Exotic battery needed

I’m noodling around on a little project. I’d like to make a little motion sensor or dusk activated, solar powered LED light fixture.

And I’d like it to be maintenance free for 20 years or so. Essentially the life of the solar panel.

I’m going to put it into a steel box for it so the internals will be protected from most elements, but not from hot and cold.

Is there a battery up to this task?

-Long lived
-Not bothered by full discharge
-Not bothered by 140 eff heat
-Not bothered by use or charging when freezing
-Ideally it could be charged straight from the panel without a charge controller. May require some careful planning of capacity and panel size.
-Capable of 4000-5000 cycles.
-In the neighborhood of 100 watts would be a minimum.

Thanks

May have found a good lead. A little surprised it’s li-ion.

20 year life does not mean 20 years at 80C temperature.

Bluedog225 said:

Is there a battery up to this task?

Click to expand...

Lithium Titanite Oxide based eclls

-Long lived:
up to 25k cycles

-Not bothered by 140 eff heat:
working temperature goes up to 60c for charge and discharge

-Not bothered by use or charging when freezing:
LTO cells work without heat down to -40c, 60% rated capacity charging ability at -40f, 80% at -20c

-Ideally it could be charged straight from the panel without a charge controller:
At a working voltage of 1.8-2.9, 6 of them can be attached directly to a 12v charger with no smarts at the loss of some capacity. They will never hit max charge voltage

LTO cells also feature high charge and discharge capabilities when needing ranging from 6-20C


Downsides

Poor energy density. LTO cells are about as energy dense as lead acid chemistries. Peaking at about 90wh/kg and 200w/l , LFP cells are around double that.

Limited availability. There are not to many companies who manufacture them, so you will be limited on size and sourcing

High cost. LTO cells having more expensive raw materials so they will cost more to manufacture. This means the cells will be more money for the same wh.

To add a addendum to the above I figured I would list who I know makes the cells and a bit about them if I can

Altairnano/Yinlong/Gree
The original producer of the cell chemistry. Started as a small US company producing the chemistry as 60-70ah pouch cells. They were bought out by Yinlong in 2010. This led to an expansion of the cell chemistry into other formats such as 60mm x 130 mm and other cylindrical cells as well as a few prismatic cells. Yinlong was bought out by Gree in 2021 after a failed attempt in 2016. These are the most common LTO cells on the market you will see today. Most of them are pulls from old busses but they are also still made new. I have most of their datasheets in the resources.

Shengquan
Smaller newer producer. They only produce cylindrical cells. These are mostly smaller sizes but they do produce up to a 60mm x 137mm cell. These are available new to the average buyer. Most datasheets are available in the resources.


Tianjin Lishen Battery Co
A huge producer of cells in China. However they do not cell new cells to the grey market anymore. If you find these cells there is a very good chance that they are pulls or old stock. Lishen's LTO cells are focused around High C rates and therefore feature lower than normal density for a LTO cell. Being about half the capacity of the above brands.


Tianjin Plannano
Another newer LTO cell manufacturer. They offer 60mm cells in various lengths. Their LTO cells also span both the power focused market and the energy storage side of things. The cells are available direct from the factory online.



Regital New Energy
Interestingly enough the main business of this company is EV chargers. They now have a line of prismatic LTO cells however. I have not yet gotten the chance to truly check them out but I hope to soon. Cells are not directly available as far as I know right now.


Toshiba SCIB
Toshiba makes a line of LTO cells for various applications. They are all medium sized prismatic cells. These cells show up on places like Alibaba as pack pulls frequently.