Glider power systems

After reading the annual installment of the 12V vs.14V soap opera and the
"We can't power any more electronics" whine, I took a little time to read
the Maxwell Electronics information on their Ultracaps.

See: http://www.maxwell.com/index.html

Maxwell makes a pretty good case for combining a small ultracapcitor with a
NiMH or Lithium-ion battery for use in typical consumer electronics like
computers and cellphones. It seems to me that the devices in our gliders
could use the Maxwell approach. Transmitters place a high demand on the
batteries for short periods and the varios and flight computers place a low
demand for long hours.

The Sealed Lead Acid batteries most of us use are great for short, heavy
amperage demands but not so hot for powering electronics for long hours.
The typical NiMH or increasingly common lithium-Ion are great for low
current devices but not good at high current demands. Maxwell's solution is
to combine a low amperage power source with an Ultracap so the Ultracap
handles the high-current short-duration, demands like transmitters and the
main lithium-ion battery handles the low-current, long-duration demand.

Of course, you still need the same AH's to go the distance but your
transmitter will get the voltage it needs at the end of a long day. We need
our EE's to quit arguing about 14V vs. 12V and whip up a nice circuit for an
Ultracap + Lithium-ion battery.

Bill Daniels

I thought that some LIon are actually quite good at high current draw
applications. They are certainly making inroads into the model plane market
now their price is dropping. The main problem with them is their pontential
to explode if shorted out through thermal runaway and they require
specialised charging requirements. A secondary problem is that you cannot
measure the battery state through voltage.
The main advantages of lion are the light weight per amphour BUT they are
bulkier than lead acid by about a factor of 2.
At my level (Rank beginner using club equipment) the main problem is
normally that the battery is either getting old or is not charged. Going
back to my sailing days we converted to using NiFe batteries as we could
charge them at over 300 amps, 30mins motering gave us full batteries,, the
voltage was almost constant until completely discharged and they could be
badly abused (completely flattened) and still recover. I know that they
are/were used in aviation for engine starting but not sure if they were ever
used in flight.

For real usable results in battery technology I suspect we should look to
the new Hybrid Petrol/Electric cars being developed by Toyota but as with
all things it wil take time for them to be affordable/usable.

I suspect a real driver in Glider battieries will be the requirement in
Europe for Mode S transponders with some countries adopting them before
discrete iterrogation is switched on meaning that in some areas transponders
may be interrogated many times a min. This will require some real
improvement in battery technology for existing gliders where retrofitting
with solar charging would be difficult .

rgds
stephen

"Bill Daniels" wrote in message
news:fK5mc.27410$TD4.3881262@attbi_s01...
After reading the annual installment of the 12V vs.14V soap opera and the
"We can't power any more electronics" whine, I took a little time to read
the Maxwell Electronics information on their Ultracaps.

See: http://www.maxwell.com/index.html

Maxwell makes a pretty good case for combining a small ultracapcitor with
a
NiMH or Lithium-ion battery for use in typical consumer electronics like
computers and cellphones. It seems to me that the devices in our gliders
could use the Maxwell approach. Transmitters place a high demand on the
batteries for short periods and the varios and flight computers place a
low
demand for long hours.

The Sealed Lead Acid batteries most of us use are great for short, heavy
amperage demands but not so hot for powering electronics for long hours.
The typical NiMH or increasingly common lithium-Ion are great for low
current devices but not good at high current demands. Maxwell's solution
is
to combine a low amperage power source with an Ultracap so the Ultracap
handles the high-current short-duration, demands like transmitters and the
main lithium-ion battery handles the low-current, long-duration demand.

Of course, you still need the same AH's to go the distance but your
transmitter will get the voltage it needs at the end of a long day. We
need
our EE's to quit arguing about 14V vs. 12V and whip up a nice circuit for
an
Ultracap + Lithium-ion battery.

Bill Daniels

"Stephen Haley" wrote in message
...
I thought that some LIon are actually quite good at high current draw
applications. They are certainly making inroads into the model plane
market
now their price is dropping. The main problem with them is their
pontential
to explode if shorted out through thermal runaway and they require
specialised charging requirements. A secondary problem is that you cannot
measure the battery state through voltage.
The main advantages of lion are the light weight per amphour BUT they are
bulkier than lead acid by about a factor of 2.

I don't think you are right about the comparison with SLA's. Li-Ion has a
much greater power per unit volume and weight than Lead. The thermal
runaway has been solved with imbedded safety circuitry. (BTW, a shorted,
fully charged SLA isn't too nice to be around either but main fuses take
care of this.)

I don't need to monitor battery state if I know it will last twice as long
as I need it to. Cell phones with Li-ion batteries work just fine if
charged regularly. (A five-day battery charged daily is a no-problemo.)

BTW, I have no financial interest in Maxwell Technologies or Ultracaps, they
just have a nice web site that explains the technology well. Their point is
that batteries designed for low discharge rates will last a lot longer than
those designed for fast discharge. Ultracaps can supply short bursts of
high current for transmissions and recharge from the low discharge rate
Li-ion's. For a given size and weight, a Li-ion + Ultracap should be able
to power a lot more electronics than an equivalent SLA.

Bill Daniels

Bill Daniels wrote:
...
Cell phones with Li-ion batteries work just fine if
charged regularly.
...

No. Most lead-acid batteries in my club are much older than
my cell phone and are still working, while the battery of my
cell phone is dead.

"Robert Ehrlich" wrote in message
...
Bill Daniels wrote:
...
Cell phones with Li-ion batteries work just fine if
charged regularly.
...

No. Most lead-acid batteries in my club are much older than
my cell phone and are still working, while the battery of my
cell phone is dead.

My cell phone Li-ion battery was still working fine after five years when
the service provider went bad.

OTOH, I replace my glider SLA at every two years or sooner to be sure I have
full capacity. It makes me wonder how many complaints about $3000+ flight
computers and varios are due to the owner being too cheap to buy a new $30
battery. Flaky lead acid batteries make most electronics flaky too.

Bill Daniels

If you are interested in lithium batteries there is tons of information's on
address:

http://www.saftbatteries.com/120-Tec...ium_system.asp

Michael

"Robert Ehrlich" wrote in message
...
Bill Daniels wrote:
...
Cell phones with Li-ion batteries work just fine if
charged regularly.
...

No. Most lead-acid batteries in my club are much older than
my cell phone and are still working, while the battery of my
cell phone is dead.

On Wed, 5 May 2004 16:21:59 +0000 (UTC), "Stephen Haley"
wrote:

I thought that some LIon are actually quite good at high current draw
applications. They are certainly making inroads into the model plane market
now their price is dropping. The main problem with them is their pontential
to explode if shorted out through thermal runaway and they require
specialised charging requirements. A secondary problem is that you cannot
measure the battery state through voltage.
The main advantages of lion are the light weight per amphour BUT they are
bulkier than lead acid by about a factor of 2.

Are you sure? I made some calculations of Li-poly vs NiCd, comparing
two Kokam 145 mAh Li-poly cells delivering 5 v through a 7805 v.reg
with a five cell pack of Sanyo N50-AAA (50 mAh) cells. The Kokam pack
gives three times the capacity for 1/2 the weight and 2/3 the volume
of the NiCd pack. It's power/wt ratio is about 4.5 times better and
its power/volume ratio is 4 times better than the NiCds.

On a quick and dirty comparison using a Kobe 12v 7 Ah gel cell and
5500 mAh D-size NiCds an equivalent NiCd pack (10 x D cells) would be
very similar in power/volume ratio to the gel cell - certainly within
+/- 10%. A cross check for Sanyo 7Ah F-size cells gives the same
answer, but the super-F (10 Ah, F-size) will have a 30% better
power/volume ratio than a gel cell. I've no idea about power/weight
ratios: I haven't got anything to hand that can weigh the 12v gel
cell.

Li-poly cells are better and safer than Li-ion cells: the Li-poly seem
to be more popular with the indoor RC crowd than Li-ion. I think both
will spontaneously combust if the thin plastic cover is pierced.

As others have pointed out, you MUST have a special (and relatively
expensive) charger for Li-Poly cells.

For real usable results in battery technology I suspect we should look to
the new Hybrid Petrol/Electric cars being developed by Toyota but as with
all things it wil take time for them to be affordable/usable.

What sort of battery technology do these use?

I suspect a real driver in Glider battieries will be the requirement in
Europe for Mode S transponders with some countries adopting them before
discrete iterrogation is switched on meaning that in some areas transponders
may be interrogated many times a min. This will require some real
improvement in battery technology for existing gliders where retrofitting
with solar charging would be difficult .

Although available NiMH cells of AA cell size or smaller have double
the power density of NiCd there's nothing in Maplins or RS catalogues
bigger than 2.3 Ah C and D-size cells while NiCds go to 10 Ah per
cell. Has anybody spotted an NiMH with a capacity of 5 Ah or bigger?

So, it looks like the answer will be Li-poly, then. Expensive, and
requiring crash-proof containers to prevent the outer membrane being
pierced in a crash and causing a fire.


--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

Li-poly cells are better and safer than Li-ion cells:

Before you become convinced of their safety, take a gander at this warning
issued by the Academy of Model Aeronautics.

Emergency Safety Alert: Lithium Battery Fires
(Added 4/23/04)

Lithium batteries are becoming very popular for powering the control and power
systems in our models. This is true because of their very high energy density
(amp-hrs/wt. ratio) compared to Nickel Cadmium (Ni-Cds) or other batteries.
With high energy comes increased risk in their use.
The principal risk is fire which can result from improper charging, crash
damage, or shorting the batteries. All vendors of these batteries warn their
customers of this danger and recommend extreme caution in their use.

In spite of this many fires have occurred as a result of the use of Lithium
Polymer (Li-Poly) batteries, resulting in loss of models, automobiles, and
other property. Homes and garages and workshops have also burned.

A lithium battery fire is very hot (several thousand degrees) and is an
excellent initiator for ancillary (resulting) fires. Fire occurs due to contact
between lithium and oxygen in the air. It does not need any other source of
ignition or fuel to start, and burns almost explosively.

These batteries must be used in a manner that precludes ancillary fire. The
following is recommended:

Store and charge in a fireproof container, never in your model.
Charge in a protected area devoid of combustibles. Always stand watch over the
charging process. Never leave the charging process unattended.
In the event of damage from crashes, etc., carefully remove to a safe place for
at least a half hour to observe. Physically damaged cells could erupt into
flame. After sufficient time to ensure safety, damaged cells should be
discarded in accordance with the instructions which came with the batteries.
Never attempt to charge a cell with physical damage regardless of how slight.
Always use chargers designed for the specific purpose, preferably having a
fixed setting for your particular pack. Many fires occur in using
selectable/adjustable chargers improperly set. Never attempt to charge lithium
cells with a charger that is not specifically designed for charging lithium
cells. Never use chargers designed for Ni-Cd batteries.
Use charging systems that monitor and control the charge state of each cell in
the pack. Unbalanced cells can lead to disaster if it permits overcharge of a
single cell in the pack. If the batteries show any sign of swelling,
discontinue charging and remove them to a safe place—outside—as they could
erupt into flames.
Most important: NEVER PLUG IN A BATTERY AND LEAVE IT TO CHARGE UNATTENDED
OVERNIGHT. Serious fires have resulted from this practice.
Do not attempt to make your own battery packs from individual cells.
These batteries cannot be handled and charged casually such as has been the
practice for years with other types of batteries. The consequence of this
practice can be very serious and result in major property damage and/ or
personal harm.

—AMA Safety Committee

On 06 May 2004 16:41:36 GMT, (DGManley) wrote:

Li-poly cells are better and safer than Li-ion cells:

Before you become convinced of their safety, take a gander at this warning
issued by the Academy of Model Aeronautics.

I didn't say "safe", merely safer, but I was wrong. See below.

Here's an account with pictures of what happens when a fully charged
Li-poly cell is charged for an hour at 1 amp and twice its rated
voltage...

http://www.rcgroups.com/forums/showt...pagen umber=1

I've seen it said that Li-poly cells are more stable than Li-ion but
no supporting evidence as to why this should be so. Now here's a
statement from the manufacturer of "Thunder Plus" Li-poly and Li-ion
cells. Makes interesting reading.

"The “Lithium Polymer battery” used in the hobby and in most
commercial applications is really a Lithium-ion battery that has had
the internal power generating materials folded to a flat matrix
instead of rolled up to fit in the cylindrical can, it is then
installed in a light aluminium container that was original designed
for food storage but works great. The good news is that the “lithium
Polymer battery” is a bit lighter and has the ability to support
higher loads because of it’s ability to dissipate heat under higher
loads. This is the good part; the other side of the coin is that under
the charging process the “Lithium Polymer cells” don’t include any of
the safety systems that are part of a Lithium-ion cylindrical cell, so
the cell has no way of protecting itself. This then requires control
of the charging cycle imperative. There was/is a false presentation in
the hobby that the “Lithium Polymer Battery” is completely safe and
won’t create an unhappy experience. The electrolyte used in these
cells is liquid and flammable. If the cell or pack is overcharge
(voltage) for any reason the first indication is that the cell will
start to puff up like a balloon. If you are lucky the cell pops (gas
release vent) and you cut off the charge before further problems. I
will say that lithium doesn’t like exposure to oxygen."

I guess that answers me. Li-poly are no safer than Li-ion. I've only
looked at the Kokam website in detail, but did notice that most of the
cells they sell have protection circuitry attached to them though all
are flat and contained in just a plastic membrane.

I'm not sure whether the fire/explosion problem is due to:

1) the high energy density
2) ease of electrical damage at high discharge rates
3) ease of electrical damage with improper charging
4) using a thin plastic membrane to contain an assembly
that is spontaneously flammable in air and explosive in the
presence of water.

My guess (and that's all it is) is that (3) and (4) are the most
significant causes of Li-poly fires.

There's already a direct bearing on cockpit fires because the
batteries in iPAQ PDAs (certainly in the 36xx series and probably the
others too) are Li-poly cells. They are flat, encased in a silvered
plastic membrane and don't appear to contain cell protection circuits.
The cell is stuck to the plastic backplate of the iPAQ with nothing
separating it from the PCB except its membrane. I replaced one
recently in my iPAQ 3630: that's how I know this.

BTW, I would not want to be in a closed cockpit with a lithium cell
that had even vented without burning: the 'white smoke' is almost
certainly LiOH (lithium hydroxide) and that's at least as corrosive as
caustic soda.

From the Academy of Model Aeronautics:

Emergency Safety Alert: Lithium Battery Fires
(Added 4/23/04)

Lithium batteries are becoming very popular for powering the control and power
systems in our models. This is true because of their very high energy density
(amp-hrs/wt. ratio) compared to Nickel Cadmium (Ni-Cds) or other batteries.
With high energy comes increased risk in their use.
The principal risk is fire which can result from improper charging, crash
damage, or shorting the batteries. All vendors of these batteries warn their
customers of this danger and recommend extreme caution in their use.

In spite of this many fires have occurred as a result of the use of Lithium
Polymer (Li-Poly) batteries, resulting in loss of models, automobiles, and
other property. Homes and garages and workshops have also burned.

A lithium battery fire is very hot (several thousand degrees) and is an
excellent initiator for ancillary (resulting) fires. Fire occurs due to contact
between lithium and oxygen in the air. It does not need any other source of
ignition or fuel to start, and burns almost explosively.

These batteries must be used in a manner that precludes ancillary fire. The
following is recommended:

Store and charge in a fireproof container, never in your model.
Charge in a protected area devoid of combustibles. Always stand watch over the
charging process. Never leave the charging process unattended.
In the event of damage from crashes, etc., carefully remove to a safe place for
at least a half hour to observe. Physically damaged cells could erupt into
flame. After sufficient time to ensure safety, damaged cells should be
discarded in accordance with the instructions which came with the batteries.
Never attempt to charge a cell with physical damage regardless of how slight.
Always use chargers designed for the specific purpose, preferably having a
fixed setting for your particular pack. Many fires occur in using
selectable/adjustable chargers improperly set. Never attempt to charge lithium
cells with a charger that is not specifically designed for charging lithium
cells. Never use chargers designed for Ni-Cd batteries.
Use charging systems that monitor and control the charge state of each cell in
the pack. Unbalanced cells can lead to disaster if it permits overcharge of a
single cell in the pack. If the batteries show any sign of swelling,
discontinue charging and remove them to a safe place—outside—as they could
erupt into flames.
Most important: NEVER PLUG IN A BATTERY AND LEAVE IT TO CHARGE UNATTENDED
OVERNIGHT. Serious fires have resulted from this practice.
Do not attempt to make your own battery packs from individual cells.
These batteries cannot be handled and charged casually such as has been the
practice for years with other types of batteries. The consequence of this
practice can be very serious and result in major property damage and/ or
personal harm.

—AMA Safety Committee



--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

"Stephen Haley" wrote in message
...
I thought that some LIon are actually quite good at high current draw
applications. They are certainly making inroads into the model plane
market
now their price is dropping. The main problem with them is their
pontential
to explode if shorted out through thermal runaway and they require
specialised charging requirements. A secondary problem is that you cannot
measure the battery state through voltage.
The main advantages of lion are the light weight per amphour BUT they are
bulkier than lead acid by about a factor of 2.

The other advantage is that they work much better at low temperatures --
which is significant if you're flying in, say, wave.

snippage

Tim Ward