# Heating system design for EV



## EVDoodle (Oct 9, 2013)

I'm in the planning stage of a DIY EV build and the component that seems to be lacking is a good heating system that doesn't draw too much power from the batteries. Since I live in Winnipeg where temperatures around -30 to -40C are experienced and -10 to -20C is typical, a viable heating system is mandatory. It doesn't make sense to proceed until this item is at least bench tested. My initial thought is to have a combo fuel fired heater supplanted with a 1500-3000 watt ceramic heater or a liquid unit all managed by a temperature sensor based PID controller. Since I have limited experience with fuel fired heaters for vehicles I would appreciate it if someone could give suggestions on selecting a reliable low cost unit. The only one I have experienced is the unit on a 60-70 era VW Beetle and I might try to find this one if I cannot locate a newer technology. Your suggestions will be much appreciated.


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## Duncan (Dec 8, 2008)

That is an incredibly inefficient way of heating - heating a large uninsulated metal box

For efficient heating methods look at those used by motorcyclists - electric clothing
just heat the bit that needs it

As an intermediate electrically heated seat elements are cheap and very effective


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## z_power (Dec 17, 2011)

There're Webasto and Eberspacher heaters powered with gasoline or diesel fuel; it's a bit expensive option but for ~0.4 liter per hour you get ~3kW of heat stream without battery drain. I decided to remove factory blower and heat exchanger and associated pieces of heater box, using only "distributive" part of OEM system to direct air where it's needed. My donor car (Fiat Cinquecento) doesn't offer to much space either in engine bay nor under the dash so I had to play this puzzle game.


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## Ivansgarage (Sep 3, 2011)

Have you checked out water heaters? in-line water heater.

http://www.evsource.com/tls_heaters.php


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## EVDoodle (Oct 9, 2013)

Thanks everybody for all the useful input. This has allowed me to move forward very quickly with a good solution that will allow the EV to perform well in a cold climate. 

I was a bit puzzled by *Duncan's* response although amused by the electric clothing ( spacesuit for each one in my family would be more appropriate here). The heated seats certainly are a good suggestion and I will probably add those later. It does nothing to defrost the windshield or heat the cabin without draining the batteries which is the design goal. 

To clarify my initial plan, the first stage is going to be a gas or bio diesel fired air or water heater for getting the cabin up to temperature quickly while the vehicle is plugged in (or not). The fuel fired heaters are very efficient ( in the 85% range). For places I can't plug in, the fuel fired heater is a perfect solution. I am leaning toward the liquid option. It is easy to install and would give more even heating in the cabin using the existing components. Then have the 1500W ceramic air heater kick in to control the temperature to within +- 1 degree while driving. Will have to see how well fuel fired heater works for controlling temperature. It may be adequate to maintain a fine temperature control and I may not need the second stage. I will have to pre test it in my ICE daily driver to get a feel of it's performance.

*z_power*, thanks so much for pointing me to the Webasto and Eberspacher heaters. Those are perfect for the job and although a bit pricey it is worth every penny at -30 to -40C. I really like the remote control feature and the fuel consumption is very low (0.4 L per hour). I anticipate that half an hour would be more then adequate on the coldest days. I can see that many diesel truckers would use this instead of idling all night

*Ivansgarage* The inline water heaters from evsource certainly would be a good solution however when the vehicle is parked where there are no plug ins then that becomes a battery issue. I think the fuel fired heaters would be an advantage in this application.

If anyone has any experience with the Webasto and Eberspacher heaters I certainly would like to hear more on this thread.


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## Ivansgarage (Sep 3, 2011)

Espar or Webasto diesel fired heaters work really good but they are a bit pricey.

The smallest Espar heater whitch I use all winter in a big truck cost me 1600.00
The smallest espar does kick ass for its size about 4x4x8" in size

When at home just plug in a small ceramic heater at night and go with the water heater for driving.


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## tomofreno (Mar 3, 2009)

At -10 to -20 C the 1500W ceramic heater won't have much effect. I think you will need to mainly depend on the fuel heater. I have a 3kW ceramic heater which heats well down to around -10C, but the exiting air becomes more and more tepid beyond that. A 900W heater blew out cool air when ambient was below about -5C. Required heater power also depends strongly on air infiltration. I require significantly more power at highway speeds compared to in-town cruising. You might consider adding insulation inside door panels and firewall and making the cabin more airtight.

I have an electric seat cover and below around -5C my arse is warm but my feet freeze. 'Course you canuks are tougher...


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## EVDoodle (Oct 9, 2013)

tomofreno said:


> At -10 to -20 C the 1500W ceramic heater won't have much effect. I think you will need to mainly depend on the fuel heater. I have a 3kW ceramic heater which heats well down to around -10C, but the exiting air becomes more and more tepid beyond that. A 900W heater blew out cool air when ambient was below about -5C. Required heater power also depends strongly on air infiltration. I require significantly more power at highway speeds compared to in-town cruising. You might consider adding insulation inside door panels and firewall and making the cabin more airtight.
> 
> I have an electric seat cover and below around -5C my arse is warm but my feet freeze. 'Course you canuks are tougher...


Thanks for the info. I expected the the 3kw ceramic to be more effective at -10C so this is good to know. Will have to see how it goes with the control cycling of the fuel fired heater especially with the smaller amount of liquid in the EV application. Might require an additional reservoir to even it out. Perhaps having the heater run in low while cycling the ceramic heater will give very even temperature control. Will have to experiment. 

Heck, at -5C it is shirt sleeve weather and the BBQ's are in full operation around here. It's around -25C with a high wind that even Canucks start to hibernate.

*Ivansgarage* Wow $1600 for a smallest espar is quite pricey. I have seen them for around $800 on the web but these might be chinese knockoffs. Will have to check further. The fallback position is a VW Beetle BN2 or 4 heater which I have seen for around $100. These will require some modification to update them to perform more reliably.


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## evnz (Jul 24, 2010)

at that temp range it would be worth getting the fuel heater ever think of putting a loop to keep your batteries warm,or air coming out of your cabin to the battery pack.
a 2500 w inline heater at 150 v uses 17 amps if that any help.
our fire trucks use in line 1000 w heaters on 230v AC to keep them warm and they only go while plugged in but we dont get lower than -5 on a bad day 
have fun
owen


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## EVDoodle (Oct 9, 2013)

evnz said:


> at that temp range it would be worth getting the fuel heater ever think of putting a loop to keep your batteries warm,or air coming out of your cabin to the battery pack.
> a 2500 w inline heater at 150 v uses 17 amps if that any help.
> our fire trucks use in line 1000 w heaters on 230v AC to keep them warm and they only go while plugged in but we dont get lower than -5 on a bad day
> have fun
> owen


*Great idea*, running a loop to the batteries shouldn't cost that much and certainly would get the batteries back to their efficiency and range. That would give added fluid capacity without having to add a reservoir.


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## gdirwin (Apr 7, 2009)

I also live in Winnipeg and have driven my RAV4 electric conversion daily for almost 3 years now... I use 2 x 1500 MW ceramic heating elements (where the heater core used to be) driven by a pack which sits near 150VDC - it uses solid state relays to turn each element on and off.

I find 3kW "good enough" - no problems keeping the windows clear etc... but it will not get as hot as a fully-warmed up gas car - the heat is still better than most cars for the first 15 minutes of a drive (ie no warmup time). I pre-heat the interior with an AC heater on a timer, and also have 12V seat heaters.

I would probably look at standard AC water heater elements, fitted into coolant filled pipes... Add as many elements as you need, and selectively turn them on/off as required. Saves having to rip apart the dash, and the startup time will be pretty fast still...

I modified my temperature dial (blue or red) in the car to drive a rotary switch - if it is in the blue all heat is off (I also have AC) - as you turn it into the red it enables more and more heating elements... If you go the water-cooled route, then I think many of the car controls will automatically work (ie moving a water-valve to adjust flow) - just get the water to a high-temp set-point (with a temperature switch) - probably an on-off switch somewhere too for summer driving...

Alternatively I also tried a PWM digital controller (to drive the solid state relays) - I found this was overkill however - when you want heat you pretty much want it full on or off (no point in having it try and regulate the cabin temperature to some set-point). Perhaps with more heat then the feedback temperature regulator idea would work better...

You should check out MEVA (Manitoba EV Association) - they have a meeting this Thursday (at the University of Manitoba) and I believe there will be a panel session from a few folks who have converted vehicles. Another member drives his EVs on the highway to/from the country each day, and he used 6kW of electric heat.

Hopefully see you on Thursday...
http://www.meetup.com/Manitoba-Electric-Vehicle-Association-Meetup/events/135535712/

Garth


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## puddleglum (Oct 22, 2008)

You might want to check these out. I haven't used one personally, but I've heard they work well. RWaudio in calgary is using one, I think.
http://www.metricmind.com/category/ev-fluid-heaters/


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## Yukon_Shane (Jul 15, 2010)

I've been driving a converted EV in Northern Canada (Yukon territory) for over a year and would suggest you have two distinct challenges to address when it comes to driving in cold climates:

1. keeping the batteries warm
2. keeping your windshield ice free

I've found that the best approach to keeping the batteries warm is insulating the crap out of your battery box. I've installed approximately 3 inches of ridged foam around my battery box which allows me to keep the batteries warm with a very low wattage flex-watt heating element (about 150 watts). with this much insulation I can maintain a delta T of 20C without adding much heat at all and when it gets really cold I just turn on the heater for a few hours.

keeping your windshield ice free is trickier but I'd recommend the MES-DEA fluid heaters. I've tried to rig ceramic heaters and kat's water heaters and found that the installation was just too difficult or not reliable. I know others have had positive experience with these methods so take my experience for what it's worth.

The MES-DEA heater I'm using now plugs right into the stock heater hose and puts out a maximum of 4,000 watts but in my installations it's really only about 2,800 watts (my pack voltage is under 200V). 2,800 watts is adequate to keep the windshield clear but ideally I'd like to eventually get the full 4,000 watts so I'll probably look to increase the voltage of my battery pack in the future. If you're starting a build from scratch I'd recommend you plan to build a high voltage pack (over 200 V) and get one of these fluid heaters. You won't regret it. 

I can't speak to the viability of the gas or oil based heaters; however, I would say that (in my opinion) they seem overly complex and expensive.

It's great to see another Canadian EV builder. Good Luck!


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## EVDoodle (Oct 9, 2013)

*gdirwin* Thanks for the great tips and I look forward to attending the EV meeting

*puddleglum* Those look like nice heaters and the price is not too bad. 

Has anyone tried to take a tank 4 kw water heater and use it in this application? These are fairly low price and mounting it in a pipe should not be that difficult.

*Yukon_Shane* Great to hear from someone with a successful conversion who is even more north than we are. I think you summarized it well on your two points and it is a very important consideration and worth the effort spent in this area.

Insulating the battery box with 3 inches of rigid foam is excellent if there is space for it. I have a simple idea for a fixture to liquid warm the battery box similar to liquid cooling a cpu. Have two aluminum plate with channels grooved out in a configuration and then sandwich them together with a gasket and water fittings. Very simple and reliable. 

Thanks guys for all your great ideas and experiences.


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## Roderick (Dec 8, 2013)

Any update from these feed backs?


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## Vanquizor (Nov 17, 2009)

I think its still valid. ~3kW for comfortable, no issues with icing but not really hot at -20C is my experience.


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## dougingraham (Jul 26, 2011)

1200 watts is barely enough to defrost. In a small 2 seat sports car 3000 watts is comfortable. My Tesla reportedly has 6000 watts for the passenger compartment heater and it heats up the passenger compartment from 0F (-18C) to room temp in less than 10 minutes and will easily keep it warm at 80 mph.

If you do a water heater arrangement to feed the OEM heater core you probably want to use an un-pressurized system at temps around 212 F (100C). For this you would want to use a waterless system like Evans that boils at 375 degrees F (191C). And then you can run a huge heater element with a high flow pump and it will work just like it did as an ICE with a somewhat shorter warm up time.


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## Roderick (Dec 8, 2013)

dougingraham said:


> 1200 watts is barely enough to defrost. In a small 2 seat sports car 3000 watts is comfortable. My Tesla reportedly has 6000 watts for the passenger compartment heater and it heats up the passenger compartment from 0F (-18C) to room temp in less than 10 minutes and will easily keep it warm at 80 mph.


Is there any information on that tesla heating system?
had no idea they used ceramic heater!


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## GoElectric (Nov 15, 2015)

Hi. You live in the home of Phillips and Temro - the company which builds the heating systems for several OEM EVs. What these systems are, they won't tell, but they make a wide range of units for keeping vehicles and their fluids (like hydraulic fluid) warm. 

I am in Calgary and will be working with an automation and control engineer on my system. I have 3000W electrical on 2 elements, so low speed fan will be one element and high-speed will be both. This may be adequate for my car, and as I have lots of battery, won't be driving from Nov. through spring, I think this part will be okay. 

I have Tesla cells, which are made with heating/cooling system plumbed in already. I will need some kind of a circulation heater and controls though, and will be willing to share my design. You could use it for cab and batteries. I think if you are going to use gas/diesel powered heating, just turn the fan down if it gets too hot and skip the electric part.


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## EVDoodle (Oct 9, 2013)

An update: I have located a used webasto 5kw diesel truck heater. The unit is very compact and has been used on BMW cars among others. I have currently set it up connected to a car radiator to blow heat into my garage for the time being until I build my EV around it. It is very economical (typically less than 0.5 L per hour running continuously when required). a 5 gallon tank should keep everything toasty warm in the vehicle for at least 24 hours or more. All the big rigs have them and (I see more and more pickup trucks locally have them) as well as the air heaters for the sleeper cabin. In this Winnipeg climate the 3 kw ceramic heaters are not able to cut it especially if you want all day operation at -30-40C. 5kw is the minimum. The extra heat is worth it if you also want to keep the batteries above freezing as well. The electric heaters basically take too much energy from the batteries at the power densities available today. In the interim I think the diesel(or gas) heater is the best approach both financially and capacity for cold weather climates. They also come in higher output units.


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## Moltenmetal (Mar 20, 2014)

These threads keep popping up, so here are my two cents copied from a previous thread- in case people don't search:

Windshield defogging is a safety inspection requirement here, so it's all I have for heating. I am using a 120VAC compact (travel) hairdryer, connected to the defrost duct hose on my Spitfire with a rubber Fernco coupling, and a relay capable of stopping a DC arc to turn it on and off- that's critically important. The relay I tried to use originally, rated for 230 VAC and 40 A, wasn't able to stop the arc and it melted the first time I tested it. 

Note that the high/low/off sliding switch, as well as the thermoswitch and thermal fuse installed in that hairdryer to protect against the fan stopping - none of these are good for DC. If the fan stops you need to shut it off immediately or you're going to possibly have a fire under your dash. I removed them all. Since I use mine only for windshield defogging and then only rarely (it's a convertible), and nobody drives the car but me EVER, it's not a huge risk to me.

The hairdryer is a nichrome resistance wire type, with a little DC motor which runs the fan. It uses a parallel connection off part of the nichrome wire coil to get a low enough voltage for the motor, and a diode to convert the AC to DC. If you get the polarity right, it runs just fine directly from my 105VDC pack.

I don't drive the car in the winter. From what I've read here, you're looking for at least 2500 watts of heating in that case in a typical car to be at all comfortable.

The ceramic space heaters that I've seen all have shaded pole AC motors, so they require some Frankensteining to use. You need a DC blower or fan (generally the 12V ones are your best option here). If your heater core is amenable to swapping out the water-to-air heat exchanger with a couple of these ceramic elements in the correct geometry, then that's an approach that several people here have used successfully.

Irrespective of whether you're using air or water heating, a reliable means to shut off the DC supply to the heater is essential. A means to shut off that power when the temperature goes too high (because of a fan failure) is also a very good idea- one I haven't implemented yet in mine, but if this were a car other people were going to drive I would definitely do it for safety. But also be aware that relay contacts can stick or weld together, and solid state relays can fail in the fully on state. Generally, heater circuits require a second, independent means of shutoff in case that happens- that's what the thermoswitch and/or thermal fuse is for. You can probably safely put the AC rated thermoswitch and thermal fuse in your heater device in series with the coil of your DC relay (obviously removing them from the AC circuit they're wired into now!) and then the only thing you need to worry about is the contacts of your relay welding together.

The ceramic elements are somewhat self-regulating, but not reliably enough to be failsafe against a fan failure. All the ceramic heaters I've taken apart have at least one secondary safety against fan failure.

If you're using water heating, similarly you need a means to protect against excessive pressure due to boiling if your pump fails. Your element should be protected against boiling dry- a short circuit of your pack voltage to the chassis of your car resulting from a failed heater element is likely not something you want either. Your pump needs to be good for hot water (most of the little DC pumps aren't). 

As to the worries about galvanized parts and galvanic corrosion, here's the piece of information you're missing. A car's cooling system is FULL of dissimilar metals. The reason you can get away with that and not experience enormous galvanic corrosion of the less-noble parts is a) it's a closed system which has a minimal ingress of fresh oxygen, and b) the antifreeze mixtures are loaded with corrosion inhibitors. The steel pipes, brass valves and cast iron radiators of my house's 80+ yr old hydronic heating system are in perfect condition on the interior just because it's a closed system with minimal fresh oxygen being admitted. As to the zinc galvanizing: don't worry about it. It won't help much, but it won't hurt either. Just make sure your system has an expansion tank (water expands as it heats up, just like everything) and that the tank is sealed against fresh air entrance but also has a means to relieve pressure if you start making steam. A tube off the top of your expansion tank running into another bottle partially filled with antifreeze will do that job nicely- it will vent excess pressure while also preventing too much air from being sucked back into the system every time it cools down again.


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## bigmotherwhale (Apr 15, 2011)

If i was going to run a Hydrocarbon powered heater, i would look at something like this, 

http://www.ebay.co.uk/itm/JAGUAR-S-...403183?hash=item3abfe29eaf:g:cQAAAOSwUuFWyBzA

Very cheap and hundreds on ebay, all you would have to do is plumb one into a heat exchanger in the cabin, if you live somewhere very cold and have a water cooling / heating loop on your batteries i imagine these could come in extremely useful indeed.

If you are planning on using battery power for the heater, I would suggest a compressor driven heat pump, excellent COP, could be used for extracting waste heat from the motor and controller? i know of no one who has done it or seems keen on doing it.

The other option is thermoelectric heating and cooling, there are factory made seats with this already out there, better than a cabin heater but will not demist your windscreen, only marginally more efficient than resistive heating however.


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## GoElectric (Nov 15, 2015)

Hi. I have an update on heating the Tesla batteries. Well, progress anyway. I had an engineer run the heat-flow equations, and to heat six modules 10C in 30 minutes he calculated you need 900W. I'm not sure if others think that is a reasonable criterion, but you gotta start somewhere.

I'm going to use a 750W Temro fluid heater which is rated for 120VAC and run it at 120VDC, which will give me about 1070W. Plus I will be warming-up the batteries a bit because I am drawing power from them. 

All will be tested and data logged on the computer, so whatever happens, we can adjust and make it work.


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