Q. Do AA alkalines ‘recover’ from use if left dormant for a short while?
I’ve been testing the light output from an 8-LED headtorch (PrincetonTec Corona), setting it up 2m from a lux meter which I periodically check for a reading. I’m not much interested in the absolute output from the lamp, I just wanted to study its relative output over time.
The lamp runs off 3xAA and I’ve used new Energizer Max batteries.
So I got a consistent output of 83 lux for 12 hours, and then over the next two hours the light output declined to 19 lux. Happy with that, I turned the lamp off as I’d be away for a couple of days. When I got back I switched it on again to finish off the remaining power.
So I switched it back on and immediately got a reading of 84 lux which over the next 3 hours declined to 58 lux. An additional hour took it down to 15 lux.
Very satisfied by the longevity of light output, but a little mystified by the apparent ‘recovery’ of the batteries and their ability to give good usable light for a further few hours.
As it happens I left the light off for another two days and then, out of sheer curiosity, switched it back on again… at 78 lux! This declined to 11 lux over 4 hours. But still a period of very usable light (I went into the woods at night collecting some logs).
So, is this ‘recovery’ of alkalines a common feature of this type of battery? I’m somewhat astonished, but very happy, that I can ‘drain’ a set of AA’s, set them aside a short while, and still be able to use them again with some very usable hours of life left in them.
If you have a multimeter, could you get a reading on each cell? Try swapping the first and last cells of the series if the voltages are drastically different, a serial multi-cell setup will involve some weird zombifying of cells, where one end drains faster than the other as it bears the brunt of the current.
I remember back in the day of 2AA lights being popular that a few users noticed difference in voltage between the first and last cell.. how this makes any sense is slightly beyond me.
Assuming OP has a mechanical clicky light, the open circuit won’t allow the voltages to balance, though, so I’m still mystified.
I’m just testing it by taking an hourly reading. Nothing fancy, but every hour is consistent enough to allow some sort of graph to be drawn, I imagine. Mega accuracy isn’t important (at least to me), it’s the relative decline in out put over time. In fact I’m very happy with the output duration, I’m just a bit stumped (though pleasntly surprised) by the batteries apparent recovery and ‘ready to go again’ behavior!
Nope, it’s a click for every mode…and one of the hardest switches to operate I’ve ever come across! But I forgive it due to the amazingly long output of useful light. (this is a floody headlamp and nothing else, it has no pretences to be a darkness busting flashlight.)
The reported duration of the improved brightness is what puzzles me. In my own messing around with dead alkaleaks, the voltage will bounce back over time but any sort of load immediately drops it again.
Perhaps one cell is dead and being reverse charged by the others? Either way, seems like a recipe for leaks to me. If I were OP and desperate to keep it, I’d recycle/bin the cells before they leak and damage the light, and get some Low Self Discharge NiMh (IKEA Ladda have good price: performance ratio).
Skim read of some info on the web, seems like this light does 35lm on high for an hour then gradually tails off. The flat discharge curve of the NiMh cells might help with the regulation.
OP: I assume you’re aware there are better efficiency lights available nowadays? For example, the convoy T4 does 100lm for 3 3/4 hours on 2 NiMh AA cells according to this review
Yes, the duration of the ‘recovery’ brightness is surprising… but I’ll take it!
I’m definitely keeping this light, it’s incomparable. In fact I’ll buy another if I can find it.
No sign whatsoever of leakage on alkalines. I’ve tested it with Eneloop Pros, too, and it runs very nicely with decent duration. But they don’t self-recover like the alkalines.
More to the point, this is use for use in remote locations where there is no mains power for recharging - hence the greater facility of alkalines for my usage situation.
And hence why the convoy T4 is a non-starter… aside from the fact that it’s not a headlamp
I have found similar behavior in testing I have done as well. I imagine with 3 cells the effect is tripled, as each cell will bounce back.
Re: alkaline batteries leaking, I have seen plenty of leaks, and I have 3 Duracell D cells in a maglite for 20ish years that haven’t leaked. I check the light every few months to see the cells are still fine. More than 10 years ago I bought replacement D cells that are now expired and also not leaking.
But if you want no hassle for sure not leaking (and better performance in general) AA cells get lithium primaries.
Yes. I have a 3D Mag in my trunk. For over 15 years. I have had a single D cell of the set just mysteriously die on me. But, I have never seen a D cell leak. AAs OTH. leak all of the time. I had a 16 pack of Eveready AAs in the pack unopened and unused. I checked them at one point and they all were leaking. Which I why I try not to use AA Alkaline cells in anything that I depend on. I go with AA lithium, or NiMH cells. The solution to being away from where I can recharge is solved by keeping an extra set or two where I can get to them easily. Of course Alkaline cells can be there for backup, but I just hate to leave them in any device that I depend on.
As to the rebound effect, I am surprised that they come back for as long as what you are seeing. Like others have said, when I have seen a rebound it has been very short lived.
Do whatever works for you, but there are more efficient lights out there nowadays which means fewer cell changes required in your wilderness situation.
If anyone’s interested: I found an ancient thread (2006) on the other forum with a user measuring ~4.8lm at a 20ma drive current, efficacy calculated to 70lm/w. This correlates with the listed max output of of light of 35lm if all 8 LEDs are on.
The alkaline rebound effect is normally greater at higher draw currents; on high this light draws assuming 10% driver losses) c.528mW which 3 AA alkalines should be more than capable of, and likely show higher capacity than NiMh cells at this current. Per cell this is a draw of 129ma.
I’m not sure where you are in the world but aside from winter in the far north, a moderate sized solar panel would easily keep up with your usage, if you wanted to go the rechargeable route. Note that draining empty NiMh cells below 1v will shorten their lifespan considerably though.
For giggles I had a look at modern headlamps as I do have a fondness for low brightness, long-runtime lights; the ZL H54c claims 57lm for 6.5hours on a single AA, Even if we half the claims to 3.25hours, that’s 9.75 hours of 57lm for 3xAA!
“a moderate sized solar panel would easily keep up with your usage”
Not in a cave, unfortunately!
The Zebralight sounds good, no doubt. I have tested the Corona several times (in my rudimentary shed laboratory!) I’ve picked a switch setting of 5 LED’s + low power button, which gives a perfectly adequate amount of light for underground navigation. The results are 25 hours of a seemingly regulated 54 lux, then a further 10 hours declining to 25 lux (still adequate light). The lamp was then switched off over my bedtime (!) but restarted the next morning at 54 lux again, but declining to 12 lux over 5 hours. All told, that’s 40 hours of adequate, usable light (provided the batteries have a bedtime break!)
Given that I may be underground for over 72 hours at a time, you can probably see the value of the Corona. (I will add that my helmet also holds a powerful 18650 driven Olight baton for ‘spotting’ - and a backup/emergency headlamp is always carried, too.)
I think the Corona is great. But the AA alkaline rebound is the unexplained jewel in the crown, here!
