# Maximum voltage that a bulb can take before burning out?

• likeachild
In summary, the speaker is interested in using rechargeable batteries for a 9v flashlight, but is concerned about the peak voltage of the batteries being too high and potentially burning out the expensive bulb. They ask if it is possible to measure the maximum voltage for the bulb or if there is a way to limit the peak voltage in the flashlight circuit. The expert explains that the battery's no load charge voltage may be different from the load voltage and provides equations for derating bulbs as the voltage increases. They also caution against using extremely high voltages with low voltage bulbs.
likeachild
is it possible to measure the maximum voltage that a bulb can take before burning out?

I am interested in using rechargeable batteries for a 9v tactical flashlight that I have, but rechargeable 3v batteries actually have a peak voltage of around 3.85 when fully charged. As the bulb is kind of pricey, I don't want to burn it out by putting in rechargeable batteries.

if it's not possible to measure the maximum voltage for the bulb, is it possible to put something in the flashlight circuit to limit the peak voltage to 9 volts?

1. The no load charge voltage on a battery is different to the load voltage. When you actually load the battery it will drop rapidly down to the nominal cell voltage. It is this nominal cell voltage that you need to use.

2. There is not really a maximum voltage for a lamp as opposed to a survival period. The more volts applied the brighter you burn the shorter you live. Something I tell new staff when working on high voltage systems.

As a rule of thumb you can derate bulbs using the following equations:

Life = Rated Life * (Rated Voltage/Applied Voltage)^12

Intensity = Rated Intensity * (Applied Voltage/Rated Voltage)^3.5

Current Draw = Rated Current * (Applied Voltage/Rated Voltage)^0.55

Note that as you get further away from the rated values these equations get less and less accurate so don't try and put 240V into your 1.5V bulb.

Panda said:
don't try and put 240V into your 1.5V bulb.
That would solve Aki's rocket ignitor problem...

## 1. What is the maximum voltage that a bulb can take before burning out?

The maximum voltage that a bulb can take before burning out varies depending on the type of bulb. Generally, incandescent bulbs can handle up to 130 volts, while LED bulbs can handle up to 240 volts.

## 2. Can exceeding the maximum voltage cause a bulb to burn out?

Yes, exceeding the maximum voltage can cause a bulb to burn out. This is because the excess voltage can cause the filament or LED chip to overheat, leading to damage and eventually burn out.

## 3. How can I determine the maximum voltage for a specific bulb?

The maximum voltage for a specific bulb can usually be found on the packaging or in the product specifications. If this information is not available, you can consult the manufacturer's website or contact them directly to inquire about the maximum voltage for their bulb.

## 4. Is it safe to use a voltage regulator with a bulb to prevent burning out?

It is generally safe to use a voltage regulator with a bulb to prevent burning out. However, it is important to make sure that the voltage regulator is compatible with the bulb and that it is set to the appropriate voltage to avoid damaging the bulb.

## 5. Can a bulb still work after exceeding the maximum voltage?

In some cases, a bulb may continue to work after exceeding the maximum voltage, but its lifespan may be significantly reduced. It is recommended to replace the bulb with one that can handle the appropriate voltage to avoid potential hazards or frequent replacements.

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