# How much power required for H7 12v 100w Bike Halogen Bulb?

Discussion in 'The Projects Forum' started by paul.1911, Mar 25, 2012.

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1. ### paul.1911 Thread Starter Active Member

Mar 25, 2012
35
0
Hi,
I am new here and I've hero honda bike thinking to use 100w bulb. I know it will not support rather than 35W/35W bulb. But I want to try. Searched a lot and found magneto does not provide enough volt, you need to rewind the coil. But the thing is magneto produce 30V to upto 40V AC. That AC is being regulated for a bulb: not to fuse, and not being convert to DC for a headlamp.
Battery wires is separate. Rectifier is used to output 13.8VDC to charge it.

So I thought why I can't make my own regulator rectifier dropping 30v to such that 100W head lamp glow in its full brightness. If not at least for 60W/55W.
But I need help and found this best place to ask from you experts.

So How much volt, watt, ampere should be there to make 100W bulb to glow in its full efficiency for long time? don't want to turn it black or fuse.
I'll only replace stock regulator for headlamp not rectifier for battery.

Is this possible? I think it is

2. ### R!f@@ AAC Fanatic!

Apr 2, 2009
9,652
1,110
Well ! This is one place where u can do that and I too have done some thing similar.

But if you try to break into the scooter harness, this thread won't survive the pressure.

3. ### panic mode Senior Member

Oct 10, 2011
1,657
468
the most basic equation for power is simply:
P=V*I

where
P=power [watts]
V=volage [volts]
I=current [amps]

100W is power - you already decided on that.
and 100W is 100W regardless how you get it:

100W=100V*1A
= 30V*3.33A
= 25V*4A
= 12.5V*8A
= 13.8V*7.25A
= 10V*10A
= 1000V*0.1A
= 10000V*0.01A
etc.

note that size of wires is determined by current. (reason Edison lost war of currents).

twice the current means that cross section of wire must (at least) double as well. i used note "at least" because thicker wires have comparatively less surface and hence less cooling area.

4. ### paul.1911 Thread Starter Active Member

Mar 25, 2012
35
0
Hi

look here what i got

This can be use to convert AC to DC
this will give about 24V out.

Now can I use 12v transistor to limit volts?
can a single transistor able Handel so much volts with heat sink attached?
I don't know how much ampere will be there!!

5. ### R!f@@ AAC Fanatic!

Apr 2, 2009
9,652
1,110
My dear...do you really know what u are doing?

6. ### paul.1911 Thread Starter Active Member

Mar 25, 2012
35
0
No
I dont know thats why i want help
what to do?

7. ### panic mode Senior Member

Oct 10, 2011
1,657
468
reality check: how much power you can get from magneto? if it is rated for 40-50W, you cannot use it to power 100W load and get "full brightness". (if you can, you would solve energy crisis and become wealthiest man on planet)

8. ### R!f@@ AAC Fanatic!

Apr 2, 2009
9,652
1,110
Please explain what u are trying to do.

9. ### #12 Expert

Nov 30, 2010
18,076
9,678
Your rectifier drawing has an error. The AC input on the left has a false ground label. It must not be connected to the DC ground after the rectifiers.

10. ### R!f@@ AAC Fanatic!

Apr 2, 2009
9,652
1,110
Do you think OP understands that ?

Jul 17, 2007
22,201
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