William.P.Dube(at)noaa.go
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 Posted: Fri Sep 07, 2007 11:37 am Post subject: A123 Systems Nano-phosphate technology and aircraft (was: |
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Whomever is designing the electronics doesn't have real experience with
A123 Systems cells. They think they are dealing with conventional Li-Ion
cells, and they are wrong.
A123 Systems nano-phosphate cells are quite different than other
Li-Ion cells. They will take a LOT of abuse. About the same amount as an
AGM. It is straightforward to make a drop-in replacement for a 12 volt
(or 24 volt) lead-acid battery using A123 Systems cells. The existing
charging system will work just fine. (It must have the voltage set
somewhere between 13.5 and 14.8 volts.)
In an airplane, you would want a warning that alerted the pilot that
the system was going over 14.8 volts and would make noise if the system
was going over 15 volts. It would also be useful to know if the battery
temperature was going over 80 Celsius. (You can go up to about 100 C
without damage, but no higher or you risk venting the cells and damaging
the plastic separator.)
>>> Case study <<<<
I have had a 3.5 lb A123 Systems battery running in my completely
unmodified GMC van for the past 7 months. It snaps the engine over much
better than the original 35 lb lead-acid battery.
Let's talk about abuse. My wife left my van door unlocked and
someone rifled my glove box and left it open with the light on. This
killed the battery and it sat at ZERO VOLTS for over a week. I thought,
"So much for THAT battery." I then decided to do what the typical
consumer would do and I connected up the 3.5 lb completely dead battery
to a fully-charged car battery with jumper cables. Hundreds of amps
flowed and slightly warmed the cables. I waited a couple of minutes for
the 3.5 lb battery voltage to come up, disconnected the jumper cables
(the worst thing you could do) and cranked up the van. It started
instantly. The alternator then gave the 3.5 lb battery ~100 amps until
it came up to 13.4 volts and then tapered off. The BMS showed that all
the cells were still in balance!
This was five months ago. I haven't capacity-tested the battery, but
I can't tell the difference in cranking performance. It was just as if
nothing had happened. I even left it parked for 5 weeks while I was out
of town and it cranked right up without a problem.
If you were to torture a conventional Li-Ion battery like this, it
would have burst into flames, or at least it would have just burst. I
tell this story to folks with years of experience with conventional
Li-Ion cells and they cringe when I get to the part about the jumper
cables. 
The A123 Systems cells will, indeed, "take the abuse". I have a very
simplistic charge-balancing electronics (BMS) on my GMC van battery.
Nothing fancy is needed.
If you overcharge them grossly, they will vent a small amount of
flammable vapor (like paint thinner.) If there is an ignition source,
this vapor could catch fire. The cells can also burst if overcharged
severely. That is the extent of the hazard this technology presents.
Bill Dube'
Robert L. Nuckolls, III wrote:
| Quote: |
<nuckollsr(at)cox.net>
At 04:32 PM 9/5/2007 -0600, you wrote:
> You can do a fantastic electric motor glider, but nothing long range.
> Imagine if gasoline weighed about 100 lbs per gallon and you will
> understand the range issue.
>
> These "Nano-Phosphate" type cells will make a big dent in the weight
> of airplanes soon. As you can see, they put out a huge amount of
> power for their weight, so they will be perfect starting batteries
> for airplanes. This specific type of battery has none of the safety
> issues that other high-power batteries have.
One of my principles is working with the A123
products with an eye toward a certified replacement
of SVLA/NiCAD batteries on T/C aircraft. So far,
they've reporting nothing that suggests that the
the task is impractical but successful integration
of Li-Ion technology into aircraft WILL require
a battery-friendly charging system (read new smart
regulator for existing aircraft) or a drop-in form-fit-
function device that includes battery management
capabilities. The Li-Ion's are not drop-in replacments
for SVLA . . . they won't take the "abuse".
Bob . . .
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