Sunday, December 11, 2011


When I was a kid we always got at least one flashlight for Christmas. My brother and I played hard and I doubt if any of those lights survived. I know I don't have one.

My Great Grandfather bought a bunch of land north in Northern Michigan. We used to go up on the weekends. No plumbing or electricity. In the woods the dark is something fierce, you can't see your hands in front of your face. If you have to take a dump in the middle of the night you take a flashlight. As a result of this interesting childhood all the men (and to an extent even my sister) in my family have a kind of a flashlight fetish. If I consider you a member of the family you get a flashlight at Christmas.

I almost always have one in my pocket. When my Grandfather died I slipped a 1xAAA Maglite in his suit coat pocket during visitation. My sister cried. Everyone wanted to make sure it actually worked. A non-working flashlight is about as useful as an unloaded gun.

There are flashlights all over my house and I have a lot of experience with them. I buy different flashlights and I test them out. Over the years I have learned a lot about flashlights and I figured I would give people a few pointers from what I have learned.

Flashlights are all about electrical connections. Back in the “old days” the corrosion protection of the individual components was so poor that they often “rusted” or oxidized causing electrical connection problems. Old timers used to carry steel wool so they could clean the connections when their flashlights failed. If you have ever seen an old “steel wool and batteries to start a fire” article now you know why anyone figured you would have both steel wool and flashlight batteries.

These days the plating on the components is so good that even the cheapest flashlight typically works better than a really good fifty year old flashlight. I have cheap Chinese LED flashlights that are 7 or 8 years old and still work great.

Every electrical connection causes resistance. The cleaner the connection the less resistance. Electronics typically use gold or gold plating to reduce the potential for corrosion and resistance in the circuit. Flashlights (reasonably priced flashlights) do not use gold connectors. Some gold plating is so cheap it wears away almost instantly. Other times gold plating on spring contacts cracks and causes connection problems. A contact needs more than gold it needs quality engineering and manufacturing.

Battery technology has also improved. Most flashlight batteries are 1.5 volts. “Lantern” or “Big flashlights” have 6 or 12 volt batteries. Some batteries are made from different materials. Alkaline batteries are the most common these days. Carbon batteries are still around, if the battery is marked “Heavy Duty” and is not marked “Alkaline” it is a carbon battery. Lithium batteries are the same size as alkaline or carbon batteries, but, they are typically 3 volts. Double A batteries in lithium are 3.6 volts.

Bulb technology has also improved a great deal. We have LEDs which use less power for a reasonable amount of light. I really like LED flashlights. When I want a bright light I use an incandescent bulb. It is possible to buy High Intensity Discharge (HID) lanterns which have very bright lights and use less energy.

Typically a flashlight brightness is all about voltage and the bulb. The more voltage, the brighter the bulb. Not all bulbs can handle the voltage though. If you put 2 AA lithium batteries (14500) with a standard AA bulb the bulb will burn up. If you put a 2AA lithium batteries in a flashlight with a bulb typically used in a 4 or 5 D cell light the light will be really bright and if you have a plastic reflector it could melt.

If your flashlight quits working and you know the bulb and batteries are good it means the connections are corroded. Some flashlights have slide switches and in the old days the sliding motion rubbed off the corrosion protection. Once the corrosion protection on the switch was gone it would rust and the flashlight wouldn't work. Most good flashlights use real switches these days. Most cheap flashlights like kids flashlights still use crappy slide switches, but, the corrosion protection is better so they last longer.

Incandescent flashlight bulbs require voltage. Ohms law tells us that resistance times amperage equals voltage. Batteries have a limited voltage and amperage. As the battery is used the voltage and the amperage are reduced. A 1.5 volt battery is typically okay until the voltage comes down to around 1.1 or 1 volts. If the corrosion in the connections causes too much resistance it takes more amperage to achieve enough voltage to light the bulb. The cleaner the connections the higher the amperage and the more voltage reaches the bulb.

LED lights are dependent on amperage. I won't get into the difference in electronics. You can make an LED work by including a resistor in the circuit. Better LED lights use a special device called a “buck puck” which limits the amperage no matter what the voltage is. Some LED lights need a full amp to work. Most use about 350 milliamps, some use 700 milliamps.

Watts are determined by multiplying voltage and amperage. A 1 watt light using 2 AAA batteries has 3 volts (nominally) and so it needs about 333 milliamps.

Now that we understand the basics we can troubleshoot flashlights when they have problems. I use a multi-meter. I have a cheap Chinese 2xAA (2 double A batteries) aluminum LED light that no longer works. I tested the push button switch in the end cap and it works fine. No resistance. The tube of the light carries the electricity to the bulb. Good bulb. Good batteries. Where is the problem?

I checked the connection at the top of the tube with the bulb and it works fine. The problem is the connection between the tube and the end cap. No electrical flow. Fix the connection and the flashlight works. In this case the batteries had corroded and some of that corrosion had filled the threads. I used a 12ga brush to clean out the battery tube.

I don't believe someone can have too many good flashlights. I do believe people can overspend on flashlights. Plastic bodies are not better or worse than metal bodies. The places to look for quality in a flashlight are the connections, primarily the main spring, the switch and the bulb contact. The cheaper these pieces are the lower the quality of the flashlight.

Corrosion is a problem so find a water proof flashlight and try to minimize temperature swings which cause condensation inside of a flashlight. Water is a form of concentrated oxygen and oxygen causes corrosion. I have shoved small moisture absorbent packets under the main spring in a water proof flashlight to try and reduce condensation so the flashlight will be less temperature sensitive.

The cardinal rule, inspect your flashlights often, once a month is usually fine. More if you live in a very humid area. Inspect means, remove the end cap and pull the batteries. Switch them around. Turn the flashlight on and slap it against your hand a couple of times. If the beam wavers you have a problem. Replace the flashlight or troubleshoot and repair.

Battery tops and bottoms can become corroded. Replace the batteries or rub leather on the tops and bottoms of them. Steel wool is useful too, but, the steel wool puts tiny scratches which cause the battery contacts to oxidize faster. Test the flashlight again.

Beam still wavering? Springs can lose their “spring-y-ness” over time. Replacement springs are useful parts to keep around. Try stretching the main spring a little to increase “spring-y-ness”. This will also reduce the life of the spring.

Still wavering? Clean the contacts on the bulb contact.

Still wavering? Clean any other contacts you can reach.

Still wavering? Get a new light.

Maglites are still probably the best value in flashlights. There are lots of good manufacturers, I like Rayovac and Duracell and EverReady. I stay away from high priced lights like Streamlight. You can make your own choices and I hope this article helps you make a more educated choice.


wc42 said...

Never had any luck with Maglites.> One Christmas, I gave about 14-15 for presents. Small ones and Large ones. those maglites did not last a year. The switches went bad.
Never again.
Also, hate these pushbutton lights switches at the end of the light. Something is always turning them one.. Can't put one in a tool box or bag...or in glove compartment.
They get turned on and go bad.
So, I am back to the old sliding switch lights with d batteries or such.
Does anyone know of a good light that has a safe switch and not this push button junk??

John D. Ayer said...

Sorry, I've been busy. Everyone has their own idea of "best switch". I like the pushbuttons, but, the rubber breaks down eventually. There are some flashlights with rotating switches designed for people wearing heavy gloves, divers, etc. You might like those. Do a search on e-Bay for "led diving flashlight". Try one of the cheap ones, if you like the switch seek out a higher quality flashlight.