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Backup battery - Lightspeed EI

 
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nuckollsr(at)cox.net
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PostPosted: Sat Mar 04, 2006 9:38 am    Post subject: Backup battery - Lightspeed EI Reply with quote

At 07:00 PM 3/2/2006 +0000, you wrote:

Quote:

<czechsix(at)juno.com>

Hi Doug,
My RV is setup for day/night VFR and I have dual Lightspeeds. I pondered
the electrical system options extensively. I originally planned to go with
two alternators and one battery. The thing I kept coming back to is that
with one battery, you have a single-point failure for the entire
electrical system. Notwithstanding the opinion of others to the contrary,
it IS possible to have a battery lead break off or come loose.

The only cases I've seen for this are (1) batteries with lead posts where
the lead wires are much too stiff (e.g. 2AWG 22759 wire). (2) Another
case was where the builder had fabricated a stiff copper strap that bolted
one end to the battery (-) terminal an the other to the firewall. This
was a steel posted battery and it broke the terminal under vibration.
Make your short battery jumpers from 4AWG welding cable IRRESPECTIVE of wire
sizes used elsewhere in the system.

I'm not arguing against multiple battery installations, only suggesting
that risk mitigation for broken battery terminals is a no-brainer.

BTW, a little bird flew by a few days ago and whispered that a well
known supplier of PM alternators just might be bringing a new regulator
out that would be self-exciting. Don't quote me on that. The bird was
speaking in Swahili and the only words of that language I remember clearly
were the favorite expletives of my 8th grade science teacher. We shall
see . . .

Bob . . .


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rparigor(at)SUFFOLK.LIB.N
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PostPosted: Sat Mar 04, 2006 12:09 pm    Post subject: Backup battery - Lightspeed EI Reply with quote

"The thing I kept coming back to is that with one battery, you have a
single-point failure for the entire electrical system"

I am building a Europa with a Rotax 914 turbo. It has 2 fuel pump, 1 needs
to be running to keep the motor running.

I plan on flying Day and Night VFR.

I also have both 27 foot span go fast wings and 48 foot span go pretty
fast glider wings.

On automobiles I have had batteries fail open upon start ups. My wife and
partner have had cars die in the road from a internal open battery. That
said I had a Cessna 170 for 19 years and never had a failure of battery,
but not to say it will not happen. I still feel uneasy bout getting a
battery opening, especial on start up.

I don't like the added weight of a second lead acid battery,especial
something able to help out with starting.

I am introducing a nontraditional demand, trying to start the motor in
air.

Now one may recommend a airstart, and that works, but you are spinning a
cold motor real quick real fast, hard on motor. Best to use starter.

I have a SD-20S as primary alternator and Rotax internal Generator (not
self exciting) as back up. It is wired using Z13/8 as a starting place.

If you tickled the Rotax generator/Ducati regulator/rectifier, I am
confident with our 48K microfarad capacitor it will remain alive and
running a fuel pump.

I used my head which uses the rest behind the right seat passengers head
to make me feel better.

I have a 13 cell GP 2200mA NiMh Battery (1.62 oz ea cell) that can supply
a few hundred amps for short periods, and easily the 50 or 60 amps the
starter requires. It lives nice in the headrest easily accessable by
pilot.

I have 3 inputs it can supply:
If all went to hell, can run aux pump on it (~ 2amp draw, so without test
and very cold battery at minimum I would say 30 minutes) Pulling 60 amps,
this battery will put out 2000mAs and then still be at .9volts per cell!
I can power E-Bus (which it will be diode isolated from to not accept a
charge, but 14.4V) even if it did try to charge would not hurt battery too
much). Now powering E-Bus can allow me to run things when soaring and not
touch main battery, or if my main battery failed upon a start up, could do
a airstart running aux pump from E-Bus, then tickle the rotax generator.
Can also plumb directly in parallel with main battery to help start.
Voltage of pack will be nominal 15.6 volts.

May sound complicated, layout is simple and intuitive. I feel very
comfortable with it.

Smoke or other electrical failure? In 10 seconds I can turn off main
battery switch (Flaming River on rear of headrest), E-Bus aux feed battery
switch (in headrest) and plumb NiMh battery to pump (right in headrest)
and now have a bit of time to think things through.

The panel is recessed in headrest 3/4" and has EL strip to illuminate
headrest panel. There is a mini Blue LED Voltmeter in there as well that
tells either Main or NiMh output.

Normal failure of main alternator, just switch off and turn on Rotax.
Starter solenoid sticks when doing a in flight start, or other failure on
that side of things, turn off main battery switch and select E-Bus
alternate feed and turn on Rotax Generator
If Battery failed opened upon restart, plumb NiMh to E-Bus to run pump and
do a airstart, then tickle Rotax. Although I could probably start on the
NiMh autonomous, best not do it in air.
Battery flat when away from home, parallel main with NiMh. If NiMh failed,
am on ground, so no big deal.

Downside is you can not use a lead acid charging system to charge a NiMh
direct. If not in a hurry a C/10 by 14 to 16 hour charge is best. If in a
hurry a 1C delta peak charge is OK. If in a real hurry or you want to ask
200 amps from battery you want it nice and warm, do a 2 or 3C delta peak
charge.

Since I fly electric models and gliders, and one reason for having a
Europa is to take me to far away soaring sites, I am set up with all the
stuff I need. As a matter of fact when transporting models, future designs
will (you guessed it) be made using 13 cell packs. Chargers run off normal
1 2volt system.

Long winded all right.

Anyway if you have a electrical dependent aeroplane, for not much weight
you can give yourself imn my opinion a versatile alternative.

Ron Parigoris

Oh yea it will power something like this as well:
http://www.yourzagi.com/wagmax.htm


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nuckollsr(at)cox.net
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PostPosted: Sun Mar 05, 2006 7:03 am    Post subject: Backup battery - Lightspeed EI Reply with quote

At 11:20 PM 3/4/2006 -0500, you wrote:

Quote:


Hi Mark
You sound like you are probably well aware of this but "theoretically"
I'd expect a lot less than 3 hours at 1 amp.
www.power-sonic.com/ps-1229.pdf
These specs indicate that at a 1 amp discharge rate you shouldn't expect
more than 2 hours under ideal conditions or perhaps 1.5 hours for a cold
battery. Apologies for nit-picking.

Ken

This is not nit-picking. It's considered systems integration with
understanding. We've discussed many times here on the List how
a battery's useful capacity varies with load. We've also discussed
the pitfalls of using the battery's labeled capacity without KNOWING
what loads were used to rate that capacity.

For example, batteries for bizjets are rated for specific situations
where the generators are dead and you're required to power certain
systems for 30 minutes. Since battery manufacturers are not
regulated to do anything, their ratings may be stated in any
lucid manner they choose. Most manufacturers of batteries
label their products at a 20 hour discharge rate. Here's
a recap of situations we've discussed in the past:

In this figure, we can see the published capacity vs. load
curves for a popular 33 a.h. battery from Panasonic . . .

http://www.aeroelectric.com/Pictures/Curves/LA1233_Panasonic.gif

Note that the 33 a.h. rating is met with a 1.65A discharge
after 20 hours. Increase the load to 13.2A and you'll get
just under two hours of service for a useful capacity of
23.7 a.h. A substantial drop from the label rating.

Here are curves produced here in our shop on a single 18 a.h.
SVLA battery . . .

http://www.aeroelectric.com/Pictures/Curves/1217_3n8_Discharge.pdf

Note that due to increased losses in the battery's internal impedance,
the useful capacity at 8A is 13.5 a.h. for an operating time of 1.7
hours. Useful capacity at 3 A is 16.8 a.h. for an operating time
of 5.6 hours.

Finally, here's a discharge curve for battery from Concord
for a bizjet with a label capacity of 37 a.h. . . .

http://www.aeroelectric.com/Pictures/Curves/Capacity_vs_Voltage.gif

Note that it produces 95% of rated capacity when discharged to
22v at 74A . . . this happens in 37/74 hours or 30 minutes.

If this battery were re-labeled with a 20 hour rate, the very
same battery could be called a 50+ a.h. battery.

I'm pleased that you picked up on this Ken, I missed it.

Bob . . .

Quote:
snip

> used a PowerSonic 2.9 Ah battery (PS-1229). It's light and relatively
cheap (I think about $25-30...you can Google it and get lots of hits). I
plan to change the battery every two years to ensure that it's reasonably
fresh. I know Klaus says 4.5 Ah but I thought that was overkill (unless
you plan to be flying over some really rugged terrain/ocean with no
alternates within an hour or two of flight). The 2.9 Ah batt is
theoretically good for almost 3 hours of run time on one ignition
(drawing ~ 1A at cruise RPM's). In the unlikely event that I ever find
myself operating the engine soley on the backup battery, I will try to
have it on the ground within an hour.
>
snip

--



Bob . . .
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >


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mcculleyja(at)starpower.n
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PostPosted: Sun Mar 05, 2006 9:57 am    Post subject: Backup battery - Lightspeed EI Reply with quote

Bob,

Also, I don't want to be a nit-picker but the legend on the graph of
your shop discharge test cited below indicates that the black line is a
17AH battery at 3 Amp discharge versus the red line being an 18AH
battery at 8 Amp discharge. Is this a typo or am I missing understanding
something? I see the 1217,3n8 notation in the web address which I assume
means a 12 volt,17AH battery?

>Here are curves produced here in our shop on a single 18 a.h.
> SVLA battery . . .

>http://www.aeroelectric.com/Pictures/Curves/1217_3n8_Discharge.pdf

Robert L. Nuckolls, III wrote:
Quote:


At 11:20 PM 3/4/2006 -0500, you wrote:


>
>
>Hi Mark
>You sound like you are probably well aware of this but "theoretically"
>I'd expect a lot less than 3 hours at 1 amp <SNIP>

Bob . . .


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PostPosted: Sun Mar 05, 2006 1:15 pm    Post subject: Backup battery - Lightspeed EI Reply with quote

At 12:53 PM 3/5/2006 -0500, you wrote:

Quote:

<mcculleyja(at)starpower.net>

Bob,

Also, I don't want to be a nit-picker but the legend on the graph of
your shop discharge test cited below indicates that the black line is a
17AH battery at 3 Amp discharge versus the red line being an 18AH
battery at 8 Amp discharge. Is this a typo or am I missing understanding
something? I see the 1217,3n8 notation in the web address which I assume
means a 12 volt,17AH battery?

Good catch. I need to fix that. Both graphs were on the same
Panasonic LC-RD1217 battery . . .

http://www.aeroelectric.com/Reference_Docs/Battery/Panasonic/lc-rd1217p.pdf

The 18 a.h. reference is a typo.

Bob . . .


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brian



Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

PostPosted: Sun Mar 05, 2006 2:05 pm    Post subject: Backup battery - Lightspeed EI Reply with quote

J. Mcculley wrote:
Quote:


Bob,

Also, I don't want to be a nit-picker but the legend on the graph of
your shop discharge test cited below indicates that the black line is a
17AH battery at 3 Amp discharge versus the red line being an 18AH
battery at 8 Amp discharge. Is this a typo or am I missing understanding
something? I see the 1217,3n8 notation in the web address which I assume
means a 12 volt,17AH battery?

The curves look correct to me. They are a bit odd in that normally one
plots voltage against time for a given discharge rate (constant current)
but you can always divide the amp-hour scale by amps to get the hours.

what might be more interesting would be to plot the endpoints (11V or
10.5V, whatever you select for "dead") and the amp-hours delivered for
each discharge rate. That would show you how much energy is available
from your battery at different discharge rates. You could also calculate
Peukert's exponent for your battery so you can figure out its remaining
capacity even at varying discharge rates.

--
Brian Lloyd 361 Catterline Way
brian-yak at lloyd dot com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery


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brian-yak at lloyd dot com
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brian



Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

PostPosted: Sun Mar 05, 2006 2:07 pm    Post subject: Backup battery - Lightspeed EI Reply with quote

Robert L. Nuckolls, III wrote:

Quote:
> battery at 8 Amp discharge. Is this a typo or am I missing understanding
> something? I see the 1217,3n8 notation in the web address which I assume
> means a 12 volt,17AH battery?

Good catch. I need to fix that. Both graphs were on the same
Panasonic LC-RD1217 battery . . .

http://www.aeroelectric.com/Reference_Docs/Battery/Panasonic/lc-rd1217p.pdf

The 18 a.h. reference is a typo.

Is this a gelled electrolyte battery or an AGM battery? My guess from
looking at the voltage sag is that it is a gel-cell.
--
Brian Lloyd 361 Catterline Way
brian-yak at lloyd dot com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery


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brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery
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PostPosted: Sun Mar 05, 2006 8:02 pm    Post subject: Backup battery - Lightspeed EI Reply with quote

At 02:06 PM 3/5/2006 -0800, you wrote:

Quote:


Robert L. Nuckolls, III wrote:

>> battery at 8 Amp discharge. Is this a typo or am I missing understanding
>> something? I see the 1217,3n8 notation in the web address which I assume
>> means a 12 volt,17AH battery?
>
> Good catch. I need to fix that. Both graphs were on the same
> Panasonic LC-RD1217 battery . . .
>
> http://www.aeroelectric.com/Reference_Docs/Battery/Panasonic/lc-rd1217p.pdf
>
> The 18 a.h. reference is a typo.

Is this a gelled electrolyte battery or an AGM battery? My guess from
looking at the voltage sag is that it is a gel-cell.

Gel cells are almost non-existent in the wild. If you have a real
gel-cell it will probably say so in the literature and even on the
side of the battery. Gels are a modified flooded battery where
enough jello like stuff was added to make the normally liquid
stuff stay in place when the battery was inverted.

Globe Union were biggies in Gels about 25 years ago, Sonnenschein
makes them in Europe. The first spill proof battery B&C sold was
the Gates energy jelly-roll cells which were a true AGM, SVLA,
RG, Immmobilized Electrolyte, starved electrolyte battery . . . but
not a gel-cell. When the Gates product proved unworthy of flight
in aircraft, B&C switched to the Sonnenschein gels for a time but
those were replaced by the Genesis series (all the above types)
and ultimately STD'd onto a bunch of airplanes.

Gel-cells are popular for deep cycle applications like electric
wheelchairs. They seem to perform better than their dryer
cousins. I think B&C still has one gel-cell offering. Some folks
like Delmar Benjamin swear by them and he Bill aims to please.

The vast majority of lead-acid products are of the SVLA/RG
variety and you have to go out of your way to find a gel-cell.
Unfortunately, most of the storefronts who stock these modern
marvels refer to them as gel-cells and help perpetuate a huge
mis-information.

Bob . . .
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >


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brian



Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

PostPosted: Sun Mar 05, 2006 8:45 pm    Post subject: Backup battery - Lightspeed EI Reply with quote

Robert L. Nuckolls, III wrote:

Quote:
Gel cells are almost non-existent in the wild. If you have a real
gel-cell it will probably say so in the literature and even on the
side of the battery. Gels are a modified flooded battery where
enough jello like stuff was added to make the normally liquid
stuff stay in place when the battery was inverted.

Gel-cells are rather common in the boating community. They are clearly
delineated as such.

Quote:
Globe Union were biggies in Gels about 25 years ago, Sonnenschein
makes them in Europe. The first spill proof battery B&C sold was
the Gates energy jelly-roll cells which were a true AGM, SVLA,
RG, Immmobilized Electrolyte, starved electrolyte battery . . . but
not a gel-cell. When the Gates product proved unworthy of flight
in aircraft, B&C switched to the Sonnenschein gels for a time but
those were replaced by the Genesis series (all the above types)
and ultimately STD'd onto a bunch of airplanes.

No argument there.

Quote:
Gel-cells are popular for deep cycle applications like electric
wheelchairs. They seem to perform better than their dryer
cousins. I think B&C still has one gel-cell offering. Some folks
like Delmar Benjamin swear by them and he Bill aims to please.

I happen to like gels myself as their acceptable absorption charge
voltage range overlaps with the acceptable float charge voltage range.
You can get away with a single-voltage charging system (like an
aircraft's alternator).

Also, gels seem to tolerate extended partial discharge better than AGMs.
This makes them more attractive in power systems where the battery does
not get completely recharged every time.

But their higher internal resistance makes them poor starting batteries
unless they are oversized for the task.

Quote:
The vast majority of lead-acid products are of the SVLA/RG

Gel-cells are RG (recombinant gas) batteries also. I am not familiar
with the term SVLA tho.

RG - recombinant gas
VRLA - valve-regulated lead-acid
AGM - absorbed glass-mat
GELA - gelled-electrolyte lead-acid

BTW, VRLA or RG can refer to *either* GELA or AGM batteries.

I am attaching a really good treatise on VRLA batteries from Deka-Penn.
Clearly they are trying to sell their own product and it is a bit
simplistic in some areas but their stuff on charging and discharging is
really good. The best thing about it is that it addresses the
differences in operation of GELA and AGM batteries.

Quote:
variety and you have to go out of your way to find a gel-cell.

I disagree. I have no trouble finding gel-cells and use them where I
think they will perform better. They have higher internal resistance
than do AGMs but they are less prone to failure on overcharge than are
AGMs. They also tolerate partial or complete discharge better than AGMs.
Quote:
Unfortunately, most of the storefronts who stock these modern
marvels refer to them as gel-cells and help perpetuate a huge
mis-information.

Bob, I know the difference. I read the manufacturer's literature so I
know what I am buying. I don't trust what stores tell me because,
frankly, I usually know more about the topic than does the store. GELA
batteries are common enough that I would not pretend to know what is
inside the case unless the lit clearly states one way or another.

--
Brian Lloyd 361 Catterline Way
brian-yak at lloyd dot com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery


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_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

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- Antoine de Saint-Exupery
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PostPosted: Sun Mar 05, 2006 9:02 pm    Post subject: Backup battery - Lightspeed EI Reply with quote

At 02:01 PM 3/5/2006 -0800, you wrote:

Quote:


J. Mcculley wrote:
>
<mcculleyja(at)starpower.net>
>
> Bob,
>
> Also, I don't want to be a nit-picker but the legend on the graph of
> your shop discharge test cited below indicates that the black line is a
> 17AH battery at 3 Amp discharge versus the red line being an 18AH
> battery at 8 Amp discharge. Is this a typo or am I missing understanding
> something? I see the 1217,3n8 notation in the web address which I assume
> means a 12 volt,17AH battery?

The curves look correct to me. They are a bit odd in that normally one
plots voltage against time for a given discharge rate (constant current)
but you can always divide the amp-hour scale by amps to get the hours.

what might be more interesting would be to plot the endpoints (11V or
10.5V, whatever you select for "dead") and the amp-hours delivered for
each discharge rate. That would show you how much energy is available
from your battery at different discharge rates. You could also calculate
Peukert's exponent for your battery so you can figure out its remaining
capacity even at varying discharge rates.

Yeah . . . I've had some conversation with the folks at WestMountainRadio
about this. Obviously, the ampere-hour is NOT a measure of energy. When
I purchased my first battery tester from them, I suggested some enhancements
for the next release of their software. We engineers would really like to
see constant wattage and constant resistance discharge functions in addition
to the standard constant current function. Then too, as you've noted, a
volts vs. time and energy vs. time plots would be more meaningful along
with an box on the graph that displayed watt-seconds of energy at the
endpoint.
He seemed receptive. I'll write again and see where that might set on his
stove's burners.

I'd REALLY like to recommend his tool to others in the battery business
but most would like some features besides the arcane and poorly-descriptive
ampere-hour display. He's 100% of the way there with hardware, what he
needs now is a really cool GUI.
Bob . . .


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brian



Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

PostPosted: Mon Mar 06, 2006 6:21 am    Post subject: Backup battery - Lightspeed EI Reply with quote

Robert L. Nuckolls, III wrote:

Quote:
Yeah . . . I've had some conversation with the folks at WestMountainRadio
about this. Obviously, the ampere-hour is NOT a measure of energy.

But it is easily converted into energy (amp-hours x volts = watt-hours)
and it more readily conforms to how a battery works. Good batteries tend
to have very high coulombic efficiency (one coulomb removed requires one
coulomb to be replaced). I am used to batteries with coulombic
efficiencies on the order of 97%. The energy loss in a battery is a
function of the voltages involved, i.e. you need a higher voltage to
push the coulombs back into the battery than you get when taking them out.

(For those of you wondering what I am talking about, a coulomb is the
measure of a pot full of electrons. An amp is one coulomb of electrons
flowing through a wire in one second. Think of the cell of a battery as
a tank full of coulombs of electrons.)

Quote:
When
I purchased my first battery tester from them, I suggested some enhancements
for the next release of their software. We engineers would really like to
see constant wattage and constant resistance discharge functions in addition
to the standard constant current function. Then too, as you've noted, a
volts vs. time and energy vs. time plots would be more meaningful along
with an box on the graph that displayed watt-seconds of energy at the
endpoint.
He seemed receptive. I'll write again and see where that might set on his
stove's burners.

Well, then let's build our own. Not hard to do. It is just some simple
hardware and then SMOP (small matter of programming).

Hardware consists of a load bank made up of a bunch of paralleled
MOSFETs driven from a D:A converter. (Use MOSFETs because they won't
current hog.) The battery voltage and current is measured by an AVery Happy
converter. The software looks at these values and controls the load bank
to make it do what you want it to do.

Quote:
I'd REALLY like to recommend his tool to others in the battery business
but most would like some features besides the arcane and poorly-descriptive
ampere-hour display. He's 100% of the way there with hardware, what he
needs now is a really cool GUI.

Well, the hardware is the easy part. Smile I would like to see his tester.
You know, with the requirement for testing of batteries in certified
aircraft, you would think there would be a market for a good, cheap
battery tester.

--
Brian Lloyd 361 Catterline Way
brian-yak at lloyd dot com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery


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Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery
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