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Old 10-28-07, 08:13 PM   #1
Booger1
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Li/ion battery-Halogen bulbs

Do I need to slow start the bulb in order to use halogen bulbs with Li/ion batteries so I don't trip the protection in them.I will be over-driving a 10w-20w combo.
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Old 10-29-07, 10:47 AM   #2
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I think you need a regulatory circuit to sit between the battery and the bulb. I am doing the exact same thing. Try this link: http://www.ladyada.net/make click on bike light.
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Old 10-29-07, 05:05 PM   #3
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I started out running my 20W halogen directly from a protected 14.8v Li-Ion battery. When I would turn on the light the battery pack protection would trip and shut the light off. I would turn it off and then back on again a couple of times and it would then stay on. The problem is that a cold halogen bulb has very little resistance. This looks like a short to the battery protection circuit so it shuts down. Some current gets through and heats up the bulb enough to create some resistance. This limits the initial current and the protection circuit allows the light to stay on.

To avoid this problem I built a simple soft start circuit to ramp the voltage to the bulb. Now it starts up first time every time.
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Old 10-29-07, 07:39 PM   #4
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Thanks folks!
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Old 10-29-07, 09:36 PM   #5
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sv_ted: Thanks for the info. Can you please share your circuit? I would like to see how that compares to the one I am building.
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Old 10-29-07, 10:03 PM   #6
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Here it is. I don't recall the component values. The FET is a power pfet, the diode is a 1n914. You want the gate of the pfet to couple up to the supply voltage when the switch is turned on. Then the resistor slowly brings the gate voltage down to ground. When the switch is opened the diode keeps the gate from going much below ground.

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Old 11-02-07, 08:17 PM   #7
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Quote:
Originally Posted by Booger1 View Post
Do I need to slow start the bulb in order to use halogen bulbs with Li/ion batteries so I don't trip the protection in them.I will be over-driving a 10w-20w combo.
Why over drive a halogen bulb, Boogie? Use an energy-saver bulb (more expensive) that draws less power but puts out more light.

I use one on my bent that draws ~20W but puts out ~35W. Even if the math is skewed, it seems like a better way to go.
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Old 11-02-07, 11:36 PM   #8
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Because I can get them for .90c each if I buy ten,they work better when overdriven.

My battery/charger just came in the mail today(battery space) so I guess I'll find out soon.
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Old 11-03-07, 08:30 AM   #9
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I use one of those energy-saver bulbs (20W MR16) and then overvolt it. It puts out a lot of light. I think I paid $10 for the bulb. In my light the front half of the bulb is completely exposed. I have been using the same bulb for over a year and the rain, bumps, and higher power have not killed it.
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Old 11-03-07, 10:41 PM   #10
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I just tested my light with the new battery.A 4AH,7amp poly switch battery.First tried a 10w bulb,lights off no problem.Tried 20w bulb,lights off no problem.Tried 10w and 20w bulbs together,lights off no problem.Guess I don't need a slow start.

I'll pick up an energy saver and see how it looks.

Pictures don't do these things any justice,it's PLENTY of light for the riding I do.

Last edited by Booger1; 11-03-07 at 10:46 PM.
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Old 11-05-07, 02:46 AM   #11
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20w mr16 recommendations please

Hello fellow halogen users. I'm looking for recommendations for a 20w mr16 bulb to use @ 13.2v.

How do the "energy saver" bulbs work? Does the 20w bulb deliver extra light or does it deliver 20w worth of light but use less energy thereby extending runtime?

Specific brand, model, beam angle and retailer info would be much appreciated. Thanks
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