Using rechargeable batteries in a backup light?

[rjack321]

I change my (alkaline) backup light batteries annually in December or if I end up using the light for any significant time (more than a few minutes of checking). The reasoning is 2 fold:
1) alkaline batteries have the most reliable discharge curve of anything out there. If my 3 cell alkaline backup says 4.61V on the volt meter I am pretty sure its new and full. The only thing taking out that light is a flood.
2) they are cheap and I am not tempted to stretch out a marginal battery/light. Makes me feel good 5,000ft back in a cave when I don't have that silly monkey on my shoulder asking when was the last time I recharged some other type that may or may not have that linear of a discharge curve in the first place.

 

[Doc Harry]

In this day and age, when you can buy a "smart charger," I prefer to use rechargeable batteries in all of my lights.

I think the logic behind GUE's policy is backwards. Here's why:

With a "smart charger" I DEFINITIVELY KNOW the status of all of my rechargeable batteries. I know which ones are getting old and weak, and which ones are fresh and powerful. I know how long each battery will last. I know which batteries get put in my camera and which can go in my backup lights.

When I buy a disposable battery, I know NOTHING about it. Zilch. Nada. Zero.

Which battery would YOU want in your backup lights?

 

[Lorenzoid]

When I buy a disposable battery, I know NOTHING about it. Zero.

It seems to me that if an alkaline battery has the initial voltage it's supposed to have (i.e., it really is a fresh battery), then you don't need to know any more to be confident it will perform as expected. Has anyone ever bought a fresh alkaline battery, put it in a light, tested it, and the battery nonetheless turned out to be defective?

 

[Doc Harry]

It seems to me that if an alkaline battery has the initial voltage it's supposed to have (i.e., it really is a fresh battery), then you don't need to know any more to be confident it will perform as expected. Has anyone ever bought a fresh alkaline battery, put it in a light, tested it, and the battery nonetheless turned out to be defective?

I have purchased brand-new alkaline batteries that didn't work right out of the package. Not the answer you are looking for.

For my backup lights, I prefer to KNOW what my batteries can and will do, instead of depending on faith that the batteries will behave as expected per the manufacturer's promises.

 

[Lorenzoid]

I have purchased brand-new alkaline batteries that didn't work right out of the package.

Read what I wrote again. I said right out of the package and then tested, either by turning the light on and seeing that it's as bright as it normally is, or even more preferably, by testing the voltage. If I do that, I think it's hugely unlikely that the battery will subsequently suffer some other mode of failure.

 

[fmerkel]

I hate alka-leaks.......period. I've had way too much stuff destroyed by them, mostly while they are just sitting, which is exactly what they do in a backup light.

I think this is a "trust but verify" situation. If you "trust" that a fresh package of tested alkaline is going to be good > go for you. If you are more hands-on, and need to verify that stuff for yourself, get some good batteries and a good analyzing charger. Near as I can tell most people barely have a clue about rechargeable batteries.

People should know that VOLTAGE MEASUREMENT TO DETERMINE CAPACITY FOR RECHARGEABLE NiMh IS VERY VERY POOR. Do not rely on voltage to validate capacity for that chemistry.

You can get a rough idea of what you have via voltage measurement with alkaline and Li-On batteries if you know how to interpret the voltage discharge curve.

 

[PfcAJ]

I have purchased brand-new alkaline batteries that didn't work right out of the package. Not the answer you are looking for.

For my backup lights, I prefer to KNOW what my batteries can and will do, instead of depending on faith that the batteries will behave as expected per the manufacturer's promises.

I've found lithium and nickel packs far less reliable than quality alkalines.

I can assure you that double canister light battery failures resulting in exiting on a scout light from 5k+ at 170' is less than enjoyable.

 

[fmerkel]

I've found lithium and nickel packs far less reliable than quality alkalines.

There are quality Li-on and NiMh LONG SLOW DISCHARGE, and there is a LOT of junk. If you don't have the knowledge or the means to evaluate those then you are going to have a poor experience with them. NiCads can be fine (if low capacity) batteries but frankly most of them are junk. Same with NiMh. Old style NiXX have an unfortunate high discharge rate and are poor candidates for anything that sits (TV remotes, backup lights, etc.) Modern LSD NiMh are fine as they will retain ~ 75% of their capacity in a year even with no use.

There is a HUGE amount of ABSOLUTE CRAP being sold in the rechargeable lithium ion category. You absolutely cannot believe some of 'claims' of superior power/capacity. If a Li-on 18650 is being touted to have over 3400mA I can pretty much guarantee it is complete junk. Anything called Ultrafire is complete junk. Much of what is sold on eBay and even Amazon from 3rd party vendors should be looked at with a suspicious eye. In this realm it really pays to know what and who you are dealing with. The uninformed with be taken advantage of.

If you buy good rechargeable batteries, know how to use them, test them, and verify capacity, they are a fine option to use in most (not all) battery applications.

 

[Lorenzoid]

You can get a rough idea of what you have via voltage measurement with alkaline and Li-On batteries if you know how to interpret the voltage discharge curve.

Could you elaborate on this? Are you saying that the alkaline discharge curve is not reliable? That is, it can vary, and therefore in some instance the battery might not last as long as one would expect based on the initial voltage? In my previous couple of posts I posited that the way an alkaline discharges from whatever initial voltage is pretty reliable. Am I wrong? Just trying to learn here, as I too have been advised alkaline is a good choice for backup lights.

 

[KeithG]

Could you elaborate on this? Are you saying that the alkaline discharge curve is not reliable? That is, it can vary, and therefore in some instance the battery might not last as long as one would expect based on the initial voltage? In my previous couple of posts I posited that the way an alkaline discharges from whatever initial voltage is pretty reliable. Am I wrong? Just trying to learn here, as I too have been advised alkaline is a good choice for backup lights.

i believe the voltage curve is reliable. the means most people use to determine the voltage is incorrect. you can not simply measure the open circuit voltage with a voltmeter. you need to measure the closed circuit voltage when the battery is under load.
http://data.energizer.com/PDFs/alkaline_appman.pdf#page12