# 1.2V vs 1.5V



## MarioJP (Oct 31, 2009)

Ok I am having trouble grasping the voltage differences and wondering if 1.2 volts is a bit to low?

Many times I keep hearing about 1.5 Volt AA is better than 1.2 because of higher operating voltage, but really additional .3 volts really makes a difference??. Can this issue make NiMh obsolete??.

I been reading more about the new nickel zinc cells stating "these cells can replace NiMh due to having a higher operating voltage than NiMh. But it is only by .3 not even half a volt. I want to test these batteries in my mobile charger and see is this makes any difference at all.

That is the part I am having trouble getting over lol.

btw I been away from these forums as i been too busy but I am back!!:rock:Hope I didn't miss out on good info while I was away.


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## Marduke (Oct 31, 2009)

NiMH really aren't 1.2V. They come off the charger around 1.4v, and will maintain above 1.2v until they are nearly exhausted. In contrast, alkaline cells can quickly fall below 1.2v under even a moderate load.


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## Lighthouse one (Oct 31, 2009)

Note also that leds need a good strong current supply..so the higher voltage isn't always the most important factor.


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## MarioJP (Oct 31, 2009)

That is true a fully charged nimh cell is usually around 1.43-1.46V. But as the load is applied the voltage gradually starts to drop and eventually reaching to 1.2V, and once load stops its does not climb up to 1.4 like alkaline do. 

However though this does not matter because that's open circuit voltage.

The real question is what is the true benefit for switching from nimh 1.2v to nizn 1.6V??


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## bcwang (Oct 31, 2009)

Be careful with Ni-zn cells. I've measured them at 1.925v hot off the charger, and they maintain above 1.6v through most of their discharge. If you're using them in series, you'll quickly be putting much more voltage in the device than possibly expected.

I have this bug vac that takes 4 AA cells. With alkaline and nimh it runs at about the same speed. I guess the lower internal resistance of nimh makes up for the lower voltage. However, when I put in ni-zn cells, the thing was like running with turbo boost. I only ran it for 2 seconds and it I thought the vac was going to explode, it was spinning the motor so fast. I smelled something burning in there, so I guess no more ni-zn for the bug vac.


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## MarioJP (Oct 31, 2009)

bcwang said:


> Be careful with Ni-zn cells. I've measured them at 1.925v hot off the charger, and they maintain above 1.6v through most of their discharge. If you're using them in series, you'll quickly be putting much more voltage in the device than possibly expected.
> 
> I have this bug vac that takes 4 AA cells. With alkaline and nimh it runs at about the same speed. I guess the lower internal resistance of nimh makes up for the lower voltage. However, when I put in ni-zn cells, the thing was like running with turbo boost. I only ran it for 2 seconds and it I thought the vac was going to explode, it was spinning the motor so fast. I smelled something burning in there, so I guess no more ni-zn for the bug vac.




Wow really?? that's too high!!. If i put this on my mobile charger this can fry my charger and possibly my blackberry. I can see being a recall for these cells as they don't follow the AA standard. wow the voltage is too high for AA.


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## Swedpat (Oct 31, 2009)

If I understand it right 1,5V alkalines can sometimes provide an initial brightness which is higher than 1,2V NiMh. This is for use with bulbs who don't demand very high current. 
But using high current devices it can be the opposite. For example: when putting NiMh cells in my Maglite 6D with standard crypton bulb the brightness is much lower than initial brightness with alkalines. But using the same cells with a P7 LED the brightness is significantly higher with the NiMh cells. 
I understand the reason is that the P7 draws more current and that the voltage of the alkalines then will drop to lower value than the NiMh cells.

Regards, Patric


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## MarioJP (Oct 31, 2009)

So this does not sound like a big issue at all considering how NiMh voltage is 1.2v??

Actually about the low current bulb using nimh is lower in brightness. In reality you should get the same amount of brightness just like alkaline because a fully charged NiMh is around 1.46 volts. Now since this is a low current draw device, voltage should last longer before it drops to 1.2.

I know this because I am have been testing my 4 Ansmann cells at 500ma draw in my La crosse charger. Now depending of the draw current of these bulbs you should be able to get the same amount of brightness from fully charged cells initially. The bulb will eventually get dimmer and stay there until the cell is nearing its discharge cycle. The amount of time it takes to get there depends on the draw current.


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## TorchBoy (Oct 31, 2009)

*Re: 1.2 V vs 1.5 V*



MarioJP said:


> That is true a fully charged nimh cell is usually around 1.43-1.46V. But as the load is applied the voltage gradually starts to drop and eventually reaching to 1.2V, and once load stops its does not climb up to 1.4 like alkaline do.


And when the cell is loaded again it'll drop straight down again.

Curious_character did a lovely write-up (PDF) comparing NiMH and alkaline. https://www.candlepowerforums.com/threads/173482


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## MarioJP (Oct 31, 2009)

*Re: 1.2 V vs 1.5 V*

Yes I know lol. Which is why it does not matter as there is no load applied. I am just looking at it from the characteristics between the 2.


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## TorchBoy (Oct 31, 2009)

*Re: 1.2 V vs 1.5 V*

But that is a characteristic...


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## MarioJP (Oct 31, 2009)

So the voltage difference shouldn't be a concern at all then right??


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## TorchBoy (Nov 1, 2009)

How well they can deliver the volts at any particular current (load) is more important.


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## Radiophile (Nov 1, 2009)

MarioJP said:


> So the voltage difference shouldn't be a concern at all then right??



It depends on the device. Some older radios I own won't work well with rechargeables because they were made specifically to work with 1.5 volt batteries. A couple examples:

I have an old CB walkie talkie that came with 2 AA dummy cells to use with alkalines, but when using NiCd cells you don't use them - 8 alkalines vs. 10 NiCds. Both about 12 volts in use.

It was/is a fairly common modification to use 4 sub C rechargeable cells in the wonderful Sony ICF2010 shortwave portable rather than 3 D cells that fit the battery compartment. Why? My guess is that somewhere in the radio is a voltage regulator that needs more voltage than 3 rechargeables can provide. Probably a lot of 3v ICs in the radio and with the drop across the regulator rechargeables don't cut it. 4.5 volts from alkalines wasn't a problem, but 3.6v from rechargeables was a problem.


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## MarioJP (Nov 1, 2009)

Radiophile said:


> It depends on the device. Some older radios I own won't work well with rechargeables because they were made specifically to work with 1.5 volt batteries. A couple examples:
> 
> I have an old CB walkie talkie that came with 2 AA dummy cells to use with alkalines, but when using NiCd cells you don't use them - 8 alkalines vs. 10 NiCds. Both about 12 volts in use.
> 
> It was/is a fairly common modification to use 4 sub C rechargeable cells in the wonderful Sony ICF2010 shortwave portable rather than 3 D cells that fit the battery compartment. Why? My guess is that somewhere in the radio is a voltage regulator that needs more voltage than 3 rechargeables can provide. Probably a lot of 3v ICs in the radio and with the drop across the regulator rechargeables don't cut it. 4.5 volts from alkalines wasn't a problem, but 3.6v from rechargeables was a problem.



What about today?. Does this problem continues on or have devices gotten better that can work with rechargeables. Since alkalines are not really suited for high drain devices, my question is wouldn't the battery's voltage just plummet if devices requires 1.5 volts but the drain is high??.

Isn't that's the whole point of nimh "low voltage but high output currents makes up for it"


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## TorchBoy (Nov 1, 2009)

Radiophile said:


> I have an old CB walkie talkie that came with 2 AA dummy cells to use with alkalines, but when using NiCd cells you don't use them - 8 alkalines vs. 10 NiCds. Both about 12 volts in use.


You would have been left with 8 half used alkalines each battery change, then, unless you used the radio for monitoring only, not transmitting.


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## TorchBoy (Nov 1, 2009)

*Re: 1.2 V vs 1.5 V*



MarioJP said:


> Isn't that's the whole point of nimh "low voltage but high output currents makes up for it"


No, *more stable* voltage (meaning the equipment doesn't have to either cope with a widely varying input or waste the bottom half of the capacity) *and* higher output current.


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## Lynx_Arc (Nov 1, 2009)

*Re: 1.2 V vs 1.5 V*

you do realize the bulbs in most alkaline based flashlights are rated at 1.2v per cell instead of 1.5v per cell.


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## Radiophile (Nov 2, 2009)

MarioJP said:


> What about today?. Does this problem continues on or have devices gotten better that can work with rechargeables. Since alkalines are not really suited for high drain devices, my question is wouldn't the battery's voltage just plummet if devices requires 1.5 volts but the drain is high??.
> 
> Isn't that's the whole point of nimh "low voltage but high output currents makes up for it"



For the most part I'd say yes. For high power LED or incandescent flashlights I'd say absolutely. But again, it depends on the device. NiMH batteries aren't a direct replacement for alkalines. I think that's why they just came out with the NiZn cells. They'll work better with devices looking for higher voltage. I don't own any so I can't tell you how they behave in use, but I'd assume they're similar to NiMH with a higher voltage per cell.



TorchBoy said:


> You would have been left with 8 half used alkalines each battery change, then, unless you used the radio for monitoring only, not transmitting.



To be honest it's been a REALLY LONG time since I've used the radio, and I mostly used it with NiCd cells anyway, but I think at the output levels of the radio - 0.5W maximum, the alkalines wouldn't have sagged that much on TX.


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## alpg88 (Nov 2, 2009)

1.2v and 1.5v batts have different chemistry, 
so you have better understanding, think of it this way, a battery is a water tank, alkaline 1.5v batteries have smaller pipe connected, so the flow of water would be small, and devices that need large rate of flow wont work right, nicd, nimh have larger pipe, and can put out more flow, thus making devises that need larger flow work right. voltage would be speed of the water, amps would be water pressure.
now replace water flow for electricity, and you got difference between, alkalines and nicd, and nimh.
also high draw devices drop batt voltage, more on alkalines than nicd, or nimh, 1.5-1.6 would be no load voltage. bring resistance into equation, and your high speed low pressure flow would slow down, lower speed but higher pressure would not be affected by resistance that much.


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## Mr Happy (Nov 2, 2009)

It's not only load, it's discharge characteristics. Go to a battery manufacturer's web site and look at the discharge curves for alkaline cells. You will see that they start out at about 1.6 V when new, but they very soon drop to 1.4 V, and then it's downhill all the way to 1.0 V. Any device that "refuses" to work with less than 1.5 V is wasting most of the energy still remaining in an alkaline cell and forcing you to throw away 80% of what you paid for. Alkaline batteries *do not have* 1.5 V even on a light load unless they are brand new and unused.


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## 45/70 (Nov 2, 2009)

alpg88 said:


> .....voltage would be speed of the water, amps would be water pressure......



Actually this works better if you say "voltage would be the _*pressure*_ of the water, amps would be the _*volume*_ of water". 

Dave


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## Burgess (Nov 2, 2009)

That PDF file, written by Curious_character, is indeed* very helpful*.

(mentioned in Post #9, above)

:thumbsup:
_


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## alpg88 (Nov 2, 2009)

45/70 said:


> Actually this works better if you say "voltage would be the _*pressure*_ of the water, amps would be the _*volume*_ of water".
> 
> Dave



yes, that would be good too, i was thinking bigger column (volume) of water in the bigger pipe would make higher pressure, but yes your definition works great too.


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## mdocod (Nov 2, 2009)

I've always like the water tank/pipes analogy, but mine is a bit different:

Imagine a water tower up in the air, a place to both store water, but also provide natural water pressure as a result of the elevation of the tank and gravity. 

The voltage is how high the tank is up in the air (the height of the support legs). Water pressure (PSI if you like), is representing Voltage, or potential. 

The capacity is the size of the tank. Gallons or cubic feet or whatever you like would represent mAH or AH capacity ratings. 

A pipe leads from the tower down to ground level, the size of the pipe determines how easily or how restricted water will flow down from the tank. A large pipe diameter can maintain high operating pressure with substantial flow, whereas achieving the same flow over a smaller pipe will result in a drop in effective water pressure. The effects of different pipe size are representing a combination of internal resistance and chemical reaction speed in the cell.

The shape of the tank (tall narrow, or wide and flat) represents the discharge behavior of the cell and how well it maintains constant voltage. 

An alkaline cell would be like having a 50 foot tall by 25 foot wide tank, on 50 foot tall legs with a 1 foot diameter pipe leading down. 

A NIMH cell would be like having a 25 foot tall and 50 foot wide tank sitting on 60 foot tall legs with a 3 foot diameter pipe. 

----

While the analogy isn't perfect, it covers a lot of the bases and helps illustrate the different cell behavior reasonably well. 

-Eric


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## Mark620 (Nov 2, 2009)

Eric, I like that analogy! 

btw, a 3 foot pipe = 8 ea. 1 foot pipes


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## TorchBoy (Nov 3, 2009)

*Re: 1.2 V vs 1.5 V*



Radiophile said:


> ... I think at the output levels of the radio - 0.5W maximum, the alkalines wouldn't have sagged that much on TX.


Remember that's the transmit power, not the full power consumption.

Voltage sag is right in there as part of the problem, and I've had it happen with small radios. I hit the transmit button and transmit no more than a short burst of static as the battery voltage suddenly does a sag and is too low to sustain the transmission. A few seconds after I give up on transmitting the voltage recovers enough to receive again.

I had a look at an alkaline capacity vs power drain graph just now. It indicates ~2 Ah for 0.2 W load, but only 0.4 Ah for a 1 W load, taking the cell down to 1.1 V. (Even that should be within the normal operating territory of NiMH.) If whatever equipment was able to cope with each cell down to 0.8 V the graph shows over 0.9 Ah at 1 W. So if whatever equipment stops at 1.1 V per cell (or higher and rejects NiMH and NiCd) that's more than half the capacity of the alkaline cells unusable.

These water analogies are nice, and each is better than the one before.


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## KiwiMark (Nov 3, 2009)

MarioJP said:


> Many times I keep hearing about 1.5 Volt AA is better than 1.2 because of higher operating voltage, but really additional .3 volts really makes a difference??. Can this issue make NiMh obsolete??.



It is important to understand the difference between nominal voltage & actual voltage. Nominal voltage is the amount that the manufacturers state on the label - it doesn't mean as much as people think it does. Batteries are NOT constant voltage devices - the voltage WILL change. Actual voltage is different - in terms of actual voltage the alkaline cells are NOT 1.5V at all.

Try this:
Measure the voltage of a brand new alkaline cell, then ask yourself this "why did I bother doing that?" The voltage under no load isn't of any importance.

A better measurement:
Take a device you want to power - check to see what current draw that device has. Whatever that is (0.1A, 0.5A, 1A or whatever) test the new alkaline cell with that much load - the voltage reading will be the best case of maximum voltage of a fresh cell while in use. But within a minute the alkaline cell is no longer brand new. Let us say that under a normal load your alkaline cell does read 1.5V when new, but after an hour it is only reading 1.1V under the same load - that is only an average of 1.3V and after 1 hour you only have 1.1V. An Eneloop in the same device could be reading 1.2V after 1 hour - so that means the NiMH has a HIGHER voltage that an alkaline.

Which has a higher voltage: an alkaline battery or a NiMH battery? It depends on the load and the state of charge, the answer could be either battery.

If you want to power a low drain device an you are willing to use an alkaline battery until it is down to 75% charge (25% used) and then throw it away and put a fresh alkaline battery in - then an alkaline battery has a higher voltage than a NiMH. But for high drain or if you consider average voltage from charged to 20% left - the NiMH will have a higher voltage.


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## MarioJP (Nov 3, 2009)

KiwiMark said:


> It is important to understand the difference between nominal voltage & actual voltage. Nominal voltage is the amount that the manufacturers state on the label - it doesn't mean as much as people think it does. Batteries are NOT constant voltage devices - the voltage WILL change. Actual voltage is different - in terms of actual voltage the alkaline cells are NOT 1.5V at all.
> 
> Try this:
> Measure the voltage of a brand new alkaline cell, then ask yourself this "why did I bother doing that?" The voltage under no load isn't of any importance.
> ...



Very interesting. I think I have a much better idea to truly find out whats going on with the alkaline cell. Although this attempt requires that I DO NOT LEAVE IT UNATTENDED. I can Have my la crosse charger do a full discharge of the cell at 500ma discharge rate. But once it hits to 0.90V i am going to pull the plug right away because this charger will charge any AA batteries that you feed it lol.

That is the main reason why I got this charger over the Maha C-9000 charger. The la-Crosse does not check for resistance of the cell at all lol. This means it will charge the cell regardless if the cell has a high internal resistance.

I want to fully discharge a fully charged alkaline cell so I can find out whats the true capacity and monitor the voltage at the same time.

You think I should do this attempt or am i just crazy. Don't worry I am gong to monitor like a hawk lol.


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## mdocod (Nov 4, 2009)

Hello MarioJP,

You don't need to run that test:

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

Plenty of discharge tests to look at right there 

-Eric


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## KiwiMark (Nov 4, 2009)

mdocod said:


> https://www.candlepowerforums.com/threads/64660
> 
> Plenty of discharge tests to look at right there



That is pretty cool, I hadn't seen that lot of graphs before. It confirms what I said - alkaline batteries are NOT 1.5V in actual use. Most of those graphs show the alkalines outputting less than 1.2V well before half way through their discharge. So at a high drain like 0.5 amps or more the NiMH cells are 1.2V and the alkaline cells are also 1.2V - and that is being generous to the alkaline cells.


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## MarioJP (Nov 7, 2009)

I got a new alkaline energizer AA and test it in the battery tester first before the discharge, reports all 5 green led lit.

Then I put the energizer AA in my La crosse charger, setting it at 500mA discharge rate. Wow the voltage quickly drops really fast. 30 minutes later the voltage is at 1.12v. That's much lower than NiMh cell.

Never realize how poor alkaline performs under medium load. wow.


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## TorchBoy (Nov 7, 2009)

In SilverFox's 0.5 A test, after just 0.25 Ah only one AA cell was worse than that. Indeed, the best AAA at 0.5 A was only a little worse than that. It's more like the result from his 1 amp AA test.

But yeah, that's roughly what they're like.


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## MarioJP (Nov 7, 2009)

:nana:So this means that devices that requires 1.5V minimum is not efficient as it will never use up the battery completely. That is not being efficient.

Update: This Energizer battery has the capacity of 1320mAh. But reality is you probably won't even utilized all 1320 in a real world application though. The voltage sags too easily. I immediately pull the battery out of the charger, the moment the voltage drops to 0.90v, or else it will start charging the alkaline cell lol. At first I thought it was a defect in the charger but when I got my second one (not a replacement but another one) it too charges any AA/AAA battery regardless of the type of chemistry the battery happens to be lol.

Now if your an idiot with this charger I can see an accident waiting to happen like that lol.

Firmware version of my both la crosse is 35. Now if this is a glitch it is the awsome glitch ever!!:twothumbs lol. It shouldn't even accepted the energizer to allow me to discharge in the first place, but it did. Have I not pull the battery out it would charge the cell at 1amp. 

That would be very very bad for the alkaline cell and eventually . Don't want to lose my charger.

I guess that's one advantage the la crosse has over that big clunky Maha C9000 charger lol.

I tested the battery in the tester after the discharge 0-5. all 5 led's did not light up. Battery is fully discharged.


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