Batteries for diving headlamp

Hey:wave:

I recently bought a cheap diving headlamp from china, and I was going to mount it on my weight vest, since i sometimes spearfish at nighttime (Yes, that is legal where I live) I would like to be able to use both hands, and still be able to see, when I let go of my primary torch. The lamp should be able to accept 3 x AAA or a single 18650, but since there's only about 55mm of space for the batteri that leaves out most 18650 I guess... that leaves me with the 3 x AAA, but I'm a little cautious using those, since I've always been told to use batteries with those safe-circuit-things while diving, or they would otherwise explode if the light floods... As you may have noticed, I don't know a thing about batteries, or flashlight for that matter, and I don't really need this "head"lamp to perform like an underwater sun. I just need enough light to be able load my speargun and handle the fish. But I also need it to NOT blow up in my face...

Sooo.... could anyone please inform me on what the deal is with batteries and seawater? Is it safe to use standard IKEA non-rechargeable alkaline batteries in a diving lamp, or is Li-Ion with safe-circuit safer, or should I just develop an owl-like night vision instead?oo:

Hello Pallen,

Welcome to CPF.

If you light is functioning properly, that is if it seals and keeps the water out, there is no real problem using any battery chemistry. NiMh and Alkaline have less energy density so they will pose less risk. Li-Ion batteries offer better performance but take less abuse.

Looking at the bigger picture... If you use rechargable batteries you need to have a way to charge them and need to understand what you are doing so you don't run into problems during the charge cycle. If you settle on Alkaline batteries, you don't need a charger and simply need a supply of fresh batteries.

Tom

Hello Tom,

Thank you for the reply! What would happen IF the lamp flooded using alkaline batteries? Would it build up pressure?

Hello Pallen,

Pressure is relative to depth. As you go deeper the outside pressure increases. If your light leaks at the maximum depth of the dive then reseals, pressure would build up inside and make opening the light difficult. When you open the light the pressure would release.

To get an idea of how Alkaline batteries react to water, just toss some into a bowl of water and observe the results.

Tom

If safety of the battery chemistry is a primary consideration for you, then you should choose a light that can use either Alkaline or NiMH rechargable batteries. Li-ion batteries are less tolerant of abuse. Between alkaline and NiMH, I cannot conclusively say which would be "safer" but I generally prefer NiMH. To further the above suggestion, you'd want to throw the batteries in salinated water to better approximate salt water intrusion. Salt water is somewhat conductive and would effectively short the batteries.

You might toss them into a bowl of sea water to test them. The salt acts as an electrolyte and will conduct much better than plain water.