Backup light batteries

[OneBrightGator]

I posted something similar a while back on another forum, and since it recently came up in another thread, I thought I'd give SB a crack at it as I still haven't made my decision (not enough diving!).

I am considering switching to rechargeable batteries in my backups (Salvo Rats). I feel that the original reasoning of crappy rechargeables to justify disposables is no longer valid and the rechargeables available now are reliable. The initial idea is to use NiMH batteries and pop them on the charger before the dive, just like I do with my primary light packs.

If I do go rechargeable, I am toying with the idea of turning the lights on and leaving them on the entire dive. I have heard of quite a few failures resulting from turning the light on underwater, so if the lights stayed on the whole dive, these problems would be eliminated.

Please discuss, thanks.

 

[OneBrightGator]

NiCads and NiMH batteries tend to lose some percentage of their charge every day (there are some new NiMHs that don't) but the purpose of your back-up light(s) is/are to be there when needed. Using rechargeable batteries in your back-up isn't a good idea since they may work when you test them and die shortly afterward. And as already pointed out, when they die, they fast rather than gradually. Additionally, most back-ups like the Scout are driving a 6vdc bulb with 4.5vdc (under-driven) to increase the filament's reliability. Using rechargeable batteries would further drop the voltage to 3.6vdc.

If you top them off before a dive, they are no different then your primary light batteries though and if you have put them through a few burntests before putting them to use you should know exactly how long they are good for. I understand that every charge is going to be slightly different, but so is every alkaline battery.

 

[nadwidny]

If I do go rechargeable, I am toying with the idea of turning the lights on and leaving them on the entire dive. I have heard of quite a few failures resulting from turning the light on underwater, so if the lights stayed on the whole dive, these problems would be eliminated.

I wouldn't want to be the guy behind you.

 

[Steve R]

I wouldn't want to be the guy behind you.

lol.

yup.

As one brilliant diver once said,..........this is the tech diver equivalent of leaving your fly undone

Name the diver and the place, and you win a prize. (Bonus points for the stating the diver's right or left backup being the one that was caught on film)

 

[Thalassamania]

My advise is to use alkalines and replace them every two years, need it or not or to use NiMH batteries and charge them right up to the moment you're about to go into the water. As to burn testing or leaving them on, switch them on and off and leave it at that ... that's why you carry two backups.

 

[rjack321]

If I do go rechargeable, I am toying with the idea of turning the lights on and leaving them on the entire dive. I have heard of quite a few failures resulting from turning the light on underwater, so if the lights stayed on the whole dive, these problems would be eliminated.

LED or halogen bulb failures? Or do you mean flooding from turning them on?

The whole rechargable biz seems like an awfully convoluted way to avoid cheap alkalines. Just measure your voltage (1.5V per cell) before diving and go for it. Swap them out every couple years into a garage flashlight at home or after using a light. Simple, reliable, no recharging to deal with.

You'd have to have a really unreliable primary light to even start to make back the cost differences from the occasional replacement of alkalines. So what's the benefit of the rechargables?

 

[rainman_02]

Doesn't leaving them on during the dive defeat the purpose of a "backup?" If it's supposed to carry enough burn time to allow you to complete the dive, does it make sense to go on a 4-hr dive with a 4-hr burn time light...and turn it on so that if you're lucky you'll get exactly 4 hours of burn from it?

 

[grazie42]

I wouldn´t turn on the backups until you need them for obvious reasons...

I think the "old reasons" against rechargeables aren´t valid anymore. One of my backups is currently serving as a bicycle-light as well and I´ve been toying with the idea of going rechargeable for it but...regular ones are so cheap that it still doesen´t make sense to go rechargeable...All my backups are LED so that may have something to do with my attitude...

My regular buddy has a LED as a primary that can be used with regular rechargeables and he´s been using it with those for well over a year without any issues so the only con of them is cost/hassle, IMO...

 

[Doc Harry]

I use a lot of rechargeable NiMH batteries in my underwater camera-flash. Yes, the NiMH batteries are an improvement over the older rechargeable batteries. You might say my camera goes through NiMH batteries like **** through a goose.

My experience with NiMH does not inspire me to switch from alkaline to rechargeable NiMH for my backup lights. When I need a backup light I want it to work. I do NOT have that kind of confidence in rechargeable NiMH batteries.

In fact, I have thrown away all of my NiMH batteries. I switched to rechargeable lithium batteries for my camera and alkaline batteries for my flash.

 

[rjack321]

Doesn't leaving them on during the dive defeat the purpose of a "backup?" If it's supposed to carry enough burn time to allow you to complete the dive, does it make sense to go on a 4-hr dive with a 4-hr burn time light...and turn it on so that if you're lucky you'll get exactly 4 hours of burn from it?

On alkalines with LED modules my scouts and photos have a burn time of days. Othewise I agree with you, why waste burntime trying to avoid this apparent propensity to fail when turning on (which I have never noticed)