Car parking heater but... with BATTERIES? :phew:

[mzzj]

Not trying to tell you what to do but be aware Li-ion Batteries + Heat Source = Big Danger

Well you'd be crazy to drive around in a vehicle containing at least 475 kWh (1.7 GJ) of energy in the form of a highly volatile, potentially explosive, highly inflammable material, but I do it every time the rather small 50 litre fuel tank in my petrol car is full. What's worse is that it's engineered to deliberately produce a series of mini explosions as the form of propulsion.

One has to get the risks into perspective. The energy density of petrol is high (34.2 MJ/l), vehicles contain a lot of it and it is clearly more dangerous than any battery system but we somehow treat this with sanguity. I think the biggest concern, first and foremost, in adding any electrical heating system to a car is avoiding accidental ignition of the vehicle's liquid fuel but this never gets mentioned.

You never see anybody saying, a priori: "Petrol + Heat Source = Big Danger". Whereas there's always someone who's going to ignore that and just state (frequently overstate) the risks of adding a few megajoules of battery storage to something that already has gigajoules of stored energy on board (or of substituting Lithium energy chemistry for hydrocarbon energy chemistry in the EV case where electricity is the prime mover). Both are dangerous if not used properly, but surely gigajoules outranks megajoules in absolute risk terms. Sure, it would be foolish to ignore the known risks of any battery technology, but let's keep things in perspective - a Lithium battery isn't a bomb waiting to go off any more than a car full of petrol already is.

On a second thought your example(and my TNT comparision) ignores the Li-ion combustion energy totally.
Tesla S 100d battery contains 100kWh of electrical energy and 4 to 10MJ/kg highly combustible material in the cells. Combustion of 100kWh Tesla battery(~600kg) releases more energy  than full tank of gasoline!  (between 60 to 240 liters of gasoline!) 
https://ec.europa.eu/jrc/sites/jrcsh/files/claude-chanson_characterize-lithium-batteries-thermal-run-away-reaction.pdf

[sandalcandal]

Well you'd be crazy to drive around in a vehicle containing at least 475 kWh (1.7 GJ) of energy in the form of a highly volatile, potentially explosive, highly inflammable material, but I do it every time the rather small 50 litre fuel tank in my petrol car is full. What's worse is that it's engineered to deliberately produce a series of mini explosions as the form of propulsion.

One has to get the risks into perspective. The energy density of petrol is high (34.2 MJ/l), vehicles contain a lot of it and it is clearly more dangerous than any battery system but we somehow treat this with sanguity. I think the biggest concern, first and foremost, in adding any electrical heating system to a car is avoiding accidental ignition of the vehicle's liquid fuel but this never gets mentioned.

Energy capacity has nothing to do with the danger posed here. A block of cheddar cheese has 18MJ/kg, do you think a hot cheesy fondue is dangerous? The danger is the heat sensitive nature of li ion batteries and OPs plan to put them right next to a strong heat source.

Autoignition temperature of petrol is 280°C and it requires a source of oxygen to ignite. A combustion engine requires a purpose designed injector/carburettor to aerosolise the fuel in order to have it "explode". Even then, how would sitting an open tub of petrol next to a 800W electric heater enclosed in a passenger compartment be safe? No one's worried about OP igniting his fuel tank in it's sealed tank completely separate from the compartment where the heater is going.

You never see anybody saying, a priori: "Petrol + Heat Source = Big Danger". Whereas there's always someone who's going to ignore that and just state (frequently overstate) the risks of adding a few megajoules of battery storage to something that already has gigajoules of stored energy on board (or of substituting Lithium energy chemistry for hydrocarbon energy chemistry in the EV case where electricity is the prime mover). Both are dangerous if not used properly, but surely gigajoules outranks megajoules in absolute risk terms. Sure, it would be foolish to ignore the known risks of any battery technology, but let's keep things in perspective - a Lithium battery isn't a bomb waiting to go off any more than a car full of petrol already is.

I'm not worried about designed and tested EV systems having their batteries explode as much as I'm not worried about having my car's petrol tank explode. Maybe if I got in a bad crash? but normally, no.

The amount of energy present has nothing to do with my safety concerns here. Even if the system in question as was a single 18650 cell, if a single 18650 cell gets exposed to strong heat source then it could explode and burn OP's car down. An 800W heater definitely qualifies as a strong heat source.

Another battery tech e.g. SLA or NiMH will bust itself when exposed to heat but will do so in a way much less prone to starting a fire or exploding.

Again, not against OP doing what they're doing or Li ion tech in general, pointing out a hazard that no one acknowledged yet.

Edit: OP linked a 400W heater not an 800W heater. I got distracted by other people posting their experience with 1kW and 2kW space heaters. Still does pose some potential hazard though and Alibaba cells are less than reliable.

[Cerebus]

Not trying to tell you what to do but be aware Li-ion Batteries + Heat Source = Big Danger

Well you'd be crazy to drive around in a vehicle containing at least 475 kWh (1.7 GJ) of energy in the form of a highly volatile, potentially explosive, highly inflammable material, but I do it every time the rather small 50 litre fuel tank in my petrol car is full. What's worse is that it's engineered to deliberately produce a series of mini explosions as the form of propulsion.

One has to get the risks into perspective. The energy density of petrol is high (34.2 MJ/l), vehicles contain a lot of it and it is clearly more dangerous than any battery system but we somehow treat this with sanguity. I think the biggest concern, first and foremost, in adding any electrical heating system to a car is avoiding accidental ignition of the vehicle's liquid fuel but this never gets mentioned.

You never see anybody saying, a priori: "Petrol + Heat Source = Big Danger". Whereas there's always someone who's going to ignore that and just state (frequently overstate) the risks of adding a few megajoules of battery storage to something that already has gigajoules of stored energy on board (or of substituting Lithium energy chemistry for hydrocarbon energy chemistry in the EV case where electricity is the prime mover). Both are dangerous if not used properly, but surely gigajoules outranks megajoules in absolute risk terms. Sure, it would be foolish to ignore the known risks of any battery technology, but let's keep things in perspective - a Lithium battery isn't a bomb waiting to go off any more than a car full of petrol already is.

On a second thought your example(and my TNT comparision) ignores the Li-ion combustion energy totally.
Tesla S 100d battery contains 100kWh of electrical energy and 4 to 10MJ/kg highly combustible material in the cells. Combustion of 100kWh Tesla battery(~600kg) releases more energy  than full tank of gasoline!  (between 60 to 240 liters of gasoline!) 
https://ec.europa.eu/jrc/sites/jrcsh/files/claude-chanson_characterize-lithium-batteries-thermal-run-away-reaction.pdf

You've jumped from a small battery system to run a heater to a huge 600kg battery designed for prime traction. What was it I said about perspective?

[Cerebus]

Again, not against OP doing what they're doing or Li ion tech in general, pointing out a hazard that no one acknowledged yet.

And there's nothing wrong with that. My comment is on the sociology/psychology of it. There's something sensationalist about the way it's presented. Think for a second, who would put a heater where it would raise anything to 80ºC in a car. A comment along the lines of "Don't forget to keep the heater and the battery well away from each other, we all know the risks of overheating Li chemistry batteries" would have been proportionate. A headline, in bold, of "Li-ion Batteries + Heat Source = Big Danger" is being sensationalist, and every time this comes up someone feels that they need to be sensationalist about it.

[sandalcandal]

Think for a second, who would put a heater where it would raise anything to 80ºC in a car.

I don't know... have you been reading this thread?

Edit: I also standby "Li-ion Batteries + Heat Source = Big Danger" in bold is a valid headline to be making in general but particularly considering the Alibaba special Li ion packs OP has been considering. Maybe, I'm just hyper aware of the dangers because I work on li ion safety systems...

[Cerebus]

Maybe, I'm just hyper aware of the dangers because I work on li ion safety systems...

Ah, so you're trying to drum up work! 

[sandalcandal]

Maybe, I'm just hyper aware of the dangers because I work on li ion safety systems...

Ah, so you're trying to drum up work! 

DRATS I'VE BEEN DISCOVERED! 

[Erwin Ried]

Again, not against OP doing what they're doing or Li ion tech in general, pointing out a hazard that no one acknowledged yet.

Edit: OP linked a 400W heater not an 800W heater. I got distracted by other people posting their experience with 1kW and 2kW space heaters. Still does pose some potential hazard though and Alibaba cells are less than reliable.

All the negativity in the thread made me check more info about fuel heaters.

Why you think those cells are less reliable? I can check them for a couple of cycles, I added 1 thermal sensor just to keep them on my watch, plus is not a GIANT battery but a lot of small 18650s which, even being dangerous, will not explode like a bomb.

[sandalcandal]

Why you think those cells are less reliable? I can check them for a couple of cycles, I added 1 thermal sensor just to keep them on my watch, plus is not a GIANT battery but a lot of small 18650s which, even being dangerous, will not explode like a bomb.

Plenty of stories of dodgy cells and cell suppliers if you look around the internet. Even if just one cell goes off, the heat is sufficient to cause neighbouring cells to go into thermal runaway the name for the phenomenon is "thermal runaway propagation" and prevention of it a specific test for EV battery pack certification. Most small pack systems (<1kWh) and ebike systems aren't designed to prevent TR propagation though, cells are just packed right up against each other with no barriers https://www.eevblog.com/forum/renewable-energy/e-bike-battery-fire/ So while being made of a lot of small 18650s can help safety margins the pack as a whole needs to actually be designed exploit the ability to limit failures to smaller energy events.

While the pack as a whole is unlikely to explode all at once like a huge bomb, each 18650 cell has enough bang to be dangerous https://www.nbcnews.com/health/health-news/battery-behind-dangerous-deadly-e-cigarette-explosions-n1032901 (plenty more vape explosion deaths if you want to search) vape explosions are obviously an extreme case but should show you how potentially dangerous these things can be.

Use a BMS with thermal cutouts and separate the heater and battery pack I think you'll be fine. It's not like you're going to set this system up and sleep on top of it right? Personal injury at least shouldn't be a problem since no one needs to be in the car while this thing is in use.

[sandalcandal]

Under most circumstances, cells will leak, vent, smoke then jet flames. Explosions are obviously something everyone wants to avoid and big companies (LG, Samsung, CATL, Panasonic etc.) design their cells to try avoid explosions with venting and other safety features. The only time explosions tend to occur are when venting features are blocked or the cell is heated so rapidly that it under goes particularly violent thermal runaway which the venting cannot handle. The latter tends to only occur when external heat is applied.

[mzzj]

Why you think those cells are less reliable? I can check them for a couple of cycles, I added 1 thermal sensor just to keep them on my watch, plus is not a GIANT battery but a lot of small 18650s which, even being dangerous, will not explode like a bomb.

Even the big name manufacturers like Sanyo screw up the production sometimes. How well do you expect mystery chinese cell to perform? No known manufacturer, not any sort of traceability. Recycled cells? Cells failed testing in chinese factory?  recalled brand-name cells`?

https://youtu.be/CUgbmCSmSNY
https://youtu.be/of01p0Q-yUM?t=96

https://eepower.com/news/latest-li-ion-battery-recall-snafu-involves-lenovo-sanyo/

IIRC highest risk is during charging. When do you charge the large battery pack.. in your house, during night when you are asleep.

[Erwin Ried]

IIRC highest risk is during charging. When do you charge the large battery pack.. in your house, during night when you are asleep.

In that case I can add multiple temp sensors and a relay to shutdown everything. If is a real problem.

[Erwin Ried]

BTW, I see most of the opinions are negative, but I am still interested on evaluating this as a possibility.

I got the manual for installing a webasto in my specific car: https://docdro.id/anQarRX <- Thermo Top Evo Parking Heater Installation Documentation Hyundai Veloster.pdf

...it is a long process, and quite involved. I can do that too now that I have the guide, but a battery solution still looks charming.

[Alti]

BTW, I see most of the opinions are negative, but I am still interested on evaluating this as a possibility.

1. Put some mains supplied heaters inside,
2. Grab a shovel and put some snow and ice on a car
3. Connect extender cord through kill-a-watt to mains
4. Measure how much energy is needed just to melt the snow and get satisfactory results.

I can already tell you this is 334kJ/kg just to melt this white thing.
So if you have 10kg of snow on a car, it takes about 1kWh just to melt it.
So 1kW heater for 1 hour.

Since 90% of that heat is going to escape before it reaches snow, it does not matter if you use 1kW or 2kW, you need 20kW to make this idea practical.

[Cerebus]

Since 90% of that heat is going to escape before it reaches snow, it does not matter if you use 1kW or 2kW, you need 20kW to make this idea practical.

Since all that heat is going into a closed, thermally conductive steel box, I'd be curious as to where you think the the 90% is escaping to in such a way that it is not going to reach the snow and ice on the outside of that box.

[Clear as mud]

I suggest a mains-powered radiator-style heater, instead of one that blows hot air that others have suggested.  It's safer, just place it so that the hot metal parts don't come in contact anything inside the car.

[Renate]

If you run a department at work just tell everybody that they are assigned to work inside your car on snow days.
The average adult is in the realm of 100 Watts, 6-8 people should do the job.

[Rick Law]

Some additional thoughts:

In practice, even if the heater is running off main-AC, one would not walk out to a snow-free car, hop in, and go.  In practice, brushing off snow is going to be necessary whenever snow is reasonably heavy.

Think about it, if you have say 1/2 meter of snow on your car.  Running of main-AC, you can melt all the snow on top (roof), but the heat will have problem reaching your front-hood.  So, the windshield may be clear but you will be looking at a mountain of snow on the hood preventing you from seeing the road.  So brushing off snow is to be expected regardless of how much energy you got in your batteries.  Once you have to brush off snow on the hood, brushing off snow on the car roof is not that much more added difficulty.

If I am the user (in the Mid-West USA weather), my concern would be ice.  Snow can be brushed off easily.  Ice stuck to the windshield is a pain in the behind to remove.  So you just need enough heat to ensure that the windshield and other glass-areas are ice free.  You would have an easy job of merely brushing off loose snow.

But not so fast -- don't forget, as snow melts, the melt will turn into ice almost immediately -- think about the icicles around the roof on your house.  Your house probably stay heated all day, but icicles still stick around all day.

Therefore, one concern I have would be melted-snow refreezes, and icicle formation.    Trying to open the car door with a 5mm (or 1/4 inch) of ice shell covering it is a pain.    Now you have a problem a lot worst than what you started with which was mere snow, and that ice covering the lower part of your door probably was the snow that was on the car roof.

Since every car design is different, it would be hard to estimate how much heat is required to ensure all the glass around it being ice free, and the doors are not ice-covered.  There are so many variables (wind, ambient temperature, amount of snow cover...) over-sizing the capacity will likely be a necessity.  And, you need some mean of maintaining that heat till you get into the car -- you don't want to get back to a big icicle.

[Erwin Ried]

Some additional thoughts:

In practice, even if the heater is running off main-AC, one would not walk out to a snow-free car, hop in, and go.  In practice, brushing off snow is going to be necessary whenever snow is reasonably heavy.

Think about it, if you have say 1/2 meter of snow on your car.  Running of main-AC, you can melt all the snow on top (roof), but the heat will have problem reaching your front-hood.  So, the windshield may be clear but you will be looking at a mountain of snow on the hood preventing you from seeing the road.  So brushing off snow is to be expected regardless of how much energy you got in your batteries.  Once you have to brush off snow on the hood, brushing off snow on the car roof is not that much more added difficulty.

If I am the user (in the Mid-West USA weather), my concern would be ice.  Snow can be brushed off easily.  Ice stuck to the windshield is a pain in the behind to remove.  So you just need enough heat to ensure that the windshield and other glass-areas are ice free.  You would have an easy job of merely brushing off loose snow.

But not so fast -- don't forget, as snow melts, the melt will turn into ice almost immediately -- think about the icicles around the roof on your house.  Your house probably stay heated all day, but icicles still stick around all day.

Therefore, one concern I have would be melted-snow refreezes, and icicle formation.    Trying to open the car door with a 5mm (or 1/4 inch) of ice shell covering it is a pain.    Now you have a problem a lot worst than what you started with which was mere snow, and that ice covering the lower part of your door probably was the snow that was on the car roof.

Since every car design is different, it would be hard to estimate how much heat is required to ensure all the glass around it being ice free, and the doors are not ice-covered.  There are so many variables (wind, ambient temperature, amount of snow cover...) over-sizing the capacity will likely be a necessity.  And, you need some mean of maintaining that heat till you get into the car -- you don't want to get back to a big icicle.

Yes. I do not expect to walk into a ice/snow free car ever. Now the situation is:

-Dry and no snow = ice, enter to car and turn it on, wait 10-15 mins. Scrape any extra ice (very little). No problem entering to the car, I apply a product to the rubber every 2 months or so that prevents icying there

-Fresh snow = easiest to remove, just brush it up and turn the car for 5+ mins just to avoid fogging

-Old snow (i.e. after a weekend of not cleaning) = harder to brush, but still not as bad as ice.

If the battery heater just preheats the car, it would help. I do not think the fuel option is doable because it is expensive and complicated. Plus my ride to the office is less than 10 mins, so it will need extra work on keeping the battery alive.

[Renate]

What is this "snow" thing everybody keeps talking about?

[Rick Law]

Some additional thoughts:
...

Yes. I do not expect to walk into a ice/snow free car ever. Now the situation is:
...
...

When I was living in the mid-west USA, I wish I had an easier way to deal with ice/snow also.

We are on the same page.  I wish you success on this...  Let us (me) know how it works out.  I am curious.

[mzzj]

Yes. I do not expect to walk into a ice/snow free car ever. Now the situation is:

-Dry and no snow = ice, enter to car and turn it on, wait 10-15 mins. Scrape any extra ice (very little). No problem entering to the car, I apply a product to the rubber every 2 months or so that prevents icying there

-Fresh snow = easiest to remove, just brush it up and turn the car for 5+ mins just to avoid fogging

-Old snow (i.e. after a weekend of not cleaning) = harder to brush, but still not as bad as ice.

If the battery heater just preheats the car, it would help. I do not think the fuel option is doable because it is expensive and complicated. Plus my ride to the office is less than 10 mins, so it will need extra work on keeping the battery alive.

1 kWh estimate that I suggested is just to defrost the windows in -10c weather. Forget about melting layers of snow or heating the car to cozy warm.

Car with  2 square meters of windshield and windows in -10c weather would need 400 Watts of power just to keep the windows from freezing if we assume 20W/(m2*K) heat transfer coefficient.
Add all the mass and inertia, losses trough doors, roof and floors and you need considerably more.  1kWh in -10cel might not be enough but its reasonably close from what I recall.

If you feel that you want to play with the battery idea this might be close to rated capacity https://www.aliexpress.com/item/4000987036516.html?spm=a2g0o.productlist.0.0.7b6b6c13Dw7gsl&algo_pvid=b2a5ec17-f1aa-43ef-b279-c342012546ee&algo_expid=b2a5ec17-f1aa-43ef-b279-c342012546ee-17&btsid=0b86d80216041789854396272e22bf&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

Still about 600 euros investment if you buy 4 packs.

[Erwin Ried]

I have ordered one cheap 150W 12V heater and I will do some empirical testings with a small 12V battery. I will post the results.

[Erwin Ried]

I measured the internal temp vs the external after a short 20 mins ride months ago:



In 4-5 hours the internal temperature gets into equilibrium, at least under the conditions of that day.

[Renate]

One good plot deserves another...
I think that I'm snow-free.