Instructables
I currently live in the Phoenix, Arizona area, which gets mighty hot in the summer. This summer, we've had several days around or above 110 degrees. I have twin baby boys, and despite cracking the windows, using reflective seat covers and running the A/C full blast when driving them around, their backs are just soaked with sweat when we reach our destination. The seats bake in the car in the sun for hours, then you put a baby in it and they never really cool off. So I devised this method for cooling their car seats with pump-recirculated cold water. The end product is a cooling pad to fit underneath the car seat cover behind their backs. This can be easily modified to fit adults too.

When I was about 75% done with my system, I stumbled upon this instructable. It's pretty similar to my setup, and I ended up using his source for some of my tubing connectors, www.usplastic.com, and his idea for the quick release connectors.


 
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Step 1: Parts and tools needed

Picture of Parts and tools needed
I'm going to list the parts that I used to make my system, but offer some alternatives along the way.

Some abbreviations used (ID = inner dimension, OD = outer dimension, VDC = volts direct current, VAC = volts alternating current)

Parts:

• Plastic hard-sided cooler - In my case I went with a smallish, 12-can cooler made by Igloo, ($9.88 at Walmart.)
• 12VDC submersible bilge pump - A bilge pump is going to be the 12VDC that you'll need to run it in your car. Otherwise, you'll need to find a 12VDC fountain pump (usually sold as a "solar" pump.) Alternately, you could get a power inverter to run a standard 120VAC fountain pump from your cigarette lighter socket, which can be noisy and produce a lot of heat - unless you're willing to spend a lot of money on a really good one.
• Cigarette lighter plug power adaptor
• ~5 feet of 12VDC wire
• 4 or 5 refreezable freezer packs
• 3" of 3/4" ID vinyl tubing
• 20-24" of 3/8" ID vinyl tubing
• 14" of 1/4" ID vinyl tubing
• 30-35' of 1/4" OD tubing (use drip irrigation tubing)
• (1) 3/4" X 3/8" ID reducer coupling
• (2) Y adapters for 1/4" ID tubing
• (4) 1/4" X 5/32" reducer couplings
• (2) small screw-type hose clamps - or use 3/8" X 1/4" reducer couplings
• (2) 3/8" quick release couplings
• (1) 12" X 18" sheet "Darice Mesh" or "plastic canvas" - get the extra stiff kind
• spool of cut-to-length, plastic-coated twist ties
• 1/2 yard of woven cotton fabric (optional)
• felt fabric to cover bottom of cooler (optional)
• distilled water

Tools:

• scissors
• utility knife
• duct tape
• electricians tape, or wire-splicing connectors
• drill with 1/2" bit and 3/16" bit
• screwdriver (common head)
• hot glue gun
• sewing machine (optional)
 
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Sovereignty6 months ago

Awesome! Nice job. Being from Fl, I can certainly appreciate this.

craigxau1 year ago
Use antifreeze
P3surf2 years ago
Great Job. I have currently been working on this project myself. I have my walmart cooler and a submergable 12VDC pump with a DC socket and on/off swtich. I currently am waiting on my quick disconnect fitting to be delivered. I opted for both my male and female fittings to be valved. so when diconnected nothing leaks. I live in Panama City FL. very hot hot days. My poor little girl cant get enough AC in the back with a rear facing seat. I thought about a closed cooling system like on a CPU. but some of those fans are noisy. At least my cooler will muffle the sound.
kstruve (author)  P3surf2 years ago
Thanks for your comment! How did your installation go? Good idea on getting valved fittings - that was another minor problem I ended up having with it.
Great Instructable! Thanks for adding this.
Mackramer3 years ago
Great idea! We might try this to cool down the dog house on a hot day. Thanks
gneal3 years ago
That's really cool! Car seats for babies can become unbelievably hot, especially here in Texas. I'm glad I found this instructable. You should patent this or something!
two points
1) As an engineer and father, I understand that your "pad" has a negligible amount of give, and is "real-world" safe. A good friend was in an accident, and Britax (baby seat manufacturer) offered her a replacement seat, if she shipped the old seat to them for inspection. They did not ask about pads and such. I imagine had she painted the seat or drilled into it, they might refuse to send the replacement.  But, no one was injured, so that was as involved as the company got. Besides, are seat manufacturers even liable for injuries of seat occupants? I think it would be really hard to "prove" their seat caused an injury, short of the seat shell breaking in half.
2) Did you consider putting a coil of metal tubing on your AC heat exchanger? It would eliminate messing about with the freezer packs. Closed heat transfer systems really are much cleaner.
kstruve (author)  thumbedmonkey4 years ago
I had considered tapping into my car's AC somehow, but I didn't know how to go about doing that.
Oh and I forgot to say, great instructable!
That would be extremely difficult. Car ACs use the expansion and compression of Freon to cool the air. They are not just a heat exchange system. I thought of trying to tap into the engine cooling system (a super easy task), but then I remembered that even if you did, they run at temperatures too hot to cool a person. I think your best bet would be to mount a small radiator somewhere near airflow (in the window maybe?) and use a pump for heat exchange. Closed systems FTW.
Here is a link for a cooling pad that could be converted to this system:
http://www.buycoldtherapy.com/coolingpads/cooling-mat/

Only $47. so not a bad option... just connect the water in/out to the pad and you are good to go.
Todd22554 years ago
Why do they install lumbar (inflateable-adjustable) in the seat backs of cars ?
Ev4 years ago
Hi, I posted the original 'structable, the backcooler. I like the improvements and modifications you've made. 

A few thoughts... the in and out tubes can be insulated together because the temperature drop between them is small, much less than to the air. 

If you're worried about sloshing water, a piece of open cell foam packing material on top of the working fluid could dampen (no pun intended) waves. 

Iodine is a great idea, much better than the bleach I use. Iodophor is good too, but you may see staining. Bilge pumps are made for saltwater use, so salt may work too. 

The commercial units made by Breg and Donjoy regulate the temperature by restricting flow, using fancy devices that squeeze one tube. The plastics catalogs have squeeze devices, or you can use automotive hose clamps. Oh, you can find the "cold therapy" units pretty cheap on a major auction site. 

Be careful with tender humans! 
kstruve (author)  Ev4 years ago
Great to hear from you, Ev. Thanks for the input and good ideas on how to improve this.
Just a warning that this is SUPER unsafe and it voids your car seat warranty. It doesn't matter that no holes have been added or that no changes have been made to the straps - anything that you add to a car seat that is not tested and approved not only voids your warranty but makes your car seat dangerously unsafe. (And by voiding your warranty, I mean that if you get into an accident and the car seat fails, the manufacturer legally has the right to - and probably will - reject your claim since you altered the seat.) Essentially, by adding additional materials under the seat cover, you are adding compressable materials to the seat which means that when you buckle your child in and tighten the belt the belt is not actually as tight as it should be. The force of an accident will then compress those tubes and extra padding, making the belt too loose on the child and allowing for the potential of the child flying out of the seat. This is the same reason you should NEVER buckle your children into car seats while they are wearing puffy winter jackets, blankets or very thick sweaters. Try a little test - remove the tubes and stuff and buckle a kid in wearing normal clothes (tshirt, maybe a light jacket) - make the straps so that they are loose enough that you can slip ONE finger in under the chest clip. Then either put the tubes back in or put the kid in a heavy coat - can you buckle the straps without loosening them? That's how much extra compression space you have introduced into the straps. I get that it's hot - I live in Texas and we've had our fair share of 100+F days this summer but I'd rather sweat - and have my kid sweat than risk their safety.
I see.... so in the dead of winter, when the temperature has plummeted to zero or below, you would make your kids strip down to minimal clothing so that you can strap them in to be "safe".... I think it would be better to risk the fraction of a percent higher risk probability then to subject the kids to hypothermia. Just remember that these car seats are built to encompass ALL areas of climate... that is one reason why the straps are adjustable. The seat is built to distribute forces more equally and to restrain from gross movement, not to keep them rigidly in place. Statistically it is far more "Dangerously unsafe" to be in your own home then strapped into a car seat.
I never said "minimal clothing" - I said that you should never buckle them in while they are wearing heavy or puffy jackets or wrapped in blankets. Stand on a puffy jacket - see how your weight compacts the jacket? If you had adjusted the tension of the straps to accommodate the jacket, the forces of the crash will compress the jacket making the straps too loose (just like your weight compressed the jacket when you stood on it). Hey, you don't have to believe me but I'm not making this up: http://www.associatedcontent.com/article/439521/winter_coats_and_car_seat_safety_what.html?cat=25 Also, I'm pretty sure that the time between getting the car started, the kid buckled and the car being warm isn't going to cause hypothermia. If you're that worried about it, you can always buckle them in and cover them in blankets or um, warm up the car before you put the kid in. All I'm saying is that I think this is an irresponsible project to be posted - it puts kids at risk and it voids any legitimate claim against a manufacturer should a child be injured in an accident.
It does not matter... the jackets are still "compressible" so therefore you MUST remove the jackets prior to strapping them in or else you are making it "Extremely unsafe" That means that you will be exposing them to the cold weather at least twice (getting them in and out) for any given trip, not to mention if you are taking them to some short term outing where they may be exposed several times. Your arguments for "safety" are null and void because you are merely substituting one "safety" for another... and the ones involved, very cold weather which is an immediate threat, versus the remote chance of an accident mean that your arguments are ridiculous. Not to mention that the manufacturers have already taken "puffy jackets" into account in the design of the seats. The strapping is meant to be enough to keep them within the seat, not to clamp them down, therefore the slight variation in "tightness" is a moot point. How about driving while talking on a cell phone or worse yet texting? How about applying makeup, eating or any of the myriad other things people do besides paying attention to the road and driving? Those things are far more inherently unsafe then whether a strap (including a seat belt) is tight enough. H

Most of your response is quite reasonable, but there's one little point about which I'd like to nit-pick.

The strapping is not meant to just "keep them within the seat." It needs to be tight enough (the usual guideline is that you can insert two fingers) so that in the event of a crash, the child's momentum transfers to the straps before they start moving significantly. If the straps are loose enough that the child can move forward more than about 2", that's enough distance for neck flexion (whiplash) to cause injury.

The recommendations against thick soft clothing (including winter coats) under the straps is precisely because those soft materials do not transfer the momentum of an impact, so the child can move forward then back rapidly (whiplash).

Having said that, it is obvious (to a physicist, at least) that a 1/4" pad inserted in the existing gap between the approved padded seat cover and the plastic body of the seat does not affect the momentum transfer the same way that loose straps, or padding between the child and the straps, does.

So you are a physicist... that is very nice it lends a bit of creedence to your claims, However, I am a Robotics Engineer with a degree in Kinematics which is the study of motion and the transfer of forces. I have also workes in the automotive industry. Perhaps you have heard of "crush zones" in cars? That is the collapsible zone meant to reduce forces transferred to the bodies inside. That two inches you quote is a lot of room to travel before arresting motion. Interestingly enough, that padding actually assists in taking up some of that force and distributing it in a slightly wider path, somewhat like a bulletproof vest. I will agree with you that the more gap allowed (as in loose straps) the more time before the child will start slowing down, however that very same padding will also compress and start slowing the child down a bit before hitting the hard stop of the straps and for the transfer through the seat to the car straps. The key is to tighten the straps as much as possible every time. The bulk involved is irrelevant unless you are leaving the straps loose in the first place.

That's awesome! So you have much better direct experience than I do (except for getting to watch the crush zone on my former Honda Civic work the way it was designed!). My analysis was based on some simplifying assumptions and idealizations, for which you have the more complex data.

Yes, two inches is a lot of travel, and I suspect that it's a bad quote on my part: the rule of thumb I have read is that want the straps as tight as possible, and that you should be able to slip no more than two of your fingers between the child and the strap. I'm playing with that now, using my belt, and it looks like the gap is more like 3/4" or so. Does that sound more reasonable?

One of our car seats (the Sunshine Kids) actually came with a short length of what I recognized as fall protection, a shock-absorbing "lanyard" that clips between the anchor on the back of the seat and the Y-clip for the shoulder straps.

Pretty much... even with fall protection devices used for climbing there is a bit of "normal travel" to allow for normal movement. the key is progressive give in order to spread out the shock either across time or across area. In each case you are reducing the overall final impact. The main worry about puffy coats and such is that people will not tighten the straps sufficiently to properly maintain the progressive give that keeps you safer (in a relative way compared to none at all) in an accident. Another example is that cell phones have been conclusively proven to be unable to cause a gas station fire and yet the warnings remain... this is primarily because you are not paying attention to what you are doing and are more likely to create static electricity and less likely to remember to discharge it prior to reaching for the pump handle. Paying attention to what you are doing is one of the biggest safety factors in ANY situation that can cause harm.

Hear, hear! I fully agree with both the physics and the philosophy; thank you.

You wrote, "Another example is that cell phones have been conclusively proven to be unable to cause a gas station fire and yet the warnings remain... " Exactly what I meant by "lawyerly fear of responsibility" in another comment. No physics or engineering reality there, just "we told you so you can't sue us."

I also forgot to add that many of these car seats are also specifically made so that the BACK of the seat is facing forward in which case the straps are only keeping the child contained as I stated earlier, they play little to no role in actually restraining the child from impact forces in the event of a crash. Finally, how many times per year are you in a car crash versus how many days of freezing cold are you exposed to in an average year? The former can be measured in single digits even across multiple years even if you are a rather bad driver, the latter can number into the hundreds during a given year if you are living in the northern latitudes. The translation is that you are exposing the kids to very cold temperatures several times on each cold day of a given year as opposed to the remote chances of getting into a high impact crash.
Like I said before, this is not my opinion. Manufacturers, the AAP, and NHTSA have all issued statements regarding the wearing of heavy or compressible jackets in car seats. But do what you want with your car seats.
"Irresponsible"? So, first, you haven't looked at the dimensions of the material used in this instructable. And second, you either do not live in a climate where the external temperature rises routinely above 100 F (and the car interior temperature therefore rises above 130 F), or you don't actually care about children overheating.
It doesn't matter what the dimensions are - adding ANYTHING to a car seat compromises the safety of the seat. NHTSA and AAP routinely advise to not wear puffy clothes in seats and to not use seat covers that were not made by the manufacturer - any modifications to the seat make the seat unsafe. Also? I live in central Texas so no need to be snotty about the heat - we've had our fair share of 100+F days this summer. This isn't an issue of children overheating - kids shouldn't be in a 130F car in the first place. Talk to any trained car seat technician and they will agree with me - encouraging people to modify car seats in any way is irresponsible and dangerous.
"any modifications to the seat make the seat unsafe." That is a lawyerly oversimplification whch is useful for both public announcements and protection from liability. A more nuanced statement would be, "any modifications to the seat make the seat different from how it was tested to be safe." That does not mean it is inherently unsafe, but rather that the manufacturer cannot know, and therefore will not assume liability for, whether it is safe or not.
You are absolutely right. Now flip it around - do YOU know that the modifications will not affect the performance of the seat? Do you understand car seat technology and crash forces to TRULY understand how the modifications you are making will impact the functioning of the seat? Have you run impact tests on a modified seat? I don't pretend to understand the specific details of crash technology but I've seen enough crash photos to know that I don't want to put my kids at unnecessary risk for injury or car seat failure.

I'm not an automotive engineer. I'm a professional physicist. I understand momentum transfer and dynamics enough to tell the difference between the (properly warned against!) effect of soft squishy stuff interfering with momentum transfer to the safety straps in front of the seat, and the effect of a thin non-compressible layer placed in an existing air gap behind the seat.

I can also tell the difference between safety warnings based on sensible physical principles (use the LATCH clips whch are bolted to the car frame, use the full five-point harness tightened to no looser than two-finger insertion) and warnings based on lawyerly fear of responsibility (don't use a seat cover of a different color! Danger: that hot coffee might burn you!).

kstruve (author)  jlfmcnichols4 years ago
I appreciate your very well intended concerns. I think that what you say would be absolutely true if I were adding compressible materials like a heavy, puffy coat or extra foam padding. However, what I am adding is, for all intents and purposes, not compressible, and doesn't add much thickness to the seat back, since the tubing only covers about 5% of the cooling pad area. It also does not alter the angle of the car seat back, which could increase the risk of whiplash or internal decapitation. We did not have to loosen the car seat straps the first time we used the seat coolers, so the boys are sitting just as snug as before. If anything, these seat pads are making our driving experience safer. Two screaming babies does not make for a driver who is focused on the road, especially if it's a lactating mother behind the wheel.
espdp2 kstruve4 years ago
Very, very true. A distraacted driver is vastly more likely to be the cause of a crash than to be ready to prevent one. I simply won't drive until the car has cooled to a tolerable level. I can't stand when my kids are screaming! Happy = safer. .
+1 An excellent project.
I don't see how he's added something "compressible" here. The thickness of the pipes added, as a fraction of the thickness of his children is so minor as to be neglible. The pipe is 1/4" OD, its rigid PVC, and won't crush under an impact load over a large area.
kstruve (author) 4 years ago
Funny. This is how a link to this instructable on a Russian blog translates:

"Even if your machine is always working air conditioning, from sitting in a chair sweats spin. Now imagine what your baby, who even upside-down properly in the child seat can not. It was on this crazy pen of Instructables, give detailed instructions modify the child safety seat for the introduction of liquid cooling in English."

From http://botinok.co.il/

:)
Great write up. I'll be making a set of these for all seat backs in my minivan. I'm in Houston and I can really appreciate your concern with high temps. Dry heat, wet heat, what ever! Once you hit 100, it's just hot! Thanks for sharing your build.
kstruve (author)  FamilyGuy20064 years ago
Thanks FamilyGuy2006. I hope to hear about how yours turn out!
kelseymh4 years ago
Congratulations! You were picked up on the MAKE blog :-)
kstruve (author)  kelseymh4 years ago
@kelseymh: Hey, very cool!
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