Upgrading Heating System - Independent Battery Source

[Don]

The factory could have saved quite a bit of money if they had just used a cheap ceramic element in place of the water heater core they installed in the heating system, but they probably spent the extra money because an element which heats the air directly would be hot enough to cause a fire. When the car gets old and there's lint built up in the HVAC system, the possibility of a fire, or at least melting something exists

That plus there's no other safe way to put 5KW of heat into the car without using the water heater core and we know that a measly 1500 watts isn't going to defrost the car when it's icy

Unless your heating element can be regulated, you would need to make sure it only operated with the OEM fan set to the high speed to carry away that heat - A lower fan speed could be dangerous and allow the heating element to overheat and melt something

Since the system is already set up with the 5KW water system, it just makes more sense to me to keep things safe and just add a bit more heat to the water as Aerowhatt has proposed. Compared with trying to stick an unregulated ceramic element into the plastic heater housing, adding more heat to the water seems to be the simplest and safest way to go . . . . but I'm always happy to be proven wrong - Post some pictures of your project when you get it finished and let us know how it works out

Don

 

[PV1]

Jay, the pre-heat function works well to "pre-heat" the water loop for Defrost mode . Five minutes of HEAT followed by 25 minutes of DEFROST works like a charm.

I think Mitsubishi went with a water-based heater mainly because the existing HVAC system was already designed for a water-based heater core (holdover from the ICE i). Plus, water makes a better conduit for several kWs of thermal energy and avoids any dangerous temperatures (plus that burnt dust smell you get from a space heater).

The heater would need to have a robust design to function safely in the filter slot (though that is likely the best place for factory HVAC integration). 800 watts of heat would be enough for the vents to feel warm, but more would be needed to heat the car up. I suppose one could pre-heat from the wall, then use the filter slot heater to maintain it.

 

[jray3]

Well Don, ceramic elements are regulated by their very nature. They will not go above design temperature even if connected directly to the battery with zero airflow. Their resistance has a Positive Temperature Coefficient, so that the hotter they get, the less current they draw. Regulation can be accomplished simply with varying the airflow. This is why they've been successfully used in hobbyist conversions for decades. My RX-7 EV has been running 'em since 1993 in place of the heater core, and there is no heat distortion of the surrounding plastic. I ran both heaters continuously for several hours (while plugged in) as a test last month, (both with and without airflow) and they passed like new. Yes, you may get a whiff of singed hair when firing up the heater for the first time each season, but enough dust to cause a fire would be a real outlier. Especially in the case of replacing the air filter with a heater seasonally, there shouldn't be a big dust buildup on the grid to create any fire hazard. On a typical consumer-grade ceramic heater, resistance begins to rise significantly at 120 C and the heater will remain below 200 C. The minimum ignition temperature of paper dust (one of the most flammable dusts), is 360 C.

That being said, I'm not going to do it. The stock heater is plenty powerful, and if I really needed supplemental heat on a regular basis, I'd go for the fuel burner rather than buy enough extra battery to make a difference (3-4 kWh). UNLESS one of you brainiacs figures out how to easily add 330 VDC from a supplemental battery to provide both summer range and winter heat.

A pusher trailer does this in spades, btw... My pusher-trailer buddy just passed through town on his annual pilgrimage, pushing his EV with an aircooled VW engine for over 2500 miles round trip. I'm not pushing on long trips any more after demonstrating the concept in 2014 because our VW pushers only averaged 20 mpg in steady-state operation (after using the i-MiEV's first 50% SOC in engine-off pulling). Our minivan exceeds that for 100+ mile trips in greater comfort and with less risk, and for sub-100 mile trips, CHAdeMO fills the bill nicely. A motorcycle drivetrain that can output 20 hp continuous would be my next preference for pusher trailer experimentation (singlewheel), unless I score a small modern fwd automatic on a subframe.

 

[PV1]

I don't know about a 4 kWh 330 volt aux. pack running parallel (ran the math a while back, and the cells at the time couldn't handle the amps), but a Model S battery module runs just shy of 24 volts and contains 5.3 kWh. If you could find a 24 VDC heater or use a space heater and power inverter, then that could be worth looking into (but a fuel heater is much cheaper).

 

[Lic]

I did extra insulation for doors, floor, top. So I am kind of fine in car with my small home heater working from 60v battery. Only problem - I keep it in passenger compartment and it's look like it's better to get this heater working through regular ventilating system to be able to move air flow to windshield or to legs and etc.

 

[clifforde]

I have been looking for a heating solution myself, something safer than what I've had to resort to. My commute is 38mi. one way where I put it on a charger near my office for the trip home. I'm in Pennsylvania north of Pittsburgh. I've been freezing my tail off every winter because the range is 40 miles for me. The turtle indicator is on by the time I get to work and again when I get home most of the time. I really can't run the heater or defrost at all or I will not make the trip. That happened to me once, I came up 150 yards short where it died and I put the car in neutral and pushed it to the charger. For now I'm running a propane fuel "Mr Heater" I bought before the car for camping. I crack the window for a bit of fresh air. This is ridiculous and dangerous.
The car needs double the range it has to be a viable car for winter. That's the bottom line. I want more/better batteries. I don't want to fool with accessories and for $29k that I paid for the car, I should be able to drive it 38 miles and run the heater.

 

[Don]

It sounds as though you're a perfect candidate for the diesel heater upgrade. You're into it for $29K now, what's another $750 to make the car work the way you want/need it to?

We have several Canadian owners here who drive in conditions far worse than typical Pennsylvania winters and for many more weeks of it that you get there and several of them have made the car a perfectly viable winter transportation alternative by burning a cupful or so of diesel fuel every few days. I often wish (no, not really - I'd hate to live where it gets really cold) that I could find an excuse to install the diesel water heater myself, but where we live and with the range we need, using the car's stock heater in the winter is about all we need

It's unlikely you're going to find a cheap, easy way to double the battery capacity or double the cars range, so installing a real heater would seem to be the obvious choice

Don

 

[PV1]

Ah, someone from my neck of the woods. I merged your post into this existing thread where we talk about a 2nd battery for heating, but if this conversation morphs into a discussion about the drive battery more than heating options, then I can split these posts off into a more appropriate thread.

Regarding range, 40 miles without any heat is rather low (64% of the original range). The worst range prediction I've seen at a full charge was 40 miles on a -10 degree morning with heat on MAX. Even last weekend when temperatures were in the single digits, I made the 35 mile drive to the Convention Center at 60-65 MPH and used just over half a charge (didn't use heat on the trip because I heat-soaked the car with a space heater before leaving). Running heat on the return trip left me with 4 bars when I got home.

With that much range degradation, I'd have the alignment checked. Some of us have also found that tires other than the stock Dunlop Enasave could noticeably impact range. If tires and alignment didn't help, I'd try to pressure the dealer into diagnosing the battery pack and possibly a warranty replacement. Though our warranty doesn't specifically cover capacity loss, it does say to expect 20% loss over 8 years, and you've lost almost double that in half the time.

 

[Aerowhatt]

So after a long search for the proper CPVC components for this project and not finding some of what is needed even being made in CPVC, in addition to large size CPVC fittings generally only available by the case. Then looking at metal alternatives. It occurred to me while doing some wire runs that PVC conduit is rated to 90C wire. So I did the boil test on a sample and sure enough immersed in boiling water PVC conduit retains it's structural integrity

So now that I have a new material which is more readily available in "single fitting" purchase reality, progress is once again possible.

In the interim I have made some snow hiking trips to the mountains and have come to the conclusion that I don't really need this system as much as, I want to tackle it. Clearly keeping the car comfortable on minimum watts is practically and art form. But it's amazing using canion to record the results. There is a marked difference in the percentage of power used for heating under identical conditions depending on whether I'm driving or my wife is. Both drives being equally comfortable. She uses the system more like one would in an ICE car. She use more than 4X the power as I do for heating!I I imagine that most people do? But that is another discussion entirely.

I now think that the housing can be fabricated from PVC conduit parts. And thinking during the "suitable materials crisis" brought me to the conclusion that It should replace the expansion tank instead of being an add on to the system. With the controls integrated in the housing and the hose terminations in the original locations so that it would/could be a very straight forward install for most anyone.

Now if I just didn't have so many other things on my plate :roll:

Aerowhatt

 

[blackheart]

)A motorcycle drivetrain that can output 20 hp continuous would be my next preference for pusher trailer experimentation (singlewheel), unless I score a small modern fwd automatic on a subframe.

I'm working on it ;-). If anyone has or knows of a wrecked 650cc step thru (Suzuki makes one) let me know ;-)

 

[blackheart]

Ok - side stepped the pusher trailer for a while - expensive helper project...
BUT, I did order a cradle for my Dolphin 48v 11aH ebike battery from Luna Cycle.... Why? So I can mount the 10 lb battery in the car safely and wire it to a 48V heating element that I will mount someplace in the heating fluid system. I am thinking close to the inlet side of the heater core, so there will be less heat loss for water (coolant) traveling around in our 'engine' bay (what do you call the space under the front hood in our little cars???)
This should give me about 500 watts of heater helper power. If that is too small, Luna is also selling a 48v 17.5aH battery they call the "Killer whale". That would give you around 700-750 watts of power. Not enough to drive all day, but should be enough to warm me and passengers in my normal 30 min drive time. And the 'heater' battery can be charged at my work, or at a friends house, or pretty much anywhere - and NO diesel....
Thoughts???

 

[Don]

Thoughts???

500 watts isn't much heat . . . . 750 is not much times 1.5 :lol:

Before you go to the trouble, I would pick a cold morning and put a small 120 volt household heater set on 'Low' (should be 500 to 750 watts on most of them) in the car for 20 minutes or so and see what that gives you

I know that using the remote heating system with the OEM L1 EVSE (8 amps . . . . probably provides about 750 watts of heat) does very little to heat up the car in 20 or 30 minutes before it shuts off, so maybe you'll discover that 500 watts isn't worth the trouble??

FWIW, there are 3,412 btu's of heat in a kilowatt hour of electricity and 8,687 btu's in a cupful of diesel fuel . . . . and the car comes with a 5 kw heater

Don

 

[blackheart]

On cold mornings, I have pre-heated the car with my L2 plug. When leaving the house, I see the Heater using electricity (via Canion) within one mile. By the time I get to work, it shows that I have used about 500 watts. So, for my ride to work, all I should need is 500-700 watts to keep things up to temp. True it is not very much. But it sure seems to kill my range. If I get 4 miles per KW, that is 250 W per mile? So, the heater 'seems' to only take about 4 miles of range - but my RR meter seems to take a bigger hit than that.
But, If all I needed was another 4 miles (2 miles savings to work and two miles savings leaving work) it may just be worth it.
Just looking for something to get me over the edge on the cold days. During the times of year that I don't need the heat - I have range to spare. But during the winter - the miev becomes a two point car - work and back. I take the truck to go get the wife... All I need is a couple more miles ;-)
Plus, I have the battery, the cradle was $30. An element is $30ish. I work at a manufacturing company, so I can make a reservoir from scrap. A thermostat and some wire - it might be a fun project.
Though I would probably get more 'savings' from insulating the car and existing heat system better.
No offense - I am not to the point of needing that much heat - and if I can do it without diesel = win.

 

[Don]

By all means, give it a shot! - I wasn't trying to talk you out of it . . . . just suggesting you try something simpler to see if 500 watts of heat would make much difference

More neat things have been learned about these cars by those with a bit of ingenuity who were willing to give something a try to see what's practical. If you're only looking to 'save' a few miles of range, this just might be something that will work for you. If the car is already preheated when you leave, maybe some sort of portable heater sitting on the floor would do the job without needing tomodify the car to build something in permanently?

Don

 

[blackheart]

Didn't take it that way at all - And me being a newb to all things electrical - this forum has been a great place to learn - so that's why I made the post - 'give your thoughts' ... I know it won't make much - but looking at my Canion during my morning commute, when I am using heat, 500-700W seems to be the ticket. And I have the battery - so why not?

However, I am very interested in hearing what folks have done as far as insulation. I can tell the second the heater is turned off in the little car. Due to living it the wet NW, I haven't crawled around much under the car this winter, but I suspect that there could be some fairly draft inlets along the firewall, or something. Maybe the cabin is just not insulated at all? I have seen people post about wrapping insulation around the hoses of the heating system - I hope to do some of that during our 'dry season' (best two weeks of the year!!).

Per the interwebs "One BTU is the amount of heat energy required to raise one pound of water by 1ºF. Water weighs 8.33 pounds per gallon so we can calculate that one gallon of water requires 8.33 BTU to raise the temperature 1ºF." But I read (and correct me if I am wrong) that our little car's heating systems only hold like 2.2 quarts of fluid. And since the fluid is being actively cooled by the air flow over the heater core, I am not sure what those losses are.
The ebike battery (not accounting for losses) should equate to 1700ish BTU's right? So, i should be able to raise the temp of 1° (1700/8.33) 204 times??

Like I said, new to electrical math - but it should heat it some. Between that and some insulation (to make the heating system more efficient) It should help some - don't you think????

oh well, if it doesn't, I'l have a cradle to use the batter elsewhere ;-)

 

[Don]

Have you read through this thread?

http://myimiev.com/forum/viewtopic.php?f=9&t=224&hilit=heater+insulation

Don

 

[blackheart]

I have a bit - but I will run through it again
Thanks!!

 

[Aerowhatt]

Bump! So Getting back to this project. I have had all of the parts etc. and a completed design for months. But once we got the recall notice on the airbags I put off going forward. Unlike some of my other mods to the car which are, for all practical purposes, invisible. This one will be obvious, right under the hood. Like everything I do, with something under warranty, the design allows reasonably easy removal with no trace that it was ever added. However in the interest of laziness I wanted to get the airbag done first. Got my wife’s cars airbag done last week and (another story :x ) I am NOT looking forward to going back to the dealer for my own to be done.

We had a rare day for NM recently so I took the opportunity to do some testing. Conditions were dark overcast and 29 Deg F. I preheated the car at 240 volts input. Then went for a long drive. Dark overcast is important since the sun here at 5000 ft elevation is so powerful. If the sun is out, far less heat is required. Mainly my goal was to measure the best practice usage and resulting power consumption of keeping comfortable. I didn’t dress any warmer than I would for, say a grocery run in an ICE. I don’t like to drive with a coat on (so no coat) no insulted boots, no hat, gloves or anything like that. Just good over the calf socks, summer hiking shoes, jeans and a t shirt under a long sleeve henley.

Doing hiking trips to the mountains for two full winters (this is the third) has helped me find the best most efficient way to use the stock heat. It makes sense when you think about it and is different than we are conditioned to use the heat from years of ICE driving.

Preheat the car if you can.
Use the seat heater. I usually turn it off after ~10 minutes because it gets too hot
Direct the heat to the floor only, on recirculate (it will keep all of you warm, heat rises).
One notch toward defrost if needed to prevent fogging.
Start driving with the fan on high (I like the setting just below high because it is a bit quieter)
Temperature setting should be where ever you need it to be. I generally start high and end up on the second or third position up from the green dot.
If and when the heat is adequate inside the car turn the temperature down, not the fan!

#6 is critical! The heated fluid goes from the heating element right into the cabin. The more heat that you take out of that fluid before it makes the long trip outside of the cabin (under the hood etc.) the less heat is wasted to the cold environment.

So back to my test run. I drove around town town for 1.5 hrs using the Canion heater power graph to average my power consumption for heating. The average for the trip was 638 watts/hr. That (generously) equates to about 3 to 4 miles of worth of lost driving power (per hour) for staying comfortable. I know from previous non preheat trips at around 33F that approximately an extra 800 watts of power is required to warm the car up inside (just the front, heat directed to floor only using the “max” button until the the chill retreats). Which yields ~1500 watts for the first hour starting out cold (up to ten miles worth of range).

The 2014’s have a styrofoam piece under the front carpeting. I don’t think the 2012’s have this and it would make a difference, I’m sure. But overall, if one optimizes usage of the heating built into the car and it isn’t to to cold (29F is reasonably cold though).

The point of my test run was to take advantage of the unusual weather conditions to see if the 1200 watt output of the designed separate battery powered heating unit would be enough. Looks like it should be even capable in worse conditions than I encounter. Perhaps with an initial boost from the onboard system to speed the initial response time of warming the cabin when not preheating from the mains.

Aerowhatt

 

[JoeS]

...Got my wife’s cars airbag done last week and (another story :x ) I am NOT looking forward to going back to the dealer for my own to be done...

I just had all the recalls done on my two i-MiEVs over the last couple of days (including vacuum pump replacement) and I hope the squishy brake pedal is just temporary...

If and when the heat is adequate inside the car turn the temperature down, not the fan! #6 is critical! The heated fluid goes from the heating element right into the cabin. The more heat that you take out of that fluid before it makes the long trip outside of the cabin (under the hood etc.) the less heat is wasted to the cold environment.

I understand the logic and am now doing that, although it's disconcerting to see the RR gauge react to the fan and not the temperature control!

So back to my test run...

Great that you've got data for the "before" scenario. Looking forward to your installation which is environmentally 'cleaner' than the diesel heaters our northern brethren have been using. Where will you physically locate your 36v LiFePO4 battery pack? Do you think there's enough time to recharge that 36v pack using a dc-dc off 12v in your usual main pack recharging regimen timeframe? I'm impressed that you're doing this as a fully automatic hands-off installation (mine would be something Rube Goldberg would be proud of) .

 

[Aerowhatt]

JoeS wrote:
I just had all the recalls done on my two i-MiEVs over the last couple of days (including vacuum pump replacement) and I hope the squishy brake pedal is just temporary...

Yeah dealers, sheesh, seems like they screw up more than they fix! They were pushing me hard to change the transmission fluid in my wife's car. Service requirements say 24 months, or 30k miles. Hers is at 21 months and 11K miles. They made sure to put it on the paperwork that I refused the service! $118.00 plus tax they want for that. Amazon has the exact Mitsu tranny fluid for $12.88 per quart (car takes .76 quart for a refill). I'll definitely do it myself to prevent mechanical problems down the road. Now what kind of documentation do I need to not have warranty issues?? Two witnesses and my lawyer present? That would cost the same but at least I would know it was done right . I need to figure it out and do mine before I take it in for the airbag recall. I'm at 32 months and 22k miles. So past due in their eyes :lol:

JoeS wrote:
Great that you've got data for the "before" scenario. Looking forward to your installation which is environmentally 'cleaner' than the diesel heaters our northern brethren have been using. Where will you physically locate your 36v LiFePO4 battery pack? Do you think there's enough time to recharge that 36v pack using a dc-dc off 12v in your usual main pack recharging regimen timeframe? I'm impressed that you're doing this as a fully automatic hands-off installation (mine would be something Rube Goldberg would be proud of) .

I have decided to get AC power from the mains instead of taxing the DC to DC. It's a 40 amp hour 36volt pack, so three hours at 15 amps. Easy enough to source a charger that runs on 240AC and puts out 15 to 20 amps "36 volts". Ideally picking up the AC power between the charging port and the cars charging unit. That way it will charge while the car charges and be disconnected by the EVSE when the car finishes charging. Honestly though I'm feeling gun shy about proceeding with the installation. With our Canadian friend having to fight for having his traction battery warranty honored because of the diesel heater installation. :roll: This is what I was worried would crop up when Nissan got a controlling share of Mitsu motors. Still on the fence about battery placement. Either the cars trunk or the hitch mounted tool box. Tool box makes more sense for safety but I don't always have the rack and tool box along for the ride :?

E-truck2
Aerowhatt