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Glider power systems



 
 
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  #1  
Old May 5th 04, 02:11 PM
Bill Daniels
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Posts: n/a
Default 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


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  #2  
Old May 5th 04, 05:21 PM
Stephen Haley
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Posts: n/a
Default

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:[email protected]_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




  #3  
Old May 5th 04, 06:13 PM
Bill Daniels
external usenet poster
 
Posts: n/a
Default


"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

  #4  
Old May 5th 04, 07:45 PM
Robert Ehrlich
external usenet poster
 
Posts: n/a
Default

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.
  #5  
Old May 5th 04, 09:00 PM
Martin Gregorie
external usenet poster
 
Posts: n/a
Default

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.


--
[email protected] : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

  #6  
Old May 5th 04, 09:05 PM
Bill Daniels
external usenet poster
 
Posts: n/a
Default


"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

  #7  
Old May 5th 04, 09:22 PM
Mihael
external usenet poster
 
Posts: n/a
Default

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.



  #8  
Old May 6th 04, 01:27 AM
Mike Borgelt
external usenet poster
 
Posts: n/a
Default

On Wed, 05 May 2004 13:11:39 GMT, "Bill Daniels"
wrote:

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



Do we really have a problem that requires this if we use 2 x 7 A-h
sealed lead acid batteries? I use one routinely, keep the other
charged and when #1 dies, switch to # 2 which doesn't have any
charge/discharge cycles on it (you might like to do one to confirm it
is a good battery). After the flight put #2 in the #1 position and put
a new battery in #2.

Automatic chargers for lead acid are cheap and available. Li-ion
batteries are *very* fussy about charging and can be dangerous if this
is done incorrectly.

In many respects our power requirements are lower nowadays. We aren't
running old 360 channel radios full of TTL logic that drew up to 800mA
on standby receive.

Modern radios have standby receive currents of 25 to 100mA.
A B50 vario draws about 100mA
A B40 18mA until you turn the volume up.
GPS receivers are now available that will draw as little as 30Ma from
a 12 volt source.
Our B2000 glide computer draws 50mA.

Allow about 300mA for continuous load and the 7 A-h battery has plenty
of capacity for the whole day even allowing for some reduction with
age and receive/transmit loads.

Add a transponder and you get about another 400mA continuous.

Still likely OK for normal use and you have the other battery at the
end of the day.

What you should do is actually measure what your systems consume. You
may get a surprise.

Also check that you aren't losing volts between the battery and the
systems. Measure the voltage at the battery and at the system. You may
have some unwanted resistance in the circuit.

Use good mil- spec aircraft wire to do your installation. Put a fuse
right on the battery terminal.

We may get a reduction of a few pounds of weight by going to Li
batteries and supercaps and /or some increase in capacity. The
question becomes - how much do you want to pay for this?

Mike Borgelt
  #9  
Old May 6th 04, 02:54 AM
Tim Ward
external usenet poster
 
Posts: n/a
Default


"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


  #10  
Old May 6th 04, 03:31 AM
Bill Daniels
external usenet poster
 
Posts: n/a
Default


"Mike Borgelt" wrote in message
...
On Wed, 05 May 2004 13:11:39 GMT, "Bill Daniels"
wrote:

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



Do we really have a problem that requires this if we use 2 x 7 A-h
sealed lead acid batteries? I use one routinely, keep the other
charged and when #1 dies, switch to # 2 which doesn't have any
charge/discharge cycles on it (you might like to do one to confirm it
is a good battery). After the flight put #2 in the #1 position and put
a new battery in #2.

Automatic chargers for lead acid are cheap and available. Li-ion
batteries are *very* fussy about charging and can be dangerous if this
is done incorrectly.

In many respects our power requirements are lower nowadays. We aren't
running old 360 channel radios full of TTL logic that drew up to 800mA
on standby receive.

Modern radios have standby receive currents of 25 to 100mA.
A B50 vario draws about 100mA
A B40 18mA until you turn the volume up.
GPS receivers are now available that will draw as little as 30Ma from
a 12 volt source.
Our B2000 glide computer draws 50mA.

Allow about 300mA for continuous load and the 7 A-h battery has plenty
of capacity for the whole day even allowing for some reduction with
age and receive/transmit loads.

Add a transponder and you get about another 400mA continuous.

Still likely OK for normal use and you have the other battery at the
end of the day.

What you should do is actually measure what your systems consume. You
may get a surprise.

Also check that you aren't losing volts between the battery and the
systems. Measure the voltage at the battery and at the system. You may
have some unwanted resistance in the circuit.

Use good mil- spec aircraft wire to do your installation. Put a fuse
right on the battery terminal.

We may get a reduction of a few pounds of weight by going to Li
batteries and supercaps and /or some increase in capacity. The
question becomes - how much do you want to pay for this?

Mike Borgelt


With what's in my glider now, one 7.5AH 12V SLA is good enough. I was just
answering the question, "Are we running out of power to run all these
electronic gadgets". The answer is no, there are plenty of options for the
future even if that future means full glass cockpits, transponders and
situational awareness aids.

Better battery options are available now and they will get better in the
future. As you point out, Mike, electronics makers are constantly lowering
power demand. Taken together, the two trends insure that we can add a lot
of avionics if we choose to.

Your point about wiring is very true. We tend to put the batteries behind
the pilot and the electronics forward. A much lighter battery could go
right in the panel without affecting the CG much and the wiring runs would
be much shorter.

I have a friend who mixes his metaphors. He says that lead batteries in
gliders makes as much sense as an air-cooled submarine.

Bill Daniels

 




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