1.2V vs 1.5V

[MarioJP]

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.

 

[Marduke]

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.

 

[Lighthouse one]

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

 

[MarioJP]

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??

 

[bcwang]

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.

 

[MarioJP]

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.

 

[Swedpat]

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

 

[MarioJP]

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.

 

[TorchBoy]

Re: 1.2 V vs 1.5 V

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. http://www.candlepowerforums.com/vb/showthread.php?t=173482

 

[MarioJP]

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.

 

[TorchBoy]

Re: 1.2 V vs 1.5 V

But that is a characteristic...

 

[MarioJP]

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

 

[TorchBoy]

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

 

[Radiophile]

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.

 

[MarioJP]

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"

 

[TorchBoy]

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.

 

[TorchBoy]

Re: 1.2 V vs 1.5 V

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.

 

[Lynx_Arc]

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.

 

[Radiophile]

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.

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.

 

[alpg88]

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.