I didn’t know about this chemistry. not the best energy density but super high power and better cycle life and safety than anything else
o my god here’s a deal
at 2.4 volts nominal voltage this is more than a complete pack.
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These things are super cool. They have awesome discharge and charge capability, but pretty poor energy density. They would be a great choice for a last mile board.
The hardest part is dealing with a really low cell voltage of 2.8-3V fully charged. The unfortunate result of the lower energy density is that these discharge to ~1.2V when empty, which is a 60% decrease in voltage, versus typical 18650’s which discharge from 4.2 to 3.4ish, which is a 20% decrease. Basically means you lose tons of top speed over the capacity of the battery, similar to lead acids. That being said, if you can keep the current draw to 1-5C they should perform similiarly to li-ions but with lower voltage.
Here is a great post by a very biased author about them. Even if this guy/girl really likes these batteries, the info is pretty accurate I think.
http://www.lithiumion-batterypack.com/lithium-titanate-battery.html
These things are kind of like a mix of lead acid, li-ion, and lipo. They have great charging and discharge capacity (like lipo), are very safe (like li-ion) and have lower per cell voltage (like lead acids).
edit - the charge voltage is 3.0v, and they probably shouldn’t be discharged at anything above 1-2C as you can see from the voltage-discharge curves
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They would be viable with a voltage step up probably, get a 11s pack and always bring it to 40v or something
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That’s a cool idea worth experimenting with, but I would probably advise against that with these
Buck/boost and similiar work for pretty much only Lipo’s as they have much higher discharge capacities and do not voltage sag as badly as other types of batteries. As you increase the voltage step, more current has to be drawn from the battery with those converters, and you can get a runaway situation when the battery gets near the end of its discharge cycle, especially with these since the voltage sags so quickly at anything above 1-2C. When you get near the end or punch the throttle and voltage sags, the converter will try everything in its ability to keep the voltage you are trying to get, which pulls more current, which lowers the voltage even more, and GG battery haha
I might be mistaken though, the voltage converters i’ve used have always been sketchy to use in any situation other than one where it is controlled with a power supply and used to control a pretty much constant current draw (as an example, I use one for my 3d printer’s heated bed that runs at 24V from my PSU’s 12v)
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What you should do is buy enough of these to make a 12s1p pack (~34V charged w/ 11ah as they say) and perform science. They have pretty good discharge capacity so it would be cool to see how they perform on boards. The ebay link is a pretty good deal considering
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They came up before on the last forum, and I looked into them. You would need 15-16 of them in series when charged to get to the equivalent of a 10S Liion. The problem is that they use A LOT of space. I tried to stack them and move around to fit under a deck in CAD using their measurements, but I was unable to make them fit on deck where I am currently building a 10S8P and there’s extra space left. The high power and cycle life seem to be outweighed by their size.
In UK you can get them for even cheaper: https://www.ebay.co.uk/itm/LTO-11ah-Altairnano-by-Kokam-Lithium-Titanate-LITO-battery-cell-22-Pack/283471842350?hash=item42003d0c2e:g:t5IAAOSwX4VcERqE
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If anyone wants to experiment with them, the chemistry is already in the calculator linked from the top 
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the graph shows theyre good to discharge up to 20c with only 10percent loss of capacity and far from how an ion cell performs even at 5c
these are much safer than ion cells
the graph shows they’re good to be charged up to 10c without a flinch
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Yea! Keep in mind though that these graphs are for a single 1000mah cylinder cell that is larger than an 18650.
Either way, the 20C would be 20A output, so we can compare it to something like the sony VTC5 which is a cheap 2300mah cell. At 20A the VTC5 voltage drops from 4.2V to 3.75V immediately, which is only a 11% decrease in voltage, and at 75% depleted capacity it has dropped to about 3.15V which is a 25% decrease. at almost 100% depletion it only drops to 2.9V which is a 31% decrease in voltage.
So over the entire capacity of the VTC5 the voltage drop of 31% is significantly better (2x better) than that of the LTO cell which drops from 2.8V to under 1V (64% drop).
Thats a pretty big consideration because even at 50% capacity depleted you are looking at a drop from about 2.8v to 1.75 (37.5%)
It would be interesting to find manufacturer data on those LTO polymer cells, generally they have better characteristics than cylindrical cells so maybe they can offer improved capability over the cylinder cells.
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