At what voltage AA battery needs binned? - Page 1
Forum section: electronics / general

author: vinlove
author_rank: Frequent Contributor
timestamp: April 29, 2025, 04:14:27 pm
content: I found a bunch of AA Alkaline batteries in the drawer. Measured the voltages on some of them, and they range from 1.1V - 1.3V.What is the voltage that an AA battery cannot be used, and thrown out?Also the age of the AA batteries - are the old AA batteries need to be thrown out because they could leak? Or are they ok to use?

author: tunk
author_rank: Super Contributor
timestamp: April 29, 2025, 04:21:19 pm
content: Depends on what you will be using them for.I had an mp3 player that worked down to 0.9V.In clocks they can also work for quite some time.Otoh, I have a radio that doesn't like 1.2V.Edit: For discharge curves, EEVblog memberHKJ has tested quite a few cells, e.g.:https://lygte-info.dk/review/batteries2012/Ikea%20AA%20UK.html

author: IanB
author_rank: Super Contributor
timestamp: April 29, 2025, 04:30:13 pm
content: Quote from: vinlove on April 29, 2025, 04:14:27 pmHow to use alkaline batteries:1. Take new batteries out of the packaging, put them in the device, and use them until the device stops working.2. When the device stops working, remove the old batteries and dispose of them--do not keep them in a drawer.3. Always install brand new, fresh batteries from the package. Never install old, previously used batteries.Step 4:If possible, do not use alkaline batteries, because sooner or later one will leak and destroy something. Either use rechargeable batteries like Eneloops, or use lithium batteries (the silver Energizer ones).

author: Kleinstein
author_rank: Super Contributor
timestamp: April 29, 2025, 04:38:12 pm
content: Anything below some 1.4 V is usually not worth keeping. One may keep a few for tests and limited use, but most of the charge would be lost. For the age, there should be a best before date on the batteries. Because of the leakage risk I would be careful when approaching that date - still depends on the use case. For a short time use (or leak resistant device) it could be OK.

author: themadhippy
author_rank: Super Contributor
timestamp: April 29, 2025, 04:58:48 pm
content: Quotenonsense,for years most of my AA battery's were ex radio mic batteries

author: tunk
author_rank: Super Contributor
timestamp: April 29, 2025, 05:02:19 pm
content: Quote from: Kleinstein on April 29, 2025, 04:38:12 pmIf you look at the discharge curves in the link above, and assumea 1.2V cut-off, then you only use around 20% of the capacity.

author: IanB
author_rank: Super Contributor
timestamp: April 29, 2025, 05:27:30 pm
content: Quote from: themadhippy on April 29, 2025, 04:58:48 pmThis has got nothing to do with reusing old batteries that have been lying around in a drawer for who knows how many months or years.

author: bdunham7
author_rank: Super Contributor
timestamp: April 29, 2025, 08:04:41 pm
content: Quote from: tunk on April 29, 2025, 05:02:19 pmThose curves are under a substantial load--100mA minimum. If you are looking at OCV of a cell that has been resting for days or weeks, the numbers are different.

author: Smokey
author_rank: Super Contributor
timestamp: April 29, 2025, 08:14:52 pm
content: Quote from: bdunham7 on April 29, 2025, 08:04:41 pmYa I'm surprised until then, no one had pointed out that you really can't determine the capacity of a battery based on only the unloaded voltage. You need to apply a load and then match that loaded voltage to a curve on the datasheet for that type of battery.If you play this unloaded voltage game, you will eventually come to a battery with like 1.2V on it unloaded, but ANY load drops it to essentially 0V immediately.

author: Gyro
author_rank: Super Contributor
timestamp: April 29, 2025, 08:17:31 pm
content: Quote from: IanB on April 29, 2025, 05:27:30 pmConsidering the number of Durahell and Energizer batteries that leak while still in the packaging, there may be an argument that any that have survived lying in a drawer for months or years are probably good'ns.

author: armandine2
author_rank: Frequent Contributor
timestamp: April 29, 2025, 08:51:52 pm
content: Quote from: Smokey on April 29, 2025, 08:14:52 pm...you may find a few other things too, and have some fun

author: richard.cs
author_rank: Super Contributor
timestamp: May 01, 2025, 01:31:49 pm
content: I tend to measure short circuit current (briefly) with a DMM on the 10A range. New cells are normally 8-10A, part discharged around 5A, and and anything under 2A tends to go straight into the bin, though they'd probably do TV remotes OK.

author: RoGeorge
author_rank: Super Contributor
timestamp: May 01, 2025, 02:09:06 pm
content: As opposed to rechargeable batteries, which have an almost constant voltage of about 1.2V while discharging, an alkaline will gradually go from 1.5V to 1V or even less. The min accepted voltage depends on the device the battery is powering. A 1.3V alkaline should be about half discharged.However, when measured with a casual DMM (so without any load), the 1.3V might not guarantee it means 50%.Best way to decide if an alkaline battery is to keep (or to throw away) would be to test it under some load. In practice, I found a simple incandescent flashlight bulb to be the best tool, like this:https://www.eevblog.com/forum/chat/invention-of-the-day-the-battery-tester-with-zif-socket/

author: vinlove
author_rank: Frequent Contributor
timestamp: May 01, 2025, 09:18:55 pm
content: I used to throw out used AA batteries anything below 1.2V in the past. But when my radio scanner was ran with the new fresh 6x AA batteries, and scanning the VHF band for 3 days, the AA batteries in the scanner ran out making the scanner stop scanning, and the scanner going off. I took out the AA batteries from the scanner, and measured the voltage of all the 6x batteries. Every one of them were 0.92 Volt. They were straight thrown to the recycle bin.

author: Bud
author_rank: Super Contributor
timestamp: May 01, 2025, 11:23:22 pm
content: My Logitech wireless (not bluetooth) mouse goes down to 0.8v .

author: wraper
author_rank: Unknown
timestamp: May 01, 2025, 11:32:46 pm
content: Don't play with questionable alkaline batteries. They'll likely leak and damage the devices. I no longer use them at all because the damage they caused was many times more than it costs to buy high quality rechargeable batteries for every single device that uses AA/AAA batteries.

author: vk6zgo
author_rank: Super Contributor
timestamp: May 01, 2025, 11:34:52 pm
content: Quote from: Smokey on April 29, 2025, 08:14:52 pmExactly! a DMM with its 10Minput impedance is "near as dammit" to infinity, & the cell will quite happily produce a quite good voltage.Even the cheapest & nastiest battery tester will give a better result.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 26, 2025, 08:53:33 pm
content: Voltage does not mean much for alkaline batteries. When it's above 1V5 it's full, and when below 0V9 it's empty but in between a lot of things happen, especially with old or long unused batteries.It's fairly common for old batteries to have a high voltage (1V3), but then the voltage sags quickly when you attempt to use them. A much better indication is when the batteries stop to be able to deliver current (power) to your appliance. Measuring alkaline cells by shorting them with an 1Ohm resistor is good. Current will never be more then 1A5, and when you do this for a handful of seconds, you also get an idea of how quickly the current sags under a load. Note that an AA cell has about 2Ah capacity, so a 10 seconds test @1A is 0.1% loss of energy. Also note that during a high current test, the voltage will always sag because of the internal resistance of the battery. As long as it's still capable to deliver >100mA there is some life left in it. Maybe its not good enough for your fancy electronic gadget, but it may still work appropriately in a flashlight. Especially single cell flashlights have an SMPS that can squeeze the last drop of energy out of a battery. But I do prefer flashlights that slowly decrease their light output when the battery depletes, as this is a built in double function as a battery tester.

author: BadeBhaiya
author_rank: Regular Contributor
timestamp: May 29, 2025, 09:09:58 am
content: As a rule of thumb, 0.7V to 0.8V is quite low.You should only throw them out when the cells in question stop working with the last device in your house.Brand new cells go into your random WiFi doohickey. They stop working at 1.3V. They then go into the wireless doorbell, they stop working at 1V. Then that goes into the TV remote, which works for a long time, but at 0.7V even it stops working. If you have anything that will work with 0.7V cells (unlikely), put them in. If not, throw them away.

author: tooki
author_rank: Super Contributor
timestamp: May 29, 2025, 09:18:47 am
content: Quote from: BadeBhaiya on May 29, 2025, 09:09:58 amI’d say it’s extremely low. Few devices can operate down that low — most give up at 0.9-1V, and of course as you describe, some much higher. But in the low-current devices we tend to use disposable batteries in nowadays (since all the high-current stuff uses rechargeables, mostly lithium), there is very little extra energy to extract below 0.9V. Look at the discharge curve linked to farther up the thread: on the two lowest-current discharge curves, you see a sharp “knee” at 0.9V, meaning that between 0.9V and the 0.7V where the test ended, very little energy was extracted.IMHO, trying to eke out that last tiny bit is NOT worth the increased risk of battery leakage.

author: BadeBhaiya
author_rank: Regular Contributor
timestamp: May 29, 2025, 09:26:22 am
content: Quote from: tooki on May 29, 2025, 09:18:47 amThat is indeed fair. The equipment being powered is likely more important than a tiny bit of energy left in the cells.

author: bdunham7
author_rank: Super Contributor
timestamp: May 29, 2025, 11:58:40 am
content: Quote from: BadeBhaiya on May 29, 2025, 09:09:58 amMy general policy for alkaline cells is that I measure the voltage and then throw them away no matter what the voltage was. I would only use alkaline cells in products that are worth less than the cells themselves and that I don't need for any reason. That way when the cells leak, I can throw away the device as well and clear up some clutter.

author: Freesurfer
author_rank: Regular Contributor
timestamp: May 30, 2025, 11:23:53 am
content: I believe that Dave covered this in one of the episodes about the "Batterizer" and said that the industry standard target cut-off voltage for alkaline cells in a properly designed product, is about 0.8V.But some devices may require more, others can run on less. One thing to consider is that PN junctions need 0.6-0.7V to activate, and you need at least that to bootstrap a DC boost circuit (unless specifically designed for something lower). And depending on the power draw of the device, the cell may dip below that under load. So based on that I would say 0.8V is a reasonable number.However I wouldn't keep batteries that are any less than 1.2-1.3V if I found them laying around.Unlike what others say, I think the unloaded voltage of an alkaline cell is a quite reliable way to get an idea of the capacity of the cell. It has a relatively linear reduction of voltage to capacity, unlike other chemistries that only have a slight voltage drop but increase its ESR (equivalent series resistance) like lead acids, or maintain a steady voltage until a sudden steep drop like NiMHs etc.