Electric heating of a battery and interior

[agniusm]

Any info on this topic? Basically we get temps down to -20C and ICE car give me headaches. I am gathering parts for my enclosed velomobile and would like to implement some sort of battery heater for charging. I would like it to work of the mains so it heats up the battery and when battery reaches accepted temperature, charging begins. My first thought was peltier modules as it could help on efficiency.
Also, what sort of interior heater would suffice for such vehicle? There are many to choose from but i don't want it to be too powerful (overkill), just enough to raise temps inside to 10, 15C when outside is -10,-15, -20 in reasonable amount of time.

There is this one at over 1kw:
http://www.ebay.com/itm/48v-1152w-D...750374?hash=item2ca5a71066:g:ybwAAOSwwE5WarEu
This at 400W which i like:
http://www.ebay.com/itm/56-126-2-Radiator-heater-400W-145-C-48V-DIN-EN50022-35mm-120x152x56mm-/201376708746?hash=item2ee2fcb88a:g:rTgAAOSwyQtViqQx
Perhaps something could be salvaged from modern ICE vehicles?

 

[Drunkskunk]

Peltier Sounds like a good idea. In theory, a Peltier diode should be more efficient than resistive heating. They are essentially a solid state heat pump.

For heating the batteries, a resistive heater might be better, since you can get one between the cells. a mat of carbon fiber can be used as a resistive heater, and be woven between the cells or packs. Its much easier to control the heat with a carbon heater than a metal heater.

 

[edventure]

A Peltier system could definitly work, especially since your outside air is so called it would do a good job of keeping the cool side of the Peltier element cool and allowing the TEC to operate more efficiently. You could theoretically use it to cool in the summer time, but I would not recommend it, because it is a very inefficient means of cooling and will use a lot of power to cool when the outside temperature is elevated. You want to do some reading up, because in certain situations a resistive element may still be the better way to go. Anything you use is going to use significant power to create heat, typically resistances are low and allow high currents to flow that generate the heat and it is these high currents that will rob your battery. Here is a link to a company that makes different peltier coolers and heater assemblies. You don't have to buy their assemblies but they have a lot of useful information. http://tetech.com/faqs/#5

Your best option may be a heated Jacket like I use on my bike. This is probably the most efficient, because you are only heating the surface in direct contact with your skin and not wasting energy on heating a volume of air that is not insulated very well from the outside environment. Typically what I would do on mine is put the heated jacket on and then place a second Jacket over this and it would keep me warm down to about -5C. If your inside a sealed velo-mobile it would probably keep you warm at even lower temperatures. If you use the jacket option you will also leave yourself more power to heat the batteries. Here is a link to the company I purchased my jacket from. http://www.powerlet.com/product/microclimate-h1-jacket-liner-w-g1-remote-garment-controller/683 I did not buy this specific model of jacket. I purchased one from them that did not include a controller and was not this expensive. I supplied my own PWM "pulse width modulated" controller and placed a knob on my battery box that allows me to control the temp.

I would probably use a silicone matt type heater to heat the batteries since they are naturally electrically insullating and once they build up heat they do a good job of keeping the heat in the device you are trying to warm. The silicone is the same material they use in oven mitts that allows you to pick up a 500F pan without burning yourself. Here is a link to one supplier, but there are many. http://www.briskheat.com/c-73-silicone-rubber-heaters.aspx

Good luck. I am curious to see what you end up doing.

Ed

 

[tunnel_run]

What are the approximate length, width, height dimensions of the enclosure?

 

[tunnel_run]

I made my best guess at the dimensions and plugged your temperature numbers into an enclosure heater calculator that outputs a wattage requirement and also suggests a type of enclosure heater. The inputs I selected look like this…

Enclosure is Free-Standing
No Adjacent Objects
Enclosure Dimensions
(Looking at velomobile pics on google I guessed at these):
Height: 36”
Width: 30”
Depth: 48”
Enclosure Material is Plastic
Enclosure Location is Outside
Desired enclosure interior temp: 15°C
Lowest ambient (outside) temp -20°C
Heating Power (PV), from existing components: 150W
(The number I used here is for the PV provided by the human body. If a human body at rest puts out ~100W of heating power, I’m assuming with some peddling that it would be something close to double. 150W seemed like a good conservative number.)

The calculation tool says that 1,058.03 Watts are needed to heat the interior. The calculator further recommends a heater with some sort of blower or fan perhaps suggesting that a still air convection method will not be enough.

I ran it again using numbers from the less extreme end of the ranges suggested and also bumped up the heat contribution from your body assuming a more vigorous workout so that…
Desired enclosure interior temp: 10°C
Lowest ambient (outside) temp: -10°C
Heating Power from existing components (your body): 200W

The calculator says that 490.30W are needed. The same types of heaters are recommended. It doesn’t seem to think that natural convection from a standard silicone rubber enclosure heater will be enough. I expect that if you made one large enough it would work fine… but then you’d have to figure out where to put it? If I drop the outside temperature to 0°C with a desired enclosure temp of 10°C then it starts recommending silicone rubber enclosure heaters.

These are very rough numbers!

• I guessed at the enclosure dimensions while looking at pictures of velomobiles and thinking about the volume of air that must be inside.

• I am making an assumption that the enclosure is closed.

• I have not calculated for the vehicle moving through cold air.

• I am assuming that the driver is peddling.

• We did not consider heat from the battery warming circuit.

 

[Dylandesmond]

What about insulation？
peltiers arent that great on efficiency

insulation with simple lightbulb and tiny fan inside box would be a better use of power

peltier are 5％ efficient making cold when its hot ambient temps its the same in cold situation （not as bad but a waste of time）

an arduino or simple temperature sensitive relay circuit to light bulb setup with removable y（if you have summer also）insulation setup would save alot of battery life