24volt vs 12volt light bulbs as used in cars
Willem-Jan Markerink
Hi,
I have a question regarding differences between 12V and 24V light bulbs as
used in cars and trucks.
Standard H3 bulbs for 12volt are 55W, for 24V this is 75W. Both are
the lowest sizes available. Same difference goes for H4, 55/50W is
for 12V, 75/70W is for 24V. Mind: these are the only legal bulbs in
Europe.
My question is whether the 24V version emits as much
lumen/lux/candles as the 12V version, or *more*....and whether they
have different thermic properties. I know that for a given output
the wiring for a 24V system can be less than half the thickness, but
I lack the knowledge to expand this stuff to light filaments.
Can anyone help here?
I have to find out if I can replace the stock 12V/55W H3 bulbs with
24V/75W, and what my pro's (extra light?) and con's (extra heat?)
will be. This is for a stock 12V search light. It has a metal coated
resin reflector, so heat is a major concern.
Bye,
W.J. Markerink
<w.j.ma...@a1.nl> (a-one & en-el)
The desire to understand
is sometimes far less intelligent than
the inability to understand
Kirk McGraw
w.j.ma...@a1.nl (Willem-Jan Markerink) wrote:
>Hi,
>I have a question regarding differences between 12V and 24V light bulbs as
>used in cars and trucks.
>Standard H3 bulbs for 12volt are 55W, for 24V this is 75W. Both are
>the lowest sizes available. Same difference goes for H4, 55/50W is
>for 12V, 75/70W is for 24V. Mind: these are the only legal bulbs in
>Europe.
>My question is whether the 24V version emits as much
>lumen/lux/candles as the 12V version, or *more*....and whether they
>have different thermic properties. I know that for a given output
>the wiring for a 24V system can be less than half the thickness, but
>I lack the knowledge to expand this stuff to light filaments.
>Can anyone help here?
>I have to find out if I can replace the stock 12V/55W H3 bulbs with
>24V/75W, and what my pro's (extra light?) and con's (extra heat?)
>will be. This is for a stock 12V search light. It has a metal coated
>resin reflector, so heat is a major concern.
For a given type of bulb (halogen/conventional) wattage is a good
indicator of both brightness and heat output.
Watts are volts times amps. Heat produced in the wire depends
on the square of the amps. So, high voltage allows small wires
without over heating. High voltage filaments have to be skinnier
so they heat up and glow (I am guessing now). The length and
diameter of the filament changes its resistance, which affects how
much current flows through it. So if you try 24V bulbs in a 12V
system, there will not be enough current and you get a dim red
glow. As we all know, putting the 12V bulb in a 24V system results
in a brief, very bright light...
Kirk McGraw
george
:I have a question regarding differences between 12V and 24V light bulbs as
:
:Standard H3 bulbs for 12volt are 55W, for 24V this is 75W. Both are
:the lowest sizes available. Same difference goes for H4, 55/50W is
:for 12V, 75/70W is for 24V.
All of the power is converted into heat+light, mostly heat.
First guess is both the heat and light should go up with the
increased power.
:Mind: these are the only legal bulbs in
:Europe.
this would seem to say that the light output is comperable,
which would mean that all of the extra 20watts is heat..
That is unless there is something fishy with the ratings or the laws..
:I know that for a given output
:the wiring for a 24V system can be less than half the thickness
For a given power you have half the current (hence smaller wires).
But in this case you've increased the power, so the current 'savings' is
somewhat less than half.
:but
:I lack the knowledge to expand this stuff to light filaments.
Light filaments are tricky. You cannot apply v=ir to a light,
because a bulbs resistance varies greatly with its temperature.
--
george
geo...@mech.seas.upenn.edu
Willem-Jan Markerink
In article <4qes1v$6...@vixen.cso.uiuc.edu>,
>>used in cars and trucks.
>
>>Standard H3 bulbs for 12volt are 55W, for 24V this is 75W. Both are
>>the lowest sizes available. Same difference goes for H4, 55/50W is
>>Europe.
>
>>My question is whether the 24V version emits as much
>>lumen/lux/candles as the 12V version, or *more*....and whether they
>>the wiring for a 24V system can be less than half the thickness, but
>>I lack the knowledge to expand this stuff to light filaments.
>
>>I have to find out if I can replace the stock 12V/55W H3 bulbs with
>>24V/75W, and what my pro's (extra light?) and con's (extra heat?)
>>will be. This is for a stock 12V search light. It has a metal coated
>>resin reflector, so heat is a major concern.
>
>For a given type of bulb (halogen/conventional) wattage is a good
>indicator of both brightness and heat output.
>
>Watts are volts times amps. Heat produced in the wire depends
>on the square of the amps.
That would mean that a 24v bulb with the same wattage as a 12v bulb will only
have 1/4 of the heat output. Is this conflicting with your first line, or is
the explanation below?
The problem is that the wire is not the lead, but the output source....
>So, high voltage allows small wires
>without over heating. High voltage filaments have to be skinnier
>so they heat up and glow (I am guessing now). The length and
>diameter of the filament changes its resistance, which affects how
>much current flows through it. So if you try 24V bulbs in a 12V
>system, there will not be enough current and you get a dim red
>glow. As we all know, putting the 12V bulb in a 24V system results
>in a brief, very bright light...
So 70Watt 24Volt or 12V does not make a difference, neither in lumen nor in
heat output?
I guess one could back up the latter with a black body radiation curve, but I
still feel 24V should give some advantage other than less strain on the
wiring....
Jerry Bransford
Willem-Jan Markerink wrote:
>
> Hi,
>
> I have a question regarding differences between 12V and 24V light bulbs as
> used in cars and trucks.
>
> Standard H3 bulbs for 12volt are 55W, for 24V this is 75W. Both are
> the lowest sizes available. Same difference goes for H4, 55/50W is
> for 12V, 75/70W is for 24V. Mind: these are the only legal bulbs in
> Europe.
>
> My question is whether the 24V version emits as much
> lumen/lux/candles as the 12V version, or *more*....and whether they
> have different thermic properties. I know that for a given output
> the wiring for a 24V system can be less than half the thickness, but
> I lack the knowledge to expand this stuff to light filaments.
>
> Can anyone help here?
> I have to find out if I can replace the stock 12V/55W H3 bulbs with
> 24V/75W, and what my pro's (extra light?) and con's (extra heat?)
> will be. This is for a stock 12V search light. It has a metal coated
> resin reflector, so heat is a major concern.
You don't say if you're also planning on upgrading your electrical
system to 24 volts if you go to 24 volt bulbs. This may or may not be
obvious to you, but unless you're upgrading your vehicle's entire system
to 24 volts, using 24 volt bulbs in a 12 volt system will just give you
very weak light output from 24 volt bulbs. The increased bulb wattage
is only going to happen with the higher 24 volt electrical system.
--
Jerry Bransford
PP-ASEL, KC6TAY, C.A.P.
The Zen hotdog... make me one with everything!
Kirk McGraw
w.j.ma...@a1.nl (Willem-Jan Markerink) wrote:
>In article <4qes1v$6...@vixen.cso.uiuc.edu>,
> k-mc...@cecer.army.mil (Kirk McGraw) wrote:
>>w.j.ma...@a1.nl (Willem-Jan Markerink) wrote:
>>
>>>Hi,
>>
>>>I have a question regarding differences between 12V and 24V light bulbs as
>>>used in cars and trucks.
>>
<snip>
>>Watts are volts times amps. Heat produced in the wire depends
>>on the square of the amps.
>That would mean that a 24v bulb with the same wattage as a 12v bulb will only
>have 1/4 of the heat output. Is this conflicting with your first line, or is
>the explanation below?
>The problem is that the wire is not the lead, but the output source....
I am no expert on electricity, and am working from memory here (a
dangerous thing) thus I apologize for being confusing and/or wrong.
I was trying to explain that the power to do a given job is watts. You can
get these watts using different combinations of volts and amps. So you
can get 48 watts using 4 amps at 12 volts or 2 amps at 24 volts. Same
power. The folks who design the filament adjust its length and diameter
to provide a certain resistance such that when the _proper_ voltage is
applied, a certain amperage flows through the wire, thus heating the wire
to a certain temperature. The higher the temperature, the more light is
emited in the visible spectrum and the less heat (light in the infra red) is
emitted. Problem is the tungsten filament vaporizes and deposits on the
glass (and old light bulb turns black). Halogen bulbs are about 10%
more effiecient because the gas around the filment encourages the
tungsten to redeposit on the filament instead of the glass (or so I've
heard), this allows the wire to be run hotter and still have a reasonable
life. Different types of light sources have different efficiencies, so you
can't compare a carbon arc with a halogen bulb. A higher efficiency means
you get more light and less heat from your power.
>>So, high voltage allows small wires
>>without over heating. High voltage filaments have to be skinnier
>>so they heat up and glow (I am guessing now). The length and
>>diameter of the filament changes its resistance, which affects how
>>much current flows through it. So if you try 24V bulbs in a 12V
>>system, there will not be enough current and you get a dim red
>>glow. As we all know, putting the 12V bulb in a 24V system results
>>in a brief, very bright light...
>So 70Watt 24Volt or 12V does not make a difference, neither in lumen nor in
>heat output?
Only if they are both really consuming 70 watts.
>I guess one could back up the latter with a black body radiation curve, but I
>still feel 24V should give some advantage other than less strain on the
>wiring....
Sorry, no. This may not be the case when it comes to starter motors, but
that is another thread...
Kirk McGraw
E.J.W.Hannivoort
george (je...@blue.seas.upenn.edu) wrote:
[..]
: Light filaments are tricky. You cannot apply v=ir to a light,
: because a bulbs resistance varies greatly with its temperature.
Sorry, I don't agree: v=ir is certainly valid.
As you say, when the filament heats up, the resistance changes.
But, both v=ir and p=ei are valid (Ohm's law).
In a steady state, when the filament dissipates and radiates
as much energy as it receives, the following is valid:
55 watt = 24 volt x 55/24 amp ( about 2.3 amp )
55 watt = 12 volt x 55/12 amp ( about 4.6 amp )
so the heated resistance is:
24 volt bulb: 24/(55/24) = 24 x 24 / 55 = about 10.5 ohms
12 volt bulb: 12/(55/12) = 12 x 12 / 55 = about 2.6 ohms
Only, when a 24 volt bulb is connected to 12 volt:
If the resistance were (!) 10.5 ohms,
12 v / 10.5 ohm = 1.15 amps so: 12 x 1.15 = 13.8 watt
(Yes indeed, half the voltage gives a quarter of the
wattage, relation is off course quadratic.)
BUT: as the temperature differs, resistance differs,
so consumed wattage will differ !! And because efficiency
at lower temperature is lower, more is dissipated as heat,
and much less as light, and that light is of lower frequency,
so reddish in colour.
---------
Evertjan Hannivoort
email: ehan...@inter.nl.net
Willem-Jan Markerink
In article <31CB21...@cts.com>, Jerry Bransford <jer...@cts.com> wrote:
>Willem-Jan Markerink wrote:
>>
>> Hi,
>>
>> I have a question regarding differences between 12V and 24V light bulbs as
>> used in cars and trucks.
>>
>> the lowest sizes available. Same difference goes for H4, 55/50W is
>> for 12V, 75/70W is for 24V. Mind: these are the only legal bulbs in
>> Europe.
>>
>> My question is whether the 24V version emits as much
>> lumen/lux/candles as the 12V version, or *more*....and whether they
>> have different thermic properties. I know that for a given output
>> the wiring for a 24V system can be less than half the thickness, but
>> I lack the knowledge to expand this stuff to light filaments.
>>
>> Can anyone help here?
>> I have to find out if I can replace the stock 12V/55W H3 bulbs with
>> 24V/75W, and what my pro's (extra light?) and con's (extra heat?)
>> will be. This is for a stock 12V search light. It has a metal coated
>> resin reflector, so heat is a major concern.
>
>You don't say if you're also planning on upgrading your electrical
>system to 24 volts if you go to 24 volt bulbs. This may or may not be
>obvious to you, but unless you're upgrading your vehicle's entire system
>to 24 volts, using 24 volt bulbs in a 12 volt system will just give you
>very weak light output from 24 volt bulbs. The increased bulb wattage
>is only going to happen with the higher 24 volt electrical system.
Sorry, I explain some more:
This is about a search light that comes in a stock H3 12V/55W bulb (actually
twin bulb, but that is not relevant). I want to use it on a 24V vehicle
(trucks, Toyota Land Cruiser diesels, Nissan Patrol diesels), but the H3 in
24V starts at 75W.
Yeah, converters, but I have seen to many go up in smoke. Any TLC diesel
owner can tell you stories about that....:-((
Perhaps I should ask the question more extreme:
If you had the choice between a 1volt 50W lamp, and a 1000volt 50W, which one
would you use, and why? Considerations like wire thickness are obvious, but
what about heat and light output?
Andy Dingley
The moving finger of w.j.ma...@a1.nl (Willem-Jan Markerink) having
written:
>If you had the choice between a 1volt 50W lamp, and a 1000volt 50W, which one
>would you use, and why?
I'd break the glass off the 100V bulb, then use the bare filament to
light a pile of petrol soaked rags. It's the only way to get any
useful light from either of these bulbs on a 12V or 24V supply.
Get the voltage right. It won't work at all unless you do.
Your lamp uses a H3 bulb ? You can buy replacement bulbs cheaply for
either 12V or 24V and get them in any power rating you might want.
Ignore what you have and concentrate on what you want.
Gary McCoy
w.j.ma...@a1.nl (Willem-Jan Markerink) wrote:
>Hi,
>I have a question regarding differences between 12V and 24V light bulbs as
>used in cars and trucks.
><w.j.ma...@a1.nl> (a-one & en-el)
> The desire to understand
>is sometimes far less intelligent than
> the inability to understand
-snip-
The light output is proportional to the wattage, less any conducted
heat losses for the filament, and less any losses in the wires that
supply the searchlight. The higher wattage bulb will be brighter, and
will also stress the reflector / housing with more waste heat.
The correct voltage to use would be the one that matches the
electrical system of the vehicle. This will avoid energy losses and
potential reliability degradation caused by the equipment to convert
one voltage to another (if it has electronics, it's less reliable than
a lightbulb).
24v electrical systems have less energy losses in the supply wires
than do 12v or 6v systems. This results from a law of physics called
"Watt's Law"(Power in watts =voltage x current). Even fat copper wires
have some resistance, and any heat coming from such wires is wasted,
since they are not being heated to an incandescent temperature as is
the bulb filament. For a given wattage bulb, the current in the wires
of a 24v system is half of the current in a 12v system. In practice,
theses losses are far below those that would result from converting
one voltage to another.
Aside from losses, with bulbs of similar consruction, the 12v bulb
would be more durable, as the wire gauge of the filament would be
heavier to handle the double current. However, if I were designing a
24v bulb (I'm an Electrical Engineer), I would use extra supports for
the longer thinner filament, to give better shock resistance. If I
knew that the intended application was a spotlight and thus subject to
being dropped, I would build a heavy duty bulb, sacrificing some light
output for ruggedness and shock resistance.
Gary McCoy
'67 Commando
'92 Cherokee
'97 Wrangler TJ
george
:: Light filaments are tricky. You cannot apply v=ir to a light,
:: because a bulbs resistance varies greatly with its temperature.
:
:Sorry, I don't agree: v=ir is certainly valid.
:
:As you say, when the filament heats up, the resistance changes.
of course its just a matter of language. Ohms law says for a linear
resistor the voltage drop is proportional to the current. The constant
of proportionality is called the resistance. Now you want to
take something which isn't a linear resistor and call "v/i" its
resistance. Sure, you could do that with say a diode as well.
It just isn't very useful, unless you know how your pseudo-resistance
varies.
just for example, with a resistor you can substitute v=ir into
the definition of power = iv, you find that power = v^2/r, so
doubling the voltage means you have 4x the power disapation.
-but not for a light bulb. If you double the voltage to a
bulb (assuming it doesn't blow) it will be so hot that its "resistance"
goes up dramatically. In fact, I think bulb power is approximately
linear with voltage (rather than squared).
--
george
geo...@mech.seas.upenn.edu
Russ Poffenberger
Willem-Jan Markerink wrote:
>
> In article <4qes1v$6...@vixen.cso.uiuc.edu>,
> k-mc...@cecer.army.mil (Kirk McGraw) wrote:
> >
> >>Hi,
> >
> >>I have a question regarding differences between 12V and 24V light bulbs as
> >>used in cars and trucks.
> >
> >>the lowest sizes available. Same difference goes for H4, 55/50W is
> >>for 12V, 75/70W is for 24V. Mind: these are the only legal bulbs in
> >>Europe.
> >
> >>My question is whether the 24V version emits as much
> >>lumen/lux/candles as the 12V version, or *more*....and whether they
> >>have different thermic properties. I know that for a given output
> >>the wiring for a 24V system can be less than half the thickness, but
> >>I lack the knowledge to expand this stuff to light filaments.
> >
> >>Can anyone help here?
> >>I have to find out if I can replace the stock 12V/55W H3 bulbs with
> >>24V/75W, and what my pro's (extra light?) and con's (extra heat?)
> >>will be. This is for a stock 12V search light. It has a metal coated
> >>resin reflector, so heat is a major concern.
> >
> >indicator of both brightness and heat output.
> >
> >on the square of the amps.
>
> That would mean that a 24v bulb with the same wattage as a 12v bulb will only
> have 1/4 of the heat output. Is this conflicting with your first line, or is
> the explanation below?
> The problem is that the wire is not the lead, but the output source....
>
> >without over heating. High voltage filaments have to be skinnier
> >so they heat up and glow (I am guessing now). The length and
> >diameter of the filament changes its resistance, which affects how
> >much current flows through it. So if you try 24V bulbs in a 12V
> >system, there will not be enough current and you get a dim red
> >glow. As we all know, putting the 12V bulb in a 24V system results
> >in a brief, very bright light...
>
> So 70Watt 24Volt or 12V does not make a difference, neither in lumen nor in
> heat output?
> still feel 24V should give some advantage other than less strain on the
> wiring....
Pretty much. watts is watts. Whether it is 24V or 12V makes no difference.
It is true for a transmission line of power, that power lost to dissipation in the
wiring is current squared time resistance. This is basic Ohms law, so yes, the wiring
and such will be stressed less. Why do you think that commercial power lines
delivering electricity over long distances use very high voltage (up to 100,000 volts
or more)? The reason is that there is less loss, since the same amount of power can be
delivered using less current, this means much less (by a factor of the square of the
current) power lost and they can use smaller wire.
--
Russ Poffenberger Engineering Specialist
Schlumberger Technologies ATE DOMAIN: pof...@San-Jose.ate.slb.com
1601 Technology Drive CIS: 72401,276
San Jose, Ca. 95110 Voice: (408)437-5254 FAX: (408)437-5246
Bill Mounteer
In article <4qm887$a9g...@a1-42-130.a1.nl>, w.j.ma...@a1.nl says...
>Perhaps I should ask the question more extreme:
>If you had the choice between a 1volt 50W lamp, and a 1000volt 50W, which one
>would you use, and why? Considerations like wire thickness are obvious, but
>what about heat and light output?
>
You are still not asking the right question. A 50 watt bulb draws 50 watts of
power regardless of the voltage. If you incease the voltage while keeping the
power draw fixed, the only effect is the current draw decreases and the wire
size required decreases.
The question to ask is - "what form does the power draw take, ie., how much of
the power is used to produce light and how much is wasted as heat? ". A
typical filament type bulb uses all the wattage to heat the filament and
create radiated light. As such the hotter the bulb, the brighter the light.
The composition of the filament will mostly affect the color of light
produced. About the only way to "increase" the light output from a filament
based bulb is to make sure the filament is positioned at the focal point of a
parabolic mirror. This will cause "most" of the light to be focused in the
direction you wish to see. Headlights are an example of this application.
Back to your question of 1 volt vs 1000 volt 55 watt bulbs. The high voltage
bulb would use fine wire but would present a significant shock hazard. The low
voltage bulb would use bigger wire less likely to break in use and would
eliminate and shock hazard. However in context with the thread, 12v vs 24v is
essentially the same. A 24v car will save a few dollars in copper.
Bill Mounteer, P.Eng.
Andre Maritz
>Hi,
>
>I have a question regarding differences between 12V and 24V light bulbs as
>used in cars and trucks.
>
>Standard H3 bulbs for 12volt are 55W, for 24V this is 75W. Both are
>the lowest sizes available. Same difference goes for H4, 55/50W is
>for 12V, 75/70W is for 24V. Mind: these are the only legal bulbs in
>Europe.
>
>My question is whether the 24V version emits as much
>lumen/lux/candles as the 12V version, or *more*....and whether they
>have different thermic properties. I know that for a given output
>the wiring for a 24V system can be less than half the thickness, but
>I lack the knowledge to expand this stuff to light filaments.
>
>Can anyone help here?
>I have to find out if I can replace the stock 12V/55W H3 bulbs with
>24V/75W, and what my pro's (extra light?) and con's (extra heat?)
>will be. This is for a stock 12V search light. It has a metal coated
>resin reflector, so heat is a major concern.
If you need more light, why don't you just fit 12V/100W or 12V/150W
spotlight globes?
Cheers
Andre
Vic Watson
A 75W/24V bulb will produce more light (and heat) then a 50W/12V bulb, WHEN
INSTALLED IN A 24V ELECTRICAL SYSTEM. From my reading of the original post, it
would appear that it is intended as a direct replacement for the 12V bulb.
This won't work. For a start, the resistance of a 24V bulb is significantly
higher than a 12V bulb (about 2.5 times as much), so the power output would in
fact be 2.5 times less - i.e. about 20W output (dim).
Secondly, this is probably a halogen bulb. Because of the way halogens work, it
is important to use them at the correct voltage. Using a 24V bulb at 12V will
give it a very short lifetime indeed.
Vic.
george
:Have I missed the point?
:
:A 75W/24V bulb will produce more light (and heat) then a 50W/12V bulb, WHEN
:INSTALLED IN A 24V ELECTRICAL SYSTEM. From my reading of the original post, it
:would appear that it is intended as a direct replacement for the 12V bulb.
see, I figured he knew that and was converting the system to 24v.
I really hate it when a thread drags on for weeks and the guy
who asked the question is nowhere to be found.
--
george
geo...@mech.seas.upenn.edu