Winter sick need Heater

[tim.moore]

I am sick of the winter, and I want a heater in my electric car NOW.  I realized this week it is a safety hazard with people stranded on the sides of the road.  I have a few hundred dollars to spend from my tax return.  First can anyone recommend an  inverter that will work for a small space heater and a separate deep cycle battery that I have.    I know I can get a system like Ted Lowe's but I do not see a free weekend  or more to do it.  If someone has another plug and play system that I can get NOW I will ante up for it.   Signed Cold as Ice.

[ken.simmermon]

What's your pack voltage? You do not want to use an inverter you should use the main pack. A small space heater can be modified and will end up being more efficient.

[todd.dore]

Tim -

There's no easy way that I'm aware of to do a 'plug and play' for heat.  I know you don't see a free weekend, but if you can set aside 4-6 hours for 2 separate weekend days, we'll get heat in your car.  With enough advanced warning I will be able to help you out.

The easiest way is to get one of those space heaters like 1500 watts, take out the AC motor/fan for the blower, install a DC fan from radio shack, and hook the fan up to the 12V power and the heater up to your 120V DC power.  A couple of fuses for safety should do the trick.  The difficult part is getting some decent size wire (at least 12 guage) through your firewall to feed into the space heater.

[ted.lowe]

Tim, come by my house anytime to borrow mine!  i'm not driving much since i'm working at home now.  You need the heater way more than me!  What is your pack voltage?
Kind regards,
ted

[ted.lowe]

The reason Ken and i asked about your pack voltage is because the PTC ceramic heaters are essentially a (non-linear) resistor and in normal operation will behave according to Ohm's Law:  V=I*R.  The heat output is proportional to the current (I).  The R is fixed (until too high temperature is reached), so the current (heat) is proportional to the voltage.  i've experienced this many times when i drive: lots of heat when i start out with a freshly charged 120v (nominal) pack, but when i discharge towards the end of my charge, the heat output is almost nil.  So, if you have 19 bats (114 nominal), i suspect my heater won't work too well for you.

So what we (EVers) need is a PTC heater that will run at various pack voltages (think EVX prize idea:-).  i got the idea for my heater from John Emde (he had made one for George Gladic).  Because my pack voltage is reasonably high, a home-type heater designed to work from 120V AC (rms) will work (marginally) from 120V DC.   There is no control of the amperage (except fan speed controlling air movement).  This is like a dirty-heater (like a simple dirty-charger).  Instead we need to apply a little more electronic control to get a better result.  Using a much smaller version of a motor-controller, we can pulse-width-modulate (PWM) our pack voltage into a lower-voltage PTC heater element (say 72V).  This would allow us to have more heat longer (at expense of range of course).  Here is a company that will customize the PTC heater elements per customer specs:

http://www.specsensors.com/hph.asp

Some links to better understand the PTC ceramic heaters we're using:

http://en.wikipedia.org/wiki/Positive_temperature_coefficient
http://en.wikipedia.org/wiki/Heating_element

ps.  Don't forget to install heated seats... you can't beat the bang for the buck (or BTU from the kwh:-)

[tim.moore]

Thanks Ken, Ted and Todd for your quick response.  I was a little more than disheartened to realize that  a heater is a much higher draw than a sump pump.  I always joked about heat and not needing it but it really is something we have to address better so as to make Electric cars more appealling without losing range.  I heat in a microwave a bedbuddy for 2 minutes and I am toasty warm for the 30 minute drive.  Maybe we can install microwaves in a our cars and heat that way (smile).  I'll make it through the winter while someone invents a better "mouse trap". 
http://www.bedbathandbeyond.com/product.asp?order_num=-1&sku=10573050

[terry.kane]

The Prius has a "heat battery" that is just a thermos that keeps some coolant "hot" for a time after one parks it.  When the car is started again, the thermos gives up its heat to the engine block for lower emissions purposes (primarily).  I imagine being able to use a similar system with the water-heater method like in the Porsche.  The operator could design a circuit to heat the thermos during/after the charging cycle off of house current.  The energy stored in the thermos would then be given to the passenger compartment.  You could choose whether to use battery capacity to keep the thermos hot, or just deal with the residual heat only. 

Of course, such a system would add weight.

I also dream of an integrated Stirling plant that would be able to manage the relationship between mechanical, thermal and electrical forms of energy to the maximum effect.  This may be my X-prize entry...

Imagine using kinetic energy from braking to heat the thermos - use the thermos to recharge the battery in a pinch - in Summer - turn the thermos into air-conditioning - use solar heat to charge the battery - a Stirling oscillating engine can do it all.