Heater In a Box

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LeftieBiker

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This idea started out as a way to provide the Prius PHEV (aka "PIP") with a heater that doesn't rely on the gasoline engine starting and running, but I soon realized, as I imagined a more portable version, that it can also work for the Leaf. It's basically a portable (as in "You can move it" not "You can easily carry it") heating system that would save the considerable drain on the Leaf's battery pack from the car's heaters in cold weather. The Leaf heaters are designed to provide substantial heat almost instantly. This system should provide enough heat to both warm the driver quickly, and warm the whole cabin eventually, which means it can use substantially less energy for this purpose than the car's built-in heaters. It consists of:

* The power source. A sealed deep cycle 12 volt storage battery of at least 60 amp-hours (AH) in a marine type battery box. If a marine battery is used the maximum safe drain is only 50% of capacity, so I'd suggest a 75AH minimum capacity for that type. Otherwise assume that you can use 80% of the battery's rated capacity, although 60% is best. Do NOT use an automotive starting battery, as these are meant for high current but low drain situations, and will soon expire in deep-cycle use. While you don't necessary need them, I suggest a couple of marine-grade accessory sockets be installed in the lid of the battery box.

* The heater. While you could use a 12 volt automotive type interior heater, reviews of these heaters suggest that they are a waste of time, providing little actual heat. You can also simply plug them into the car. Instead, I suggest a ceramic type (for safety) 120 volt, personal-sized space heater. Lasko makes a 200 watt unit that I have personally tried in a cold indoor environment; it provides surprisingly warm air, with a modest but adequate airflow. Its biggest advantage is its low power consumption, but it also has disadvantages: no thermostat, and a shape that is "tippy" enough that it would have to be secured to a more stable base for use in a vehicle. I have seen listings for another heater, by Holmes, I think, that has both a 1500 watt setting that could be used for preheating the car with house current, and a 375 watt setting that would seem to be ideal for heating a car. I have not, however, tested this heater. There may be other, better choices available.

* The inverter. A good quality inverter is used to convert the 12-14 volt output of the battery to 120 volt AC house type current. It must be remembered that when you multiply the voltage by 10, you need 10X the rated current of the device to be drawn from the battery. Thus the 200 watt heater, which draws about 1.7 amps at 120 volts, would draw 17 amps from the 12 volt battery. (This is why I suggest a fairly large, heavy battery. While a 12 volt lithium battery pack would be great for this application, most people would opt for the much less expensive lead-acid type, so I'm concentrating on that.) The inverter does not have to provide pure sine wave output to run a simple heater, it just has to be well-made and provide its rated output. If using a 200 watt heater I'd suggest a 400 watt inverter, as you don't want to run an inexpensive inverter at or near 100% for extended periods of time. For a 375 watt heater I'd suggest at least 500-600 watts for the inverter. That's 500 watts *continuous*, not "peak" which can be maintained only briefly. If you use a good inverter you can also use it for things like picnics in warm weather.

* Battery charger. While it is theoretically possible to keep the storage battery recharged from the car's own electrical system, either through the "cigarette lighter" / accessory port or from a hardwired connection, the safer option is to use a dedicated 12 volt deep cycle charger. The charger should be at least 10 amps, and more would be better, as the battery will get drained substantially with each trip in which the heater is used, and if recharged too slowly it will both be impractical and possibly suffer sulfation damage. If the charger is carried in the car, then a compromise between size and power will likely be needed.

* Wiring. While a 200 watt heater could be run with standard 12 volt accessory plugs and sockets (assuming marine grade components, not low quality), it would be better and safer to use quick-disconnect high amperage connectors, like Anderson Power Pole or the more ubiquitous XT90 or XT60 (for smaller heaters) plugs. A separate plug for the charger would facilitate fast, safe recharging. Do NOT attempt to run higher wattage units using 12 volt accessory plugs. Do use a fuse or circuit breaker in the positive lead from the battery terminal. Amperage of the fuse will depend on the power required for the heater.

A word about safety: it's sometimes easier to assemble components quickly and sloppily, but when working with high amperages, even at low voltages, short circuits can VERY easily start fires. Use only quality wiring and connectors, properly assembled with shrink tubing at the ends, and electrical tape wherever needed. Don't route wires where they can tangle in feet or rub against metal or sharp edges. Make sure that the heater is secured to a stable base that keeps it away from all combustibles. Ceramic disk heaters are fairly safe, but nothing is perfectly safe. Finally, while sealed batteries generally only vent gas under extreme heat caused by over-charging or excessive discharge rates, don't assume that venting will never occur. This means don't put the battery in a sealed box!

As you can probably tell, I haven't yet built a prototype unit. Logistical and health issues will slow the process for me, so I'm putting the idea out here for you Leafers to try as well. Good luck, and *be careful*.
 
Typing is hard for me, and I forgot something important while fixing typos: a fuse or circuit breaker should be installed in the battery box, so that it protects everything from short circuits and overloads. The rating would depend on the draw from whatever heater is used. I've now added this to the original post.
 
Looks like only you agree. ;-) There are issues with this approach, like having to be more careful with a 120 volt heater in the car, but I don't see why it couldn't be used to great effect to at least maintain heat for the driver once the car's heating system has warmed it up. The people who drive with no heat now, to extend range, would think it was nice and warm!
 
I've decided to go with two of the 200 watt Lasko heaters for the prototype, because they are so well reviewed, and apparently produce more usable heat (each) than the 375 watt Vornado (not Holmes) unit. I will mount them on a support of some sort, with the option to run one heater or both at once. I also dug out an 800 watt inverter I've had sitting around for years. I hope to have it all assembled and ready to test at the end of next week. I will be using them at floor level in the driver's area, below my legs in front of the seat, because I have poor circulation and feel heat the most when it's on my feet and legs. The power cords will run through a protective plastic tube to the battery / inverter setup, in one of the rear foot wells. I want to be able to reach the power switches while driving, without taking my eyes off the road.
 
Not sure why you need a separate lead-acid battery, and then charging it from the cigarette lighter! Quite a lot of conversion losses there, and carrying unnecessary weight.

Seems to me the existing 12V system should be able to easily provide 200 watts and still keep the onboard 12V battery charged. For a more robust 12V onboard battery, I replaced mine with this guy:

http://www.solar-electric.com/concorde-sunxtender-pvx-420t.html" onclick="window.open(this.href);return false;
 
Nubo said:
Not sure why you need a separate lead-acid battery, and then charging it from the cigarette lighter! Quite a lot of conversion losses there, and carrying unnecessary weight.

Seems to me the existing 12V system should be able to easily provide 200 watts and still keep the onboard 12V battery charged. For a more robust 12V onboard battery, I replaced mine with this guy:

http://www.solar-electric.com/concorde-sunxtender-pvx-420t.html" onclick="window.open(this.href);return false;

The idea is to have a system that is not wired into the car, for the benefit of people who lease. This approach would also extend range and raise eMPG. Charging the battery through the accessory outlet is possible (while losing net charge) but if you read what I wrote again, I don't propose doing that. The charger is a separate unit. Only a hardwired installation would work to power the heaters, and few people would go for that idea. If Leaf owners want to try that, all you have to do is, as you imply, wire the inverter to the larger accessory battery you'd probably want to install first.
 
The heaters arrived today, the day after I ordered them, so I did some preliminary testing of components. After testing each heater in an outlet to make sure it wasn't defective, I then tested each one with a 300 watt inverter, plugged into a modest-sized deep cycle battery in a box that I have in the house for power failures. The Lasko 200 watt heaters do very well with inverters, apparently: I was expecting them to run slower than on household current, but they seemed to run exactly the same. Smooth and quiet, with lots of heat output. I then brought one onto the front porch, where I have an outdoor outlet. The temp outside was about 34F, so I plugged the heater in and let it run in the cold to see if it produced enough heat rise in cold air. It does indeed. The air coming out felt about 100F, even in the cold. I'm guessing that the ceramic disks are regulated to produce a fixed output temp, and will do so to the best of their ability. If there is a deficiency, it will be with airflow, and I may be able to fix that with a booster fan in front of or behind the heaters. Hopefully that won't be necessary. I'm into my work week(end) now, so it may be next week when I put everything in the Leaf and test it with the 800 watt inverter and both heaters.
 
kubel said:
I was thinking a Mr Heater with a 20lb tank in the trunk. Resistance heat isn't a very efficient use of electricity.

If it works it will provide over an hour's worth of heat - maybe two - with no explosives in the passenger compartment. (A battery can explode, but not under these conditions.)
 
LeftieBiker said:
The heaters arrived today, the day after I ordered them, so I did some preliminary testing of components. After testing each heater in an outlet to make sure it wasn't defective, I then tested each one with a 300 watt inverter, plugged into a modest-sized deep cycle battery in a box that I have in the house for power failures. The Lasko 200 watt heaters do very well with inverters, apparently: I was expecting them to run slower than on household current, but they seemed to run exactly the same. Smooth and quiet, with lots of heat output. I then brought one onto the front porch, where I have an outdoor outlet. The temp outside was about 34F, so I plugged the heater in and let it run in the cold to see if it produced enough heat rise in cold air. It does indeed. The air coming out felt about 100F, even in the cold. I'm guessing that the ceramic disks are regulated to produce a fixed output temp, and will do so to the best of their ability. If there is a deficiency, it will be with airflow, and I may be able to fix that with a booster fan in front of or behind the heaters. Hopefully that won't be necessary. I'm into my work week(end) now, so it may be next week when I put everything in the Leaf and test it with the 800 watt inverter and both heaters.


Unfortunately it seems like a lot of work and hassle to essentially get the extra energy of a 12volt battery.

And this is coming from a guy in Montreal who knows all about how much energy the heater takes.....for me preheating as much as I can (the heat from the vents is 140-150 degrees and then driving with minimal heater use does the trick, along with blocking the grill and wrapping all the underhood heater components (I don't have the heat pump).

it is fairly comfortable to get in a super warm car and drive with minimal heat as opposed to getting in a cold non electric car and waiting for the engine to warm up.

But that said if it works then that would be great.
 
Unfortunately it seems like a lot of work and hassle to essentially get the extra energy of a 12volt battery.

For me, maybe. If it works, it will be minimal work for others. That's why I'm making it modular and off the shelf. Now, if anyone wants to be helpful, let's try to locate a 120 volt heater that is configured so it can sit on a dashboard (think "clock radio shaped") and defrost the dashboard. 500 watts maximum. Failing that, by leaving the car's electrical system out of the design, the 12 volt accessory port is still free to power a 12 volt vehicle defroster that actually works.
 
Hello everyone, I have used above idea already,and made big mistake-test set up first before you build it.
My idea was to warm up my 2001 prius with remote.I bought on ebay great fob/receiver 12v with 3km range.I tested-indeed works around 2km from my house-plenty for remote aplication.I used 400W heater,1000W motomaster I inverter and 92Ah deep cycle powerjack battery.Conclusion---works good for about 15 min and then inverter shoot down on low battery voltage. So for those who want to try this here is my tip-test it on the floor first before you invest time and money to build this in the car.It make sense now to me ,when I look at 92Ah battery is drop in the ocean compare to Leaf 24Kw battery and the fact -using Leaf heater greatly reduce the drive range.Leaf PTC heater is about 5000 W and runs direct from high voltage.
 
I'm not sure what happened in your case, but a 400 watt heater would draw about 35 amps from the storage battery. If the battery was rated at 95AH, then it should have been able to power that setup for two hours, not less than 15 minutes. I think you had a bad battery (or one one that was depleted to start with), or a bad inverter. I have been testing my components first, and so far, no problems with them.
 
Inverter I bought in Canadian Tire and used few times on camping trips. Battery about 1 year old and was always charged 14.3V. Inverter shut down at 11.2 V. I will bring DC amp meter from work to see what is A draw from battery to inverter.
I'm planning however to install remote climate to my Leaf (I post already in Nissan suggestion tab) using this fob and receiver.
I like similar design in Chevy Volt and C-Max energy I had for few days. Way more practical with single push,when car is just outside restaurant or home then using cell phone and internet.
 
tszukow said:
Inverter I bought in Canadian Tire and used few times on camping trips. Battery about 1 year old and was always charged 14.3V. Inverter shut down at 11.2 V. I will bring DC amp meter from work to see what is A draw from battery to inverter.
I'm planning however to install remote climate to my Leaf (I post already in Nissan suggestion tab) using this fob and receiver.
I like similar design in Chevy Volt and C-Max energy I had for few days. Way more practical with single push,when car is just outside restaurant or home then using cell phone and internet.


My first guess would be a bad inverter that draws way too much power. My second guess would be a battery that has much less than original advertised capacity...
 
Having a 95Ah battery means that it is rated to provide 4.75A for 20 hours. Pulling 35A, you will get far less than 95Ah (Peukert's law). That will account for some of the shortfall.

You will also get significant voltage drop drawing 35A, so while 11.2V might be the open-circuit voltage of a "dead" lead-acid battery, (I'm not sure that it is.) you could have a lot of life left when the inverter cuts off. (BTW my Xantrex cuts off at 10.5V, I believe.)

You might have better luck with a 12V heater, and watch the voltage yourself. You could also do a load test on your battery using a halogen headlight. (If you're like me and have a lot of those hanging around the garage.) A 55W headlight should pretty much run for the full 20 hours if the battery is at its rated performance.

95Ah could be almost 1KWh in this application, and 1Kwh that doesn't have to be drawn from the pack for heat is 1Kwh extra that can drive the wheels. So I wouldn't call it a drop in the ocean, but then again, it's really only worth another 2-3 miles. If those are the 2-3 miles you desperately need, then it may be worth it.

Personally, if I'm nervous about range going into a trip, I preheat, and set the heat on 60F and recirculate. My energy meter shows the tiny sliver I associate with mild A/C in the summer.
 
Make sense above comment, but using 12 V heater instead inverter and all power losses on the way that was my next idea , there is heater on ebay http://www.ebay.com/itm/181258439598?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT" onclick="window.open(this.href);return false; but not I'm not sure how many BTU and if it's worth the hassle. I stay with leaf heater. I have gas heater from Volkswagen beetle (very powerful) but that will not fit going green with investing in electric car and 3.2Kw solar PV on my house.
 
95Ah could be almost 1KWh in this application, and 1Kwh that doesn't have to be drawn from the pack for heat is 1Kwh extra that can drive the wheels. So I wouldn't call it a drop in the ocean, but then again, it's really only worth another 2-3 miles. If those are the 2-3 miles you desperately need, then it may be worth it.

You're assuming equivalence between the car's heating system and the portable unit. I believe it would work more like this: by concentrating the heat on the driver only (or half as much heat each on driver and passenger), the portable heater should save much more than its capacity in KWH. Someone experiencing a 9 mile drop in range using the heat full time might, by using the car's system only for preheating and occasional defrosting and/or re-warming, might see only a 3 or 4 mile drop in range. I think that future EVs will feature a heating system incorporated into the seats, blowing hot air right on the occupant, and not sending much or any air into the open space of the cabin, except in the footwells.
 
Extra range is not issue -at least here in in Vancouver,charging stations are here,every few km in any direction and free :D (http://www.plugshare.com" onclick="window.open(this.href);return false;). Please let us know how it works for you.
 
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