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Water heaters and PTC heaters have different pros and cons
Water heater
  • Often easy drop in for cars with a decent heater and heating distribution
  • Large heat transfer capacity
- Slow, takes time for the cabin to become warm

PTC
+ Quick heat, direct hot air
- High blower power (thus noise) at highest power

Another advantage of the water heater is that in theory you can use it for both cabin and batteries (if thermal control with fluid).
However. I would not recommend that.
Simplicity with two dedicated devices in my view outweighs the benefits of one device with complex controls and valves.

In terms of power consumption: compared to what the traction motor draws, even two heaters at the same time is not that much kW.
 

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The Bolt pulls about 7kW using its PTC heater in a cold cabin, so I wouldn't say it's trivial. Even that can't get warm enough.

Scavenging heat is the best way on paper, but there's nothing to scavenge when it's 20F outside and you stepped out of the shower ten minutes ago.

You're right about having to get the water loop warmed up first - takes time.

And a heat pump will be crap at pulling heat from 20F outdoor temps.

Strangely, nobody has mentioned heated seats (electric or liquid heating loop?) and steering wheel...
 

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^^Again, I would not use anything that is not automotive use qualified on a car. The environment is too harsh to use bench-playtime hobbyist garbage.

I've built too many cars that have left me stranded to know not to use crap pieces, safety critical or otherwise. One tow pays for having used automotive qualified parts. Annoying AF if the heater's not working and you need to get to work.

Your build, your decision. If I saw an Arduino garden hose, or Keurig Coffee Maker, solenoid under the hood, I'd take a pass on buying your $50,000 build.
 

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I think the only issue with a development board is having a solid power supply that can handle awful vehicle power, (ideally hardware) watchdog functionality, waterproof & EMF blocking enclosure. The good dev boards aren't really that sensitive to an automotive environment. That said, someone must market a microcontroller for this application...
 

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Discussion Starter · #28 ·
Another advantage of the water heater is that in theory you can use it for both cabin and batteries (if thermal control with fluid).
However. I would not recommend that.
Simplicity with two dedicated devices in my view outweighs the benefits of one device with complex controls and valves.
I was actually thinking that initially, having one heater for each system. Figuring out the electrical accommodations for a second water heater would be the only bridge to cross. The use of the heater for the HVAC would be minimal as a majority of the time the vehicle I am building would be a fair weather driver. The only exceptions would be the crisp dry fall days and any cool dry spring days. I may just go that route. Thanks for your input!
 

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I think the only issue with a development board is having a solid power supply that can handle awful vehicle power, (ideally hardware) watchdog functionality, waterproof & EMF blocking enclosure. The good dev boards aren't really that sensitive to an automotive environment. That said, someone must market a microcontroller for this application...
Nope.

Commercial semiconductors are not rated for operation below 0C. Or above 70C.

Our techs would troubleshoot circuit packs using freeze spray - a complete shock of ignorance epiphany when you hit the shop floor to train them with your wet behind the ears engineer-degree qualifications 😂
 

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I am all about hearing others experiences with certain products and avoiding any pitfalls. Do you have bad experiences with Arduino products on things you have built? Do you have any recommended alternatives?
It's not "Arduino products". It's using components not intended for automotive applications. An Arduino board is not designed for auto use. Developing using the Arduino IDE and prototyping using an Arduino board is ok. Putting an Arduino board in your engine bay (ICE present or removed) would be bad practice.

Buy stuff designed for use in cars, where possible. If not, design it for use in cars using automotive components (not that many here can do that). If you must use commercial-rated crap, keep it in the soft environment of the passenger cabin, though it too can be brutal until conditioned.

Lastly, duct tape and baling wire, live with the bad choices.
 

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Except the one I posted rated from -40C to 150C. But don't go out of your way to read anything tonight.

Edit: and yes, there is a difference between the mc and a dev board, which is just that, a dev board, not for actually placing in the finished product, before you jump to conclusions.
 

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Discussion Starter · #34 ·
Except the one I posted rated from -40C to 150C. But don't go out of your way to read anything tonight.

Edit: and yes, there is a difference between the mc and a dev board, which is just that, a dev board, not for actually placing in the finished product, before you jump to conclusions.
As the saying goes, you learn something every day! That's good to know there are components with different ratings. I will be sure to pay close attention to that if I go that route. Thanks for the info to both Remy and Asymtonic!
There is also the option of laying out the Arduino board and once one has it functioning the way they want it, take it to an electronics manufacturer and have them make a more hearty and compact version. It will have a cost for sure but hey, maybe it can turn into the first open source controller for coolant valves!
 

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Fully agree on that Arduino stuff is not a true automotive solution. On the other hand, it helped me in my hobby project a lot. I learned a lot and it worked (to a certain extend). I used two Teensy 3.6's. And even though I embedded it with all relevant protections such as TVS diode's, gate drivers and DC/DC with wide voltage input range I managed to kill one once it was installed in the car. Still don't know why. Trigger was the alarm being triggered while not being connected completely so perhaps it was being powered via the alarm status feedback analog signal, who knowns?
http://instagr.am/p/B_RZk62nu2i/ Still don't know why. Another event where the Teensy tripped is when a connected DS18B20 sensor failed. All OK secondary systems in a hobby environment.

Nowadays for customer projects (my hobby turned into a business) I stay away from those solutions and prefer components with ECE-R10 certificates.
But there are options in between.
For example the Controllino CONTROLLINO – 100% Arduino compatible PLC | Industry-ready hardware
 

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There is also the option of laying out the Arduino board and once one has it functioning the way they want it, take it to an electronics manufacturer and have them make a more hearty and compact version. It will have a cost for sure but hey, maybe it can turn into the first open source controller for coolant valves!
There is a half-way point, services like OSHPark will fabricate a PCB with your design on it for not too much. As mentioned above, it's really about the ancillary components feeding your microcontroller for power protection and the like. And as myself and D&V note, not using your own electronics to run anything safety related.
 

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What coolant heater are you using?

In my own build I've looked at the OEM ones but of course they're all made to run at 400v. I have a 100v Hyper9, so that's not an option for me unfortunately. Unless I make a boost converter for just the coolant heater...

Any thoughts here?

For what it's worth, I don't think the coolant in an EV gets nearly hot enough to heat the cabin on it's own just from battery/motor/electronics heat. And heating liquid is far less efficient than heating air. Ceramic heating element is the way to go for cabin heat, its instantly hot and very simple.

Any thoughts here?
 

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For what it's worth, I don't think the coolant in an EV gets nearly hot enough to heat the cabin on it's own just from battery/motor/electronics heat.
Yes. Even with an ICE that has a faulty thermostat which drops the temp to 60degC, the heater almost stops working completely. Needs 80C to be a useful cabin heater, anything less and it'll need a massive radiator inside.

There are plenty of generic PTC heaters available for different voltages, much more efficient for cabin heat.
 

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What coolant heater are you using?

In my own build I've looked at the OEM ones but of course they're all made to run at 400v. I have a 100v Hyper9, so that's not an option for me unfortunately. Unless I make a boost converter for just the coolant heater...

Any thoughts here?

For what it's worth, I don't think the coolant in an EV gets nearly hot enough to heat the cabin on it's own just from battery/motor/electronics heat. And heating liquid is far less efficient than heating air. Ceramic heating element is the way to go for cabin heat, its instantly hot and very simple.

Any thoughts here?
Lucky you on the voltage. All kinds of appliances heat water at what is essentially 110VDC...

Do it right and you can make tea or coffee as your cabin coolant 😂

Keurigs are cheap and have solenoid valves as well...

Some demand domestic water heaters' 110V immersion elements may be more suitable for heat output, though.

note: this is not an Arduino component being suggested 😅
 

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Coolant heater that runs off 12v 30A
Bicycle part Nickel Gas Auto part Rim
not sure how hot it will heat the coolant. Three VW coolant glow plugs 10A per glow plug.

later floyd tdi coolant glow plugs normal glow plugs burn out if left on for more than 15-30 seconds
 
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