# Best metals to make homemade battery?

Discussion in 'Electronic Basics' started by A Man, Jan 12, 2006.

1. ### A ManGuest

My goal is to work with my son to make a home made battery. The basic battery
uses a lemon (or lemon juice) with a copper part and zinc part. But that only
produces about .8v. (I think this is called a wet cell.)

My question is, what are the 2 best metals to use to maximize voltage?
What are the best 2 metals to use to maximize runtime? I want to run an LED
for about 8 hours consecutively. (But LEDs draw about 3.0-3.2 volts, even red
ones.)

Should I try lead in place of zinc?
What lead items can I use?
How much lead is in solder?

Thanks for the help.

--
Sig: Say no to fixed width HTML tables. They look terrible in most browsers.

A Man, Jan 12, 2006

2. ### GarethGuest

A Man wrote:
> My goal is to work with my son to make a home made battery. The basic battery
> uses a lemon (or lemon juice) with a copper part and zinc part. But that only
> produces about .8v. (I think this is called a wet cell.)
>
> My question is, what are the 2 best metals to use to maximize voltage?
> What are the best 2 metals to use to maximize runtime? I want to run an LED
> for about 8 hours consecutively. (But LEDs draw about 3.0-3.2 volts, even red
> ones.)
>
> Should I try lead in place of zinc?
> What lead items can I use?
> How much lead is in solder?
>
> Thanks for the help.
>
>

I'm not sure which metals are best, but have you considered 3 (or more)
lemons in series, that should give you just enough to light a red LED.
You normally need a current limiting resistor in series with the LED,
but I expect the internal resistance of your lemon will limit the
current to a safe value. Have you tried measuring the current?

You could try different metals as part of your experiment.

--
-----------------------------------------------------------------------

Replace privacy.net with: totalise DOT co DOT uk and replace me with
gareth.harris

Gareth, Jan 12, 2006

3. ### Roger DewhurstGuest

"A Man" <> wrote in message
news:43c69ed3\$0\$8443\$...
> My goal is to work with my son to make a home made battery. The basic

battery
> uses a lemon (or lemon juice) with a copper part and zinc part. But that

only
> produces about .8v. (I think this is called a wet cell.)
>
> My question is, what are the 2 best metals to use to maximize voltage?
> What are the best 2 metals to use to maximize runtime? I want to run an

LED
> for about 8 hours consecutively. (But LEDs draw about 3.0-3.2 volts, even

red
> ones.)
>
> Should I try lead in place of zinc?
> What lead items can I use?
> How much lead is in solder?
>
> Thanks for the help.
>

You will find a table "Electro-motive series" in a good physics or chemistry
textbook or indeed on the internet. You may use that table to deduce the
best metals to use. Try magnesium in place of zinc.

R
>
> --
> Sig: Say no to fixed width HTML tables. They look terrible in most

browsers.

Roger Dewhurst, Jan 12, 2006
4. ### Yukio YANOGuest

A Man wrote:
> My goal is to work with my son to make a home made battery. The basic battery
> uses a lemon (or lemon juice) with a copper part and zinc part. But that only
> produces about .8v. (I think this is called a wet cell.)
>
> My question is, what are the 2 best metals to use to maximize voltage?
> What are the best 2 metals to use to maximize runtime? I want to run an LED
> for about 8 hours consecutively. (But LEDs draw about 3.0-3.2 volts, even red
> ones.)
>
> Should I try lead in place of zinc?
> What lead items can I use?
> How much lead is in solder?
>
> Thanks for the help.
>
>

It's not what's best but what is most practical (read available and
cheap)eg You wouldn't consider Gold and Platinum foils for example,
available is Sheet Copper or Copper-plated PC board and Zinc coated
(galvanized iron). Carbon rods used to be readily salvaged from
flashlight batteries before they went into more exotic chemistries.
Aluminum foils tend to develope an insulating Anodic Coating, a process
use to make Capacitors. You need more Voltage ? Use several Cells in
series ie make a battery of cells. Electrolytes, HCl, Hydro-Chloric
(muriatic acid) is readily available from the hardware stores, Sulfuric
acid , H2SO4 is a little harder to get but is used in Automotive
Batteries other acids eg Citric acid (lemon
juice), Formic acid and Vinegar (acetic Acid)are not as highly Ionizing
as HCL, H2SO4, HNO3, Nitric acid or H3(PO4) Phosphoric Acid don't even
think about HF (Hydro-Fluoric Acid) same class as HCN, Prussic acid or
Hydrogen Cyanide both are extremely toxic !
anyway, so much for the lesson in practical Chemistry and Physics.

most common grade of electronic Solder
You could take some Wire solder and hammer it flat.

you could use a copper penny or a piece of copper pipe or copper wire.
You could find a SILVER dime or quarter or some Sterling SILVER jewellry
You could find some Gold jewellry
You could recover some Mercury and use that for an electrode (Not
Recommended)
You could take some (un-plated, un-coated) nails for Iron electrodes
You could recover the Tungsten filement from a light bulb
you can find Aluminun foil in any kitchen

Yukio YANO

Yukio YANO, Jan 13, 2006
5. ### A ManGuest

On Fri, 13 Jan 2006 11:55:11 +1300 in article <dq6mpv\$mc4\$>,
spoke thusly...
>
> "A Man" <> wrote in message
> news:43c69ed3\$0\$8443\$...
> > My goal is to work with my son to make a home made battery. The basic

> battery
> > uses a lemon (or lemon juice) with a copper part and zinc part. But that

> only
> > produces about .8v. (I think this is called a wet cell.)
> >
> > My question is, what are the 2 best metals to use to maximize voltage?
> > What are the best 2 metals to use to maximize runtime? I want to run an

> LED
> > for about 8 hours consecutively. (But LEDs draw about 3.0-3.2 volts, even

> red
> > ones.)
> >
> > Should I try lead in place of zinc?
> > What lead items can I use?
> > How much lead is in solder?
> >
> > Thanks for the help.
> >

>
> You will find a table "Electro-motive series" in a good physics or chemistry
> textbook or indeed on the internet. You may use that table to deduce the
> best metals to use. Try magnesium in place of zinc.
>

You are correct. I did find those tables. The positive electrode corresponds
to the metal with a positive "electric reduction potential" (ERP) I think it
was called. The negative electrode metal corresponds to the negative ERP.
Subtract the 2 and you get the total potential, which is the POTENTIAL
voltage produced by the cell. The ACTUAL voltage is less than that.

So, for the negative part, lithium is -3.04. I don't think that's practical
because I thought elemental lithium was very toxic to the skin and other
organs. Next best was Mg (magnesium?) at -2.38. But that's hard to find. Next
best was aluminum at -1.66, and I do have aluminum foil. Next best is silver
at -.799. I might have some old silver plated US coins before 1964.

For the positive electrode we have gold at +.799 (I do not have any gold
coins but I might have gold-plated headphone plugs) and copper at +.34.

So if I use aluminum and copper, we have a potential voltage for one cell of:
..34- (-1.66) of 2.0 volts. Looking at studies the actual voltages runs about
60-80% of potential voltage.

Before I start linking multiple cells together I want to maximize the voltage
for one cell. Other studies I read yesterday showed the electrolyte with the
lowest pH produced the most voltage. I think vinegar was the best overall.

--
Sig: Say no to fixed width HTML tables. They look terrible in most browsers.

A Man, Jan 13, 2006
6. ### Charles JeanGuest

Magnesium is available in rod form with a wire already connected to
it. It is used as a sacricial anode in water heaters and evaporative
If it is lower pH you need, acetic acid(vinegar) won't get you much
lower than 4. Best bet is pool acid(hydrochloric acid) or battery
acid(sulfuric acid). CAREFUL with both of these! Both are toxic and
highly corrosive-sulfuric mixed incorrectly with water can boil and
splatter on you.

On Fri, 13 Jan 2006 05:38:52 GMT, Yukio YANO <> wrote:

>A Man wrote:
>> My goal is to work with my son to make a home made battery. The basic battery
>> uses a lemon (or lemon juice) with a copper part and zinc part. But that only
>> produces about .8v. (I think this is called a wet cell.)
>>
>> My question is, what are the 2 best metals to use to maximize voltage?
>> What are the best 2 metals to use to maximize runtime? I want to run an LED
>> for about 8 hours consecutively. (But LEDs draw about 3.0-3.2 volts, even red
>> ones.)
>>
>> Should I try lead in place of zinc?
>> What lead items can I use?
>> How much lead is in solder?
>>
>> Thanks for the help.
>>
>>

>It's not what's best but what is most practical (read available and
>cheap)eg You wouldn't consider Gold and Platinum foils for example,
>available is Sheet Copper or Copper-plated PC board and Zinc coated
>(galvanized iron). Carbon rods used to be readily salvaged from
>flashlight batteries before they went into more exotic chemistries.
>Aluminum foils tend to develope an insulating Anodic Coating, a process
>use to make Capacitors. You need more Voltage ? Use several Cells in
>series ie make a battery of cells. Electrolytes, HCl, Hydro-Chloric
>(muriatic acid) is readily available from the hardware stores, Sulfuric
>acid , H2SO4 is a little harder to get but is used in Automotive
>Batteries other acids eg Citric acid (lemon
>juice), Formic acid and Vinegar (acetic Acid)are not as highly Ionizing
>as HCL, H2SO4, HNO3, Nitric acid or H3(PO4) Phosphoric Acid don't even
>think about HF (Hydro-Fluoric Acid) same class as HCN, Prussic acid or
>Hydrogen Cyanide both are extremely toxic !
>anyway, so much for the lesson in practical Chemistry and Physics.
>
>most common grade of electronic Solder
>You could take some Wire solder and hammer it flat.
>
>you could use a copper penny or a piece of copper pipe or copper wire.
>You could find a SILVER dime or quarter or some Sterling SILVER jewellry
>You could find some Gold jewellry
>You could recover some Mercury and use that for an electrode (Not
>Recommended)
>You could take some (un-plated, un-coated) nails for Iron electrodes
>You could recover the Tungsten filement from a light bulb
>you can find Aluminun foil in any kitchen
>
>Yukio YANO

Charles Jean, Jan 13, 2006
7. ### Bill BowdenGuest

A Man wrote:

> So if I use aluminum and copper, we have a potential voltage for one cell of:
> .34- (-1.66) of 2.0 volts. Looking at studies the actual voltages runs about
> 60-80% of potential voltage.
>
> Before I start linking multiple cells together I want to maximize the voltage
> for one cell. Other studies I read yesterday showed the electrolyte with the
> lowest pH produced the most voltage. I think vinegar was the best overall.
>
>

Besides voltage, also consider surface area of the electrodes to
extract more total energy. Electrodes using small rods probably won't
work very well. Better to use plates of several square inch area. The
battery will produce more current with larger area electrodes.

-Bill

Bill Bowden, Jan 13, 2006
8. ### Rich GriseGuest

On Fri, 13 Jan 2006 12:45:32 -0500, A Man wrote:
> spoke thusly...
>> "A Man" <> wrote in message
>> > My goal is to work with my son to make a home made battery. The basic

>> battery
>> > uses a lemon (or lemon juice) with a copper part and zinc part. But that

>> only
>> > produces about .8v. (I think this is called a wet cell.)
>> >
>> > My question is, what are the 2 best metals to use to maximize voltage?
>> > What are the best 2 metals to use to maximize runtime? I want to run an

>> LED
>> > for about 8 hours consecutively. (But LEDs draw about 3.0-3.2 volts, even

>> red
>> > ones.)
>> >
>> > Should I try lead in place of zinc?
>> > What lead items can I use?
>> > How much lead is in solder?
>> >
>> > Thanks for the help.

>>
>> You will find a table "Electro-motive series" in a good physics or chemistry
>> textbook or indeed on the internet. You may use that table to deduce the
>> best metals to use. Try magnesium in place of zinc.
>>

> You are correct. I did find those tables. The positive electrode corresponds
> to the metal with a positive "electric reduction potential" (ERP) I think it
> was called. The negative electrode metal corresponds to the negative ERP.
> Subtract the 2 and you get the total potential, which is the POTENTIAL
> voltage produced by the cell. The ACTUAL voltage is less than that.
>
> So, for the negative part, lithium is -3.04. I don't think that's practical
> because I thought elemental lithium was very toxic to the skin and other
> organs. Next best was Mg (magnesium?) at -2.38. But that's hard to find.

Huh?

> Next
> best was aluminum at -1.66, and I do have aluminum foil.

That will make a very good capacitor.

> Next best is silver
> at -.799. I might have some old silver plated US coins before 1964.

There have never been silver plated US coins. They were some silver
alloy, until they decided to omit silver entirely, and came up with
that copper/nickel sandwich.

There _is_ silver plated silverware, however. Poke a fork in your
lemon, and you'll have a lot of electrode area too!

> For the positive electrode we have gold at +.799 (I do not have any gold
> coins but I might have gold-plated headphone plugs) and copper at +.34.

Does that table have carbon?

And what is the table actually of? I thought gold was practically inert,
i.e, neutral, more or less. Can you expand on this?

> So if I use aluminum and copper, we have a potential voltage for one cell of:
> .34- (-1.66) of 2.0 volts. Looking at studies the actual voltages runs about
> 60-80% of potential voltage.

Until the oxide layer forms on the aluminum.

> Before I start linking multiple cells together I want to maximize the voltage
> for one cell. Other studies I read yesterday showed the electrolyte with the
> lowest pH produced the most voltage. I think vinegar was the best overall.

Good Luck!
Rich

Rich Grise, Jan 13, 2006
9. ### Rich GriseGuest

On Fri, 13 Jan 2006 19:35:46 +0000, Charles Jean wrote:

> Magnesium is available in rod form with a wire already connected to
> it. It is used as a sacricial anode in water heaters and evaporative
> coolers. Check your hardware stores.
> If it is lower pH you need, acetic acid(vinegar) won't get you much
> lower than 4. Best bet is pool acid(hydrochloric acid) or battery
> acid(sulfuric acid). CAREFUL with both of these! Both are toxic and
> highly corrosive-sulfuric mixed incorrectly with water can boil and
> splatter on you.

Add the H2SO4 to the water - do not _EVER_ add water to concentrated
H2SO4!

Good Luck!
Rich

Rich Grise, Jan 13, 2006
10. ### Tim WilliamsGuest

"Rich Grise" <> wrote in message
news...
> Does that table have carbon?

No- carbon ions are notoriously difficult to utilize in solution.

> And what is the table actually of? I thought gold was practically inert,
> i.e, neutral, more or less. Can you expand on this?

The table is based on reduction potentials, which means you have the metal
*ions* in solution (like auric chloride, Au(3+) + 3Cl(-) since it ionizes in
solution) and, somehow or another, you apply a certain amount of voltage (or
produce a certain amount) to cause zero current, depending on whether it
wants to be in or out of solution.

A classic example is the gravity cell, where you put a wire at the bottom
among copper sulfate crystals. Fill with water and put a zinc bar anode on
top. The heavy, Cu-saturated solution remains at the bottom, keeping it (to
some extent) from depositing directly on the zinc, which would be useless.
Instead, the zinc's potenential is brought down to the copper wire by an
external circuit (the load), where the copper plates out. The plating
action frees sulfate ions, which grab protons and form sulfuric acid, which
attacks the zinc, freeing some electrons in the process (Zn(0) = Zn(2+) +
2e-).

If you use salt water instead, sodium cannot come out of solution (too damn
reactive!), and zinc can't reduce it anyway (2.7 vs. 0.76V!). The only
reaction that can occur is hydrogen being displaced (having null potential
by definition, H > H+ + e- = 0V). Zinc is above hydrogen (by 0.76V), so
that'll work. The reaction would be 2H2O + Zn > Zn(OH)2 + H2. The cathode
can be something unreactive like platinum or, cheaper yet, graphite can be
used.

This reaction is used in "dry cells", except the electrolyte is NH4Cl, and
they add manganese dioxide for the dual purpose of absorbing the hydrogen
(also preventing polarization) and generating more voltage (2MnO2 + H2 >
Mn2O3 + H2O). In total, the reactions produce about 1.5V, and there you go!

If you use inert electrodes, they do not contribute any voltage. If you use
a solution of a noble ion (like Cu(2+) or Au(3+)), making sure to seperate
it (permeable membrane, etc.) from the reactive anode, you can drive up the
voltage.

Aluminum works fine in acid (hydrochloric) or basic solution, where the
oxide is unstable. I've had about 0.8V from the reduction of hydrogen in
NaOH solution (Al + 2H2O > AlO2- + 3H, that's the aluminate ion).

Tim

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Tim Williams, Jan 14, 2006
11. ### A ManGuest

On Fri, 13 Jan 2006 21:56:42 GMT in article <pan.2006.01.13.21.56.57.519902
@example.net>, spoke thusly...
> Does that table have carbon?

Yes, but carbon has a relatively low reactivity.

>
> And what is the table actually of? I thought gold was practically inert,
> i.e, neutral, more or less. Can you expand on this?
>

Gold is an excellent conductor of electricity, but it is expensive. That's
why you see gold-plated connectors on audio plugs, as well as on PC cards
(and the slots they go into). And I think many of the runways in PC boards
are actually made of a micro thin layer of gold.

Though gold is a better conductor of electricity, I don't know if that means
electrical noise from external sources is reduced. Regular headphones sound
the same to me.

So, as copper is the next best thing, it is more widely used.

--
Sig: Say no to fixed width HTML tables. They look terrible in most browsers.

A Man, Jan 16, 2006
12. ### A ManGuest

On Fri, 13 Jan 2006 19:35:46 GMT in article
<>, spoke
thusly...
> Magnesium is available in rod form with a wire already connected to
> it. It is used as a sacricial anode in water heaters and evaporative
> coolers. Check your hardware stores.

And at \$30-50 each (I had to replace one once), not a great choice for budget
armchair scientists, but thanks anyway. But then, science is not about cost,
is it?

--
Sig: Say no to fixed width HTML tables. They look terrible in most browsers.

A Man, Jan 16, 2006
13. ### GuestGuest

Charles Jean <> wrote:
: Magnesium is available in rod form with a wire already connected to
: it. It is used as a sacricial anode in water heaters and evaporative
: coolers. Check your hardware stores.
: If it is lower pH you need, acetic acid(vinegar) won't get you much
: lower than 4. Best bet is pool acid(hydrochloric acid) or battery
: acid(sulfuric acid). CAREFUL with both of these! Both are toxic and
: highly corrosive-sulfuric mixed incorrectly with water can boil and
: splatter on you.

Isn't magnesium also available in those fire-starting kits? The
kits where you scrape magnesium shavings off, and then use a flint to
start the fire?

Seems like a good source of Mg to me....

Joe

Guest, Jan 16, 2006
14. ### GuestGuest

A Man <> wrote:
: On Fri, 13 Jan 2006 19:35:46 GMT in article
: <>, spoke
: thusly...
:> Magnesium is available in rod form with a wire already connected to
:> it. It is used as a sacricial anode in water heaters and evaporative
:> coolers. Check your hardware stores.

: And at \$30-50 each (I had to replace one once), not a great choice for budget
: armchair scientists, but thanks anyway. But then, science is not about cost,
: is it?

Here is what I was talking about in a previous post:

Go to www.campmor.com
Search by item number
Enter item number 23131
There you go -- the price is only \$6.99. I'm sure you can find
this at your local camping store, as well.

Have Fun,

Joe

Guest, Jan 16, 2006
15. ### Bill BowdenGuest

> Gold is an excellent conductor of electricity, but it is expensive.

Gold is not as good as copper, gold has 1.4 times more resistiance than
copper.

> That's why you see gold-plated connectors on audio plugs, as well as on PC cards
> (and the slots they go into). And I think many of the runways in PC boards
> are actually made of a micro thin layer of gold.

> Though gold is a better conductor of electricity, I don't know if that means
> electrical noise from external sources is reduced. Regular headphones sound
> the same to me.

> So, as copper is the next best thing, it is more widely used.

Copper is used because it has has much less resistance than gold.
Gold is used only because it doesn't corrode.

-Bill

Bill Bowden, Jan 17, 2006
16. ### Don KlipsteinGuest

In <43c7e7a9\$0\$98229\$>, A Man wrote:
>On Fri, 13 Jan 2006 11:55:11 +1300 in article <dq6mpv\$mc4\$>,
> spoke thusly...
>>
>> "A Man" <> wrote in message
>> news:43c69ed3\$0\$8443\$...
>> > My goal is to work with my son to make a home made battery. The basic

>> battery
>> > uses a lemon (or lemon juice) with a copper part and zinc part. But that

>> only
>> > produces about .8v. (I think this is called a wet cell.)
>> >
>> > My question is, what are the 2 best metals to use to maximize voltage?
>> > What are the best 2 metals to use to maximize runtime? I want to run an

>> LED
>> > for about 8 hours consecutively. (But LEDs draw about 3.0-3.2 volts, even

>> red
>> > ones.)
>> >
>> > Should I try lead in place of zinc?
>> > What lead items can I use?
>> > How much lead is in solder?
>> >
>> > Thanks for the help.
>> >

>>
>> You will find a table "Electro-motive series" in a good physics or chemistry
>> textbook or indeed on the internet. You may use that table to deduce the
>> best metals to use. Try magnesium in place of zinc.
>>

>You are correct. I did find those tables. The positive electrode corresponds
>to the metal with a positive "electric reduction potential" (ERP) I think it
>was called. The negative electrode metal corresponds to the negative ERP.
>Subtract the 2 and you get the total potential, which is the POTENTIAL
>voltage produced by the cell. The ACTUAL voltage is less than that.

Usually in simple homebrew batteries the positive electrode cannot have
much improvement over hydrogen (going downward) in the electromotive
series.

>So, for the negative part, lithium is -3.04. I don't think that's practical
>because I thought elemental lithium was very toxic to the skin and other
>organs.

Also lithium has severe spontaneous rections with water. So do all
other metals in the first column of the periodic table - there is some
fame for at least sodium and potassium to react with water so violently as
to achieve spontaneous combustion. All metals in the first colum of the
periodic table also react with air so rapidly that a shiny bare metal
surface lasts only seconds. Metals in the first column of the periodic
table are normally kept in a petroleum product to protect them from water
and air - but lithium has the extra problem of floating in anything that
is liquid at or near room temperature and any Earth surface atmospheric
pressure.

Next in line are the metals of the second column of the periodic table.
But calcium, strontium, barium and radium go plop-plop-fizz-fizz in water
(to form hydrogen and hydroxide of the metal in question) - that leaves
beryllium and magnesium as usable in that column of the periodic table.
Of these, beryllium has bigtime toxicity and cost problems, leaving
magnesium as the most electropositive common metal.

>Next best was Mg (magnesium?) at -2.38. But that's hard to find. Next
>best was aluminum at -1.66, and I do have aluminum foil.

Aluminum's main problem is its tendency to form an insulating oxide
layer.

> Next best is silver at -.799. I might have some old silver plated US
> coins before 1964.

1964 and older US dimes and quarters and 1965 and older Canadian dimes,
quarters and nickels are solid silver alloy that is mostly silver...BUT:

Silver is not more electropositive than hydrogen (useful for negative
terminal) on the electromotive scale but below copper (good for positive
electrode and and not much more useful in homebrew batteries that
typically have plenty of hydrogen ions that limit the potential of the
negative electrode). I would use copper.
In addition, achievement of positive electrode much improving over
hydrogen in a cell having water typically requires at least one of:

1. The cell having a solution of a salt of a metal that is below hydrogen
on the electromotive scale. But a simpler homebrew cell with that tends
to have problems with the dissolved salt reacting spontaneously with
any metal positive electrode material higher in the electromotive series.

2. Oxidizing agents such as some metal oxides - like lead dioxide or
manganese dioxide - which I do not cosider quite to be in the realm of
homebrew "science fair" batteries.

>For the positive electrode we have gold at +.799 (I do not have any gold
>coins but I might have gold-plated headphone plugs) and copper at +.34.

The positive electrode in a homebrew science fair style cell has little
chance of benefiting much from choice among metals below hydrogen in the
electromotive series.

>So if I use aluminum and copper, we have a potential voltage for one cell of:
>.34- (-1.66) of 2.0 volts. Looking at studies the actual voltages runs about
>60-80% of potential voltage.

The positive electrode will in most homebrew batteries be no better or
not much better than hydrogen. So I would expect only about 1.66 volts.

>Before I start linking multiple cells together I want to maximize the voltage
>for one cell. Other studies I read yesterday showed the electrolyte with the
>lowest pH produced the most voltage. I think vinegar was the best overall.

Slightly more voltage, much more current, but with the disadvantage of
making the negative electrode react spontaneously. Metals well above
hydrogen in the electromotive scale outright go plop-plop-fizz-fizz in
strongly acid solutions. Life of a zinc electrode could be merely a day
in vinegar, a couple days in lemon juice, a week in orange juice, a month
in a tomato, and a few months in a potato - and I might be somewhat
optimistic for at least some of these!

Standard conditions for electromotive scale are solvent being water.
In addition, when hydrogen is involved (most cases of homebrew batteries
with positive electrode being below hydrogen on the electromotive scale):

1. pH of 0

2. Temperature where product of molarities of H+ and OH_ ions is 1E-14
(a bit above 20 degrees C)

3. The atmosphere above the solvent having hydrogen of pressure (or
partial pressure in a gas mixture) 760 mmHg.

Additional requirement whether or not hydrogen is involved:

Concentration of ions of active ingredients is 1-molar (or is it
1-normal?) 1 molar is per liter grams in solution being same as molecular
weight. For 1-normal grams in solution is molecular weight divided by
valence.

But with typical homebrew batteries concentration of compunds of the
negative electrode material likely to be less than 1-molar and even
1-normal, I would expect potential to improve a little from the
electromotive value of the negative electrode metal. Maybe aluminum's
1.66 will improve to 1.75 or 1.8 or so (with pH 0) oe be 1.5-1.6 (if pH
is between 2 qnd 3) - maybe only if you draw no more than a fraction of a
microamp. But don't expect positive elecrodes to gain much over hydrogen,
which normally forms bubbles on the positive electrode when current is
taken from such an electrochemical cell.

- Don Klipstein ()

Don Klipstein, Jan 17, 2006
17. ### Don KlipsteinGuest

In article <>, Rich Grise wrote:

>Does that table have carbon?

In most cells with water solvent and where the positive electrode
reaction is reduction of dissolved ions (most homebrew batteries but not
usual commercial ones with carbon positive electrodes), the positive
electrode potential is limited to that for dissolved ions of active
ingredient.
In any case carbon is not an active ingredient.

In acid solution, positive electrode potential is largely limited to how
low in the electromotive series hydrogen is.

Also - keep in mind that positive ions of an active ingredient low on
the electromotive scale may get spontaneously reduced by the negative
electrode.

A homebrew battery with aluminum and copper electrodes in a 1-molar (or
1-normal?) aqueous solution of a copper compound should deliver 2 volts -
except the aluminum will like to replace the copper ions - getting
simultaneously corroded and plated with copper, spontaneously.

>And what is the table actually of? I thought gold was practically inert,
>i.e, neutral, more or less. Can you expand on this?

Relevance of gold is for either 1-molar or 1-normal solution of a gold
salt. The positive electrode will plate with gold when current is drawn.
Voltage attributable for that electrode is fully available if the
electrode is or is covered with gold - easily enough achievable once
current flows assuming solution of a gold salt.

Carbon is not on the scale since there are no carbon compounds that form
carbon ions when dissolved in water. Use of a truly inert positive
electrode has its potential determined by what positive ions in the
electrolyte contact the positive electrode.

- Don Klipstein ()

Don Klipstein, Jan 17, 2006
18. ### Don KlipsteinGuest

In article <>, Rich Grise wrote:
>On Fri, 13 Jan 2006 19:35:46 +0000, Charles Jean wrote:
>
>> Magnesium is available in rod form with a wire already connected to
>> it. It is used as a sacricial anode in water heaters and evaporative
>> coolers. Check your hardware stores.
>> If it is lower pH you need, acetic acid(vinegar) won't get you much
>> lower than 4. Best bet is pool acid(hydrochloric acid) or battery
>> acid(sulfuric acid). CAREFUL with both of these! Both are toxic and
>> highly corrosive-sulfuric mixed incorrectly with water can boil and
>> splatter on you.

>
>Add the H2SO4 to the water - do not _EVER_ add water to concentrated
>H2SO4!

I have heard the saying:

"Do as you oughta - add acid to water"!

And I remember a comic strip having a character saying,
"Or is it, to keep the lab placid, add water to acid?" BAD MOVE!!!
(Comic strip character adds water to acid and then appears to make the
school nurse's day interesting!)
I say "water to acid means that you're plastered"!

Same for sodium and potassium hydroxides - mixing these with water can
cause boiling.

One reason for adding to water rather than adding water - that way if
boiling occurs and causes splashing, what splashes out will be mostly water.
Another reason - water makes a better heatsink than acids and alkali
metal hydroxides.

And in any case, add slowly and cautiously while mixing.

- Don Klipstein ()

Don Klipstein, Jan 17, 2006
19. ### Jasen BettsGuest

On 2006-01-16, A Man <> wrote:
> On Fri, 13 Jan 2006 21:56:42 GMT in article <pan.2006.01.13.21.56.57.519902
> @example.net>, spoke thusly...
>> Does that table have carbon?

> Yes, but carbon has a relatively low reactivity.
>
>>
>> And what is the table actually of? I thought gold was practically inert,
>> i.e, neutral, more or less. Can you expand on this?
>>

> Gold is an excellent conductor of electricity, but it is expensive.

gold is a so-so conductor of electricity, but is very resistant to
tarnishing that's why it's used to coat contacts.

silver is a marginally better conductor than copper.

Bye.
Jasen

Jasen Betts, Jan 17, 2006
20. ### ehsjrGuest

Jasen Betts wrote:
> On 2006-01-16, A Man <> wrote:
>
>>On Fri, 13 Jan 2006 21:56:42 GMT in article <pan.2006.01.13.21.56.57.519902
>>@example.net>, spoke thusly...
>>
>>>Does that table have carbon?

>>
>>Yes, but carbon has a relatively low reactivity.
>>
>>
>>>And what is the table actually of? I thought gold was practically inert,
>>>i.e, neutral, more or less. Can you expand on this?
>>>

>>
>>Gold is an excellent conductor of electricity, but it is expensive.

>
>
> gold is a so-so conductor of electricity, but is very resistant to
> tarnishing that's why it's used to coat contacts.

Actually, as I recall gold is the third best conductor.

Only copper and silver are better - silver is best.
Ed

>
> silver is a marginally better conductor than copper.
>
> Bye.
> Jasen

ehsjr, Jan 17, 2006