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12v dc cooler (instructables)

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12v dc cooler (instructables)

Post by Admin on Thu Apr 02, 2015 3:31 pm

This project is my dad's $10 solution
to a $500 solution to a $25,000
problem. As I have previously
mentioned around the site, my Dad
owns an electric 1979 Ford Courier
pickup, and is cool enough to let me
drive it around. We absolutely love it,
and wouldn't trade it for a Tesla
Roadster, but one of the few problems
with electric cars is heating and
cooling. In a gas car, heat is provided
by the 80% of the gas that is wasted
as heat, and air conditioning is
provided by a crankshaft-driven
compressor system. Many EVs use hair
dryer elements and fans for heat, and
some, ours included, feature a
powerful gasoline-burning heater.
(Update from 4-22-08: I'd forgotten
that I mentioned the gas heater on
here. Last fall the gas tank and heater
were removed, and a ceramic heater
was built in. It works great, although
not quite as fast, and doesn't use gas.)
However, air conditioning is trickier
because the shaft of an electric motor
doesn't always spin. Some have used
a compressor driven by the motor
shaft anyway, while others have
turned a compressor using a separate
motor. Finally, my dad came up with
part of the concept for this system. It
pumps ice water through an
evaporator core, which has fans that
blow air through it. It is very simple,
but we found what we were looking
for at Sporty's Pilot Shop. They sell air
conditioners built into ice chests for
prices ranging from $475 for a basic
model to $625 for a 24V, dual fan
model.There is also an ArcticAir unit
for $4750 with a full compressor unit.
However, we like our $10 version
better. I saw the ArcticAir display at
EAA AirVenture Oshkosh this summer,
and our unit is more compact and
puts out cooler air. All you need is
materials, basic construction/assembly
and wiring skills, and a bag of ice.
Let's go!
Update, 5-12-08: 100,003 views! Yay!
I'm no Kipkay, but I'm still proud.
arcticair brochure.pdf
This project is very similar to the
ArcticAir Package Unit. In fact, I
attached two pictures of it I took at
AirVenture this past summer. It looks
almost identical to ours, and we built
this without ever seeing a picture of
the inside! The basic concept is to use
a boating bilge pump to circulate iced
water through a heater core, then use
12V fans to blow air through that
core, which cools the air and pulls out
water through condensation.
Advantages: Very compact and
portable, lightweight without the ice,
no environmentally not-so-friendly
chlorofluorocarbons, hydrogenated
chlorofluorocarbons, or
hydrofluorocarbons, very quiet, and
operates off 12VDC, AKA a cigarette
lighter. The only disadvantage is that
it the ice will melt after 30-60
minutes of operation, depending on
the size of your cooler. However, it
was built for an EV, so we are only
ever out for an hour or two
maximum, and the ice lasts longer
when it's not running. The third image
on this step shows the operation.
Have I convinced you to build one
You can't very well build this without
materials to build it with, can you? I
have included the prices we paid for
them in italics, as well as prices you
might pay and places to get them.
Ice Chest-free, had it on hand If at
all possible, get one with a hinged lid.
Free from a storage shed or a
dumpster. Or, the Igloo Ice Cube 14
looks like it would work,well, as do
the Cool 16 and the MaxCold 24. We
used an old 12 quart cooler, and it fit
a 7 pound bag of ice.
Heater Core-free, salvaged from a
'77 VW Rabbit we're parting out You
can find these on eBay for 99 cents to
$20, or from an auto store for around
20 bucks, or at an auto salvage yard.
Also, I haven't tried it, but
Ufixitautoparts sells heater cores for
under 5 bucks apiece.
Box Fans and Blade Guards-free,
from stock in basement They're sold
out of $5 120mm 12VDC fans at All
Electronics, but Jameco carries these
for $12.95 each. Newegg has a nice
assortment, too. Under $10 on eBay.
Bilge Pump-$10.44 for a 500GPH
unit at Wal-Mart The Attwood V500
was at our Wal-Mart for $10.44-you
can get a similar pump for under $10
on eBay.
Hose-free, had it in stock Ours came
from an auto-parts store, but it can be
found at hardware and auto-parts
stores for a dollar or so for a few feet.
12V plug-free, chopped off a car
accessory Cut one off an old phone
charger or other device, or $5 at
Radio Shack, or $3.75 at All
Caulking-free, from the stock in the
shop Can be found near the bilge
pump, or from a hardware store. A
couple bucks.
Piano hinge (depending on cooler)
-free, in stock Only necessary if your
cooler isn't hinged. A couple bucks at
the hardware store.
Inner tube piece (optional)-free,
blown tube You may or may not need
this-see step 7. If you do, use a blown
one, or another piece of rubber, or
come up with a substitute. You did
save the last blown tube for future
projects, didn't you? A couple bucks,
Assorted wire, wire nuts, and
screws -free, in stock Depends on
what you have in stock and where
you get it. It's all at the hardware
store, too.
Ice-free, freezer's ice maker If you
need me to tell you where to get ice,
you shouldn't be doing this project.
Cutting devices
Obligatory safety spiel: Cutting
devices cut. Don't cut yourself on
them. Drills drill. Don't drill a hole in
yourself, my dad says it hurt when he
did it once. Screwdrivers don't really
do anything, but don't throw them
into running jet turbine engines. 12V
doesn't do much, but watch out. Oh,
and wear safety glasses while you're
at it.
An ice chest/cooler has a double lid
with a cavity. This is convenient
because we can cut separate holes for
the fan and heater core.
On the underside of the lid, mark the
outline of the heater core, then go in
about a quarter inch and cut out a
rectangular hole through ONLY the
first layer. This will allow airflow
through the core, but still make it
easy to attach.
Next, you will need to mark the inside
of the fans and cut out two circular
holes. We originally planned to use a
hole saw to cut the holes, but found
that we didn't have a bit that big, so
we chucked a saw blade into the
Dremel Rotary tool and zipped it out,
of course wearing safety glasses (hint
Tada! You now have a rectangle on
the inside and two circles on the
outside. Now that you cut out these
lovely holes, lets fill them in.
The next step is to attach the fans.
This is fairly straightforward--simply
drill a small pilot hole at each corner
of each fan, and put a small screw
through the bottom hole into the
plastic lid. Don't block the top hole if
you want to add a fan guard later.
To attach the heater core, we used
silicone caulk. A bead all the way
around seals the lid and provides
plenty of bonding force to hold the
heater core in place. Make sure to get
the core centered, straight, and with
the nozzles pointing in. If your lid is
hinged, you will want to do a test fit
before attaching the core to ensure
that the nozzles clear the edges. If
your lid is not hinged, it may be
easier to attach it first. We ended up
cutting the output off to make it fit
The ArcticAir unit just leaves their
bilge pump just dangling from the
hose, but we wanted it to be more
secure. The pump has a twist-off base,
so we twisted it off and Gorilla Glued
it to the bottom of the cooler. Make
sure that it is angled so that you can
easily run a hose from the pump
output to the heater core input. We
attached the base directly to the
bottom of the cooler, which works
fine, but we probably should have put
some spacers in to increase water flow
underneath. Also, the picture just
shows where it goes. We haven't
attached that hose yet, so ignore it.
If you used a cooler with a hinged
lid, skip this step. Otherwise, read on.
By hinging the lid, it makes it easier
to open for loading ice and letting air
flow in during operation. It also
prevents the lid from sliding off and
dribbling water out of the heater core
while driving. You can use whatever
you want for a hinge-a rubber strip
glued on, a couple of cabinet hinges,
whatever. We used a piano-type hinge
that we found in our stockpile of
random stuff. It goes all the way
across the back, and allows the lid to
flip all the way back, but still close
This is fairly straightforward. Connect
a hose from the output of the bilge
pump to the input of the heater core.
In most cases, it doesn't matter which
nozzle is used as the input. We just let
the output dribble back in, but if the
noise bothers you, you could attach a
hose to the output. This would also be
used as a drain hose.
We also attached a piece of bicycle
inner tube rubber to catch water that
drips from the output and that
condensates on the core. It was cut to
fit around the back edge and a couple
inches up he sides, and secured with a
mega-rubber band we found. This
may be unnecessary if you attach a
hose to the output, or if your heater
core is configured differently.
This would also be a good time to
attach wire fan guards to the fans.
Just put some screws through the
guards into the top holes.
It would be difficult to make the
make the wiring for a project easier
than this. There should be a red and a
black wire coming from each fan, the
bilge pump, and the 12V plug. Use
wire nuts to attach them all together,
and make sure the pump and fans are
going the right directions. The fans
should be blowing out, and the pump
should be pumping through the hose.
After everything is moving correctly,
you can solder the wires together, or
put a switch in the power cord. We
also used small zip ties to hold the
wires together and to the fan.
Pretty easy, really. Dump in enough
ice to fill the cooler about 3/4 of the
way, pour in about a half-gallon of
water (thats two liters for the smart
people) so that the bilge pump can
work, and plug it in! And flip the
switch if you installed one. Make sure
that you open the lid slightly for
return airflow. We found that flipping
the handle over to prop up the lid
provides plenty of airflow without
letting the ice get too warm.
If everything is hooked up right, the
pump should be humming away, and
the fans should be blowing. The water
is chilled enough to cool the air
within a few seconds. You can put this
in your car with the dead A/C (note:
this will cool pickups and small cars.
Don't bother on your Ford Excursion),
you can hook it up to a wall outlet
through a 12V battery charger, or you
can clip it onto a small 12V gel cell.
We took the unit out to the truck for
a test run when it was well over 90
degrees Fahrenheit (mid to high 30s
for Celsius people). My dad set it in
the truck and plugged it in, then went
back to the house to get a camera. By
the time he returned to the truck, the
air inside had already dropped below
80, and the air was much drier,
making it also feel much cooler.
I attached a PDF of JPEG of a scan of
a notecard that my dad took notes on.
What it basically says is the following:
When the unit was started, the air in
the cab was 95 degrees, parked in the
shade after a morning of sun,and the
outside heat index was 108 degrees.
Within five minutes the cab had
cooled to 75 degrees, and the air
output was 65 degrees. With two
quarts of water that had been
refrigerated and 8 pounds of ice
cubes, the ice had melted after 40
minutes, leaving 50 degree water,
with an output of 65 degree air.
In other words, it works! And it works
great! On Sunday, August 12 we
brought it to Kansas City for a
monthly meeting of our electric auto
group. WE met in a small meeting
room of a library, and ran the air
conditioner off a small 12V battery on
a table. Many of the members were
impressed that they could feel the
room getting cooler, and many tried
to buy it from us on the spot. We are
also in correspondence with an EV
owner from Alabama who is eagerly
awaiting the publication of this
Instructable (I hope). If you're
reading this, you know who you are,
and I hope you like it.
We have some ideas for further
modification that we may or may not
implement. For starters, we will
probably connect a hose to the heater
core output. This will eliminate the
burbling, trickling sound that is hard
on one's bladder, as well as make it
easier to drain. The ArcticAir units
have a valve inside that you turn to
redirect the output to an external
hose so that you can drain the cooler
out the window onto the flight line
without wrestling it through the door.
Another option would be a drain plug
on the bottom, which is already on
many models of coolers. We also are
considering a vent system, so that the
lid could remain closed while still
allowing air to circulate. The ArcticAir
units have a louver vent on one side
for this purpose. A third modification
would be some way to redirect the
airflow. ArcticAir units have adjustable
flaps over the fans, which could work,
or some have a duct hose assembly to
redirect the airflow where it is
needed. A fourth, and painfully
obvious, step would be to enclose all
the wiring inside the lid or in a
project box to make it look neater.
However, for the time being, the zip
ties are plenty for us. Also, we may try
using Blue Ice-type ice packs, so that
it would be reusable and not waste
This being a Go Green contest, I
should put in a spiel about why you
would bother with this. The main
purpose is to make it more
comfortable to drive a zero-emissions
electric truck in Kansas in August. This
runs off any 12V power source that
can shove out 3 amps, so it can be
used in other areas that need cooled,
such as a hot workshop. Also, the ice
lasts for hours when it's not running,
and you can leave it on while you run
into the store. The only disadvantage
is that you could say it wastes water
in the form of ice, but you can empty
it out on your garden or lawn. It uses
only ice water for cooling, which is
about as non-toxic and
environmentally friendly as you can
get, and it kept a hose, a cooler, and
a heater core out of a landfill. In
other words, it uses environmentally
friendly power to run environmentally
friendly coolant through recycled
parts in a zero-emissions vehicle. Can
you get greener than that? I mean,
this is #008000 at its best! Just make
sure to recycle batteries.
Thank you for reading!
9 April 2010: I'm adding this step to
address some of the comment
subjects of the comments...with 384
comments and counting, it's not
nearly as easy to just read through
Dry ice instead of water ice
First, a clarification: water ice isn't
32°F, it's whatever the temperature of
the freezer is, anything below
32degF...just like how the steel on
your car can be 10°F on a cold day, or
100°F on a hot day. Dry ice can be
any temperature below -109°F. Since
it is much colder, id would
theoretically put out colder air. The
two main problems with this idea are:
1) Dry ice has a lower specific heat
capacity than water ice, so while it is
colder, it won't last as long.
2) Dry ice sublimates to CO2, which,
in a confined space, will at best
impair judgment, and at worst cause
loss of consciousness. Driving a car
requires being alert. I highly
discourage using dry ice.
Peltier Junctions
Seems like a good idea, I know--add
12V and that little plate gets frosty
cold. But you have to consider the net
movement of heat. All that a peltier
does is create a heat differential...a
difference in temperature between the
two sides. It does this by moving the
heat from one side to the other. If
you put a peltier inside the car, it
won't cool anything down, because
the same amount of heat that is
removed to make one side cool is
released on the other side right back
into the car. The only way this could
possibly work is if it was mounted so
that the heat was released outside the
Isn't this just a swamp cooler?
Uhhhhhhhhhh....NO. A swamp cooler
works by blowing air over wet stuff
(straw, wool, air, you name it), which
evaporates the water. Since
evaporation is an endothermic process
(splash alcohol on your hand and feel
how much it cools as it evaporates),
the air is cooled down---BUT is also
wet and full of all the water that just
evaporated, making it only suitable
for places that are hot and dry. This
air conditioner is simple heat
transfer--heat is transferred out of the
air into the ice water. Since the ice
water is cold, vapor in the air
condenses on the coils, so it actually
pulls water out...making it much more
suitable for humid Kansas summers.
Ye salty sea dog!
Using salt water or alcohol to lower
the freezing point, so it will be
colder...not really. The temperature is
determined by how cold your freezer
is. Oh, and salt water is corrosive and
will OM NOM NOM your heater core.
Liquid Nitrogen
Er...for the same cost, you could buy a
new car...which has air
conditioning...and doesn't involve
Let's take this Outinside
Remember the energy flow. If you
freeze the ice in your own freezer, all
the heat that is pulled out of the ice,
and then some, is released into your
house from the coils in the back of
the freezer. You could use this to cool
that hot bedroom, but the house as a
whole will be warmed.
Yeah, yeah, it takes energy to freeze
water, yada yada yada. If you can't
handle your freezer running a bit
extra, then quit whining and roll
down the window.
Using the existing core
Yes, you can hook it up to run cold
water through the original heater core
so it blows through the original ducts.
The whole point of this was to be
portable, though. If you want a more
permanent installation, have at it.

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