I have several devices (two way radios, a gps, a graphing calculator, and a camera) that burn thru batteries and quit when they discharge below 1.4 volts. Hence they don't use rechargeables like enloops, at least not for long. So I end up with piles of alkaline batteries with quite a bit of charge. And a lot of rechargeables with no use.

Suggestions? There is only so many flashlights I can use at one time the DO take the weaker batteries. Is there some sort of " Joule Thief "
for AA's that would fit in devices?

Hi,
Really 1.4 volts?
I always wondered why the dollar stores didn't have 1xAA or 1xAAA flashlights
...
did a bit of searching and I see compact joule thief isn't too hard to build



and that you can just get one from solar garden light



so no reason the cheapest flashlights couldn't have one of these
4 legged integrated circuits joule thieves
...
I also figure one ought to exist already that clips onto a battery
and it almost does , the Batteriser
naturally lots of smoke and mirrors and no actual product yet

A lot of older gear was designed for 1.5V alkalines and doesn't get along with 1.2V rechargeables. Expensive and wasteful to say the least.

External Pack:
Sometimes equipment has an external power jack (for wall warts) that will accept a higher voltage.

If you can wire up an external battery pack made of rechargeables with roughly the right voltage, you can save a bundle. You can always add a small value 1-watt resistor (cheap) if you need to drop the voltage a little.

Reuse:
The problem with reusing alkalines is leakage: as the voltage declines, the likelihood of leakage goes way up. Especially when they sit.

The simplest reuse option I've found is to "digest" them using cheap battery holders off eBay and use the old alkalines in LED lanterns or old big-body flashlights with those 6V square batteries.

You can get holders for any number of AA cells. If you can match the voltages of the used alkalines fairly closely, you'll get less leakage. And if it does leak, it's not in something you care deeply about.

Where it is most troublesome is things that require 4 batteries or more. Rechargeables lose 1.2 voltes off the bat in a 4 cell device.

Since lithium cells usually have over 1.5 volts, could I slip one lithium in with 3 lower voltage cells somewhat safely? Or would this just be asking for leaks, fire, loss of hair and looks of disdain by my neighbors?

No, please do not ever mix cells of different chemistry and voltage. This turns the battery compartment into a toaster, chemical goo experiment, and/or micro-Chernobyl. It will not end well.

What rechargeables are you using? And what charger? It's really odd that so many pieces of gear are not happy with them. Maybe the problem lies elsewhere -- like a faulty charger.

I think it might be safer to jump into a swimming pool carrying a plugged in toaster.

Throw away the partially discharged alkalines (dispose of them properly). Use the rechargeables in other devices that work properly with them. Get rid of the gear you have that only partially utilizes batteries and doesn't work with rechargeables - it is poorly designed and not worth the hassle and waste of keeping around.

Probably good advice - I have switched to rechargeables, mostly Eneloops, from alkalines, and me and my wallet are glad we did. I find that lith-ions are even better for many applications. My 18650 headlamp is the best illumination I have ever used.

Which headlamp is that? I have enough 18650 flashlights that an 18650 headlamp is probably a good idea. I see that both ThruNite and NiteCore have 18650 headlamps on Amazon. I kinda like the versatility of the ThruNite® TH10 especially in neutral white.

FWIW, one of the primary drivers for my switching to Eneloop AA's was my Garmin GPSMAP 60CSx which couldn't use lithium primaries. I don't use that enough to justify wasting alkalines; the charge in a set of Eneloops is more than enough. I also like that Eneloops don't leak when they're dead. Just drop them in the charger...