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How long does an LED Torch or Flashlight Last?

This question is asked by many people when they are looking to buy a new torch, and they want to know how long the torch will produce light before the batteries run out.  This is important as if you buy a torch which only runs for a few hours on a set of new batteries then you will start to realise that it may not be the torch for you.  Many people look for a torch that can run for a set amount of time before they have to put in new batteries, some torches range from a couple of hours to some that last over 100 hours on a set of batteries.

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LED Torches are power efficient and use fewer batteries.

One of the key variables that impacts how long a flashlight will last is the efficiency of the torch bulb, if a bulb is inefficient and takes a lot of power to produce a certain amount of lumens then it goes without question that the battery life would not be as good as a very efficient bulb which produces a similar amount of lumens. One of the main benefits of LED light bulbs is that they are more energy efficient than old incandescent bulbs and they take less power (longer battery life) to produce light, which means that batteries will last longer. They take less battery power to run, which means they reduce the amount of batteries needed over time, thus reducing the pollution of our world with dead batteries. Many good quality LED flashlights come with rechargeable batteries making them that much more of a “green” alternative. It also makes them perfect for household emergencies.

LED Flashlights will last a long time

Not only do LED bulbs use less energy and thus extend the battery life, these bulbs will also last a very long time when compared to their predecessor’s the incandescent bulbs, some LED light bulbs can work for over a 100,000 hours which basically means they will still be going beyond the typically life span of a typically torch. The length of the battery life is dependent on the rate of current draw, and the initial battery capacity. If you have a battery which has a high capacity and use a low current draw led light bulb then it makes sense that the battery will last longer. To determine the battery life, divide the capacity by the actual load current to get the hours of life. A circuit that draws 10 ma powered by a 9 volt rectangular battery will operate about 50 hours: 500 mAh /10 mA = 50 hours The cell voltage of alkaline cells steadily drops with usage from 1.54 volts to about 1 volt when discharged. The voltage is near 1.25 volts at the 50% discharge point. Alkaline cells exhibit a slightly increased capacity when warmed and the capacity drops significantly at temperatures below freezing.

There are some great designs on the market that use large/high capacity batteries with low energy consumption LED bulbs that draw less current, some devices can run from a set of batteries for a few hundred hours, yet some designs use so much power to produce a high lumen light beam that the batteries will only last between 3-4 hours. An example of a LED torch with a long battery life is the LED Lenser  P7, With its searchlight-like beam, this is perhaps the best torch of its size for under £100. You can go from flood to spot beam in a twist. Plus you get 130 hours of power from a device that weighs under 200g, and fits in your pocket. Small, but powerful with it.