3 general battery questions

I have 3 questions about batteries. I've learned a lot recently, but these few points still elude me. They're not complicated things (I assume), they're just some minor points that I haven't been able to clear up from general reading.

So, here goes...

1. Lithium primaries, CR123As, or Energizer AA/AAA.
These are known to have a long shelf life, 10 years or more. If you buy one and don't use it, then it will still be usable for a long time. My question is this. What happens if you use it a little, then either take it out of a light, or leave it in but not used, does it then start to self discharge a lot faster, like weeks or months, because it has been started, or does it still have the same shelf life for the remaining charge? A little like long life foods for example, the jar might have a 5 year shelf life, but "consume within 3 days once opened". Does that happen with lithium primaries?


2. AA/AAA Nimh rechargeable batteries.
Alkaline and lithium AA and AAA primaries are 1.5v, Nimh rechargables are 1.2v. Why are the Nimh lower?


3. I have seen some posts recently asking about the effect of magnets on lights. My question relates just to batteries. If batteries are stored in a pouch with a magnetic closure, so the batteries are stored long term with just a thin layer of material between them and a magnet, does that have a negative effect?


Thank you.

1. A slightly used lithium primary cell shouldn't self discharge much faster than a completely unused lithium primary cell.

2. NiMH cells have a lower voltage because of the different anode and cathode materials. Lithium "1.5V" primary cells actually have a higher voltage than alkaline cells, but not so much higher that it generally causes problems.

3. There won't be any negative effect on batteries if they are stored in close proximity to a magnet.

hope these answers help.

Some of the Lithium primaries I've bought, tested at 1.78 Volts unloaded. Although I've not had any problems, I'm somewhat hesitant to use them in ultra-sensitive electronics, especially in Series.

MorePower said:

...hope these answers help...

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They certainly do, thank you

BVH said:

Some of the Lithium primaries I've bought, tested at 1.78 Volts unloaded

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As well as testing the voltage for primaries, is it also possible to test the remaining capacity, or is that only possible for rechargables? If so, can you recommend a tester?

I don't have one but many here have the ZTS tester which is supposed to actually measure remaining capacity.

My Energizer Lithium Primaries - L91 tests at 1.815 volts unloaded.

Niconical said:

As well as testing the voltage for primaries, is it also possible to test the remaining capacity, or is that only possible for rechargables? If so, can you recommend a tester?

Click to expand...

The only commonly available cells where open circuit voltage gives a good indication of remaining capacity are lithium ion cells. OCV for primary lithium cells, alkaline cells, or NiMH cells is not indicative of state of charge. The ZTS tester mentioned by BVH will give you a ballpark idea of remaining capacity for primary cells.

MorePower said:

The only commonly available cells where open circuit voltage gives a good indication of remaining capacity are lithium ion cells.

Click to expand...

Actually, that's not quite true. The open circuit voltage of a rested alkaline cell is almost directly proportional to the remaining charge. It ranges from 1.6 V when fresh to about 0.9 V when no longer very useful. (There is still charge remaining at 0.9 V but not many devices are able to extract it. I took one out of a stopped clock this week and found it reading 0.89 V.)

Voltage is a decent determining factor for alkaline and NiMH, but not lithium.


Rated voltages are funny though.

Alkalines start out around 1.5v, but under load their voltage is quite low. NiMH start out about 1.4v (not 1.2v), and keep a higher voltage under load than alkalines. At 1.2v, a NiMH cells is getting pretty close to being dead.

Mr Happy said:

Actually, that's not quite true. The open circuit voltage of a rested alkaline cell is almost directly proportional to the remaining charge. It ranges from 1.6 V when fresh to about 0.9 V when no longer very useful. (There is still charge remaining at 0.9 V but not many devices are able to extract it. I took one out of a stopped clock this week and found it reading 0.89 V.)

Click to expand...

If the OCV of a rested alkaline cell is 0.9V, then yes, it is pretty much dead. However, there isn't a good way to correlate other than 1.6V is good and 0.9V is dead. How about 1.55V OCV? Is that 90% capacity remaining? 80%? 40% left? You can't tell.

After a day of rest, the OCV of a 50% discharged alkaline AA may bounce back to well over 1.5V, or, depending on the zinc alloy, EMD potential, free electrolyte, anode surfactants, etc, it may read 1.4V.

MorePower said:

If the OCV of a rested alkaline cell is 0.9V, then yes, it is pretty much dead. However, there isn't a good way to correlate other than 1.6V is good and 0.9V is dead. How about 1.55V OCV? Is that 90% capacity remaining? 80%? 40% left? You can't tell.

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Well I'm afraid we will have to agree to disagree on this one.

I have measured the voltage of alkaline AA cells in low drain devices like my cordless mouse, and if I plot voltage against weeks of use since installed, it makes almost a straight line.

I find typical alkalines are pretty much depleted between 1.0 and 1.1v unless it is a low drain device less. You can measure right after using on alkalines to get an idea of capacity for that device by the voltage sag..... but if the current drain is high on the device you will have more trouble figuring out how to measure it and may have to let the battery recover before voltage measurement. If you ever use heavy duty or unknown battery types that are not alkaline these can be weird and measure full with nothing left to them when put under a load. I had some cells that came with an RCA remote that measured 1.5v and the remote wouldn't work I put in new alkalines it worked.. put the betteries in a low power LED flashlight it it wouldn't come on... put it on a meter that uses a resistance load and they were dead.. no load.... 1.5v... lol

Also I've got something to add here and pls correct me if I'm wrong. While Alkaline batts are rated at 1.5 Volts they stay that way, actually to be honest an Alkaline isnt really exactly 1.5V but lets say 1.49 etc, 1.5 is just a rounded off figure the manufactures use. Now with NiMH they can actually peak their voltage so instead of being 1.2 they could go up to 1.4V or close to. NiMH can hold their charge/stamina better than Alaklines. This means the Alkaline (though rated at a higher voltage) will drain quicker than what a NiMH will for eg a Sanyo Eneloop. NimH can be charged up fully and ready for the next round. I've also noticed when I charge my Eneloops in my Maha and measure the voltage afterwards with my DM I get around 1.42volts, thought the reading is not the same all the time, as it can vary.

Albinoni said:

Also I've got something to add here and pls correct me if I'm wrong. While Alkaline batts are rated at 1.5 Volts they stay that way, actually to be honest an Alkaline isnt really exactly 1.5V but lets say 1.49 etc, 1.5 is just a rounded off figure the manufactures use. Now with NiMH they can actually peak their voltage so instead of being 1.2 they could go up to 1.4V or close to. NiMH can hold their charge/stamina better than Alaklines. This means the Alkaline (though rated at a higher voltage) will drain quicker than what a NiMH will for eg a Sanyo Eneloop. NimH can be charged up fully and ready for the next round. I've also noticed when I charge my Eneloops in my Maha and measure the voltage afterwards with my DM I get around 1.42volts, thought the reading is not the same all the time, as it can vary.

Click to expand...

But as soon as you put load on alkalines, their voltage will quickly sag BELOW that of NiMH

Niconical said:

I
1. Lithium primaries, CR123As, or Energizer AA/AAA.
These are known to have a long shelf life, 10 years or more. If you buy one and don't use it, then it will still be usable for a long time. My question is this. What happens if you use it a little, then either take it out of a light, or leave it in but not used, does it then start to self discharge a lot faster, like weeks or months, because it has been started, or does it still have the same shelf life for the remaining charge? A little like long life foods for example, the jar might have a 5 year shelf life, but "consume within 3 days once opened". Does that happen with lithium primaries?

Click to expand...

Here's my current understanding of why the shelf life of lithium primaries is so long. This is definitely open to correction if I goof it up.

When left to rest the cells form a passivation layer. This basically means that the chemical reactions that happen inside a resting cell are mostly stopped. Then, the next time you start pulling amperage from the cell it will be depassivated so the juice can get to your device.

In a low drain device like a remote control where small loads are repeatedly demanded from the cell, the passivation layer can be weakened. This causes the lithium to corrode faster meaning greatly decreased capacity in the cells.

In the situation you talked about I think a lithium battery will still give you close to the expected lifespan.

#1 , i tested some lithium AA primaries in a device, then pulled them while they still acted brand new. then the pack of 4 has just parked for months on end.
the "used" one still reads about the same voltage (which doesnt mean a lot) as it did 1.78 and the new ones are still reading 1.8+ . i wont know till i fully discharge them, but using it up for a bit , doesnt seem to have started any cold fusion from sitting there afterwards.

#2) look at the GRAPHS for how an alkaline and a ni-mhy discharge under loads, i think that the ni-mhy voltage is a good balance for a replacement for alklaine, most devices will work great with it, Some dont :-(.
the graphs on thier discharge will give you the best visual perception as to what the batteries act like when used.

https://www.candlepowerforums.com/threads/79302
https://www.candlepowerforums.com/threads/64660

when it comes to some devices, the ni-mhy and its instant high ouput power stomp all over alaklines so badly, that you will use Ni-mhy just because alaklines suck, not just for the reusable money and enviroment savings. like a camera flash for example. anything that uses lots of power at any one time, ni-mhys are the choice of "experts" just because of how potent they are under load.

#3) i havent yet seen a magnet effect a battery by magnatising its case, or pulling things in the battery around, i would bet you could get some huge electromagnet out and do something crasy with it, that changes stuff, but i doubt that consumer magnets would mess with any battery significant enough to care.

This is easier to see:





1,14 is the mid voltage for Varta Alkaline
1,25 is the mid voltage for Maha Imedion

After 0:34:00 the voltage was down to 1,2 Volt for Varta Alkaline
After 3:14:10 the voltage was down to 1,2 Volt for Maha Imedion

The tested capacity was 1.04 Ah for Varta Alkaline and 1,97 Ah for Maha Imedion, the load was 0,5A for both.

Anders