Bulbs and batteries: A diver’s guide to finding your way in the dark.

Bulbs and batteries: A diver’s guide to finding your way in the dark.

So, you want to go diving in the dark? It might be a night dive. You’ve waited so long for it. There’s always an excuse for the boat not to launch; bad weather, drunk skipper, lazy DM. But this time it’ll be different. You are going to see the reef at night.

Or you’re one of those divers who always peeked under the overhangs. Trying to find every swim-through on the reef. And before you knew it the darkness started pulling you in. It began with that intro to cavern course, and now you spend your coffee time searching the web for tips on cave diving gear and wreck diving destinations.

You might also be that guy with the camera that holds up the dive group taking a gazillion pictures of a fish that might look better in a beer batter and with a side of chips. If you have a good light that picture might actually look good. It will bring back some color into the picture.

Then there is the fourth group of people. You’ve been diving since Jacques Cousteau’s days. But now there are new toys on the market. That old DIY canister light has a dim yellow light. It has a faint, almost limp, beam when you compare it to some of the newer, much smaller, dive lights. It’s time to upgrade. But, what should you look for in a good dive light?

 

Part 1. Bulbs


Let’s take a look at the three most common light bulbs used in dive light: Halogen lamps, high-intensity discharge lamps (HID) and light-emitting diodes (LED).

Halogen lamps are really just souped-up incandescent light bulbs. Most of the older dive lights use these bulbs. They are very affordable and readily available. Almost any automotive shop should have the replacement bulb you need as most of these lights used automotive light bulbs. The lights are also easy to fix in the field if something goes wrong as there are no complex electronics. It is usually just a simple circuit like the one you made for your kindergarten science fair.

It is not very energy efficient and the lightbulb has a limited lifespan. It is not uncommon for divers to change a lightbulb on every other dive trip. They are also not as bright as the other lightbulbs discussed in this article.
Pros:

  • Cheap
  • Easy to come by
  • Usually runs on standard 12v batteries.
  • No complex electronics. 

Cons:

  • Short lifespan
  • Low beam intensity


High-Intensity Discharge (HID) lamps were revolutionary technology for divers as it had a light intensity like nothing before it. These lamps are bright. Unlike an incandescent lamp that has a filament that produces light, a HID generates light by means of an electric arc between tungsten electrodes. So, what’s the catch? Well, these light bulbs are expensive. They are not very energy efficient. And they are very sensitive to impact and cycling. Do not turn them off and on again. They need time to cool down before you turn them back on.
Pros:

  • Bright

Cons:

  • Expensive
  • Poor energy efficiency
  • Sensitive to impact and power cycling

 

Light emitting diode (LED) lamps seems to be the new standard in dive lights. They had a slow start due to complex electronics and low power output when it was first introduced. However, with the promise of energy efficiency and a wide range of applications (like household, automotive, aviation, medical, industrial…), there has been a lot of research and development over the past few years. It has matured into a technology that surpasses the previously mentioned ones in almost all areas.
Pros:

  • Bright
  • Cheap
  • Long lifespan (up to 50,000 hours)
  • Very energy efficient
  • Durable

Cons:

  • Complex electronics. If something goes wrong, you are not going to fix it with your pocket-knife.


Part 2. Batteries

For the purpose of diving I will break up the discussion of batteries into two categories: Rechargeable and non-rechargeable batteries.

 

Rechargeable batteries:
By far the most popular batteries in this category is Lithium Ion Batteries. They have a broad range of consumer applications like cell phones, laptop computers, power tools, video cameras, handheld electronics and even electric cars. Demand drives development and this is good for the end-user. Almost like the story of NASA and the non-stick pan, the technology that powers your mobile phone can now benefit you on your next dive trip. These batteries are excellent for use in your primary light.
Pros:

  • High energy capacity (small battery with lots of power)
  • Quick charging
  • Low self-discharge
  • Long lifespan

Cons:

  • Expensive to buy
  • Can overheat and ignite with internal short circuit

 


Non-rechargeable batteries:
Alkaline Batteries are widely used in dive lights because of their availability and price. It is also common practice for cave divers to use a new set of high-quality alkaline batteries in their backup lights. 
Pros:

  • Cheap and widely available
  • Long shelf life
  • Very safe

Cons:

  • High internal resistance with lower power output
  • Often performs worse in cold temperatures
  • Leakage is possible

 

Diving in the dark is very rewarding. Whether you are going on a night dive or venturing into a cave or wreck, enjoy it. It might be some of the best dives you have ever done. Make sure you have a high quality primary and backup dive light to make your dive safe and enjoyable. A LED light with a lithium ion battery is a good choice for a primary light and a LED light with a set of fresh alkaline batteries is the best bet for a good backup light.


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