Why not 120 VDC ? Why invert?
E. Michael Smith
to ask it ...
In the descriptions of converting a house to PV/wind/off the grid,
they always seem to describe one of two types of conversion: Invert
some {12,24,36,48} VDC to make 120 VAC for the whole house or...
Convert some fixtures to take straight 12 VDC and convert all the
involved lighting or appliances to 12 VDC.
Pondering this ... Why not just use a 120 VDC battery pack and use
120 VDC for a bunch of stuff? Lightbulbs don't care if they are
AC or DC, nor do electric stoves and ovens or other resistive heat
sources. Some tools have AC/DC motors. 120 VDC was a common motor
type not too long ago, so I'd expect some motors to be available
for things like house fans.
Yeah, I know, you shouldn't have an electric stove or oven. But
the house already has one and my wife doesn't want to learn to
cook on gas. (though I think it is really 220 ... more batteries...)
Yeah, you should use CF bulbs, not incandecents. However, many
of the low usage locations don't pay for a CF. I also took the
liberty of looking into the ballast of one of my LOA CF electronic
bulbs. It has a filter cap accross the line, then runs the AC
into a full wave bridge... Ought to work on DC too...
So why not? Why not have a 120 VDC battery bank directly running
the incadecent lights, and any easy to change motors like heaters,
and any suitable electronic ballast CF bulbs? Then you only need
an inverter for the electronic stuff, some general purpose outlets
in the kitchen and other parts of the house, and maybe the fridge.
Why bother with the 12 VDC junk, and why run everything through
the inverter?
--
E. Michael Smith e...@apple.COM
'Whatever you can do, or dream you can, begin it. Boldness has
genius, power and magic in it.' - Goethe
I am not responsible nor is anyone else. Everything is disclaimed.
Rod Anderson
>It seems like an incredibly stupid question to me, but I've got
>to ask it ...
>
>120 VDC for a bunch of stuff? Lightbulbs don't care if they are
>AC or DC, nor do electric stoves and ovens or other resistive heat
>sources. Some tools have AC/DC motors. 120 VDC was a common motor
>type not too long ago, so I'd expect some motors to be available
>for things like house fans.
>
and add capacity in parallel. If you are on 120 volts dc you have 10
times the number of cells. The initial cost for a 120 volt system will be
much higher.
>Yeah, I know, you shouldn't have an electric stove or oven. But
>the house already has one and my wife doesn't want to learn to
>cook on gas. (though I think it is really 220 ... more batteries...)
Gas stoves are better, They heat faster, you can see if the burner is on
and you will not have to add solar cells to use them.
Check power useage of a electric stove and see how much you will have
to spend on cells to run it.
--
Rod Anderson N0NZO | A life consisting exclusively of things
Boulder, CO | that are Good for You is bad for you.
rcan...@nyx.cs.du.edu | Kelvin Throop
satellite N0NZO on ao-16 |
Carl J Lydick
>Pondering this ... Why not just use a 120 VDC battery pack and use
>120 VDC for a bunch of stuff? Lightbulbs don't care if they are
>AC or DC,
Well, actually, the fluorescents with transformer ballasts *DOL* care. They
need the AC for the transformer to work right. Now, incandescent lamps will
handle DC quite well, and fluorescents with electronic ballasts want DC, I
think (but not necessarily 120-volt DC).
>nor do electric stoves and ovens or other resistive heat
>sources.
True. However, if you care anything at all about energy efficiency, you don't
use resistive heat sources.
>Some tools have AC/DC motors. 120 VDC was a common motor
>type not too long ago, so I'd expect some motors to be available
>for things like house fans.
But it doesn't work very well for driving synchronous motors.
>Yeah, I know, you shouldn't have an electric stove or oven. But
>the house already has one and my wife doesn't want to learn to
>cook on gas. (though I think it is really 220 ... more batteries...)
Cooking with gas it a lot easier than cooking on an electric range. With an
electric range, you actually get near-instantaneous control of the amount of
heat you're generating, instead of the 15-30 second lag with electric. Of
course, induction ranges are a whole different kettle of fish.
>So why not? Why not have a 120 VDC battery bank directly running
>the incadecent lights, and any easy to change motors like heaters,
>and any suitable electronic ballast CF bulbs? Then you only need
>an inverter for the electronic stuff, some general purpose outlets
>in the kitchen and other parts of the house, and maybe the fridge.
Well, you've already told us you don't want to replace your range. Switching
to DC means you've probably got to replace your refrigerator, your vacuum
cleaner, your television set, your stereo....
--------------------------------------------------------------------------------
Carl J Lydick | INTERnet: CA...@SOL1.GPS.CALTECH.EDU | NSI/HEPnet: SOL1::CARL
Disclaimer: Hey, I understand VAXen and VMS. That's what I get paid for. My
understanding of astronomy is purely at the amateur level (or below). So
unless what I'm saying is directly related to VAX/VMS, don't hold me or my
organization responsible for it. If it IS related to VAX/VMS, you can try to
hold me responsible for it, but my organization had nothing to do with it.
Daniel Burstein
regarding putting incandescants on 120V DC. yep. it works.
personal experience: Here in NYC the electrical utlity company (Con
Edison) until recently supplied both 120V AC (or 220 via dual legs, but
that's another story)
AND... also could supply, in SOME areas of town, 120V DC. yep, that's
right, direct current.
This was because way back when, DC was part of the original distribution
system.
No new hookups were allowed after more or less 1970, but the buildings
that had it were allowed to keep it.
The building I managed had DC coming into it, which was used for the
elevator motor. (for reasons beyond the scope of this discussion DC is
much more civilized for operating elevators).
For the hell of it, I hooked up a lighting circuit to it and the light
output from the INCANDESCANT bulbs was just about the same as on teh AC.
More relevantly, a friend lived in an apartment building which had DC
outlets (yep, here in NYC, on 110th street near Columbia). He and his
roomates had marked off which outlets wer DC and which were AC (for some
reason, the outlets were physically the same.) They could, and did, plug
incandescant lamps into the DC outlets, but nothing else.
Flourescants CAN be designed to run on DC, but you need special
circuitry designed for it. a common place you;ll find this is:::
On buses (they operate on the ?12v? ?24v? electrical system)
On the NYC subway system: third rail power is 600V DC, which gets
stepped down to something or another.
Most other subway systems are also DC. some use a very strange 25 Hz.
others have gone to some pretty high voltage AC circuits...
So yes, you can set up 120V DC with series battery units, and run stuff
off it.
Why not commonly done?
1) 120V is less forgiving than 12v for most stuff. remember, we're
dealing with a lot of DYI types here.
2) A LARGE number of electronic applainces are designed for (nominal)
12V dc, usually obtained via a transformer. trying to kick 120VDC back
down to 12vdc ain't easy.
3) You have LOTS of options on charging a 12volt system. charging 12oV
is pretty diffcult in comparison.
btw, if you want to see some strange things done with direct current,
take a look at a phonecompany central office. you've got everything from
AC to 48V Dc to 12V DC and all sorts of other wierd stuff.
John De Armond
>Pondering this ... Why not just use a 120 VDC battery pack and use
>120 VDC for a bunch of stuff? Lightbulbs don't care if they are
>AC or DC, nor do electric stoves and ovens or other resistive heat
>sources. Some tools have AC/DC motors. 120 VDC was a common motor
>type not too long ago, so I'd expect some motors to be available
>for things like house fans.
There are a couple of issues. Filament-type lamps DO care about DC
according to my lighting handbook. Seems the cathode end of the
filament thins faster than the rest because of voltage potential between
the anode and cathode strips off vaporized tungsten atoms. The
suggestion is of the lamp is run on DC to make some provision for
reversing the polarity fairly often.
The next issue is that DC motors will either be noisy (universal) or
expensive (brushless DC). A low end consumer appliance would likely
get a universal motor for both the AC and DC version.
Next is the issue of keeping that many batteries equalized. One of
the systems I was responsible for at the Sequoyah nuclear plant was
the 250 volt, 200,000 amp-hour emergency instrument battery system.
Learned a lot about maintaining large battery strings. The issue is
the cells develop sulfation and/or self-discharge at different
rates. In a long string like that, the odds will result in one or several
cells differing markedly from the rest. One technique that helps mitigate
the effect is to periodically apply an equalizing charge. This is a
fairly heavy overcharge, using the theory that the weak cells will be
charged while the strong cells are relatively harmlessly overcharged.
When you have a few thousand megawatts available, hard overcharging
isn't hard :-). A solar charger would have to be oversized to do that.
Even with equalizing charging system, cells were replaced fairly
frequently. We'd do a weekly "cadmium test" that involves dipping a
cadmium rod connected to an instrument down in the acid and reading
the condition as a voltage between cadmium rod and (I think) the
+ terminal of the cell. Frequent cell replacement was the rule even
though we used the pure lead plate station type batteries.
We'd also once every outage fully discharge the battery and measure its
capacity. Mike, you'd have loved the dummy load involved :-) Trailer
mounted with a connection for a fire hose for cooling. Cable about
the size of your wrist.
I think we can probably learn something from the industrial electromotive
field. Most fork lifts and other electrically driven industrial devices
I've ever worked on use batteries somewhere close to 48 volts. I'd feel
fairly confident someone sat down and figured out the optimal balance between
cell size, voltage, maintenance and charging requirements.
John
--
John De Armond, WD4OQC |Interested in high performance mobility?
Performance Engineering Magazine(TM) | Interested in high tech and computers?
Marietta, Ga | Send ur snail-mail address to
j...@dixie.com | per...@dixie.com for a free sample mag
Need Usenet public Access in Atlanta? Write Me for info on Dixie.com.
Thomas Richard Hubbard
>
>Next is the issue of keeping that many batteries equalized. One of
>the systems I was responsible for at the Sequoyah nuclear plant was
>the 250 volt, 200,000 amp-hour emergency instrument battery system.
>Learned a lot about maintaining large battery strings. The issue is
>the cells develop sulfation and/or self-discharge at different
>rates. In a long string like that, the odds will result in one or several
>cells differing markedly from the rest. One technique that helps mitigate
>the effect is to periodically apply an equalizing charge. This is a
>fairly heavy overcharge, using the theory that the weak cells will be
>charged while the strong cells are relatively harmlessly overcharged.
>When you have a few thousand megawatts available, hard overcharging
>isn't hard :-). A solar charger would have to be oversized to do that.
Another option is to maintain the batteries on a "trickle discharge."
This can be done by connecting a large resistor across the series while
the batteries are at stand-by. The strong cells then discharge a little
more than the weak ones, and they tend to equalize. The disadvantage of
this is that you don't have 100% of the batteries capacity available
when you need it. The advantage is that you don't need a few thousand
MW available.
Tom Hubbard
E. Michael Smith
>In article <1993Jan23.0...@michael.apple.com>, e...@michael.apple.com (E. Michael Smith) writes:
>>Pondering this ... Why not just use a 120 VDC battery pack and use
>>120 VDC for a bunch of stuff? Lightbulbs don't care if they are
>>AC or DC,
>
>Well, actually, the fluorescents with transformer ballasts *DOL* care. They
>need the AC for the transformer to work right.
They are inductor ballasts rather than transformers, but that is splitting
a hair... I'd use electronics anyway ...
>Now, incandescent lamps will
>handle DC quite well, and fluorescents with electronic ballasts want DC, I
>think (but not necessarily 120-volt DC).
The ones I dissected took 120 VAC and ran it through a bridge. They
should work on 120 DC, since I say no voltage doubler or indications
that the peak, as opposed to RMS voltage was used. Other brands may
differ.
>>nor do electric stoves and ovens or other resistive heat
>>sources.
>
>True. However, if you care anything at all about energy efficiency, you don't
>use resistive heat sources.
Blanket statements don't always hold ... speaking of which, what
non-resistive electric blankets are you aware of? ;-)
There ARE places where resistive heat continues to make sense...
>>Some tools have AC/DC motors. 120 VDC was a common motor
>>type not too long ago, so I'd expect some motors to be available
>>for things like house fans.
>
>But it doesn't work very well for driving synchronous motors.
Neither my HVAC unit nor my table saw have a synchronous motor.
Nor do my clocks, come to think of it .. wonders of the
electronic age ...
>>Yeah, I know, you shouldn't have an electric stove or oven. But
>>the house already has one and my wife doesn't want to learn to
>>cook on gas. (though I think it is really 220 ... more batteries...)
>
>Cooking with gas it a lot easier than cooking on an electric range.
I think so, my wife does not. In my experience, it depends on what
you were raised with. Most folks seem to like what they learned on.
>>So why not? Why not have a 120 VDC battery bank directly running
>>the incadecent lights, and any easy to change motors like heaters,
>>and any suitable electronic ballast CF bulbs? Then you only need
>>an inverter for the electronic stuff, some general purpose outlets
>>in the kitchen and other parts of the house, and maybe the fridge.
>Switching
>to DC means you've probably got to replace your refrigerator, your vacuum
>cleaner, your television set, your stereo....
Um,the original posting stated clearly that I was looking at a mixed
mode system. (In particular, I stated that an inverter would be
needed for electronics, misc. electrical outlest {like for the vac}
and the refridgerator).
I'm not looking for a one-size fits all. But that may be the answer
as to why 120 VDC isn't used. Folks seem to want exactly that, one
size fits all. ALL inverter, or ALL 12 VDC...
BTW, to all the folks who wrote the virtues of gas stoves: I LOVE GAS
STOVES (I was raised with one)! It is my wife who wants electric...
Carl J Lydick
>>True. However, if you care anything at all about energy efficiency, you don't
>>use resistive heat sources.
>
>Blanket statements don't always hold ... speaking of which, what
>non-resistive electric blankets are you aware of? ;-)
>
>There ARE places where resistive heat continues to make sense...
Electric blankets (except, perhaps, in hospitals) don't fall into one of those
places. Maybe an electric blanket is useful when treating someone for
hypothermia. For any application where the person using the blanket is capable
of generating heat, other alternatives work equally well. For moderate (i.e.,
above -20 degrees F) conditions, simple wool blankets are quite useful (you
might need to use a few of them, but they work). For lower temperatures, a
blanket with an aluminum core works quite well.
Jus how is it that you, known, unless I'm confusing you with someone else, for
favoring energy conservation, are now advocating electric blankets in
situations where they're not required?
>Neither my HVAC unit nor my table saw have a synchronous motor.
>Nor do my clocks, come to think of it .. wonders of the
>electronic age ...
Most electric clocks still depend on supply frequency. If you've got a digital
clock, run it on batteries for a day and see how it does.
>>Switching
>>to DC means you've probably got to replace your refrigerator, your vacuum
>>cleaner, your television set, your stereo....
>
>Um,the original posting stated clearly that I was looking at a mixed
>mode system. (In particular, I stated that an inverter would be
>needed for electronics, misc. electrical outlest {like for the vac}
>and the refridgerator).
So you're going to run TWO sets of wires throughout your home, one for AC and
one for DC? Once you've committed to the expense of having an inverter in the
first place, the cost of increasing the capacity of the unit under
consideration is relatively small.
Mike Prine CIRT
mentioned yet. If you stay below 50volts DC you can avoid many national
electrical code hassles and probably do the work yourself rather than having
to hire someone who has a lisense but may know little about DC.
High voltage DC is dangerous and expensive to use. You must buy special
breakers or fuses that are DC rated or risk them not working or having a very
short life. For instance your standard AC wall switch if run on 120V DC dies
after several months due to arcing. Also unless one has just come out you can't
buy ground fault detection breakers for 110 DC but can be found for AC at just
about any hardware store.
For Photovoltaics, PV, it is also harder to find a site where 10
panels are always in the sun at the same time. With a 12volt system if one
cell in a panel is shaded you lose output from that panel. With 120volts
you must tie 10 panels in series so a loss of one cell due to shading takes
out the whole string, 10 times the impact. Thus you don't get as much
power out of a 120volt setup. When the 120volt array is dead, a 12volt array
may still be getting power from one or two panels that are still catching the
sun.
Finally there is the lack of expertise and equipment for high voltage
DC. With 12 or 24volts you can probably get what you need in a RV or Boat shop
or any of several mail order shops and magazines dedicated to renewable energy.
With 120VDC experts are hard to come by and most of the literature is from the
early days of Edison.
In closing let me say that if you are considering an alternative energy
system, please take the time to do it right and safely. Any power processing
system is potentially dangerous and if too many people do it wrong the
government and it's lawyers will make it impossible for an average citizen to
do.
Michael Lee Prine IRC (Information Resource Center) consultant
Internet: mi...@hydra.unm.edu, Bitnet: MIKEP@UNMB, Phone: 1-505-277-8135
I get most of my electricity, at home, from the sun. It's a hobby,
who cares if it's cost effective yet.
--
Michael Lee Prine IRC (Information Resource Center) consultant
Internet: mi...@hydra.unm.edu, Bitnet: MIKEP@UNMB, Phone: 1-505-277-8135
I get most of my electricity, at home, from the sun. It's a hobby,
who cares if it's cost effective yet.
E. Michael Smith
>In article <1993Jan25....@michael.apple.com>, e...@michael.apple.com (E. Michael Smith) writes:
>>>True. However, if you care anything at all about energy efficiency, you don't
>>>use resistive heat sources.
>>
>>Blanket statements don't always hold ... speaking of which, what
>>non-resistive electric blankets are you aware of? ;-)
>>
>>There ARE places where resistive heat continues to make sense...
>
>Electric blankets (except, perhaps, in hospitals) don't fall into one of those
>places. Maybe an electric blanket is useful when treating someone for
>hypothermia. For any application where the person using the blanket is capable
>of generating heat, other alternatives work equally well. For moderate (i.e.,
>above -20 degrees F) conditions, simple wool blankets are quite useful (you
>might need to use a few of them, but they work). For lower temperatures, a
>blanket with an aluminum core works quite well.
Two things: 1) I'm allergic to wool. (We use a fluffy comforter) and
2) My wife uses a heating pad for lower back pain. I suppose I could
have taken the time to clarify this, but wanted to avoid the wasted
bytes. But since the point was pressed, I'll waste em... There is
no way I'm going to get my wife off of her heating pad. (Endo...).
There a other folks who use electric blankets similarly...
>Jus how is it that you, known, unless I'm confusing you with someone else, for
>favoring energy conservation, are now advocating electric blankets in
>situations where they're not required?
I, personally, hate electric blankets for my own use. (The leave me
feeling 'drained' the next day. I don't know why.). But I've known
many folks who use them rather than heat the whole room in winter.
I've slept under a ton of blankets in cabins in the mountains in
winter. It was OK, but I can sympathise with folks who live in
places that are very cold and want an electric blanket. I HAVE
found them personally useful for pre-warming the bed, then turn
them off when I get in. (Headonism known no bounds! ;-)
I've very much in favor of any conservation that a) Doesn't require
a change of my rather comfortable lifestyle and b) would be stupid to
NOT do. I'm not in favor of conservation that is a pain or not very
cost effective. Guess I'm a bit like John DeArmond in that sense,
aint nothing gonna get me to give up my big 4x4 truck, but I've got
nothing against putting a better more efficient engine in it (or
driving my Honda most of the time and only using the truck when
justified). I'm not going to dictate to folks that they can not
use electric blankets. Many folks like them and it isn't my place
to tell them they are wrong. It is a personal decision, but useful
to me as an example.
>>>Switching
>>>to DC means you've probably got to replace your refrigerator, your vacuum
>>>cleaner, your television set, your stereo....
>>
>>Um,the original posting stated clearly that I was looking at a mixed
>>mode system. (In particular, I stated that an inverter would be
>>needed for electronics, misc. electrical outlest {like for the vac}
>>and the refridgerator).
>
>So you're going to run TWO sets of wires throughout your home, one for AC and
>one for DC? Once you've committed to the expense of having an inverter in the
>first place, the cost of increasing the capacity of the unit under
>consideration is relatively small.
That was the plan. And, as I also pointed out in the post you are
responding to (but which lines you have deleted), on reflection I
thought that the complication of dual wiring was probably why it
wasn't done.
BTW, the cost increases may or may not be 'relatively small'...
I ALREADY have dual wiring in my house. Part 120 VAC, part 220 VAC.
The cost of adding a small part of 12 VDC is trivial. (One battery
at about $100 and a panel mounted next to the main panel into
which the re-directed wires could be moved. Call it $150 total DIY.)
To go to 120 VDC would be no harder, but would, as was pointed out
by others, raise the entry point cost of batteries (since it would
take at least 5 batteries (24 VDC are available) and more likely
10 or 20 ( 6VDC ) to get deep cycle types. Then there is the
charging complication ... I think this is the 'coup de gras'.
If you have a big enough system to need 10 to 20 batteries, you
will not notice the extra cost of the larger inverter so much.
That is likely to be less cost than converting the motor in
one or two major appliances, such as the heater fan.
If you don't have a big enough system to need 10 to 20 batteries,
you don't have anything drawing enough watts to require 120 V
to push it down 12 ga. wire, so 12 VDC is enough. So why take
on all the complications of a big battery and charge management
for a small system?
And why go with complicated double wiring schemes if you already
have a bundle sunk into a large battery bank and would rather
avoid the need to dink with 120 VDC motor conversion?
Much more direct reasoning that quibbling over whether or not
folks should use electric blankets...
Carl J Lydick
>Two things: 1) I'm allergic to wool. (We use a fluffy comforter) and
That's OK. There are synthetics that are even better than wool for blankets.
>2) My wife uses a heating pad for lower back pain.
That's not the same as an electric blanket. I pointed out one use for devices
of this sort (electric blankets used in treating hypothermia). Heating pads
are another. They're both relatively uncommon uses (though the medical uses of
heating pads are much more common than those of electric blankets).
>I suppose I could
>have taken the time to clarify this, but wanted to avoid the wasted
>bytes. But since the point was pressed, I'll waste em... There is
>no way I'm going to get my wife off of her heating pad. (Endo...).
>There a other folks who use electric blankets similarly...
Could you point out to me such a use of a full-sized electric blanket?
>I've slept under a ton of blankets in cabins in the mountains in
>winter. It was OK, but I can sympathise with folks who live in
>places that are very cold and want an electric blanket.
There are synthetic blankets that are quite effective. And as I've pointed
out, there are blankets using aluminum cores that are even more effective. In
fact, you can buy something similar (I think it uses aluminized mylar) in most
any place that sells camping supplies. One term I've heard for the things is
"space blankets."
>I HAVE
>found them personally useful for pre-warming the bed, then turn
>them off when I get in. (Headonism known no bounds! ;-)
Gee. Back when I was a kid, there was something called a hot-water bottle.
>>So you're going to run TWO sets of wires throughout your home, one for AC and
>>one for DC? Once you've committed to the expense of having an inverter in the
>>first place, the cost of increasing the capacity of the unit under
>>consideration is relatively small.
>
>That was the plan. And, as I also pointed out in the post you are
>responding to (but which lines you have deleted), on reflection I
>thought that the complication of dual wiring was probably why it
>wasn't done.
OK. I may have come into this thread a bit late. I don't remember seeing that
in the post to which I originally replied.
>BTW, the cost increases may or may not be 'relatively small'...
>I ALREADY have dual wiring in my house. Part 120 VAC, part 220 VAC.
>The cost of adding a small part of 12 VDC is trivial. (One battery
>at about $100 and a panel mounted next to the main panel into
>which the re-directed wires could be moved. Call it $150 total DIY.)
Sorry. I haven't done any household wiring since the days when all you had to
do was put a metal plate on the studs where you ran the wires through them. If
you've got conduit, the cost of stringing another set of wires isn't all that
high.
Dick King
>>Pondering this ... Why not just use a 120 VDC battery pack and use
>>120 VDC for a bunch of stuff? Lightbulbs don't care if they are
>>AC or DC,
>
>Well, actually, the fluorescents with transformer ballasts *DOL* care. They
>need the AC for the transformer to work right. Now, incandescent lamps will
>handle DC quite well, and fluorescents with electronic ballasts want DC, I
>think (but not necessarily 120-volt DC).
>
Just a minor quibble. This is a question that has been annoying me just a tad
for a while, so i'm expanding the crosspost to include rec.bicycles.tech to
cast a broader net for an answer.
Many bicyclists use Halogen light bulbs in their headlights. Some run them off
generators that produce AC at several hundred Hz, and others use batteries.
I have seen two common ratings for 6V halogen bulbs that fit my particular
[Union] lamp: 2.4 W and 4 W.
The 2.4 W lamps that one buys in a bike shop have little sine waves scratched
into their bases, and in my experience they function poorly on my battery.
2.4W is a good fit for bike generators' capacity, and generators power most of
these smaller bulbs. Usually, when you buy a generator it comes with one of
these bulbs and the instructions suggest replacing them with the same bulb when
it burns out. You can't use a higher-wattage bulb. On my 6V battery, 2.4W
bulbs with tiny sine waves scratched into their bases burn out after only a few
hours.
The 4 W lamps have a little <<square>> wave scratched into <<their>> bases, and
i'm on my second one in five years. The first one lasted about 400 hours, and
the second one is still working after 2 years which is about 300 hours.
Is there some difference between the designs of these bulbs that make one work
better on AC and the other on DC? Or is my observation a fluke?
-dk
Rob Kleinschmidt
>Pondering this ... Why not just use a 120 VDC battery pack and use
>120 VDC for a bunch of stuff? Lightbulbs don't care if they are
>AC or DC,
>So why not? Why not have a 120 VDC battery bank directly running
>the incadecent lights, and any easy to change motors like heaters,
>and any suitable electronic ballast CF bulbs? Then you only need
>an inverter for the electronic stuff, some general purpose outlets
>in the kitchen and other parts of the house, and maybe the fridge.
A neighbor of ours was actually running a setup like this. Not sure
if the lines were part time D.C. part time A.C. or full time D.C. .
He had also built several small inverters for various individual
appliances.
Among other things, I understand that standard 120v switches may
not be appropriate because of D.C. arcing, and I think that it
would perhaps be a good idea to use non-standard plugs and outlets
to prevent connection of inappropriate stuff to a DC outlet.
With kids to worry about, it seemed prudent to make our house
straight A.C. and plunk down the bucks for the inverter.
R. Kleinschmidt
Gary Coffman
>
>Two things: 1) I'm allergic to wool. (We use a fluffy comforter) and
>2) My wife uses a heating pad for lower back pain. I suppose I could
>have taken the time to clarify this, but wanted to avoid the wasted
>bytes. But since the point was pressed, I'll waste em... There is
>no way I'm going to get my wife off of her heating pad. (Endo...).
>There a other folks who use electric blankets similarly...
1) Use synthetics.
2) Tell the wife that low level electric fields raise the mother's
risk of leukemia 2X and raise the unborn's risk of brain tumor
4X. Source NBC news this morning. Also tell her to get off the
phone, increases risk of brain cancer. Ditto NBC news. Or stop
watching NBC news, should lower blood pressure at least 2X.
Gary
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Kevin Cameron
|> In article <1jr751...@gap.caltech.edu> ca...@SOL1.GPS.CALTECH.EDU writes:
|> Blanket statements don't always hold ... speaking of which, what
|> non-resistive electric blankets are you aware of? ;-)
Hey. I think you're on to something there. Thing of all of the
energy that's being WASTED in the world by heating blankets with electrical
energy. What this world needs is a gas heated blanket!!
Them we'll send one to Saddam.
--
Kevin Cameron
"Those who will trade essential liberty for promise of security will
have neither" - Benjamin Franklin
Josh Rovero
The ones that come to mind are the USNS Dutton and Bowditch (now both
mercifully reduced to razor blades), which had dual AC and DC distribution
in the living quarters. Similar plugs, had to rely on labeling......
--
Josh Rovero (rov...@oc.nps.navy.mil) | or Internet 53...@cc.nps.navy.mil
Department of Oceanography, Code OC/Rv | Bitnet 5346p@NAVPGS
Naval Postgraduate School |
Monterey, CA 93943 (408) 646-2084 |
Anmar Caves
>In article <C1IpI...@usenet.ucs.indiana.edu>, ami...@bronze.ucs.indiana.edu (Anmar Caves) writes:
>>>If you use a 12 volt system you can start out with one set of batteries
>=>times the number of cells. The initial cost for a 120 volt system will be
>=>much higher.
>=
>=In addition, there will be ten times the number of cells in series.
>
>But the same total number of cells in your storage system.
Yep. But, you can get away with mixing different aged banks in
parallel. It's not the best for a system, but it isn't too
detrimental. Replacing one cell in a series system *can* be
detrimental and can lead to reverse charging and increased sulfation
if lead acid cells. It's best that all cells in a series system be
the same type, capacity and age. It's not absolutley ruinous to
replace one cell (or one battery if using 6 or 12volt batteries to
make up the 120 volt battery, hmm, a battery of batteries?) in a
120volt battery, but it is more so than replacing once battery in a 10
12volt battery system.
>=Any one cell failure can ruin a bank.
>
>The same is true if the cells are connected in parallel: One shorted cell can
>load the rest enough to damage them.
I wasn't talking about a shorted cell. In a bank of 60 cells
connected in series a shorted cell would hardly be noticed. The
charge/discharge voltage fluctuation is much higher than that (like
around 10 volts). In a bank of 60 series-parallel cells working at 12
volts it could blow up the cell (more likely it wouldn't happen
because most shorts would get burned away before they became serious).
But shorted cells in a lead acid bank for that type of application
rarely happen unless you drop your wrench on them (shame on you! why
didn't you insulate all exposed leads!). On that I speak from
experience.
With lead acid banks in stand by or home use configuration the most
common failure mode is sulfation. I generally try to avoid this by
dropping the acid content on the cells to about 1.2 sp. grav. fully
charged.
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Anmar Caves
>In article <1993Jan23.0...@michael.apple.com> e...@michael.apple.com (E. Michael Smith) writes:
>>It seems like an incredibly stupid question to me, but I've got
>>to ask it ...
>>
>>Pondering this ... Why not just use a 120 VDC battery pack and use
>>120 VDC for a bunch of stuff? Lightbulbs don't care if they are
>>AC or DC, nor do electric stoves and ovens or other resistive heat
>>sources. Some tools have AC/DC motors. 120 VDC was a common motor
>>type not too long ago, so I'd expect some motors to be available
>>for things like house fans.
>>
>If you use a 12 volt system you can start out with one set of batteries
>and add capacity in parallel. If you are on 120 volts dc you have 10
>times the number of cells. The initial cost for a 120 volt system will be
>much higher.
In addition, there will be ten times the number of cells in series. Any one
cell failure can ruin a bank. Ideally all cells in a series bank should be
of equal age and capacity. Personally, if there weren't this little
resistance problem I'd rather have everything be 2 volt (or 1.2 volt)
and run the world on very low voltage. There'd be no electrocution.
But since R rears it's head this isn't practical. It's really not
much of a problem since high efficiency inverters have become
available. BTW, some larger set ups *do* run 120VDC and use a
specially designed inverter to convert to AC.
Carl J Lydick
=>times the number of cells. The initial cost for a 120 volt system will be
=>much higher.
=
=In addition, there will be ten times the number of cells in series.
But the same total number of cells in your storage system.
=Any one cell failure can ruin a bank.
The same is true if the cells are connected in parallel: One shorted cell can
load the rest enough to damage them.
David George
|> I have seen two common ratings for 6V halogen bulbs that fit my particular
|> [Union] lamp: 2.4 W and 4 W.
|>
|> The 2.4 W lamps that one buys in a bike shop have little sine waves scratched
|> into their bases, On my 6V battery, 2.4W bulbs with tiny sine waves
|> scratched into their bases burn out after only a few hours.
Maybe it means they are rated at 6v a.c., which is about 4.2v d.c. In this
case the bulb will be subjected to about 50% overcurrent.
David.
Anmar Caves
>>>True. However, if you care anything at all about energy efficiency, you don't
>>>use resistive heat sources.
>>
>>Blanket statements don't always hold ... speaking of which, what
>>non-resistive electric blankets are you aware of? ;-)
>>
>>There ARE places where resistive heat continues to make sense...
>
>Electric blankets (except, perhaps, in hospitals) don't fall into one of those
>places. Maybe an electric blanket is useful when treating someone for
>hypothermia. For any application where the person using the blanket is capable
>of generating heat, other alternatives work equally well. For moderate (i.e.,
>above -20 degrees F) conditions, simple wool blankets are quite useful (you
>might need to use a few of them, but they work). For lower temperatures, a
>blanket with an aluminum core works quite well.
Maybe for you Carl, but this doesn't extrapolate well. Specific
examples are elderly people, IE people who are prone to developing
chronic hypothermia, you know, those people who keep their houses at
80F. Many of these people *don't* generate enough heat at basal
metabolism to keep warm unless they're in a very warm environment.
Other examples are people with poor peripheral circulation. These
people will have cold legs and feet no matter how many blankets they
have. This includes a large percentage of the female population.
Personally, I like it cold, and generally don't like electric
blankets, but that's just my prference.
>Jus how is it that you, known, unless I'm confusing you with someone else, for
>favoring energy conservation, are now advocating electric blankets in
>situations where they're not required?
I can see it quite easily. Someone can have an electric blanket which
may use 500-600 watts over the night (most blankets are between
100-150 watts and may have a duty cycle of 50-70%), and be able to
keep the house cooler during the night, or keep a lower overall temp
in the house, or avoid heating at all in warmer climes. In that case
such an item would be appropriate to conservation.
Please note that I'm not saying that it's appropriate in all cases,
merely that it's not as innappropriate as you seem to think.
>
>So you're going to run TWO sets of wires throughout your home, one for AC and
>one for DC? Once you've committed to the expense of having an inverter in the
>first place, the cost of increasing the capacity of the unit under
>consideration is relatively small.
Running both makes a lot of sense from the efficiency standpoint. Low
demand items such as doorbells, DC clocks, answering machines, some
lighting such as closets or marker lights, etc, can be run a lot more
efficiently on low voltage because they were designed that way from
the start. I've only done one all-120VAC design, I've done dozens of
mixed designs and a couple of small low voltage only designs.
As far as inverters go, I'd rather my inverter set be able to go into
sleep mode when there is no draw than to have it constantly running
supplying all those low draw appliances. The best designs have a
dedicated inverter for the lighting circuit, and another for the high
demand items like the fridge or microwave or the like.
This stuff is fun to play with because it can be mixed and matched to
suit an individuals needs and wants, in other words, no absolutes.
Duane P Mantick
Point of technical correction: overVOLTAGE, not overcurrent.
Current is measured in AMPS, not volts. If you want to get a feel for the
average voltage of an AC wave, consider that peak-to-peak 10 volts
would be 5 volts PEAK. RMS average is .707 times PEAK, or .707 x 5,
in this case approx. 3.5 volts.
Many light bulbs DO list a spec for the maximum current that they
will draw, which is useful for determining how many of them an X-watt
generator will run, OR, how many you can hang on an X amp-hour battery.
As far as running bulbs off AC or DC, that's a good question.
I *can* tell you that there are bulbs for RV's that have exactly the same
base as what you'd use in your livingroom lamp at home. BUT, they are
12VDC lamps, NOT 120VAC. So there are some differences in filament
design.
If I had to guess, I'd bet that a bulb with a sine wave etched on
it is probably supposed to be run from a generator, which will put out
(nominally) sine waves. A bulb with square waves on it is probably
designed to be run from an inverter of some sort, which usually puts
out something that more closely resembles square waves, due to the
switching action going on inside.
Duane
Carl J Lydick
=da...@postman.gr.osf.org (David George) writes:
=
=>In article <1993Jan25.2...@kestrel.edu>, ki...@reasoning.com (Dick King) writes:
=>|> I have seen two common ratings for 6V halogen bulbs that fit my particular
=>|> [Union] lamp: 2.4 W and 4 W.
=>|>
=>|> The 2.4 W lamps that one buys in a bike shop have little sine waves scratched
=>|> into their bases, On my 6V battery, 2.4W bulbs with tiny sine waves
=>|> scratched into their bases burn out after only a few hours.
=>Maybe it means they are rated at 6v a.c., which is about 4.2v d.c. In this
=>case the bulb will be subjected to about 50% overcurrent.
=
= Point of technical correction: overVOLTAGE, not overcurrent.
=Current is measured in AMPS, not volts. If you want to get a feel for the
=average voltage of an AC wave, consider that peak-to-peak 10 volts
=would be 5 volts PEAK. RMS average is .707 times PEAK, or .707 x 5,
=in this case approx. 3.5 volts.
Minor technical point: For a purely resistive circuit (e.g., an incandescent
light bulb), overvoltage and overcurrent are synonymous.
= As far as running bulbs off AC or DC, that's a good question.
=I *can* tell you that there are bulbs for RV's that have exactly the same
=base as what you'd use in your livingroom lamp at home. BUT, they are
=12VDC lamps, NOT 120VAC. So there are some differences in filament
=design.
By the way, one justification for using a sine-wave to label lamps intended for
AC and a square-wave for DC lamps is that the peak-to-peak and RMS voltages for
a square wave are identical, so you can (for something like a light bulb) treat
a square wave pretty much as if it were DC.
= If I had to guess, I'd bet that a bulb with a sine wave etched on
=it is probably supposed to be run from a generator, which will put out
=(nominally) sine waves. A bulb with square waves on it is probably
=designed to be run from an inverter of some sort, which usually puts
=out something that more closely resembles square waves, due to the
=switching action going on inside.
And, as I pointed out above, for the most part, for an incandescent lamp, a
square wave and the same DC voltage are nearly indistinguishable.
David George
[ re: running 6v a.c. bulbs off 6v d.c. ]
|
|> >Maybe it means they are rated at 6v a.c., which is about 4.2v d.c. In this
|> >case the bulb will be subjected to about 50% overcurrent.
|>
|> Point of technical correction: overVOLTAGE, not overcurrent.
|> Current is measured in AMPS, not volts.
Hmmmm but considering a simple incandescent bulb the filament presents a
certain electrical resistance therefore (ignoring temperature
dependancies) voltage and current are directly related.
That is: I = V/R. For a constant R an increase in V will result in an increase
in I. It is the heating effect of the current which will burn out the filament, hence my terminology.
I think the sentence you corrected is valid in this context.
David.