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LTO woes and features, etc
eetcowie   1/26/2015 4:40:16 PM
@Opbrid and @2joncole:

Thank you both for your excellent information.

...The Toshiba cells come with aluminum tabs that can only be interconnected with a $100,000 laser welder...
One solution to making connection to the tabs, is highly electrically conductive grease, with a wide copper wiper-tab to contact it. The nice thing about this arrangement, is that the cell simply slides out of its holder, with no permanent connections. I think this is what they had in mind at first design. The grease is most often used with high-amperage switch contacts and male/female connectors. In fact, this approach (which I have tested) can also be used with cylindrical cells, where wipers attached to the pack's walls contact each cell, making for easy cell replacement.

...burn rate...
I like the idea of having a new specification added that gives the cost per cycle till end-of-service-life. I mostly call this the cost-of-ownership, though, because ocasionally when I do this I include all the costs, including the cost to store the cells on the shelf (plus loss of capacity), labor to install & replace/dispose them, cost of electricity to charge them, and obviously the price to buy/ship them, etc. I had one government customer that even built in a factor that acounted for inflation of the dollar...who would have figured!

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LTO, cold weather, and "burn rate" in Electric Buses
Opbrid   1/22/2015 7:30:45 AM
You failed to mention another very interesting feature of LTO, cold weather. Take a look at the specs, and you see that LTO operates to -40C. Most other batteries start to become useless at about -10C. This can be a huge advantage in cold climates.

Next, you didn't mention MicroVast as a vendor. They have made some good advances in LTO, in particular, solving the "off gassing" problem in a proprietary way. LTO cells can create internal gas when fast charging. Other companies solve this by mechanically compressing the cells - a second best solution. Microvast also claim 30,000 cycles, but I think this is down to 70% of capacity instead of 90%. Still, an amazing claim. MicroVast also is completely vertically integrated, making all components of the cell, from basic chemistry and materials up to packaging and BMS.

Finally, if you do the math, even though LTO is more expensive per kWh than most common chemistries, the "burn rate" is very low. This is the inverse of the amount of electricity that can be stored and discharged by the battery during its lifetime.

Basically, every time you charge a battery, you use up some of its life. This has a cost. In an electric bus, this can be more than the cost of electricity in some cases. For example, a big LFE batter of 300kWh with a cost of $200,000 and a cycle life of 3000 charge cycles has a burn rate of 200,000/3000 = $66 per charge. Since the charge is 300kWh, this works out to $66/300kWh or 22 cents per kWh. Pretty steep!

If instead you have an LTO pack of 100kWh at $200,000, and 20,000 cycles, this gives $200,000/20,000 = $10 per cycle, or $10/100kWh = 10 cents per kWh, or better than half of the burn rate cost of a comparable LFE.

There are other considerations for electric buses, the 300kWh bus can run most or all day on a single night charge, whereas the LTO battery needs to charge every couple of hours. However if you manage this, then the LTO starts looking better than LFE in total lifetime cost.

Opbrid makes overhead conductive charging systems for both types of battery, so we are pretty agnostic.

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The trouble with LTO
2joncole   1/21/2015 3:04:28 PM

I have been following LTO batteries since Altairnano first came up with them a number of years ago. I am now building prototypes that incorporate them into a PV panel. It has not been been the most trouble free of experiences.

First of all YABO is a battery distributor and not a manufacturer. The LTO battery that they once were selling was manufactured by Tiankang, a Chinese company. I have been working with products from them but have not been satisfied with the product or their support of their products. It has taken the purchase of 10 cells to get 5 mostly matched working cells and the BMS they provided does not work properly and they have not been willing/able to provide a replacement.

I chose Tiankang LTO cells because unlike the Toshiba cells, they are delivered with threaded terminal studs which allows simple connection and interconnection. The Toshiba cells come with aluminum tabs that can only be interconnected with a $100,000 laser welder. They will sell you a cell with threaded attachments but is is a very flimsy add-on that idoes not appear durable enough for anything but bench testing of individual cells. Plus Toshiba does not provide any battery management system. Let's face it any lithium battery without a battery management system that can last the life of the battery is not much of an advance.

These LTO batteries are an important technological development but from what I can see the companies that are manufacturing them are totally mismanaging the development and marketing of this product. With a higer degree of safety, environmentally benign chemistry and extremely long life (20+ years when operated correctly), this technology is perfectly suited to PV storage since just like a solar panel it has extremely long life. LTO coupled with PV could be a  planet saving technology since it could, together with PV, be the most rapidly deployable non carbon energy technology delivering us from the worst effects of climate change.

For more information on this open source PV/LTO project, see http://www.lightontheearth.org/sunpax.html

Jonathan Cole, Founder - Light on the Earth Systems

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