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LTO Battery question
#1
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 45KW Hrs 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 should make assembling the 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
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#2
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, so I 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 day doesn'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 out a 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
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#3
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#4
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
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#5
(07-19-2018, 12:58 AM)completelycharged Wrote: 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-detail/K...474cGhsFpi

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 cut so I went with the 40A ones found here https://www.alibaba.com/product-detail/K...474cy22mlc

I found your post on your LTO powerwall, did you run into any importation issues on your order?
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#6
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#7
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 them to 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 if purchased with the aliexppress android app) https://www.aliexpress.com/item/5pcs-Lii...4c4dwEXDnv

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
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#8
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#9
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-abou...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
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#10
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