. There are these purple ones marked 1865CCW

image.jpg

from the 10 I’ve tested they’re all within 25mAh to a nom of 1500mAh.
They are a 25% match via ti bqstudio to chem 705 if you’re doing Ti battery packs..

I can dump some 0.1C and 0.2C logs when I’m on my machine later.

also handles 12A discharge... gets hot but hey

2.7v to 1.5v CVCC to 25mA
 

floydR

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Aug 23, 2017
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Thanks I didn't know of any but after seeing your post I did a search on duckduckgo and there are a few 18650 LTO cells. thanks for enlightening me.
Later floyd
 
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