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Discussion Starter · #1 ·
I've recently decided to incorporate heating in my battery cooling loop. I'm thinking about using a Tesla battery heater since I have Tesla batteries but I may use something cheaper/not as powerful since I'm only using 4 Tesla battery modules. Since I'm in a location that has cold winters and hot summers, I decided that I wanted a year round car that could take on the cold and the heat. Does anyone know where I can find the data for Tesla batteries for their nominal temperatures...like the value I would need to kick on the heater or cooling radiator? I did a quick Google search and found that the lithium's "sweet spot" is between 60F and 80F. Can someone fact check this? I want to make a system, whether it's with Arduino or Rasberry Pie or anything else, that can turn on the heater when the temperature goes below 60F and turn on the radiator when the temperature goes above 80F. Does anyone know how I might do this? Will I need to get temperature data from the battery's temperature nodes? How can I use this data with the Arduino (or whatever I use) to make this a working system?

Thanks,
Sifa
 

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With only 4 modules the original Tesla heater is almost out of the question as you'd be trying to run it on 1/4 of it's designed voltage.

I am trying to figure out a solution to the exact thing you're working on now for my own project with 10 modules. Have ordered some parts to see if I can build my own heater unit with an engine block heater and some stainless steel pipe for the heater to mount to.

From there controlling it isn't too complicated, you can just use a temperature regulator switch.

Li-ion batteries can't be charged below 0celsius without damaging them. That's the one big thing to keep in mind. Charging range between 5-45c is a comfortable range, and discharge between -5 and 55c.
 

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Discussion Starter · #3 ·
With only 4 modules the original Tesla heater is almost out of the question as you'd be trying to run it on 1/4 of it's designed voltage.
Oh good point I didn't even think about that.
I am trying to figure out a solution to the exact thing you're working on now for my own project with 10 modules. Have ordered some parts to see if I can build my own heater unit with an engine block heater and some stainless steel pipe for the heater to mount to.
Let me know how that works out for you. I might use a 12V heater if it has enough power. How much power are you expecting to use for your batteries?
From there controlling it isn't too complicated, you can just use a temperature regulator switch.
What kind of temperature regulator switch would I need? I looked some up but there are different kinds. How exactly do they work? Do they come with their own temperature sensors or do I have to take that data from the Tesla battery thermistors?
Li-ion batteries can't be charged below 0celsius without damaging them. That's the one big thing to keep in mind. Charging range between 5-45c is a comfortable range, and discharge between -5 and 55c.
Should I change the lower value to 0celsius or something slightly higher? At what temperature should the heater turn on?
 

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If you're going hillbilly on your battery heater design, which is a bad idea but better than nothing, you want two thermostats in series -- one that kicks on at the lower temperature (you said 5 degrees C) and one that kicks off at an upper bound, maybe 15 degrees C. You also ideally want a spread in the on/off, "hysteresis", so it's not "chattering"

DO NOT set the coolant thermostat to go up to 45 degrees C...
 

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If you're going hillbilly on your battery heater design, which is a bad idea but better than nothing, you want two thermostats in series
How might one not go "hillbilly" on their battery heater design? I'm new to anything super DIY control related but I'm up to give it a try. Do you have any recommendations on parts I should buy and how I can control everything? Where can I purchase the thermostats that you mention?
 

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I mean the world is your oyster on that, there are tons to chose from. The main thing is to either choose one that's automotive rated or design the heck out of it for a harsh environment with respect to voltage spikes, power delivery, EMF. Most importantly make sure your BMS can override and shut everything down if your controller fails and cooling fails. I'm just getting into this myself and what I have as a creed is that nothing I design should be involved in a safety critical part of the vehicle.
 

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To use the Tesla S battery heater you need the front high voltage junction box which you can control by pwm. The battery heater is dumb and is controlled by the front high voltage junction box. It plugs right into the hvjb and there is an internal fuse in the hvjb for the battery heater. You then just need the temperature controller with a thermocouple to sense the coolant temperature and a pwm. See also, Tesla Model S Front HVJB - openinverter.org wiki and Tesla Model S Battery Heater - openinverter.org wiki.
 

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The BMS should be the master of all things battery -- to do a separate heating loop independent of the BMS, which is what was on the table at the time I posted, is what I meant by "hillbilly".

I use a heater controller to turn on/off my Tesla battery heater for cabin heat. So far I have been heating to 140F, have it turn off and then re-start at 110F. It works really well and you can adjust the on/off trigger temperatures.
The Tesla battery heater is undersized by a factor of at least 3 for use as a cabin heater in cold climates.

We were talking about warming the HV battery, here, not the cabin.
 

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I've recently decided to incorporate heating in my battery cooling loop. I'm thinking about using a Tesla battery heater since I have Tesla batteries but I may use something cheaper/not as powerful since I'm only using 4 Tesla battery modules. Since I'm in a location that has cold winters and hot summers, I decided that I wanted a year round car that could take on the cold and the heat. Does anyone know where I can find the data for Tesla batteries for their nominal temperatures...like the value I would need to kick on the heater or cooling radiator? I did a quick Google search and found that the lithium's "sweet spot" is between 60F and 80F. Can someone fact check this? I want to make a system, whether it's with Arduino or Rasberry Pie or anything else, that can turn on the heater when the temperature goes below 60F and turn on the radiator when the temperature goes above 80F. Does anyone know how I might do this? Will I need to get temperature data from the battery's temperature nodes? How can I use this data with the Arduino (or whatever I use) to make this a working system?

Thanks,
Sifa
i have a heat pump i use with a inverter. not a bad option and also solves the cooling for if it is hotter than 80F outside. i'm using a portable hisense heat pump with the thermostat controls being replaced with an arduino and a 400v DC to 120v AC inverter.
 
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