Lithium technology batteries

"Ken Kochanski (KK)" wrote in message
oups.com...
Although the technology is still pricy vs lead-acid batteries, the
power/weight/size vs cost equation is getting better. Anybody using
lithium model airplane packs bundeled to produce 12 - 14 v @3 - 6 amps
as a power source for their glider? (I have been looking at the
duralite site ... I'm sure there are others.)
http://www.duralitebatteries.com/batteries.html

KiloKilo


I've been watching this too. (The model airplane guys always seem to grab
the latest technology and run with it.) The early Li-Po batteries had some
problems with catching fire when charging but it's clear that the technology
has come a long way in the last year.

There are 14V Mil-Spec Li-Po packs that would be safer to use but the prices
are still astronomical. There are also some 14.8V laptop computer battery
packs that look interesting.

One thing that worries me is that a freshly charged Li-Po "14.8V" pack will
produce a no-load voltage over 16V. A lot of avionics specify that the
maximum voltage is 16V.

Bill Daniels

voltage regulator
williscomb

"WilLiscomb" wrote in message
...
voltage regulator

...or just a forward-biased diode or three.

Vaughn

"WilLiscomb" wrote in message
...
voltage regulator
williscomb



Hmmmm

Build a 'better' battery so that you can dump power into a voltage
regulator. Cute.

Actually the forward biased semiconductor junction in the form of a diode is
a much easier way to do things.

Ian

"tango4" wrote in message
...

"WilLiscomb" wrote in message
...
voltage regulator
williscomb



Hmmmm

Build a 'better' battery so that you can dump power into a voltage
regulator. Cute.

Actually the forward biased semiconductor junction in the form of a diode
is
a much easier way to do things.

Ian



You could use a step-up switching regulator. This would, of course, have
the minor drawback of eliminating the annual "6 or 7 cell" argument on RAS.

Tim Ward

On Sun, 19 Dec 2004 19:09:49 +0000 (UTC), tango4 wrote:

"WilLiscomb" wrote in message
...
voltage regulator
williscomb



Hmmmm

Build a 'better' battery so that you can dump power into a voltage
regulator. Cute.

Actually the forward biased semiconductor junction in the form of a diode is
a much easier way to do things.

Ian

Only problem is that the voltage drop is also present at the
end-of-charge point, thus losing the last 0.7v of possible battery
voltage before things start working strangely.
If you use a well designed switching regulator which can boost as well
as buck, the voltage supplied to the instruments can be maintained in
the ideal range until the battery is almost completely flat, and at an
average efficiency of about 80%. AFAIK, complete discharge is not
harmful to NiCd, Lithium types etc. It is harmful to lead acid
batteries.
Cheers, John G.

John Giddy writes:

If you use a well designed switching regulator which can boost as well
as buck, the voltage supplied to the instruments can be maintained in
the ideal range until the battery is almost completely flat, and at an
average efficiency of about 80%.

With carefull design and construction, you can get over 95% efficient
converters running from a 12v source.

AFAIK, complete discharge is not harmful to NiCd, Lithium types
etc. It is harmful to lead acid batteries.

Full dischare of a NiCd *battery* is bad news, it is OK to fully
discharge a single cell on its own though. Lead acids can be run
totally flat, but must be put on charge imediatly or they
`sulphate'. Don't know about the various Li batteries.

--
Paul Repacholi 1 Crescent Rd.,
+61 (08) 9257-1001 Kalamunda.
West Australia 6076
comp.os.vms,- The Older, Grumpier Slashdot
Raw, Cooked or Well-done, it's all half baked.
EPIC, The Architecture of the future, always has been, always will be.

Nickel Metal Hydride packs also dislike being too deeply discharged. Apart
from that they offer a lot of the benefits - High density, high current,
low temperature operation of other modern batteries. Compared to lead acid
'gel cell' types they offer a reduction in mass of 50%.

My 9Ah 14.4volt NiMh battery is 2/3 the size of a standard 7 Ah 12v gell
cell and weighs 1/2 as much.

Ian

wrote in message
...
John Giddy writes:

If you use a well designed switching regulator which can boost as well
as buck, the voltage supplied to the instruments can be maintained in
the ideal range until the battery is almost completely flat, and at an
average efficiency of about 80%.

With carefull design and construction, you can get over 95% efficient
converters running from a 12v source.

AFAIK, complete discharge is not harmful to NiCd, Lithium types
etc. It is harmful to lead acid batteries.

Full dischare of a NiCd *battery* is bad news, it is OK to fully
discharge a single cell on its own though. Lead acids can be run
totally flat, but must be put on charge imediatly or they
`sulphate'. Don't know about the various Li batteries.

--
Paul Repacholi 1 Crescent Rd.,
+61 (08) 9257-1001 Kalamunda.
West Australia 6076
comp.os.vms,- The Older, Grumpier Slashdot
Raw, Cooked or Well-done, it's all half baked.
EPIC, The Architecture of the future, always has been, always will be.

tango4 wrote:
Nickel Metal Hydride packs also dislike being too deeply discharged. Apart
from that they offer a lot of the benefits - High density, high current,
low temperature operation of other modern batteries. Compared to lead acid
'gel cell' types they offer a reduction in mass of 50%.

My 9Ah 14.4volt NiMh battery is 2/3 the size of a standard 7 Ah 12v gell
cell and weighs 1/2 as much.

I'm looking for ways to fit more AH into standard glider battery boxes,
so people can add a transponder without decreasing the battery run time
or going to the trouble of installing another battery box. For example,
going from a 7 AH battery to a 10 AH pack might achieve this,
particularly if it's a 14 volt pack instead of a 12 volt pack.

What battery (brand and part numbers, if you can) and charger do you
use, and where can we get them?

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

AIK, complete discharge is not harmful to NiCd, Lithium types
etc. It is harmful to lead acid batteries.

The latest designs of Lithium batteries accomodate larger discharge rates and
are becoming price efficient. But they will drop dead below a threshold level,
with no hope of salvage.

Lithium packs are designed in increments of 3.7V nominal per pack. Packs are
combined in series or in parallel to achieve desired voltage and amperage
levels.

In RC airplanes, we use a voltage cutoff device integrated with the speed
control (throttle). That cuttoff level is set at 3.0V per pack. When the
motor blips, you know the cutoff level is met and it is time to land. Go much
longer and the pack is dead.

I haven't used the Lithium batteries in cold weather yes. From what I've read
their performance does decline somewhat.

There is little risk of explosion with the latest versions of chargers and
batteries. As long as the pack is not abused, there is effectively zero chance
of fire or explosion.

I'm thinking about putting Lithium batteries in my sailplane but the price
point is not good yet on 12-14V, 7AH systems.



Jim Vincent
N483SZ
illspam