flashlight

Ah, magnetic charging tail caps. To charge the battery, electricity must be able to flow to the battery via the tail cap. Unfortunately, a lot of earlier/cheaper implementations accomplished this via a direct connection, which didn't prevent current from leaving the tail cap should it short against something (steel wool, water, etc), although the usual suspects like coins were usually not physically able to make contact with the recessed center pin.

There was quite a kerfuffle about it. Thanks to people like Zak, olight issued replacement tail caps that contained a protection circuit, likely a diode, to prevent this.

https://www.reddit.com/r/flashlight/comments/6lk901/olight_h2r_ignites_steel_wool_with_its_tailcap/

https://www.candlepowerforums.com/threads/olight-h2r-nova-quick-review-new-improved-tailcap-available-now-see-post-32.436167/

You may have to look at reviews to see if the light you're considered includes protection. As for salt water, it is what it is there. Give your lights a good rinse when you're back home in the sink and don't worry too much about it.

Skilhunt recently upgraded its charging pad to fix the sparking problem. If you buy direct, you can email them and ask whether your unit will have the upgraded port.

I'm my testing, nothing caused the old pad to output current continuously. I don't think water is a problem. I can dunk an H150 in salt water in a few days if you're curious.

I immersed an H150 in salt water for 30 minutes. There was no decrease in battery voltage, no water ingress, and no effect on function.

Basically there are two common charging systems:

• Armytek like, where you have to loosen the tailcap to charge the battery. When tightened, the terminals are shorted, so it's absolutely safe. When loosened, they are in series with the battery, but the driver limits the current. So the current would be whatever the flashlight draws in regular use - while it's off just a few microamps.

• Olight or Skilhunt like, where the charging terminals are separate from the normal circuit. It needs some kind of protection. Either a clever circuit using a FET, a diode or something like a polyfuse that disconnects the terminal if the current gets too high. These type is prone to leakage, for example 2mA for many Olight or much higher current for most Skilhunt. These methods are safe for short circuit situations (although a short pulse of current could cause sparks), but canddrain the battery if the terminals are bridged with some resistance. Depending on the water/mud properties it could pass some current, too little to trigger the protection, but enough to drain the batteries over a longer duration.