Battery Source

By now, most will realize that electricity is pretty dangerous stuff and not
to be trifled with. Yeah, it's maybe okay in small doses, flashlight
batteries come to mind as being pretty safe if not swallowed.

Not a believer? If you want to see the incredible destructive power that
lurks in seemingly innocent, but higher voltage batteries, try touching the
terminals on a cute little 9 volt battery to a scrap of fine steel wool!!
(use caution and make sure the steel wool in on a surface that won't burn)

Yup, 12 volts DC is right at the maximum sane voltage. Any more is downright
foolish. In fact, the force fields that result from adding just 2 additional
volts (14 volts DC) will cause the hapless pilot to undergo some sort of
cultish brain damage. In some cases these poor deranged pilots will then
start preaching on street corners, warning those who use lesser voltages
that the end is near and they will be discharged.

Curiously, by abandoning the idea of using DC (direct current), and
switching all systems over to AC, alternating current, one can safely
increase voltage doses up to about 120 VAC or so, with little attendent risk
of dain bramage. Beyond that, there is the ever present risk of
vaporization. Which is, of course, why pilots should do their best to avoid
high voltage transmission lines.

all the best,

bumper (12 volts DC and proud of it)

OK. I'm laughing out loud at that one. Well done.

Paul Remde

"bumper" wrote in message ...
By now, most will realize that electricity is pretty dangerous stuff and
not to be trifled with. Yeah, it's maybe okay in small doses, flashlight
batteries come to mind as being pretty safe if not swallowed.

Not a believer? If you want to see the incredible destructive power that
lurks in seemingly innocent, but higher voltage batteries, try touching
the terminals on a cute little 9 volt battery to a scrap of fine steel
wool!! (use caution and make sure the steel wool in on a surface that
won't burn)

Yup, 12 volts DC is right at the maximum sane voltage. Any more is
downright foolish. In fact, the force fields that result from adding just
2 additional volts (14 volts DC) will cause the hapless pilot to undergo
some sort of cultish brain damage. In some cases these poor deranged
pilots will then start preaching on street corners, warning those who use
lesser voltages that the end is near and they will be discharged.

Curiously, by abandoning the idea of using DC (direct current), and
switching all systems over to AC, alternating current, one can safely
increase voltage doses up to about 120 VAC or so, with little attendent
risk of dain bramage. Beyond that, there is the ever present risk of
vaporization. Which is, of course, why pilots should do their best to
avoid high voltage transmission lines.

all the best,

bumper (12 volts DC and proud of it)

When I started this thread, all I was looking for was a source for a
battery for my Discus fin box. My backup battery under my panel is
about to be switched to a dedicated source to my new transponder and I
like the idea of having a separate source for my main panel instruments
and radio just in case. I lost my main battery in a glider some years
ago when a wire joint failed at the faston tab at the battery, so I
believe that a backup source is common sense.

I was considering using a 14 V seven-stack of D+ del cells for my tail
fin to take account of the extra voltage drop in the longer wiring to
the fin but decided it wasn't worth the hassle when I calculated 12 V
would work fine for the hour or two I might need it.

In any case, I hadn't intended starting rival polemics about 12 V
versus 14 V systems!

Having said that, some of the arguments for 14 V sources don't seem to
make much sense. One main argument seems to be that the higher voltage
removes the need for a second backup. Presumably using this thinking
the authors have installed heavy-duty tires on their cars and removed
their spares.

The extra 20% to 30% power from a radio transmitter also makes very
little difference. If the radio quits because of low voltage, that's a
different matter, but the extra power from a working radio is
inconsequential. Most communication problems arise from either bad
antennas or defective ones. The rubber duckies on handhelds are a
particular example of this and are horribly inefficient. Some years
ago, I did tests on the 144 MHz FM amateur frequencies from a glider
and using standard commercial equipment with good antennas was able to
maintain perfect communications with 1 watt at up to a hundred miles
with line-of-sight conditions. The 120 MHz AM aircraft radios might
not be quite so good, but a couple of watts should be good enough for
50 miles or more.

Udo Rumpf wrote:

It's possible you have a problem not related to the voltage; e.g.,
maybe the voltage is dropping well below the 11.8 volts when the
transmitter is keyed, or the radio is not functioning within
specifications.

Eric Greenwell


I have a 720A Dittle radio
Power requirements;
Receive .1 - .4 amps
Transmit (tone) 1.4 amps (.8 amps unmodulated)
The 11.8 volts I was referring to is before transmit.
If I remember correctly when the battery is fully charged
and I hit the transmit button the voltage drops from 12.7 to 12.2.
Udo

With the battery run down to 11.8 volts, measure the voltage right at
the radio connector while keying the transmitter for 5-10 seconds. If it
drops more than it does when the battery is fully (or nearly so)
charged, the problem might be the battery.

However....
I found a German manual for the ATR720A (and ATR70C in English) on the
Filser site (I think they took over the radios from Avionic Dittel).
The specifications don't make any mention of what voltage range the
radio will function over, so I suspect 12 volt battery operation wasn't
on their minds when it was designed. This appears to be an older design
radio, and likely is one that would benefit from 14 volt operation.

So, if it's not the battery, your choices seem to be a modern radio
(like the Walter Dittel FSG 2T I mentioned) or going to a 14 volt
battery pack. Or waiting till you get closer to the airfield to make
your call :^)

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Eric Greenwell
Washington State
USA

I have a 720A Dittle radio
Power requirements;
Receive .1 - .4 amps
Transmit (tone) 1.4 amps (.8 amps unmodulated)
The 11.8 volts I was referring to is before transmit.
If I remember correctly when the battery is fully charged
and I hit the transmit button the voltage drops from 12.7 to 12.2.
Udo

With the battery run down to 11.8 volts, measure the voltage right at
the radio connector while keying the transmitter for 5-10 seconds. If it
drops more than it does when the battery is fully (or nearly so)
charged, the problem might be the battery.

However....
I found a German manual for the ATR720A (and ATR70C in English) on the
Filser site (I think they took over the radios from Avionic Dittel).
The specifications don't make any mention of what voltage range the
radio will function over, so I suspect 12 volt battery operation wasn't
on their minds when it was designed. This appears to be an older design
radio, and likely is one that would benefit from 14 volt operation.

So, if it's not the battery, your choices seem to be a modern radio
(like the Walter Dittel FSG 2T I mentioned) or going to a 14 volt
battery pack. Or waiting till you get closer to the airfield to make
your call :^)

Eric Greenwell

I have this Radio now for many years.
Based on what you and Tim are saying, I concluded that
this radio does not perform very well at lower voltage.
Only in the past couple of years while flying a glider with restrictive
space for a batteries (the standard 12v 7amp) have I noticed any
deficiency at low voltage even with fresh sets of batteries.
also this radio seem to eat more on stand by.
Prior to this I had no restriction in capacity and the problem never
came up. Other then that the radio works fine and has good range
when the voltage is up.
Thanks
Udo

Paul Remde mentioned that he replaces his batteries after two years of use.

The sealed lead acid batteries we use, start life with a given capacity,
rated in amp hours. After manufacture, and during the first several
charge/discharge cycles, these batteries will actually gain a small amount
of capacity. After that, it's all downhill, with the battery losing capacity
over time and discharge cycles.

In the alarm industry, we replace the batteries at 5 year intervals. At this
point, most of the batteries will be down to about 70% of capacity. However,
these batteries have a pretty easy life, rarely being called upon to provide
power and generally not bieng discharged deeply.

In a glider, life for a battery is tough. Deep discharge cycles and wild
temperature swings being the norm. Generally, discharging a lead acid below
80% charge will have an impact on its remaining life, below 50% is not
recommended. So life will be short, so to speak.

I agree with Paul, replacing batteries often is cheap insurance. I change
mine at 3 years and always store them fully charged.

all the best,

bumper (12 volts and proud of it!)

Udo Rumpf wrote:

So, if it's not the battery, your choices seem to be a modern radio
(like the Walter Dittel FSG 2T I mentioned) or going to a 14 volt
battery pack. Or waiting till you get closer to the airfield to make
your call :^)

Eric Greenwell


I have this Radio now for many years.
Based on what you and Tim are saying, I concluded that
this radio does not perform very well at lower voltage.
Only in the past couple of years while flying a glider with restrictive
space for a batteries (the standard 12v 7amp) have I noticed any
deficiency at low voltage even with fresh sets of batteries.
also this radio seem to eat more on stand by.
Prior to this I had no restriction in capacity and the problem never
came up. Other then that the radio works fine and has good range when
the voltage is up.

It's possible the radio is not performing as well at low voltages as it
did when new. Electronic parts do age, particularly capacitors. If this
is the problem, a clever and determined technician might be able to
discover the correct parts to replace. A couple calls to people that
repair these would be worth the effort - perhaps there are common
problems that are cheaply fixed.


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Eric Greenwell
Washington State
USA

T o d d P a t t i s t wrote:

I've run 12 volts and I've run 14 volts. The charger
comment above is the main disadvantage of 14 volts. The
secondary disadvantage is the "non-standard battery stack"
may not want to fit into your standard-sized battery
location.

An advantage to 14 volt is more radio power/longer range on
transmit. Modern radios don't cut out at lower voltage, like
older radios that assumed 13.8 volts, but they all drive the
output stages off the full voltage - the more voltage, the
more output power.

Other advantages are that you can run the battery longer
before it gets too low, and for any switchmode DC-DC
downconverters, such as I use for my IPAQ's 5 volt...

What about getting the best of both worlds? It seems agreed that only
the radio's performance improves with higher voltage. Why not keep a
12V system with its easy charging and standard sizes but add a DC-DC UP
converter into the radio circuit so that a constant 13-14V is supplied
to the radio even though the battery supply voltage drops?

I have no technical skill in electronics - meaning my ego isn't involved
if I'm told it's a stupid idea. Would it just be a further drain on the
battery or would it usefully improve the radio's range? Does such a
converter exist?

More specifically on batteries, my glider has 4 x 6V 12ah cells arranged
in two series pairs connected in parallel (no, not my idea, the
manufacturer did it) which have reached the end of their life. The
original cells are clearly a carefully matched set (marked 6.47, 6.47,
6.45, 6.46).

How important is it that I match the replacements - and on which
characteristics? The Yuasa website seems to imply that the only
important things are that the cells be the same and the same age.

Oh ...and the cells are almost impossible to remove from the glider so
they have to be charged in place in the series/parallel configuration.

Any advice welcomed.

Graeme Cant

"Graeme Cant" wrote in message
...
T o d d P a t t i s t wrote:
What about getting the best of both worlds? It seems agreed that only the
radio's performance improves with higher voltage. Why not keep a 12V
system with its easy charging and standard sizes but add a DC-DC UP
converter into the radio circuit so that a constant 13-14V is supplied to
the radio even though the battery supply voltage drops?


By the time most modern radios would start to falter, the battery is already
pretty much discharged. Using an up-converter is this circumstance would
only result in a very limited amount of additional radio use - - along with
a very discharged battery!

Better and cheaper to insure you have adequate battery capacity by replacing
batteries on a regular basis, as these batteries lose capacity with time (I
replace mine at 3 year intervals - - 2 years is probably better). If room
allows, consider adding an additional battery pack.

Fortunately, Schleicher was kind enough to install two 12 volt 18 amp hour
batteries in my ASH26E (bless their little hearts!).

bumper

Graeme Cant wrote:

What about getting the best of both worlds? It seems agreed that only
the radio's performance improves with higher voltage. Why not keep a
12V system with its easy charging and standard sizes but add a DC-DC UP
converter into the radio circuit so that a constant 13-14V is supplied
to the radio even though the battery supply voltage drops?

I have no technical skill in electronics - meaning my ego isn't involved
if I'm told it's a stupid idea. Would it just be a further drain on the
battery or would it usefully improve the radio's range?

Older radios would generally benefit, but modern radios would see less
improvement.

Does such a
converter exist?

Yes; in fact, modern radios often have exactly this kind of power supply
built into them (my Becker transponder is an example of this). A
potential problem with an "add-on" external unit is the losses of the
conversion might overcome the value of the improved operation. I hope
someone will determine what's available out there and let's us know how
good they are.


More specifically on batteries, my glider has 4 x 6V 12ah cells arranged
in two series pairs connected in parallel (no, not my idea, the
manufacturer did it) which have reached the end of their life.

I've always wondered why DG thought that was a good idea.

The
original cells are clearly a carefully matched set (marked 6.47, 6.47,
6.45, 6.46).

How important is it that I match the replacements - and on which
characteristics? The Yuasa website seems to imply that the only
important things are that the cells be the same and the same age.

The DG owners here seem to just buy 4 batteries at the same time from
the same place and not worry about matching them. If you don't get a
good answer here, try the DG owners group listed on the
www.motorglider.org site.


Oh ...and the cells are almost impossible to remove from the glider so
they have to be charged in place in the series/parallel configuration.

Again, the DG owners group will offer a plethora of ideas, but this is
common for motorgliders anyway. The batteries are usually large enough
that they have to be mounted more firmly than the usual 7 AH unit,
making it hard to remove them. A solar panel on the trailer is a
favorite (or one placed next to the glider if it's tied down). I just
put charger on mine while it's at home in the trailer, then remove it
after it's charged. There's no need to keep it "topped up" if you are
flying at least once every month or so.


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Eric Greenwell
Washington State
USA