Dive light burn test: how long does your light really last?

Your light works fine in the workshop, but will it last the whole dive? Battery cells age. Over time and charge cycles their capacity drops and your burn time gets shorter. You often only notice that underwater. A burn test tells you in advance.

What is a burn test?

In a burn test you run your light on a fully charged battery until it is empty and measure how long that takes. You compare that time with the burn time stated by the manufacturer. If you are well below it, your battery is on its way out.

How to do a burn test yourself

• Charge the battery fully. Has your light been sitting for a few weeks? Charge it again, because a battery slowly discharges in the meantime.
• Look up the burn time in the manual for the setting you are testing. It differs per model and per setting.
• Set the light to its highest setting and measure how long it burns.
• Compare your measurement with the stated burn time.

Note: check in the manual whether your light head may run on full power out of the water for a long time. Some light heads get too hot. If in doubt, let us do the test.

When should you test your light?

Do a burn test when your light gets older, when you notice it runs out sooner than it used to, or before a dive trip or a dive where you really have to rely on your light. Going on a cave or wreck dive? Then you want to be sure your burn time is right.

Maintaining your light

• Rinse your light with fresh water after every dive.
• Check the O-rings of your battery canister for sand, hair and damage.
• With a canister light, inspect the cable. It is bent all the time and can get damaged on sharp edges. A hole in the jacket is an entry point for water.
• Charge your battery as the manufacturer prescribes.

Burn test and repair at Scuba Support

In our workshop in Hilversum we do burn tests with burn testers, a computer-controlled system for battery analysis and a light intensity meter. The fully charged battery is discharged at a constant load while we measure the time. That way you see in black and white how long your light still lasts.

Disappointing result? Then we replace the battery pack and test the light again. We work on lights from Halcyon, Metalsub, Ammonite, Light Monkey, Salvo and our own brand Dive Elements, among others. Read more about our dive light repair.

Source: Light & Motion, Run-time / burn-time test dive lights; Scuba Support workshop practice.