Forums

9V Battery or 2 x AAA with 9V Converter

Started by Unknown May 12, 2014
On Tue, 13 May 2014 03:50:05 -0500, John Fields
<jfields@austininstruments.com> wrote:


Thanks for explaining the calculations in detail.

>The AAAs have a capacity of 1000mAH so, with a 45mA drain, they'd >last for 1000mAH/45mA, or about 22 hours. >
So, if I understand correctly, due to the effect of the voltage step up, the AAA's have a shorter life than the 9V battery, 22 vs 33 hours, even though they can supply twice as many mAH's at 3V.
>a 50mA load will get you about 21 hours to 1V cutoff, so I suspect >56 mA would get you about 10% less than that, or about 19 hours. >
Assuming the converter will operate down this low, its output would then be 3V? Not many circuits would even continue to operate below that. I would think a more practical cut-off for a 9V supply would be 5 or 6V. Kevin Grant
On Tue, 13 May 2014 20:53:11 +1000, kgrant@protec.com wrote:

>On Tue, 13 May 2014 03:50:05 -0500, John Fields ><jfields@austininstruments.com> wrote: > > >Thanks for explaining the calculations in detail.
--- You're welcome. :-) ---
>>The AAAs have a capacity of 1000mAH so, with a 45mA drain, they'd >>last for 1000mAH/45mA, or about 22 hours. >> > >So, if I understand correctly, due to the effect of the voltage step >up, the AAA's have a shorter life than the 9V battery, 22 vs 33 hours, >even though they can supply twice as many mAH's at 3V.
--- Yes. The brunt of it is that since the 3 volt source has to supply the same power as the 9 volt source, its output current will have to be three times higher than the 9 volt source's. ---
>>a 50mA load will get you about 21 hours to 1V cutoff, so I suspect >>56 mA would get you about 10% less than that, or about 19 hours. >> > >Assuming the converter will operate down this low, its output would >then be 3V?
--- I made a mistake in that cutoff for the cells would be 1 volt each, but 2 volts for the 3 volt battery; but no, the converter acts like a DC power transformer, so its input current would increase as its input voltage fell in order to keep the power into the load constant. ---
>Not many circuits would even continue to operate below that. I would >think a more practical cut-off for a 9V supply would be 5 or 6V. > >Kevin Grant
--- Properly designed, the converter would keep its output voltage constant until its input voltage dropped to some predetermined value where it would cease to function properly. John Fields
On 5/13/2014 4:50 AM, John Fields wrote:
> On Tue, 13 May 2014 07:22:35 +1000, kgrant@protec.com wrote: > >> >> >> In terms of battery life, and assuming the same brand of Alkaline >> battery, is it more efficient to use a 9V battery or 2 AAA cells with >> something like the TL496 converter pictured here. >> >> http://www.electroschematics.com/6788/3v-to-9v-dc-converter/ >> >> If not, what is the approximate difference either way? >> >> The circuit involved is a test audio oscillator. >> >> Would be nice if they made more handheld cases to fit 4 x AAA's. >> >> Kevin Grant > > --- > According to this chart from: > > http://www.techlib.com/reference/batteries.html > > > Battery Type Capacity (mAh) Typical Drain (mA) > --------------------------------------------------- > D 12000 200 > 6 Volt Lantern 11000 300 > C 6000 100 > AA 2000 50 > AAA 1000 10 > N 650 10 > 9 Volt 500 15
I wouldn't take this table as Gospel. Lantern batteries typically have cells half again as large as D cells and so should have half again the capacity. Some are actually made with D cells and a filler in the bottom. Those should have exactly the same capacity as D cells. I wonder where this web site got their data? -- Rick
On Tue, 13 May 2014 16:50:37 -0400, rickman <gnuarm@gmail.com>
wrote:

>On 5/13/2014 4:50 AM, John Fields wrote: >> On Tue, 13 May 2014 07:22:35 +1000, kgrant@protec.com wrote: >> >>> >>> >>> In terms of battery life, and assuming the same brand of Alkaline >>> battery, is it more efficient to use a 9V battery or 2 AAA cells with >>> something like the TL496 converter pictured here. >>> >>> http://www.electroschematics.com/6788/3v-to-9v-dc-converter/ >>> >>> If not, what is the approximate difference either way? >>> >>> The circuit involved is a test audio oscillator. >>> >>> Would be nice if they made more handheld cases to fit 4 x AAA's. >>> >>> Kevin Grant >> >> --- >> According to this chart from: >> >> http://www.techlib.com/reference/batteries.html >> >> >> Battery Type Capacity (mAh) Typical Drain (mA) >> --------------------------------------------------- >> D 12000 200 >> 6 Volt Lantern 11000 300 >> C 6000 100 >> AA 2000 50 >> AAA 1000 10 >> N 650 10 >> 9 Volt 500 15 > >I wouldn't take this table as Gospel. Lantern batteries typically have >cells half again as large as D cells and so should have half again the >capacity. Some are actually made with D cells and a filler in the >bottom. Those should have exactly the same capacity as D cells. > >I wonder where this web site got their data?
--- The data's described as being "conservative" on the web site, so it's probably taken from Duracell's alkaline specification summary: "Duracell Alkalines" on abse: news:sr45n9lou24kcsi1ng3m9e7auggq3gb846@4ax.com John Fields
Martin Brown wrote:

> On 13/05/2014 08:27, miso wrote: >> Never use AAA cells. You get twice the capacity in a AA cell at about a >> third the cost. > > The most annoying things are low current devices that will only run on > two AAA cells and will not work with NiMH rechargables at all. My phones > LED display when the phone is off hook for instance. >> >> I know people who use the type of battery in the remote to pick between >> brands of TVs. I try to run make everything I own AA cell compatible. >> >> No matter where you go, you can find chickens, 7.62 ammo, and AA cells. > > Only in the USA and some third world countries. > > AA cells are the only one of those three commonly stocked in Europe. >
You say I can't find chickens and ammo in Europe? What about Poland?
John Fields wrote:

> On Tue, 13 May 2014 20:53:11 +1000, kgrant@protec.com wrote: > >>On Tue, 13 May 2014 03:50:05 -0500, John Fields >><jfields@austininstruments.com> wrote: >> >> >>Thanks for explaining the calculations in detail. > > --- > You're welcome. :-) > --- > >>>The AAAs have a capacity of 1000mAH so, with a 45mA drain, they'd >>>last for 1000mAH/45mA, or about 22 hours. >>> >> >>So, if I understand correctly, due to the effect of the voltage step >>up, the AAA's have a shorter life than the 9V battery, 22 vs 33 hours, >>even though they can supply twice as many mAH's at 3V. > > --- > Yes. > > The brunt of it is that since the 3 volt source has to supply the > same power as the 9 volt source, its output current will have to be > three times higher than the 9 volt source's. > --- > >>>a 50mA load will get you about 21 hours to 1V cutoff, so I suspect >>>56 mA would get you about 10% less than that, or about 19 hours. >>> >> >>Assuming the converter will operate down this low, its output would >>then be 3V? > > --- > I made a mistake in that cutoff for the cells would be 1 volt each, > but 2 volts for the 3 volt battery; but no, the converter acts like > a DC power transformer, so its input current would increase as its > input voltage fell in order to keep the power into the load > constant. > --- > >>Not many circuits would even continue to operate below that. I would >>think a more practical cut-off for a 9V supply would be 5 or 6V. >> >>Kevin Grant > > --- > Properly designed, the converter would keep its output voltage > constant until its input voltage dropped to some predetermined value > where it would cease to function properly. > > John Fields
There are some controllers that will keep running down to 2V, but can't start there. That is because they bootstrap power to the chip from the DC/DC output using a LDO. That is, sometimes the datasheet curves show low voltage operation, but the electrical tables won't indicate operation at low voltage. This is the electrical equivalent of I have fallen and can't get up.
On 5/13/2014 6:03 PM, John Fields wrote:
> On Tue, 13 May 2014 16:50:37 -0400, rickman <gnuarm@gmail.com> > wrote: > >> On 5/13/2014 4:50 AM, John Fields wrote: >>> On Tue, 13 May 2014 07:22:35 +1000, kgrant@protec.com wrote: >>> >>>> >>>> >>>> In terms of battery life, and assuming the same brand of Alkaline >>>> battery, is it more efficient to use a 9V battery or 2 AAA cells with >>>> something like the TL496 converter pictured here. >>>> >>>> http://www.electroschematics.com/6788/3v-to-9v-dc-converter/ >>>> >>>> If not, what is the approximate difference either way? >>>> >>>> The circuit involved is a test audio oscillator. >>>> >>>> Would be nice if they made more handheld cases to fit 4 x AAA's. >>>> >>>> Kevin Grant >>> >>> --- >>> According to this chart from: >>> >>> http://www.techlib.com/reference/batteries.html >>> >>> >>> Battery Type Capacity (mAh) Typical Drain (mA) >>> --------------------------------------------------- >>> D 12000 200 >>> 6 Volt Lantern 11000 300 >>> C 6000 100 >>> AA 2000 50 >>> AAA 1000 10 >>> N 650 10 >>> 9 Volt 500 15 >> >> I wouldn't take this table as Gospel. Lantern batteries typically have >> cells half again as large as D cells and so should have half again the >> capacity. Some are actually made with D cells and a filler in the >> bottom. Those should have exactly the same capacity as D cells. >> >> I wonder where this web site got their data? > > --- > The data's described as being "conservative" on the web site, so > it's probably taken from Duracell's alkaline specification summary: > "Duracell Alkalines" on abse: > > news:sr45n9lou24kcsi1ng3m9e7auggq3gb846@4ax.com
I can't seem to open that link. You do see my point though, right? It is very unlikely in my opinion that the lantern battery with much larger cells would not be able to supply as many mAHr as a D cell. -- Rick
On 5/14/2014 2:47 AM, rickman wrote:
> On 5/13/2014 6:03 PM, John Fields wrote: >> On Tue, 13 May 2014 16:50:37 -0400, rickman <gnuarm@gmail.com> >> wrote: >> >>> On 5/13/2014 4:50 AM, John Fields wrote: >>>> On Tue, 13 May 2014 07:22:35 +1000, kgrant@protec.com wrote: >>>> >>>>> >>>>> >>>>> In terms of battery life, and assuming the same brand of Alkaline >>>>> battery, is it more efficient to use a 9V battery or 2 AAA cells with >>>>> something like the TL496 converter pictured here. >>>>> >>>>> http://www.electroschematics.com/6788/3v-to-9v-dc-converter/ >>>>> >>>>> If not, what is the approximate difference either way? >>>>> >>>>> The circuit involved is a test audio oscillator. >>>>> >>>>> Would be nice if they made more handheld cases to fit 4 x AAA's. >>>>> >>>>> Kevin Grant >>>> >>>> --- >>>> According to this chart from: >>>> >>>> http://www.techlib.com/reference/batteries.html >>>> >>>> >>>> Battery Type Capacity (mAh) Typical Drain (mA) >>>> --------------------------------------------------- >>>> D 12000 200 >>>> 6 Volt Lantern 11000 300 >>>> C 6000 100 >>>> AA 2000 50 >>>> AAA 1000 10 >>>> N 650 10 >>>> 9 Volt 500 15 >>> >>> I wouldn't take this table as Gospel. Lantern batteries typically have >>> cells half again as large as D cells and so should have half again the >>> capacity. Some are actually made with D cells and a filler in the >>> bottom. Those should have exactly the same capacity as D cells. >>> >>> I wonder where this web site got their data? >> >> --- >> The data's described as being "conservative" on the web site, so >> it's probably taken from Duracell's alkaline specification summary: >> "Duracell Alkalines" on abse: >> >> news:sr45n9lou24kcsi1ng3m9e7auggq3gb846@4ax.com > > I can't seem to open that link. You do see my point though, right? It > is very unlikely in my opinion that the lantern battery with much larger > cells would not be able to supply as many mAHr as a D cell.
Perhaps this is because the data given was from lantern batteries which were made using D cells. I see the stated drain current is half again as high for the lantern battery, so that may explain the difference in rated capacity if they were tested at those values. -- Rick
On Tue, 13 May 2014 22:47:55 -0700, miso <miso@sushi.com> wrote:

>Martin Brown wrote: > >> On 13/05/2014 08:27, miso wrote: >>> Never use AAA cells. You get twice the capacity in a AA cell at about a >>> third the cost. >> >> The most annoying things are low current devices that will only run on >> two AAA cells and will not work with NiMH rechargables at all. My phones >> LED display when the phone is off hook for instance. >>> >>> I know people who use the type of battery in the remote to pick between >>> brands of TVs. I try to run make everything I own AA cell compatible. >>> >>> No matter where you go, you can find chickens, 7.62 ammo, and AA cells. >> >> Only in the USA and some third world countries. >> >> AA cells are the only one of those three commonly stocked in Europe. >> > >You say I can't find chickens and ammo in Europe? What about Poland?
--- You might have a hard time of it, but if you were diligent you'd probably find Poland in Europe. John Fields
On Wed, 14 May 2014 02:50:55 -0400, rickman <gnuarm@gmail.com>
wrote:

>On 5/14/2014 2:47 AM, rickman wrote: >> On 5/13/2014 6:03 PM, John Fields wrote: >>> On Tue, 13 May 2014 16:50:37 -0400, rickman <gnuarm@gmail.com> >>> wrote: >>> >>>> On 5/13/2014 4:50 AM, John Fields wrote: >>>>> On Tue, 13 May 2014 07:22:35 +1000, kgrant@protec.com wrote: >>>>> >>>>>> >>>>>> >>>>>> In terms of battery life, and assuming the same brand of Alkaline >>>>>> battery, is it more efficient to use a 9V battery or 2 AAA cells with >>>>>> something like the TL496 converter pictured here. >>>>>> >>>>>> http://www.electroschematics.com/6788/3v-to-9v-dc-converter/ >>>>>> >>>>>> If not, what is the approximate difference either way? >>>>>> >>>>>> The circuit involved is a test audio oscillator. >>>>>> >>>>>> Would be nice if they made more handheld cases to fit 4 x AAA's. >>>>>> >>>>>> Kevin Grant >>>>> >>>>> --- >>>>> According to this chart from: >>>>> >>>>> http://www.techlib.com/reference/batteries.html >>>>> >>>>> >>>>> Battery Type Capacity (mAh) Typical Drain (mA) >>>>> --------------------------------------------------- >>>>> D 12000 200 >>>>> 6 Volt Lantern 11000 300 >>>>> C 6000 100 >>>>> AA 2000 50 >>>>> AAA 1000 10 >>>>> N 650 10 >>>>> 9 Volt 500 15 >>>> >>>> I wouldn't take this table as Gospel. Lantern batteries typically have >>>> cells half again as large as D cells and so should have half again the >>>> capacity. Some are actually made with D cells and a filler in the >>>> bottom. Those should have exactly the same capacity as D cells. >>>> >>>> I wonder where this web site got their data? >>> >>> --- >>> The data's described as being "conservative" on the web site, so >>> it's probably taken from Duracell's alkaline specification summary: >>> "Duracell Alkalines" on abse: >>> >>> news:sr45n9lou24kcsi1ng3m9e7auggq3gb846@4ax.com >> >> I can't seem to open that link. You do see my point though, right? It >> is very unlikely in my opinion that the lantern battery with much larger >> cells would not be able to supply as many mAHr as a D cell.
--- I agree. ---
>Perhaps this is because the data given was from lantern batteries which >were made using D cells. I see the stated drain current is half again >as high for the lantern battery, so that may explain the difference in >rated capacity if they were tested at those values.
--- Here are some relevant data sheets: http://ww2.duracell.com/media/en-US/pdf/gtcl/Product_Data_Sheet/NA_DATASHEETS/MN1300_US_CT.pdf http://data.energizer.com/PDFs/E95.pdf