Cave Diving Backup Lights / Rechargeable Batteries

[Swedinsidemount]

Dive boat? Maybe the thread topic has drifted, but it was originally about backup lights for cave diving. If you're going cave diving, you're likely going to have a lot more "extra" (that is, backup/spare) stuff than even what Manatee mentioned. In your car, you'll probably have a whole bin/box full of stuff you hope you won't need. A few extra batteries, whether rechargeable or not, a charger for rechargeables, and if you're going to go the alkaline route, a voltmeter.

I would loveee to see someone sitting in their car waiting to charge their batteries and not be pissed about it wishing they had just the normal alkaline battery from 1906

 

[tbone1004]

I still don't trust rechargeable, for my lights computer and even the o2 analyzer. AA batteries are still the most widely available and cost effective choice. You can't plug in a rechargeable on a dive boat now can you( at least most of the time). I always throw a couple extras in my med bag just in case. And if I run out then just pop into the gas station and there, your dive is saved.

what is not to trust?

Looking at Dive Rite BX1 since it is comparable
Amazonbasics AAA batteries are $0.23 each and requires 6 of them to match an 18650, $1.38 per charge of the 18650.
Highest end 18650's out there are $8.50 each from liion wholesale and requires a "nice" charger which is $16 for a usb powered Nitecore 2-slot. Call it a $35 investment total

35/1.38=25
You have to use the light 25x for the cost to wash, so please explain how alkalines are more cost effective? Carry a pair of them, charge them over night, and you're good to go.

Why don't you trust them? We are using them in cave diving, so if we can trust them more than a mile back in a cave for our backup lights, I don't understand what is not to trust on a boat

 

[Manatee Diver]

I would loveee to see someone sitting in their car waiting to charge their batteries and not be pissed about it wishing they had just the normal alkaline battery from 1906

The fact is that cave diving relies on rechargeable batteries, and has for years. Even Jim who is skeptical of them in a back up light, will carry a primary light that uses rechargeable battery.

Tomorrow is my charging day for my Saturday cave diving trip. My can light and my Terics will be charged. I will do a quick voltage check on my backup light batteries and the spares.

 

[UCFKnightDiver]

I would loveee to see someone sitting in their car waiting to charge their batteries and not be pissed about it wishing they had just the normal alkaline battery from 1906

Just have an extra 18650 battery... Isn't it the same as having extra AA batteries?

 

[Swedinsidemount]

Just have an extra 16850 battery... Isn't it the same as having extra AA batteries?

My point was, for me, alkaline batteries are more effective solution over an rechargable unit. Personaly I have found that they are somewhat lighter, readily available, and proven on some models of coms/lights to last longer.

 

[rjack321]

My point was, for me, alkaline batteries are more effective solution over an rechargable unit. Personaly I have found that they are somewhat lighter, readily available, and proven on some models of coms/lights to last longer.

What? Alkaline's are a fraction of the energy density of li-ion. Not only that, but at best you get a weak candle of output compared to li-ion because alkaline can't deliver the amperage required by a "bright" light.

It's fine if you don't like them, but I've had a li-ion primary light for 12+ years and the battery is the least likely part of fail (in fact it never has). I've broken switches, globes, bulbs, igniters, and ballasts, but never had the actual battery fail.

 

[Miyaru]

I've been reading along and I'm surprised by some statements. Like lights that will run 1.5 hours on batteries. Seriously?

I'm using these:

LED, 1000 lumen, takes 3x C or 2x 18650 or 2x 26650. The rechargeable C batteries in the picture were from the local supermarket, €2,99 for two (NiMH 1.2V 4000mAh). There's a video version as well (the head on the right), useless for signaling in a cave but perfect for lighting up a section for pictures or video. No switch, rotate to turn on. 3 o-rings seal the head and battery compartment. Price used to be and still is around €30.

With the three batteries the burn time is 8 hours. These lights and batteries are now over 3 years old, have taken a beating, have been to 90m, and I never ever had a failure or flood. During OW courses, I give each student one of these so they stop sculling. They're quite good at abusing them, like pushing themselves off the rocks with the light or occasionally dropping them.

Main light or backup light, no difference. When cave diving, each battery is charged before the dive. For other dives, I just use them until they start going dim. It doesn't have to be expensive to be good and reliable.

 

[tbone1004]

My point was, for me, alkaline batteries are more effective solution over an rechargable unit. Personaly I have found that they are somewhat lighter, readily available, and proven on some models of coms/lights to last longer.

it sounds like you are lumping all rechargeable batteries in the same category. If you are using AA's and rechargeables interchangeably, then you are likely using NiMH chemistry which does have less energy density than alkaline.
In terms of cost effectiveness, it still doesn't work as 4x Eneloops with a charger are $18 and after 17 sets of AA's they become more cost effective. The alkalines do last longer though, and in things like Comm units that can be beneficial, especially if they give you battery readouts in the head set. I deal with this by charging everything prior to doing pre-dive checks, so I don't have to worry about it as I am trying to be more eco-conscious and alkaline batteries are pretty nasty for the environment.
This thread though is about the use of lithium chemistries in backup lights, and for that the lights are significantly smaller and brighter than their alkaline counterparts.

@Miyaru if that light burns for 8 hours it is NOWHERE near 1000 lumen. Those C-cells at best are 6wh with only about 5 usable. 15wh total over 8 hours is call it 2w consumption. LED's at their absolute best are around 150 lumens/watt, so over those 8 hours it is putting out an average of around 300 lumen. A far cry from 1000. The 1000 lumen is what the LED is capable of, but that is not what it is actually putting out. Common issue with false advertising in the light industry and there are very few manufacturers out there that actually tell you the true lumen output of the lights which is usually around half of what is claimed.

 

[Miyaru]

@Miyaru if that light burns for 8 hours it is NOWHERE near 1000 lumen. Those C-cells at best are 6wh with only about 5 usable. 15wh total over 8 hours is call it 2w consumption. LED's at their absolute best are around 150 lumens/watt, so over those 8 hours it is putting out an average of around 300 lumen. A far cry from 1000. The 1000 lumen is what the LED is capable of, but that is not what it is actually putting out. Common issue with false advertising in the light industry and there are very few manufacturers out there that actually tell you the true lumen output of the lights which is usually around half of what is claimed.

That could be correct. I never counted the lumens. But if I can still signal to a diver 40m in front of me, 2 hours into a dive, I'd say it functions fine.

 

[tbone1004]

That could be correct. I never counted the lumens. But if I can still signal to a diver 40m in front of me, 2 hours into a dive, I'd say it functions fine.

it does, but when you compare it to a light that is actually 1000 lumen, you'll be blown away. Most of claims of the backup lights are pretty funny when you do the math since what they claim defies the technology that is inside of them, but that's fine so long as you are an informed consumer