More grist for the battle of the battery

Bill Daniels wrote:
Lithium Ion rechargeables seem to have recently seen a 50% or so price drop.
A 4-cell, 14.8V, 8AH with charger and mounting plate can be had for $169.99
(USD).

Can you supply a URL? While I strongly discourage people from making up
their own Li-ion battery packs for their glider due to potential safety
problems, a _production_ battery pack with it's dedicated charger would
likely alleviate most of the concerns I have about using a large Li-ion
battery in a glider. I don't worry about the little ones in my PDA, cell
phone, or camera.

These are basically long endurance laptop batteries.

What would be the advantage of this battery over the 12 volt, 7 to 9
amphour SLA for your application? Neither size nor weight seem important
in a battery of only 8 amphours, whether SLA or Li-ion. That's a Nimbus
you fly, right?


This is still too much for me given that a SLA with the same capacity is
around $25 but the downward price trend is hopeful. Someone contemplating a
transponder, electric T&B and other juice hungry gadgets in a $100,000+
glider might see Li-Ion as a possibility now.

Unless it allows the pilot to mount significantly more capacity in the
original battery box, eliminating the need to find a place to mount more
batteries, I don't see any benefit. Saving a few pounds seems pointless
in most gliders, even a SparrowHawk.


Beyond price, my concern is voltage. 4-cell Li-Ion packs produce 14.8V and
a detail in the spec sheet admits that a new, fully charged pack might
produce 16.2V into a high resistance load. My avionics manuals say 16V max.
Is that 0.2V overvoltage likely to be a problem?

"Probably not", but I don't know how much margin is built into that
specification. Routinely operating at the high end of the voltage range
might be a different situation than the specification addresses. Ask the
manufacturer, I think.

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Eric Greenwell
Washington State
USA

"Eric Greenwell" wrote in message
...
Bill Daniels wrote:
Lithium Ion rechargeables seem to have recently seen a 50% or so price
drop.
A 4-cell, 14.8V, 8AH with charger and mounting plate can be had for
$169.99
(USD).

Can you supply a URL? While I strongly discourage people from making up
their own Li-ion battery packs for their glider due to potential safety
problems, a _production_ battery pack with it's dedicated charger would
likely alleviate most of the concerns I have about using a large Li-ion
battery in a glider. I don't worry about the little ones in my PDA, cell
phone, or camera.

I just scanned a bunch of pages from a Google search. I'll find the one
with the specifics.


These are basically long endurance laptop batteries.

What would be the advantage of this battery over the 12 volt, 7 to 9
amphour SLA for your application? Neither size nor weight seem important
in a battery of only 8 amphours, whether SLA or Li-ion. That's a Nimbus
you fly, right?

It's about a 6 pound weight savings. (1 Lb vs 7 Lbs) for 7-8 AH. That
allows the battery to be behind the panel with short wires instead of behind
the seat with long wires. Total weight savings are not that important but
the battery's effect on balance and weight of the 'non-flying' parts is.
I've been running W&B's and 6 pounds is important.

This is still too much for me given that a SLA with the same capacity is
around $25 but the downward price trend is hopeful. Someone
contemplating a
transponder, electric T&B and other juice hungry gadgets in a $100,000+
glider might see Li-Ion as a possibility now.

Unless it allows the pilot to mount significantly more capacity in the
original battery box, eliminating the need to find a place to mount more
batteries, I don't see any benefit. Saving a few pounds seems pointless
in most gliders, even a SparrowHawk.

You can get a lot more capacity for the same volume and weight.


As for safety, the motorglider guys are flying around with GASOLINE, right?
That burns too.

Bill Daniels

Bill Daniels wrote:

What would be the advantage of this battery over the 12 volt, 7 to 9
amphour SLA for your application? Neither size nor weight seem important
in a battery of only 8 amphours, whether SLA or Li-ion. That's a Nimbus
you fly, right?


It's about a 6 pound weight savings. (1 Lb vs 7 Lbs) for 7-8 AH. That
allows the battery to be behind the panel with short wires instead of behind
the seat with long wires. Total weight savings are not that important but
the battery's effect on balance and weight of the 'non-flying' parts is.
I've been running W&B's and 6 pounds is important.

This is an interesting idea. It might be an easy way to power a
transponder with a separate battery, without the hassle and expense of
mounting a 6 pound battery somewhere it won't become a projectile.

The Becker and Microair transponders have max input voltages of 30
volts, so no problem with 16.2 full charge voltage that's an issue for
you. Encoders, like the ACK 30 I use, have similar values. It would mean
using two different chargers, one for the Li-ion, one for the SLA, but
that seems like a minor inconvenience.

snip

As for safety, the motorglider guys are flying around with GASOLINE, right?
That burns too.

Surprisingly, fire fed by the gasoline is a rare event in motorgliders
(wire fires seem more common, along with burns from the canopy focusing
the sun), and we continue to hurt ourselves in the usual ways glider
pilots do.


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Eric Greenwell
Washington State
USA

"Eric Greenwell" wrote in message
...
Bill Daniels wrote:
Lithium Ion rechargeables seem to have recently seen a 50% or so price
drop.
A 4-cell, 14.8V, 8AH with charger and mounting plate can be had for
$169.99
(USD).

Can you supply a URL? While I strongly discourage people from making up
their own Li-ion battery packs for their glider due to potential safety
problems, a _production_ battery pack with it's dedicated charger would
likely alleviate most of the concerns I have about using a large Li-ion
battery in a glider. I don't worry about the little ones in my PDA, cell
phone, or camera.

Sometimes Froogle doesn't find the same things on successive searches. Here
is an example of what I'm talking about.

http://store.linkexpresspc.com/de16liprbafo.html

Specifications:
- Rating: 14.8V == DOUBLE CAPACITY 8800mAH (8.8AH)
- Capacity : 132 WHR 16CELL
$149.00 @ LinkExpressPC

As for the warning videos and scary stories in the press, most people know
these are merely efforts at proactive legal defense. (Lawyer for the
plaintiff: "You sold these CHEMICAL FIRE BOMBS for use in CHILDREN'S TOY
AIRPLANES?) (Lawyer for the defense: "Gee, yer honor, we warned 'em - see
our scary video on the web.) It's an effort to immunize the manufacturer
against 'frivolous' lawsuits.

In fact, most technically savvy users know Li-Ion batteries are plenty safe
if a few simple precautions are used. Mainly, use the correct charger in a
fire safe location. Once charged, don't damage the case or short them.
That's pretty good advice for any rechargeable battery no matter the
chemistry.

Bill Daniels

Bill Daniels wrote:

Can you supply a URL? While I strongly discourage people from making up
their own Li-ion battery packs for their glider due to potential safety
problems, a _production_ battery pack with it's dedicated charger would
likely alleviate most of the concerns I have about using a large Li-ion
battery in a glider. I don't worry about the little ones in my PDA, cell
phone, or camera.


Sometimes Froogle doesn't find the same things on successive searches. Here
is an example of what I'm talking about.

http://store.linkexpresspc.com/de16liprbafo.html

Specifications:
- Rating: 14.8V == DOUBLE CAPACITY 8800mAH (8.8AH)
- Capacity : 132 WHR 16CELL
$149.00 @ LinkExpressPC

I think this style would be much more suitable than a laptop battery:

http://tinyurl.com/8zl55

Essentially the same ratings and price ($169 with charger), it has a
standard output connector and a easier to mount shape. Google "external
laptop battery" without the quotes. There is a wide range of price and
power in this style. Something like this might be very practical for
gliders, though I still want to know more about maximum ambient
temperature and altitude allowed, and built-in safety features.

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

Eric Greenwell
Washington State
USA

"Eric Greenwell" wrote in message
...
Bill Daniels wrote:

Can you supply a URL? While I strongly discourage people from making up
their own Li-ion battery packs for their glider due to potential safety
problems, a _production_ battery pack with it's dedicated charger would
likely alleviate most of the concerns I have about using a large Li-ion
battery in a glider. I don't worry about the little ones in my PDA, cell
phone, or camera.


Sometimes Froogle doesn't find the same things on successive searches.
Here
is an example of what I'm talking about.

http://store.linkexpresspc.com/de16liprbafo.html

Specifications:
- Rating: 14.8V == DOUBLE CAPACITY 8800mAH (8.8AH)
- Capacity : 132 WHR 16CELL
$149.00 @ LinkExpressPC

I think this style would be much more suitable than a laptop battery:

http://tinyurl.com/8zl55

Essentially the same ratings and price ($169 with charger), it has a
standard output connector and a easier to mount shape. Google "external
laptop battery" without the quotes. There is a wide range of price and
power in this style. Something like this might be very practical for
gliders, though I still want to know more about maximum ambient
temperature and altitude allowed, and built-in safety features.

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

Eric Greenwell
Washington State
USA

Yep, that's a better example. I think I saw that one on my earlier search
but I couldn't find it the second time. There are quite a few of these on
the market from a variety of vendors. The price is falling as they become a
commodity. I think I could build a box for an internal laptop battery that
would have contacts and a restraining latch. Just push the battery in until
it clicks - no wires to futz with.

Many laptops and gadgets sit on car seats in the sun and then get turned on.
I have certainly done that but I don't know of any problems. I remember
trying to boot a laptop I left on a car seat in Phoenix. It was so hot I
couldn't hold it. After it booted, I couldn't read the LCD until the A/C
cooled it down. Generically, Li-ion polymer batteries are tolerant of
temperature extremes. The laptop batteries are regarded as 'smart'
batteries in that they have processor chips inside that manage them. I
think they may even limit the voltage to 14.8V.

Bill Daniels

Bill Daniels wrote:

I think I could build a box for an internal laptop battery that
would have contacts and a restraining latch. Just push the battery in until
it clicks - no wires to futz with.

Perhaps a suitable solution for a knowledgeable person like yourself,
but the typical laptop battery has a half-dozen contacts, so I wouldn't
know which ones need connecting. I don't even know if the charger can be
connected directly to battery, or if it goes through some other
circuitry in the laptop. These issues don't exist with external laptop
batteries, and their approximately 4" x 6" x 1" shape would make
mounting them easier than the oddball shapes the laptops use. We already
futz with one cable out a lead-acid glider battery - not a problem there.


Many laptops and gadgets sit on car seats in the sun and then get turned on.
I have certainly done that but I don't know of any problems. I remember
trying to boot a laptop I left on a car seat in Phoenix. It was so hot I
couldn't hold it. After it booted, I couldn't read the LCD until the A/C
cooled it down. Generically, Li-ion polymer batteries are tolerant of
temperature extremes. The laptop batteries are regarded as 'smart'
batteries in that they have processor chips inside that manage them.

I don't know how smart a laptop battery is, and I suspect some of the
smarts are inside the laptop; for example, in the situation you
describe, the laptop likely cut back it's processor speed and LCD
brightness to reduce the power taken from the battery, protecting it
from overheating. The battery used by itself might not be able to
protect itself properly, because it's designed to be used only in the
laptop. The external batteries might offer this protection, since they
are intended to be used by themselves. I don't know if that's true, but
I'd like to know before I started using one in a glider.

I think they may even limit the voltage to 14.8V.

A number of the external batteries can be set to different output
voltages, which might be useful, but I don't know how they do that.

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

Eric Greenwell
Washington State
USA