Advice on batteries for consumer use

[NOPE9]

When considering 9V , AA and AAA batteries .... does one get the best  
bang for the buck with .......
primary alkaline
primary NiMh
secondary NiMh

I have seen AA LION batteries advertised.  How is this possible?  I  
thought LION was 3.6V.

If one wants to keep all the battery powered toys going , what is the  
best choice now ?
Are cheap batteries from China going to be a safety issue ?

Gus



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[Sean Breheny]

Hi Gus,

I don't know what "primary NiMH" is. As far as I know, alkaline
batteries (especially the enhanced capacity ones like the Duracell
Ultra) have considerably greater capacity than any common rechargeable
battery. Of course, if you are considering the "total cost of
ownership" and willing to recharge you batteries many times, and do
not care too much about the run time per charge, then NiMH would be
superior to alkaline.

I think that the AA "LiON" batteries you saw were probably not Lithium
Ion but Lithium Iron Disulfide (see
http://en.wikipedia.org/wiki/Lithium_battery ). These are 1.5 to 1.6V
nominal, are not rechargeable, and have much greater capacity than
alkaline batteries - along with a higher cost.

I would recommend making a spreadsheet using data from the Duracell
and Energizer web sites, as well as price info from various retailers,
to compare the cost per energy of alkaline normal, alkaline
enhanced/ultra, lithium primary, and NiMH types. For the NiMH types,
amortize the cost of the battery over the cycle life (about 300 cycles
ideally, perhaps more like 100 cycles in typical consumer use) and add
in the cost of the charger amortized over perhaps 3 sets of batteries
worth of cycles.

Sean




On Fri, Oct 30, 2009 at 2:23 PM, NOPE9 <yes@...> wrote:

>
>
> When considering 9V , AA and AAA batteries .... does one get the best
> bang for the buck with .......
> primary alkaline
> primary NiMh
> secondary NiMh
>
> I have seen AA LION batteries advertised.  How is this possible?  I
> thought LION was 3.6V.
>
> If one wants to keep all the battery powered toys going , what is the
> best choice now ?
> Are cheap batteries from China going to be a safety issue ?
>
> Gus
>
>
>
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[peterloron]

On Oct 31, 2009, at 11:02 PM, Sean Breheny wrote:

> Hi Gus,
>
> I don't know what "primary NiMH" is. As far as I know, alkaline
> batteries (especially the enhanced capacity ones like the Duracell
> Ultra) have considerably greater capacity than any common rechargeable
> battery. Of course, if you are considering the "total cost of
> ownership" and willing to recharge you batteries many times, and do
> not care too much about the run time per charge, then NiMH would be
> superior to alkaline.
>
> I think that the AA "LiON" batteries you saw were probably not Lithium
> Ion but Lithium Iron Disulfide (see
> http://en.wikipedia.org/wiki/Lithium_battery ). These are 1.5 to 1.6V
> nominal, are not rechargeable, and have much greater capacity than
> alkaline batteries - along with a higher cost.
>
> I would recommend making a spreadsheet using data from the Duracell
> and Energizer web sites, as well as price info from various retailers,
> to compare the cost per energy of alkaline normal, alkaline
> enhanced/ultra, lithium primary, and NiMH types. For the NiMH types,
> amortize the cost of the battery over the cycle life (about 300 cycles
> ideally, perhaps more like 100 cycles in typical consumer use) and add
> in the cost of the charger amortized over perhaps 3 sets of batteries
> worth of cycles.
>
> Sean

You also need to take into account the discharge curve of the battery  
type in question, as well as the consumption of the device you're  
trying to power. Yes, rechargeables have a lower total mAH capacity  
that alkalines, etc, but their voltage/time curve tends to be much  
flatter, especially for NiMH cells. If the thing you're trying to run  
does well in the voltage range that NiMH cells tend to fall in as they  
are discharging, then you can actually get *more* runtime from them  
than alkaline cells.

Unless you have something which needs the full 1.5V from an alkaline  
cell or which MUST be ready to go without needing to muck around with  
keeping charged cells in it (emergency light, etc), you're pretty much  
always going to win with NiCD or NiMH rechargeables.

-Pete
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[Sean Breheny]

On Sun, Nov 1, 2009 at 2:51 AM, Peter Loron <peterl@...> wrote:
> You also need to take into account the discharge curve of the battery
> type in question, as well as the consumption of the device you're
> trying to power. Yes, rechargeables have a lower total mAH capacity
> that alkalines, etc, but their voltage/time curve tends to be much
> flatter, especially for NiMH cells. If the thing you're trying to run
> does well in the voltage range that NiMH cells tend to fall in as they
> are discharging, then you can actually get *more* runtime from them
> than alkaline cells.
>

Hi Pete,

I could see that this could theoretically be true, but I doubt it is
very commonly true of battery powered devices. The end-point voltage
of NiMH is about 0.9V. If you have a device which can work properly
from 1.5V down to 0.9V, then it would use the entire range of an
alkaline battery and you should still get more runtime out of the
alkaline than the NiMH. I think that the only way that an NiMH could
deliver a longer runtime would be if the device were only able to
operate below 1.3V or if it were much more efficient from 1.3V to 0.9V
than it is from 1.5V to 1.3V.

Sean
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[peterloron]

On Nov 1, 2009, at 6:35 AM, Sean Breheny wrote:

> On Sun, Nov 1, 2009 at 2:51 AM, Peter Loron  
> <peterl@...> wrote:
>> You also need to take into account the discharge curve of the battery
>> type in question, as well as the consumption of the device you're
>> trying to power. Yes, rechargeables have a lower total mAH capacity
>> that alkalines, etc, but their voltage/time curve tends to be much
>> flatter, especially for NiMH cells. If the thing you're trying to run
>> does well in the voltage range that NiMH cells tend to fall in as  
>> they
>> are discharging, then you can actually get *more* runtime from them
>> than alkaline cells.
>>
>
> Hi Pete,
>
> I could see that this could theoretically be true, but I doubt it is
> very commonly true of battery powered devices. The end-point voltage
> of NiMH is about 0.9V. If you have a device which can work properly
> from 1.5V down to 0.9V, then it would use the entire range of an
> alkaline battery and you should still get more runtime out of the
> alkaline than the NiMH. I think that the only way that an NiMH could
> deliver a longer runtime would be if the device were only able to
> operate below 1.3V or if it were much more efficient from 1.3V to 0.9V
> than it is from 1.5V to 1.3V.
>
> Sean

Please take a look at this page, specifically the chart in the middle  
to see what I'm talking about. Depending on the minimum voltage for  
your application, there can be quite a bit more area under the curve  
of the NiMH cell that is above the minimum line.

-Pete
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[Sean Breheny]

On Sun, Nov 1, 2009 at 12:16 PM, Peter Loron <peterl@...> wrote:
> Please take a look at this page, specifically the chart in the middle
> to see what I'm talking about. Depending on the minimum voltage for
> your application, there can be quite a bit more area under the curve
> of the NiMH cell that is above the minimum line.

Hi Pete,

I'd love to but I couldn't find the URL in your message. Please send me the URL.

Thanks,

Sean


>
> -Pete
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[William "Chops" Westfield]

>> Yes, rechargeables have a lower total mAH capacity
>> that alkalines, etc, but their voltage/time curve tends to be much
>> flatter, especially for NiMH cells. If the thing you're trying to run
>> does well in the voltage range that NiMH cells tend to fall in as  
>> they
>> are discharging, then you can actually get *more* runtime from them
>> than alkaline cells.
>
> I could see that this could theoretically be true, but I doubt it is
> very commonly true of battery powered devices.

(early?) Digital cameras were famous for getting MUCH longer life from  
NiMH rechargables than from alkalines (not to mention infamous for  
really TERRIBLE performance on alkalines.  I don't think that this was  
so much due to the discharge curve flatness mentioned by the original  
poster, but because the alkaline batteries of the day suffered  
terribly under the high-discharge rates (with higher discharge pulses)  
that the cameras provided.  You can look at discharge curves for all  
sorts of batteries at http://www.candlepowerforums.com, both inside  
and outside of manufacturer recommended ranges.

Also note that while "rechargables have lower capacity than primaries"  
is an old rule of thumb, it mostly pre-dates modern NiMH technology.  
Duracell rates their AA alkaline as 2850 mAH, and their NiMH at 2650  
mAH, for example.  While the extra .3 V makes the engergy difference a  
bit greater, the difference in discharge curves throws in some  
uncertainty as well.   They're REALLY close.

I love li-ion batteries, though certainly not the price premium that  
equipment manufacturers charge for them.  Or their relative danger in  
unpackaged form.
The new low-self-discharge NiMH batteries are nice too; a close  
second, and near ideal for equipment taking standard AA sized  
batteries (not available or very expensive in larger sizes, though.)  
There's still packs of alkalines for the "disposable" items and the  
things that take "big" batteries, though.

BillW

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[Russell McMahon-4]

> > When considering 9V , AA and AAA batteries .... does one get the best
> > bang for the buck with .......
> > primary alkaline
> > primary NiMh
> > secondary NiMh

YMMV.
E&OE.

AA has about 2+ x AAA capacity and are often of similar price.
AAA are generally an abomination unless small size is an essential.
AA with boost converter will usually give better energy/$ and energy
volumetric density than AAA.

Alkaline AA have ratings hardly more than the latest top NimH.
Generally under 3000 mAh in each case, so far.
NimH have a better sustained high current capability.
Various magic technologies may give primary Aa cells more current
sustainability but the mAh seems little affected across Alkalines and
consumer "Lithium" cells.

This is a retail reseller page but gives a good idea of available
primary Alkaline mAh capacity at different sizes from one maker
(Eveready).

          http://www.batterycountry.com/ShopSite/alkaline-batteries.html

Eveready have far far more data available but it's not usually all in one place.

When it comes to serious AA use, buying NimH is the overwhelmingly
most cost effective choice wrt Alkalines.
NimH cycle life is often said to be 500 cycles but DO read spec sheets
to see the conditions.
Under deep cycle use "rather less" may be achieved.
Under light depth of discharge rather more.

LiIon cells are nominally 3.6V.
They CAN be had in AA / 14500 form factor.
Some people use these with a spacer to give the voltage of 2+ x Alkalines.
Alkaline Voc new is 1.55V.
LiIon needs special chargers.
Using them bare in place of AA's is living dangerously. ALL LiIon
should have inbuilt protection circuitry but some AA do not for
certain. Even some 18650 do not but that is less common.
"Vent with flame" is a significant risk with unprotected LiIon.
And a risk with protected LiIon.

The new great hope is LiFePO4 / Lithium Ferro Phosphate.
About 3.2V means terminal voltage.
Volumetric energy densities maybe somewhat above NimH.
Cost should be 2 +/- 0.5 x NimH price but actually vary quite widely.
4 x 400 mAh LiFePO4 could be had at Walmart for $US10 a while ago.
Claimped AA LFP capacity is often 600 mAh but probably more like 500
mAh and can be lower.
Anything out of China of no-name type can be MUCH lower at any stage.
LiFePO4 can be superb and terrible depending on maker.
18650 LiFePO4 cell is about 1100-1200 mAh typical and maybe a bit more
but not much. Anything marked eg 1400 mAh is suspect for capacity so
probably for other things as well.
Special charger needed. Similar to LiIon but with differences.

> > I have seen AA LION batteries advertised.  How is this possible?  I
> > thought LION was 3.6V.

As above.
Yes, it is. So ? :-)
ie don't use on 1:1 basis. DON'T charge in std charger.

> If one wants to keep all the battery powered toys going , what is the
> best choice now ?

AA NimH usually. Reputable brand.
As others noted - SOME devices need Alkaline voltage levels and NimH
may be too low.

Some people are using LiFePO4 AA + 1 spacer to replace 2 x Alkaline AA.
Max voltage may be a bot high but most products don't care.
LiFePO4 will discharge to 2V safely typically although higher is kinder.
Lower is not recommended. Cells should have internal protectors BUT
far less dangerous than LiIon.

> Are cheap batteries from China going to be a safety issue ?

Most batteries come from China.
Cheap ones MAY be good. Or not.
Bad Alkalines are usually just low performance.
Bad NimH will usually not burn etc too too often or much.
Bad LiIon may be fun, depending on what they are in when they go bad.

NimH goodness can be sort of checked [tm] by weighing or, lacking
scales, by "hefting" in hand. Similar specs from different suppliers
should weigh similarly. Low weight is usually an indication of junk.
Alkalines also should weigh similarly to each other.

NiCd weigh somewhat heavier per mAh than NimH. A 'nice and heavy' for
the size but low capacity NimH may really be a NiCd.

For toys self discharge / shelf life doesn't usually matter much. NimH
rate is highish but has been getting better for some years.
If it does matter then newer low-self-discharge NimH are available.
Firstish was Eneloop but now there are many brands. The actual
technological cost of doing this is low (mainly a thin coating of
Copper on Ni powder during manufacture AFAIK but I may well be wrong)
- I'd expect this to become the NimH norm in a few years.

IF you have tight control of battery replacement and charging then
LiFePO4 is liable top give the cheapest per cycle cost battery over a
long period. I'm about to do some serious playing with them ... :-).


        Russell McMahon

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[Russell McMahon-4]

Martin said:
> Does rercharging  make them heavier...

Yes - charging adds about 20 nanograms of electrons per milliamp-hour. See
below.

E&OE / YMMV.
Electron mass to charge = - *e* / *m**e* = -1.758 820 ... E11 C/kg
150(44) [image:
\times 10^{11} {C / kg}].
1 Coulomb = 1 A.s
A 2000 mAh cell will gain 2000 mAh  / 1000  mA/A * 3600s/h ~~~= 7200 Coulomb
when charged.
This will mass 7200 / 1.76E11 kg or about 4E-8 kg or about 40 micrograms of
electrons.
Or, about 20 nanograms per mAh.


    Russell McMahon




2009/11/3 Martin Ryder <martinz@...>

> Hi Russell,
>
> Thanks - backs up my suspicions!
>
> Does rercharging  make them heavier...
>
> Martin R
>
>
> --- On Tue, 3/11/09, Russell McMahon <apptechnz@...> wrote:
>
> > From: Russell McMahon <apptechnz@...>
> > Subject: Re: [EE] Advice on batteries for consumer use
> > To: "Microcontroller discussion list - Public." <piclist@...>
> > Received: Tuesday, 3 November, 2009, 12:56 AM
>  > > > When considering 9V , AA
> > and AAA batteries .... does one get the best
> > > > bang for the buck with .......
> > > > primary alkaline
> > > > primary NiMh
> > > > secondary NiMh
> >
> > YMMV.
> > E&OE.
> >
> > AA has about 2+ x AAA capacity and are often of similar
> > price.
> > AAA are generally an abomination unless small size is an
> > essential.
> > AA with boost converter will usually give better energy/$
> > and energy
> > volumetric density than AAA.
> >
> > Alkaline AA have ratings hardly more than the latest top
> > NimH.
> > Generally under 3000 mAh in each case, so far.
> > NimH have a better sustained high current capability.
> > Various magic technologies may give primary Aa cells more
> > current
> > sustainability but the mAh seems little affected across
> > Alkalines and
> > consumer "Lithium" cells.
> >
> > This is a retail reseller page but gives a good idea of
> > available
> > primary Alkaline mAh capacity at different sizes from one
> > maker
> > (Eveready).
> >
> >           http://www.batterycountry.com/ShopSite/alkaline-batteries.html
> >
> > Eveready have far far more data available but it's not
> > usually all in one place.
> >
> > When it comes to serious AA use, buying NimH is the
> > overwhelmingly
> > most cost effective choice wrt Alkalines.
> > NimH cycle life is often said to be 500 cycles but DO read
> > spec sheets
> > to see the conditions.
> > Under deep cycle use "rather less" may be achieved.
> > Under light depth of discharge rather more.
> >
> > LiIon cells are nominally 3.6V.
> > They CAN be had in AA / 14500 form factor.
> > Some people use these with a spacer to give the voltage of
> > 2+ x Alkalines.
> > Alkaline Voc new is 1.55V.
> > LiIon needs special chargers.
> > Using them bare in place of AA's is living dangerously. ALL
> > LiIon
> > should have inbuilt protection circuitry but some AA do not
> > for
> > certain. Even some 18650 do not but that is less common.
> > "Vent with flame" is a significant risk with unprotected
> > LiIon.
> > And a risk with protected LiIon.
> >
> > The new great hope is LiFePO4 / Lithium Ferro Phosphate.
> > About 3.2V means terminal voltage.
> > Volumetric energy densities maybe somewhat above NimH.
> > Cost should be 2 +/- 0.5 x NimH price but actually vary
> > quite widely.
> > 4 x 400 mAh LiFePO4 could be had at Walmart for $US10 a
> > while ago.
> > Claimped AA LFP capacity is often 600 mAh but probably more
> > like 500
> > mAh and can be lower.
> > Anything out of China of no-name type can be MUCH lower at
> > any stage.
> > LiFePO4 can be superb and terrible depending on maker.
> > 18650 LiFePO4 cell is about 1100-1200 mAh typical and maybe
> > a bit more
> > but not much. Anything marked eg 1400 mAh is suspect for
> > capacity so
> > probably for other things as well.
> > Special charger needed. Similar to LiIon but with
> > differences.
> >
> > > > I have seen AA LION batteries advertised.  How
> > is this possible?  I
> > > > thought LION was 3.6V.
> >
> > As above.
> > Yes, it is. So ? :-)
> > ie don't use on 1:1 basis. DON'T charge in std charger.
> >
> > > If one wants to keep all the battery powered toys
> > going , what is the
> > > best choice now ?
> >
> > AA NimH usually. Reputable brand.
> > As others noted - SOME devices need Alkaline voltage levels
> > and NimH
> > may be too low.
> >
> > Some people are using LiFePO4 AA + 1 spacer to replace 2 x
> > Alkaline AA.
> > Max voltage may be a bot high but most products don't
> > care.
> > LiFePO4 will discharge to 2V safely typically although
> > higher is kinder.
> > Lower is not recommended. Cells should have internal
> > protectors BUT
> > far less dangerous than LiIon.
> >
> > > Are cheap batteries from China going to be a safety
> > issue ?
> >
> > Most batteries come from China.
> > Cheap ones MAY be good. Or not.
> > Bad Alkalines are usually just low performance.
> > Bad NimH will usually not burn etc too too often or much.
> > Bad LiIon may be fun, depending on what they are in when
> > they go bad.
> >
> > NimH goodness can be sort of checked [tm] by weighing or,
> > lacking
> > scales, by "hefting" in hand. Similar specs from different
> > suppliers
> > should weigh similarly. Low weight is usually an indication
> > of junk.
> > Alkalines also should weigh similarly to each other.
> >
> > NiCd weigh somewhat heavier per mAh than NimH. A 'nice and
> > heavy' for
> > the size but low capacity NimH may really be a NiCd.
> >
> > For toys self discharge / shelf life doesn't usually matter
> > much. NimH
> > rate is highish but has been getting better for some
> > years.
> > If it does matter then newer low-self-discharge NimH are
> > available.
> > Firstish was Eneloop but now there are many brands. The
> > actual
> > technological cost of doing this is low (mainly a thin
> > coating of
> > Copper on Ni powder during manufacture AFAIK but I may well
> > be wrong)
> > - I'd expect this to become the NimH norm in a few years.
> >
> > IF you have tight control of battery replacement and
> > charging then
> > LiFePO4 is liable top give the cheapest per cycle cost
> > battery over a
> > long period. I'm about to do some serious playing with them
> > ... :-).
> >
> >
> >         Russell McMahon
> >
>
>

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[John Gardner-3]

 ROTFL  :)  Very good!

Jack

>> Does recharging  make them heavier...

> Yes - charging adds about 20 nanograms of electrons per milliamp-hour. See
below...
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[Dave Tweed]

Russell McMahon wrote:

> Martin said:
> > Does rercharging  make them heavier...
>
> Yes - charging adds about 20 nanograms of electrons per milliamp-hour. See
> below.
>
> E&OE / YMMV.
> Electron mass to charge = - *e* / *m**e* = -1.758 820 ... E11 C/kg
> 150(44) [image:
> \times 10^{11} {C / kg}].
> 1 Coulomb = 1 A.s
> A 2000 mAh cell will gain 2000 mAh  / 1000  mA/A * 3600s/h ~~~= 7200 Coulomb
> when charged.
> This will mass 7200 / 1.76E11 kg or about 4E-8 kg or about 40 micrograms of
> electrons.
> Or, about 20 nanograms per mAh.

You are just being silly, right? Charging does not add electrons to a
battery, it just moves them around inside (true of capacitors, too).
Otherwise, the battery as a whole would acquire a huge negative charge
relative to its surroundings.

There is a tiny mass change arising from charging, but it's just the
relativistic mass-equivalent of the potential energy you've added to the
battery. (M = E/c^2).

2 Ah * 1.5 V * 3600 s/h = 10.8e3 J = 10.8e3 kg*m^2/s^2

10.8e3 kg*m^2/s^2 / (3e8 m/s)^2 = 1.2e-10 g

... or 0.12 nanogram for the entire cell, about six orders of magnitude
less than your estimate.

-- Dave Tweed
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[Marechiare]

>> Does rercharging  make them heavier...
>
> Yes - charging adds about 20 nanograms of
> electrons per milliamp-hour. See below.
>
> E&OE / YMMV.
> Electron mass to charge = - *e* / *m**e* = -1.758 820 ... E11 C/kg
> 150(44) [image:
> \times 10^{11} {C / kg}].
> 1 Coulomb = 1 A.s
> A 2000 mAh cell will gain 2000 mAh  / 1000  mA/A * 3600s/h ~~~= 7200 Coulomb
> when charged.
> This will mass 7200 / 1.76E11 kg or about 4E-8 kg or about 40 micrograms of
> electrons.
> Or, about 20 nanograms per mAh.

I doubt it adds, when the battery is getting charged, those electrons
seem to be drained from "+" and sinked to "-" of the battery.

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