Backup light batteries

[Web Monkey]

NiMH batteries are better than they were, but unless you have a source for a really good charger, most are c*** and will overheat and ruin your batteries if you constantly "top them off".

Also, opening and closing your light to recharge before every dive (or even once a week) is certainly going to give you a better chance for an o-ring failure than if you carefully cleaned the light, put in a nice new o-ring, a set of first-class alkalines and closed it up for the year.

Terry

 

[OneBrightGator]

The point is that every time you open and close a light you run a risk of flooding it when it goes in the water. If I'm going to open it and check the voltage for every dive, I'd start giving thought to NIMH. What I really want is a backup light that shows me that the voltage is good with an LED when I flip it on so that I don't have to open it to check the batteries. I's a rather simple circuit (you can buy a 12 volt one for your car for ten bucks).

Yeah, an internal indicator would be nice and I personally don't see the benefit of checking the voltage every dive if you use good battery replacement practices. I'm not saying there's anything wrong with the current methods, just wondering if there isn't something better.

 

[OneBrightGator]

NiMH batteries are better than they were, but unless you have a source for a really good charger, most are c*** and will overheat and ruin your batteries if you constantly "top them off".

Also, opening and closing your light to recharge before every dive (or even once a week) is certainly going to give you a better chance for an o-ring failure than if you carefully cleaned the light, put in a nice new o-ring, a set of first-class alkalines and closed it up for the year.

Yeah, crappy batteries and chargers are going to be an issue, a couple good burntests are going to be required, for sure.

I'm not sure doing leaving them closed up for a year is good practice either. For one, I don't think unscrewing them all the way is going to hurt anymore then when you check their operation. You don't inspect the inside of your backup lights before and after dives? I've had mine work after being flooded, so I would hate to get some minor intrusion that ended up sitting in there and ruining the light, especially if it worked before the dive and something happened during the dive to ruin it.

 

[Web Monkey]

check their operation. You don't inspect the inside of your backup lights before and after dives? I've had mine work after being flooded, so I would hate to get some minor intrusion that ended up sitting in there and ruining the light, especially if it worked before the dive and something happened during the dive to ruin it.

Actually, I don't open it unless it's time to change the batteries. If you look at computer failures, a huge percentage of the time, the owner will say "But I just changed the batteries."

My backup is an 8 cell LED light, so an hour or so of use is pretty insignificant compared to the useful battery life. If it works before the dive, chances are excellent it will still work if I need it. There really isn't much that's going to happen in the next hour under water that hasn't already happened in the past week on the surface.

This may come back to bite me some day, but I'm a firm believer in "If you mess with something long enough, it will break."

Terry

 

[Thalassamania]

Here's a circuit designed to tell you when a 9v battery drops to 7.2 volts. I think it could be rather easily modified to turn on the LED whenever the voltage drops below a designated set point. Make the mods, install it in the light and then all you have to do is see if the LED is on, if it is not the light is good to go.

 

[Doc Harry]

I can understand your logic, but is it really a fair comparison? High drain devices such as digital cameras and flashes compared to a low drain device such as a LED backup light? I imagine that NiMH is the most widely used cannister light battery right now. Perhaps Li-Ion batteries would be even better in backup lights?

To clarify my point, I fully charge my NiMH batteries, place them in the camera, and immediately get the error message REPLACE THE BATTERIES whereupon the camera goes completely dead. Imagine if that happened when I turned on my backup light...

I don't leave alkaline batteries in my light for very long. They're cheap, so even if I don't use my backup light I retire the batteries to other non-diving uses and buy new alkaline batteries for the backup light. There are always fresh alkaline batteries in my backup llights.

 

[OneBrightGator]

Actually, I don't open it unless it's time to change the batteries. If you look at computer failures, a huge percentage of the time, the owner will say "But I just changed the batteries."

True, but computer battery compartments weren't made to twist on and off every dive, backup lights are or should be. Not apples to apples for me.

 

[OneBrightGator]

To clarify my point, I fully charge my NiMH batteries, place them in the camera, and immediately get the error message REPLACE THE BATTERIES whereupon the camera goes completely dead. Imagine if that happened when I turned on my backup light...

I don't leave alkaline batteries in my light for very long. They're cheap, so even if I don't use my backup light I retire the batteries to other non-diving uses and buy new alkaline batteries for the backup light. There are always fresh alkaline batteries in my backup llights.

Me thinks your batteries are toast, regardless of material. No device could drain batteries that fast.

They are cheap, but like I said, I'm not trying to save $5. What if you buy a 6-pack of C's and they were from a bad batch? Is that really better then a freshly charged set that you've had multiple "full burn" dives on?

 

[Aquamaniac]

If its not a cost saving exercise, then exactly what issue are you trying to resolve?

Alkaline: Are they working? Yes, go diving
NiMh: Are they working?, did I charge them?, did I even bring the charger?, did the oring seal OK after I put them back in last night? Is the charger working OK?

Why complicate a solution that has no issue?

 

[Doc Harry]

Me thinks your batteries are toast, regardless of material. No device could drain batteries that fast.

That's my point. NiMH batteries are unreliable. I had fully-charged NiMH batteries showing full voltage. You'd think they would be fine. But then - BAM! - in a matter of a minute they're dead. How can you predict which fully-charged, full-votlage NiMH batteries will last and which will die in a matter or minutes? You can't. That's my point.

Not the kind of performance and reliability you'd want in a critical piece of equipment like a backup light.