Cave Diving Backup Lights / Rechargeable Batteries

[Capt Jim Wyatt]

This topic has been discussed but I am looking for the most recent thinking.

Background: Years / Decades ago we NEVER trusted rechargeable batteries in our cave diving backup lights because they were not reliable. We taught our students to use alkaline batteries.....

Fast Forward to today - Some / Many cave divers are now using rechargeable batteries in their cave diving backup lights. The thinking seems to be that they are now reliable enough to trust in a cave diving backup light.

I'd like to better understand the "thinking" behind this premise. What makes them better nowadays? Which ones are better? What brands are better? Is there a difference in the chargers for these batteries?

 

[Manatee Diver]

This topic was never mentioned to me, and my back ups have always been rechargable (Dive Rite CX-1s).

 

[Capt Jim Wyatt]

This topic was never mentioned to me, and my back ups have always been rechargable (Dive Rite CX-1s).

What year did you take your cave classes?

 

[Scubaroo]

Well years ago the rechargeables in the market were either NiCd or NiMH, which have fast self discharge rates in storage. Li-Ion chemistries have a much slower self discharge rate.

NiMH batteries can self discharge 1% a day, Li-Ion is about 1-2% a MONTH.

 

[Jack Hammer]

To date I only use Energizer or Duracell non-rechargeable batteries in my backups. They get checked before every dive and replaced annually. I've had Costco and Sam's Club non-rechargeables fail and ruin several backups over the years so major name brand batteries only for me.


I think batteries have gotten better. I know several folks who will use quality rechargeable 18650 batteries and have been doing so without issue for a while. Considering there are proven primaries that reliably run on the same rechargeables I personally dont see an issue with them used for backups as long as they are checked and recharged as needed.

 

[Dominick Gheesling]

Still using alkaline batteries. For me it just makes things simpler (one less thing to think about): I load fresh batteries, Clip backup lights to harness, Never take them off the harness, Only turn them on to check pre-dive, replace batteries annually. For me personally, it makes one less failure point and the failure point is my brain being certain that I charged the batteries. I finished my Cave training within the past 3 years. I was presented with the pros/cons of both types of backup lights.

 

[Miyaru]

I use NiMH rechargeables in all my divelights (is there supposed to be a difference between backup and main light?).

After a day of cave diving, all batteries go into the chargers, regardless of being used or not.

 

[Manatee Diver]

What year did you take your cave classes?

Early 2019 until about a week ago.

 

[Vicko]

I use rechargable 18650 bateries in my primary and backups, the primary takes 3 so after a dive i just cycle them, the primary gets 2 from the backups and a fresh one and the backups get fresh ones, that way i'm sure that my backups work. I don't do long penetrations so I dont need that much run time.

 

[hroark2112]

I just did my CCR cave course. I did notice when I was reading the Tao of Cave Diving it still says to use non-rechargeable batteries in your backup lights.

I think if you compare the lights used today as backup lights, many of them have a similar burn time to the primary lights from days gone by. I’d be comfortable with rechargeable batteries in at least one backup light if not both.