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As an interesting side note...

When I was testing the modified Leaf BMS I/O (I replaced the micro with my own), I could not get the heater relay to switch on and off, nor could I detect the state of it.

Turns out that the BMS unit I was using, (from eBay, not from my battery), came from a pack that did not have the heater option.

And thus, Nissan did not populate the MOSFETs to turn on the heater relay, or any of the relay state sense components.
Cause, you know, got to save those penny parts. ;)


So if you want to install the battery heaters in your pack, you will also need to upgrade the BMS too. ;)
 

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Really? The Leaf, including the 2017 version, permits 50 kW DC fast charging and manages to do that without any active cell cooling? With really large-format rectangular cells? That's incredible if true...
50 kW charging is a heating challenge, but presumably somewhat comparable to 80 kW motor operation. Right? :confused:

The success of Nissan's approach to battery cooling and the conservative rating of the Leaf's motor might be related. Instead of building the pack and motor cooling to handle drag races, Nissan limits the motor to 80 kW (even in brief bursts); meanwhile, Tesla puts a lot of effort into finding how hard they can push the battery for a few seconds at a time... and needs a liquid cooling system to deliver the performance (both in acceleration and in "Supercharging") that they have chosen.

GM uses large-format pouch cells in their cars, too, and runs higher (motor, not charging) power than a Leaf... but uses liquid cooling to do it.

I don't think Tesla's little cells would help cooling so much if they were packed in sealed box; the small size and metal cases provide more heat transfer capacity for cooling with circulating coolant. The cell format and the cooling approach seem related.
 

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It has gotten down to -18F / -28C here this winter.
We rarely get below freezing in this part of the UK which is why we can survive without battery heating in the Leaf. However, I understand the Tesla cells are less tolerant of low temperatures and I will include the fluid battery heater in my conversion :cool:
 

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It's in the manual:

When the temperature decreases [approximately −20°C (−4°F)] extremely in the battery pack, the Li-ion battery
heater control system automatically activates the Li-ion battery heater to warm the inside of the battery
pack for protecting Li-ion battery from freezing and preventing the decline in battery output. In addition, when
the temperature in the battery pack is restored [approximately −10°C (14°F)], the Li-ion battery heater stops.
Wow, thanks for the info. That's a lot lower than I thought. That would seem to suggest that the battery will be fine both charging and discharging so long as you don't let it go under -10C. That's good to know, hopefully I'll remember that number for the future.
 

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It appears that there are two interesting features of the Model 3 battery heating scheme (which appears to be relatively ineffective):
  • the HVAC system is used as a heat pump in the S/X, but not in the 3
  • the heater which is used in the 3 is the drive motor, rather than a separate resistive element.
(I just read the article and comments; ten minutes of some guy whining about the cold wasn't worth watching, just to see if he had some additional information)

Using the motor's windings essentially as a resistor is kind of clever; it reminds me of an animal shivering to generate heat in muscles without doing any actual work.
 

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The difference between 50 kW DC recharging and 80 kW motor operation is that the problem isn't temperature so much as the combination of high voltage and high temperature...

It does seem likely that they limit power to protect the pack, but don't they also make the inverter cheaper by doing so?

It's hard to heat something which is designed to self-cool...

I'm guessing the reason Tesla is sticking with the small cylindrical cells with active cooling is that a) it works b) they love and sell performance that Nissan doesn't seem to care about so much and c) their Li-NCA chemistry becomes unstable (starts to go auto-thermal) at a much lower temperature than Li-NCM does.

Fascinating, guys- since I built my conversion, my interest in the OEM vehicles remains strong but despite how much is written about the new EVs- it's voluminous- finding information that is detailed enough to make it useful to me is challenging. I come across it here most often- I hate the Endless Sphere interface so much that I stay away from there despite the cool stuff going on there sometimes.
 

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It does seem likely that they limit power to protect the pack, but don't they also make the inverter cheaper by doing so?
Good point... there are several links in the chain, and it's not always obvious which one is the controlling factor. I have no idea what the inverter costs an EV manufacturer, but it must be significant.

Although it's probably a very minor point, the front-wheel-drive layout of the Leaf (driven by use of chassis components in production for other models) is not well-suited to very high power (especially with the rear weight bias caused by the battery), so the Leaf is not the platform in which to push EV performance. Tesla's rear-drive or all-wheel-drive layout is more suitable.
 

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It appears that there are two interesting features of the Model 3 battery heating scheme (which appears to be relatively ineffective):
  • the HVAC system is used as a heat pump in the S/X, but not in the 3
  • the heater which is used in the 3 is the drive motor, rather than a separate resistive element.
(I just read the article and comments; ten minutes of some guy whining about the cold wasn't worth watching, just to see if he had some additional information)
Not sure if you're aware that the Model S/X also has another 7kW (iirc) heat source over and above the HVAC?

** apologies for the rotated images... I'm tired editing photos for DIY Electric, they work fine on forums with more modern software :rolleyes:
 

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I would have guessed that it is easier to use the AC induction motor in the 'S' as as a heater...
Since you can PWM current through the stator, and not have a rotating magnetic field to drag the rotor around.

In the '3' the rotor magnets will want to align to the stator coil that is passing current, causing motion.

Unless, they only PWM current through the one stator coil that is lined up with a rotor magnet...

Or, I guess they could 3 phase PWM all the stator coils so fast that the rotor can't follow... but I would think this would become audible.


I am assuming that the vehicle is stationary and trying to heat the battery to keep it from freezing.
 

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I am assuming that the vehicle is stationary and trying to heat the battery to keep it from freezing.
Yes, that's at least one scenario... but likely heating the battery in preparation for heating or driving, rather than just parked.

I would have guessed that it is easier to use the AC induction motor in the 'S' as as a heater...
Since you can PWM current through the stator, and not have a rotating magnetic field to drag the rotor around.

In the '3' the rotor magnets will want to align to the stator coil that is passing current, causing motion.

Unless, they only PWM current through the one stator coil that is lined up with a rotor magnet...

Or, I guess they could 3 phase PWM all the stator coils so fast that the rotor can't follow... but I would think this would become audible.
How about driving all three sets of windings in-phase, instead of in the normal phase relationship? I'm sure the actual solution will come out at some point... even if someone has to put scope leads on the inverter-to-motor connection to observe it.
 

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How about driving all three sets of windings in-phase, instead of in the normal phase relationship? I'm sure the actual solution will come out at some point... even if someone has to put scope leads on the inverter-to-motor connection to observe it.
That would cause shoot through and dead short the battery pack across the IGBTs / MOSFETs (not sure which they use)...

They would be using the winding of the stator as resistive elements (since the motor is the heater, not the controller).
 

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YHow about driving all three sets of windings in-phase, instead of in the normal phase relationship?
I walked away, then realized that this would only be possible with star wiring, and of course the motor will be delta wired.

That would cause shoot through and dead short the battery pack across the IGBTs / MOSFETs (not sure which they use)...
Possible options will certainly depend on inverter design.

They would be using the winding of the stator as resistive elements (since the motor is the heater, not the controller).
Yes, that's the idea. The challenge is, of course, passing current through stator windings without causing net motor torque. The car could instead just lock the wheel brakes on, but I would want a bunch of lawyers to check out that plan before putting it in the hands of the public... :D

They could, of course, switch between forward and reverse at high frequency - truly the EV equivalent of shivering - but that would presumably be annoying to any occupant and possibly cause vibration-related problems for various components.


Anyway, this thread is supposed to be about using Leaf components, which don't include any circulating coolant and thus don't include any form of fluid heater... heat pump, dedicated resistor, or motor-based.
 

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As an interesting side note...



When I was testing the modified Leaf BMS I/O (I replaced the micro with my own), I could not get the heater relay to switch on and off, nor could I detect the state of it.



Turns out that the BMS unit I was using, (from eBay, not from my battery), came from a pack that did not have the heater option.



And thus, Nissan did not populate the MOSFETs to turn on the heater relay, or any of the relay state sense components.

Cause, you know, got to save those penny parts. ;)





So if you want to install the battery heaters in your pack, you will also need to upgrade the BMS too. ;)


how do you intend to get around this? Can you run all of the heaters off of a single BMS or so you need to get a. new BMS and put your chip in it?

I'm in San Diego, CA so I do not require the heater it my pack, but it came equipped with one. I would trade my BMS with yours, but I fear that it may be problematic because I have transferred the entire Leaf Harness into my conversion. If I remember correctly the BMS and other components are synced, complicating the introduction of a foreign BMS.
 

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how do you intend to get around this?
I have the original BMS units from both of my battery packs, they are both the heated versions. So they have the needed MOSFETs in them.

However, Since I will replace the logic board (economizer) in the Heater Relay, with my own board anyway (to support the boost converter)...

I might just make it CAN controlled.

I need 2 of them, one for the front battery box and one for the rear battery box.
 

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Hi guys.

Any conclusions yet with respect to a complete transplant?

Cause if it is possible without mods than it would be great for a conversion in some EU countries
where it takes more than a visual inspection and a firm handshake to get the papers for a road legal EV.
 

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