Hi Guys, I am a BSEE graduate from Purdue. I am currently working as a power engineer at a utility company which requires me to be in the field during below freezing temperatures. I'm either sitting at a laptop or holding a test switch outside. I don't constantly move around enough to take advantage of thermal clothing.

I have Under Armor Thermal shirt and pants. My plan is to stitch these heat pads on them
http://www.ebay.com/itm/2Pcs-Carbon-Fiber-Heated-Auto-Car-Seat-Heating-Heater-Pad-12V-Universal-/182346267753?hash=item2a74af3c69:g:IzUAAOSwcUBYIKGG&vxp=mtr

One head pad on the back of the waist line and a couple down the front and back of each leg. My plan is to wire all the pads in parallel then to a temperature controller or small fan controller to regulate the temperature.

I've seen similar tutorials on how to do this, but a lot of people are making their own heat pads instead of just buying them. The tutorials are out dated. Can anyone tell me how to go about this idea?

My basic needs are heat for longevity. I would like to hold a constant temperature for at least 4 hours. I don't need these heat pads to get extremely hot, just enough to be comfortable.

Also how do I go about picking a battery pack? I need something mobile and small enough to be stitched in my jacket, but powerful enough to last. My plan is to try to connect the pants/shirt head pads to the same controller if possible, but I do not want to feel restricted. Any help would be greatly appreciated

 

Those pads are 20W which at 12V is 1.7A. So one pad for 4 hours would require 6.7Ah then multiply by the number of pads to get the total battery capacity you would need. Lithium 12V 20Ah batteries go for around £180 (UK) or Lead Acid around £30-40 but these will be a good bit heavier. You would need something like a back pack to put the battery in - not stitch into the clothing.

 

Why would you want to do this? Heck, it's 80° outside today.

 

Looks like those pads already have a 70C thermostat built in. Much too hot for close body contact. You'd want to under-run them.

 

Those 20 Ah batteries look huge. Why do need something to put the battery in when it comes as a "battery pack" already insulated?
Are there any other options? If I get a battery pack half the size 12V 10Ah will I get same heat just less time?
Could I use a voltage regulator to lower the output of the battery so the heat pack does not get as hot, but last longer?

Those heat packs for car seats get super hot so I wont ever need it to be consistent 100% load for 4 hours. Also if I buy multiple batteries I will be able to have a 1-2 charging while the other is running. 12V 20Ah battery packs are 40$ here in the US.

 

Why would you want to do this? Heck, it's 80° outside today.

Below freezing here in Chicago IL. The snow is coming, it's only going to get colder. The wind is the most brutal part.

Looks like those pads already have a 70C thermostat built in. Much too hot for close body contact. You'd want to under-run them.

Exactly so what device can I use to under run them? I plan on attaching these to the back of my under armor thermals using adhesive cloth and an iron

 

Your attachment method is going to be adhesive cloth?? How do you plan on using it? The adhesive cloth that I am familiar with is ironed on, as you mention. That is, the adhesive is set with heat. I wonder what will happen when your pads heat up?

 

I wonder what will happen when your pads heat up?

The temperature required to warm a human is much lower than the temperature used to iron clothes.

Below freezing here in Chicago IL. The snow is coming, it's only going to get colder. The wind is the most brutal part.

Been there, done that. That's why I live in Florida now.

 

Exactly so what device can I use to under run them?

I would say put two or three of them in series. A human at rest generates 350 BTUs per hour. 10 watts generate 34.13 BTUs per hour. Two pads in series would produce almost 10% of your natural body heat...then just put a switch on it.

A good personal heater is one that you don't notice. If you generate a nice warm spot in a minute, you will regret it in an hour. And remember, humans are self regulating. If your chest and back get too warm, your blood flow will increase in your legs in an attempt to get rid of the excess heat.

 

The temperature required to warm a human is much lower than the temperature used to iron clothes.

Been there, done that. That's why I live in Florida now.

However, repeated exposure to lower temperatures will cause an adhesive failure. It is made for occasional exposure to heat during the drying process of laundry. But will degrade over time. Seen it when clothes are washed daily or more. That's why I mentioned it.

 

heat during the drying process of laundry.

Heat in a clothes dryer is typically 165F. Heat inside a winter jacket us usually less than 70F.
Do you wash your winter coat every day or every week?
If so, this guy will have to make a new jacket heater every few years.

 

Ok, this last post makes me less concerned. No, I don't wash my winter coat daily. But I have experience with adhesive cloth and garments that were washed once or twice a day.

 

Below freezing here in Chicago IL. The snow is coming, it's only going to get colder. The wind is the most brutal part.



Exactly so what device can I use to under run them? I plan on attaching these to the back of my under armor thermals using adhesive cloth and an iron

You just need advice on how to dress for outdoor living. North Dakota and Minneapolis colder and blows more than Chicago.

http://www.carhartt.com/products/Ex...Fx9WcQXRxFUZ8SWflDm7WG71UR18YPAReOxoCD6nw_wcB

When you wear that, make sure you have a scarf round your neck to slow air movement in/out and don't waste that heat. Decent boots with pants over boots - long socks - glove with gauntlets.

Wear a hat that covers your ears. remove hat first to control body temp if you start to sweat. You have to actively control your clothing to avoid sweating all day. hands and head radiate the most heat (feet too but hard to go barefoot).

 

You can pwm for the correct temp. This will reduce the current demand and increase battery time.
You will still need to tote a battery, unless you have a power supply to plug into at work station.

Two tablespoons of bacon grease will keep you warm for most of the shift. Always wise to carry some with you in cold weather.

 

You can pwm for the correct temp. This will reduce the current demand and increase battery time.
You will still need to tote a battery, unless you have a power supply to plug into at work station.

Two tablespoons of bacon grease will keep you warm for most of the shift. Always wise to carry some with you in cold weather.

I have a power supply with me in my vehicle, but sometimes I'm on top of equipment so I want to be able to be mobile. I always have a hoodie on under my heavy Carhart coat that I can easily carry a battery pack in the hoodie pouch while working. So I need to find a slim battery pack if possible.

I'm just trying to be as comfortable as possible. I'm already covered head to toe in FR gear. I feel like introducing heat will make it similar to being inside and I was to laugh when my co workers complain about the cold and i'm feeling warm.

 

When I was younger and a working man......I worked for years in sub zero weather. Snow paks....and snow mobile suit. Dry snow paks out EVERY nite. You need a cover all dress. Not pants and coat. And wear mittens....only put gloves on if dexterity is needed. And face mask for windy conditions.

You have it easy. They have excellent cold weather gear today. But you really do need to consume fat and grease.

8 hr. shifts at 30-40 below with wind. Installing repeater sites on mountain tops. Winter was the time to install them back then. One can get to the top very quickly with a snow cat. Drive right over fences, fallen trees, and boulders.

 

You just need advice on how to dress for outdoor living.

I think it was a Norwegian who said, there is no such thing as bad weather, but there are bad winter clothes.
I don't really agree, but good winter clothes are the only practical defense.

I was on The El at 3:30 AM in January. It sucks!!! Or it blows, depending on which way the wind off the lake is moving.
I was wearing 2 layers of shirts and 3 layers of jackets. Bunny fur gloves with gauntlets. I didn't hang up the jackets when I got home. I stood them in a corner!
There are some really great winter clothes in the modern world, things we didn't have in the 1960's like Gortex.
I am Tropical now. I am no authority on winter clothes, but I have friends who talk about things like that.

 

I think it was a Norwegian who said, there is no such thing as bad weather, but there are bad winter clothes.

If you knew my last name, you would have said, "I think it was GopherT who said, ..."

 

Is it 20 Watts per heating pad or 20 watts for both pads? How do I figure out what size battery will give me 2-4 hour run time at 55% of the heat pads 70 Celsius max?

 

Those 20 Ah batteries look huge. Why do need something to put the battery in when it comes as a "battery pack" already insulated?
Are there any other options? If I get a battery pack half the size 12V 10Ah will I get same heat just less time?
Could I use a voltage regulator to lower the output of the battery so the heat pack does not get as hot, but last longer?

Those heat packs for car seats get super hot so I wont ever need it to be consistent 100% load for 4 hours. Also if I buy multiple batteries I will be able to have a 1-2 charging while the other is running. 12V 20Ah battery packs are 40$ here in the US.

Just because you need 20 Ah of battery capacity that doesn't mean it has to be in one battery. Spread it over a number of smaller strategically placed packs.

Personally for worst case energy consumption to battery size scenarios I would go with a Lithium, Nicad or NiMH based battery system made of a bunch of single cells made up in strings or groups to get the your necessary energy storage capacity.