Lithium Titanate, the next great chemistry?

[witzgall]

Hi all,

Some of you around here for awhile may remember our being one of the first boats to cruise with LIFEPO4, in the 2010-2013 timeframe on our previous boat.

Last year I obtained 5, 24v lithium titanate modules, commonly known as LTO. They were Manufactured by Altairnano. I have begun to test these, and so for they are looking good.

Lto benefits are:

High charge and discharge rates. These modules, 60ah and 50ah, are rated at 6C continuous. Overkill, but charge them as fast as you dare!

High safety specifications, at least as high as lifepo4

Work well in freezing temps

Very high cycle like, in excess of 8000 to 100% DoD. If you take them to 2.1v at the cell, you are almost at zero, but can still take them down to 1.7v without any issues. Taking to zero is not great for the cells, but apparently does not kill them. For these modules, 17v would be dead zero soc.

Voltage can be an indicator of charge, unlike lifepo4.

25 year lifespan

Drawbacks are: lower energy density, lower cell voltage, my modules are 10s in config, and cell voltage is 2.3v nominal. I am running them between 25.4v (96% soc )and 21v (2.5% soc)

Cost, they are way more $ than other chemistries. I got mine for pennies on the dollar, otherwise they are too expensive to mere mortals right now.

The modules I have were engineering samples. They are mil spec in design. If anyone is interested, I can post some photos and further info as the project progresses.

Chris

[Matt Johnson]

Haven't followed the LifePO4, but how's your equipment doing with the lower voltage? Seems like it would put a lot of stress on any motor.

Matt

[witzgall]

I have not done really any testing on this, but I do not expect it to be much of an issue. I ran a 750 watt heat gun though the inverter, the voltage drop was .2v! Any voltage drop at amps I would see on the boat would be from cable losses only. Windlasses and thrusters (I have the former but not the latter) I think would work fine. The real world voltage difference is small. Actually, I think this would make a killer thruster battery for 24v thrusters. I may just be worth the $$$ in that application on some boats.

The only other motor on the boat really is the fans. My water pump is variable voltage, so no issues there. LED lighting works a treat.

I disconnected the alternator from supplying the house bank, until I can get that sorted out. As it stands, the voltage it puts out is way too high.

Having said all of this, a 11 cell version might be better on a boat.

Chris

[witzgall]

Here is the Cell brochure: http://www.witzgallphotography.com/files/60ahcell.pdf

and the module brochure:
http://www.witzgallphotography.com/f...60ahmodule.pdf

[Matt Johnson]

Cool! I was just thinking in a 12v application.... I know my windlass, watermaker, fridge and a number of other things are so voltage dependent and wouldn't be happy with 10.5 to 11.5 volts. Even down in at 12, things start to whine and protest. I would guess a dc to dc converter would be necessary.


Matt

[witzgall]

I imagine there may be some issues. We are a 24v boat, and as such have a 24-12v converter for some of the electronics, etc. We don't have a dc watermaker, but if we did, it would not put out as much water per hour. On our last boat, we had a 12v Spectra WM and LIFEPO4. There, the stated actual WM output was higher then spec because the LIFEPO4 voltage was higher.

The only item we have that may be a problem is the windlass, I will have to test in actual use conditions.

On all of the Danfoss-based fridges, they can operate quite efficiently on something like 10-28v. You can put different resistors in-between two of the control module connections to tell it the voltage range you want to work with, including one that is really wide - designed for working with solar panels.

I put a Victron battery Protect between the loads and the batteries. This will cut off the power at 21v.

[hellosailor]

A bank of six cells, based on that nominal 2.3V instead of the 2.2 from lead acid, would make a 13.8v battery which is actually LOW alternator voltage and very nicely in the acceptable range for all "12 volt" equipment on a boat.

Seems like the only trick would be making a regulator to keep them happy, whatever charge profile they require. And affording/obtaining them.

[Matt Johnson]

Originally Posted by hellosailor

A bank of six cells, based on that nominal 2.3V instead of the 2.2 from lead acid, would make a 13.8v battery which is actually LOW alternator voltage and very nicely in the acceptable range for all "12 volt" equipment on a boat.

Seems like the only trick would be making a regulator to keep them happy, whatever charge profile they require. And affording/obtaining them.

You're right. I don't know how my math kept failing me... I kept getting a 100% SOC at over 16 volts with 6 cells. Instead of the 15.24 using Witzgall's 96% SOC which seems closer to optimum for the electronics.

Matt

[hellosailor]

" I don't know how my math kept failing me"
You probably forgot the conversion: These are Italian batteries, they're rated in metric volts not SAE volts.(VBG)

[roland stockham]

Originally Posted by hellosailor

" I don't know how my math kept failing me"
You probably forgot the conversion: These are Italian batteries, they're rated in metric volts not SAE volts.(VBG)

That's a joke right!

If these are lower energy density what advantage do the have over wet cell Nicads?

[witzgall]

I have never heard of a wet cell nicad? Nicads have a memory effect, and thus are a poor choice for use on a boat.

[hellosailor]

Wet cell nicad's are old technology. They were often huge (suitcase and larger size cells) and used among other things by Ma Bell at the exchanges, where they were required to maintain a THREE DAY backup battery power source.

There are a number of older alternate battery types that most of us have never heard of, for various good reasons.

But SAFT, the owners of the "NiCad" trademark, even 20 years ago would be quick to tell you that *quality* NiCad cells (as opposed to cheap generic NiCd cells) have no "memory" problem. That has to do with the chemical mixture as well as the physical construction, they said.

The same way that not all "lithium" batteries have a fire and explosion problem.

Batteries are like mattresses and tires: All the rubes know is how to buy a pretty package. They have no idea what is inside it. They buy the sizzle, not the steak.

[roland stockham]

Wet cell NiCads are nothing like the small rechargables you use in torches and have been the standard in the power industry for emergency supply in places such as hospitals for many years. They are used to bridge the gap when mains power fails until the generators are running and stable. Normally supplied as single cells giving 1.2v per cell. They can be discharged and charged very rapidly because of very low internal resistance, can be discharged to flat without damaged and stored discharged. Standard life span is 20yrs+. The down side is that they cost about 3x the equivalent wet lead acid and have a lower charge density so not a compact solution. The electrolyte is alkaline which is significantly more dangerous to skin as it does not cause a painful burn so can go unoticed. They are also not available in smaller sizes so unless you have space for a bank of 900ah not really practical. On larger boats I would say they are ideal.
For charging you need a constant current charger that cuts off at 1.45v per cell. They can be charged to 80% in about 20min if you have the power supply but that would be around 2000A!! Unlike lead acid they do not sulfate so running between 20% and 80% charge for extended periods will not effect them.
The other problem is that they are only available from people who supply power utilities not retail.
I looked seriously into using them but my boat is too small and I could not get any that would fit.