LiPo Batteries in Gliders

Been using NIMH for 2 years in a N3DT with Xponder. Works great!

Bob

What about Li Ion batteries like these? Is the fire risk sinificantly
less than Li Polymer?

http://www.streckenflug.at//shop/pro...roducts_id=608

A bit pricey, and probably not approved in Europe, but might be a
thought when a transponder has to be carried.

John Galloway

While charging a LiPo model airplane battery with a top-of-the-line charger
at the proper rate it burst into flame. I had carelessly left it out of the
flame-proof charge bag and when I checked strange noises the room was filled
with acrid smoke and a Mt Vesuvius mass of sputtering pyrotchnics was
burning a hole in the work bench. Don't fly with you-do-it LiPos unless you
have an ejection seat!

Karl Striedieck


"johngalloway" wrote in message
...
What about Li Ion batteries like these? Is the fire risk sinificantly
less than Li Polymer?

http://www.streckenflug.at//shop/pro...roducts_id=608

A bit pricey, and probably not approved in Europe, but might be a
thought when a transponder has to be carried.

John Galloway

On Feb 25, 9:03*am, "Karl Striedieck" wrote:
While charging a LiPo model airplane battery with a top-of-the-line charger
at the proper rate it burst into flame. I had carelessly left it out of the
flame-proof charge bag and when I checked strange noises the room was filled
with acrid smoke and a Mt Vesuvius mass of sputtering pyrotchnics was
burning a hole in the work bench. Don't fly with you-do-it LiPos unless you
have an ejection seat!

Karl Striedieck

"johngalloway" wrote in message

...

What about Li Ion batteries like these? *Is the fire risk sinificantly
less than Li Polymer?

http://www.streckenflug.at//shop/pro...roducts_id=608

A bit pricey, and probably not approved in Europe, *but might be a
thought when a transponder has to be carried.

John Galloway

Karl, model gliding is DANGEROUS !
See ya, Dave

On Feb 24, 8:50*pm, GM wrote:
Hi,

it's still winter with lousy weather in the northern hemisphere, so it
is time to warm up an old discussion. I searched the forum for threads
reg. Lithium-Polymer Batteries and there have been none for a while.
Here are the questions:
- Does anyone have real life experience with LiPo's in a glider? (real
gliders, that is - not models)
- Can I combine two 7.4V packs in series to get a 14.8V unit or is
there a risk with that?
- How would one charge a combo like this? Each unit by itself and then
hook them together or with one charger while hooked together?

The prices have dropped to a very affordable level; so have the
chargers/balancers. The weight savings are considerable. My 12V/7.5Ah
standard sealed gel-cell weighs 2.35kg (5.17lbs) and it lasts a few
days. *I found two 7.4V/5.0Ah units on e-bay that weigh in at 0.3kg
each (0.6kg or 1.32 lbs in total)

Any input is welcome.

Uli Neumann
'GM'

Most of the dire "explosion-fire" warning here are several years out
of date. Chemistry's like LiFePo4 have no such dangers. Most 5AH and
larger packs have internal PCB's for safety.

Check out US manufacturers like Tenergy which offers a number of
"heavy duty" Li-Po and LiFePo4 packs with internal PCB's which limit
charge and discharge voltages and currents to safe levels.

One problem not mentioned is that 4-cell Li-Po can deliver as much as
17V when fully charged which is more than some avionics allow. I
would use a DC-DC converter to deliver a tightly regulated 13.8 V to
the avionics bus. DC-DC converters allow a wider choice of battery
voltages.

This thread reminds me of the old saying: pioneers are the ones with
the arrows in their backs. SLA batteries are cheap, and their risks
are known. Why mess around and take a chance on an in-flight fire?

-John

On Feb 25, 10:12*am, bildan wrote:
On Feb 24, 8:50*pm, GM wrote:



Hi,

it's still winter with lousy weather in the northern hemisphere, so it
is time to warm up an old discussion. I searched the forum for threads
reg. Lithium-Polymer Batteries and there have been none for a while.
Here are the questions:
- Does anyone have real life experience with LiPo's in a glider? (real
gliders, that is - not models)
- Can I combine two 7.4V packs in series to get a 14.8V unit or is
there a risk with that?
- How would one charge a combo like this? Each unit by itself and then
hook them together or with one charger while hooked together?

The prices have dropped to a very affordable level; so have the
chargers/balancers. The weight savings are considerable. My 12V/7.5Ah
standard sealed gel-cell weighs 2.35kg (5.17lbs) and it lasts a few
days. *I found two 7.4V/5.0Ah units on e-bay that weigh in at 0.3kg
each (0.6kg or 1.32 lbs in total)

Any input is welcome.

Uli Neumann
'GM'

Most of the dire "explosion-fire" warning here are several years out
of date. *Chemistry's like LiFePo4 have no such dangers. *Most 5AH and
larger packs have internal PCB's for safety.

Check out US manufacturers like Tenergy which offers a number of
"heavy duty" Li-Po and LiFePo4 packs with internal PCB's which limit
charge and discharge voltages and currents to safe levels.

One problem not mentioned is that 4-cell Li-Po can deliver as much as
17V when fully charged which is more than some avionics allow. *I
would use a DC-DC converter to deliver a tightly regulated 13.8 V to
the avionics bus. *DC-DC converters allow a wider choice of battery
voltages.

Second the max voltage warning. ILEC has already seen some fried
avionics from customers experimenting with these things...
Be careful out there (check max voltage for pack and everything
in your panel FIRST),
Best Regards, Dave "YO electric"

Years ago, a lab next to the one I worked in had experimental
batteries under development. All the high energy density ones utilize
very reactive elements, of which lithium is one. However, nothing
would beat the sodium-sulfur battery in its capacity to "go
Vesuvius". It was colloquially referred to as "the fire and brimstone
battery". The lab had a sulfurous smell that reminded one of the
entrance to nether regions.

I'm going to stick with lead-acid, thanks very much!

Mike

On Feb 25, 8:48*am, Mike the Strike wrote:
Years ago, a lab next to the one I worked in had experimental
batteries under development. *All the high energy density ones utilize
very reactive elements, of which lithium is one. *However, nothing
would beat the sodium-sulfur battery in its capacity to "go
Vesuvius". *It was colloquially referred to as "the fire and brimstone
battery". *The lab had a sulfurous smell that reminded one of the
entrance to nether regions.

I'm going to stick with lead-acid, thanks very much!

Mike

If you think lead-acid gel-cells are safe, try a dead short on a fully
charged one. Splattering hot gelled acid is pretty nasty stuff.

In article ,
Eric Greenwell wrote:

GM wrote:
The prices have dropped to a very affordable level; so have the
chargers/balancers. The weight savings are considerable. My 12V/7.5Ah
standard sealed gel-cell weighs 2.35kg (5.17lbs) and it lasts a few
days. I found two 7.4V/5.0Ah units on e-bay that weigh in at 0.3kg
each (0.6kg or 1.32 lbs in total)
Why do you wish to save 1.75 kg/3.85 pounds? That small amount can not
possibly affect your glider's performance. I mean, my drinking water
weighs about 6 pounds.

Libelle drivers understand very well why saving weight is important.
Gliders often get heavier with age. Our venerable Libelles have
accumulated repairs, more instruments, etc. so that we are often above
the (unrealistically low) "official" weight, thus incurring a handicap
penalty in sports/club class. Not really much of a competitiveness
issue, but when one nudges the "all up" weight limit, contest officials
get all serious and make unsettling noises.