dmacarthur
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Resistance heater actual amperage draw?

Tue Feb 19, 2019 7:51 am

Sorry if this has been covered, I did not find it in my searches; wondering if the resistance heater (2015 Leaf S base model) draws the same amperage when it is on, independent of the fan, or is the heater also proportional like the fan? and what is it's draw in amps ( I assume 12V?)? Also, how do the steering wheel and seat heaters compare in terms of amperage? Thanks all,...
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LeftieBiker
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Re: Resistance heater actual amperage draw?

Tue Feb 19, 2019 3:03 pm

The resistance (aka PTC) heater is NOT 12 volt. It uses high voltage from the pack, and it draws a lot of amperage. The car displays energy usage in kilowatts, and IIRC the PTC maxes out at about 3kw. I think it can throttle back a little, but I'm not actually sure - both of my Leafs had had the heat pump as well, and that affects the current draw at any given moment. I'd find it hard to believe that the PTC always runs at maximum, regardless of fan speed (the blower is 12 volt) and cabin air temperatures.

The seat and steering wheel heaters are 12 volt, and don't draw a lot of power. They are what you want to use to reduce heater use.
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SageBrush
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Re: Resistance heater actual amperage draw?

Tue Feb 19, 2019 3:27 pm

2013 LEAF 'S' Model with QC & rear-view camera
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SalisburySam
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Re: Resistance heater actual amperage draw?

Tue Feb 19, 2019 3:28 pm

On my 2012SL, I've seen the onscreen climate control dial as high as 5.5kw for heat. Hopefully, models with the newer heat pump system will see less. On the plus side, I do get lots of heat and pretty quickly. Just can't go anywhere beyond about 35 miles.
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LeftieBiker
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Re: Resistance heater actual amperage draw?

Tue Feb 19, 2019 4:55 pm

SalisburySam wrote:On my 2012SL, I've seen the onscreen climate control dial as high as 5.5kw for heat. Hopefully, models with the newer heat pump system will see less. On the plus side, I do get lots of heat and pretty quickly. Just can't go anywhere beyond about 35 miles.
Heat pump-equipped Leafs do draw that much, because the PTC operates in tandem with the heat pump, but they quickly throttle back (except maybe in frigid temps) to 1.5kw or less. I've seen as little as 500 watts.
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Lothsahn
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Re: Resistance heater actual amperage draw?

Tue Feb 19, 2019 7:21 pm

2011 Leaf (resistance heat).

I have seen the heater use as much as 4.5 or 5 kW. When the AC button is turned on, the energy use can rise another .5 to 1 kW. I don't know if this is because it increases the power to the heater or because the compressor actually runs at the same time to defrost.

Actual power draw depends on a number of factors. The temperature inside the car, the temperature outside, the temperature of the heating coolant loop, AC button, and the fan speed all play a factor. I've noticed that selecting defrost tends to increase the power consumption. Likewise, higher fan speeds will call for more heating power.

As the car and the heating liquid heats up, the power consumption of the heater will begin to drop. It tends to equalize around 1.5 kW in 20-30F temps.

I don't believe Leafs after 2012 have a heating liquid loop. I believe they have a direct PTC heater. This may cause the behavior to change.

Finally, when the car is plugged in, it will not exceed the input power from the charger. On L1, this is around 1.5kW. L2 is 3.3 kW or 6.6 kW depending on the on board charger. Heat while plugged in only works if the car has a climate control temp timer enabled and the car is started by holding the brake while pushing the power button or the climate timer triggers.

Preheating the car while plugged in has been incredibly helpful. You can preheat not only the car but also the heating coolant, meaning that the battery never sees the high initial power draw.

Go to the energy info screen and play around. You can see the real-time power output of your car.
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LeftieBiker
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Re: Resistance heater actual amperage draw?

Wed Feb 20, 2019 12:03 am

I have seen the heater use as much as 4.5 or 5 kW. When the AC button is turned on, the energy use can rise another .5 to 1 kW. I don't know if this is because it increases the power to the heater or because the compressor actually runs at the same time to defrost.
The compressor actually runs at the same time, to dry the air. In the "hybrid" system, when heat and defrost or heat and A/C are both engaged, the heat pump provides the A/C and the PTC heater provides all the heat. That makes the combination a real energy hog.
I don't believe Leafs after 2012 have a heating liquid loop. I believe they have a direct PTC heater. This may cause the behavior to change.
Correct. From 2013 on the heating is all direct to air - no coolant/heatant loop other than the one inside the heat pump.
Finally, when the car is plugged in, it will not exceed the input power from the charger. On L1, this is around 1.5kW. L2 is 3.3 kW or 6.6 kW depending on the on board charger. Heat while plugged in only works if the car has a climate control temp timer enabled and the car is started by holding the brake while pushing the power button or the climate timer triggers.
Hmmm... My understanding is that the car will draw full heating power, because all Leafs power their heaters and A/C or heat pumps directly from the battery pack. The power provided by the EVSE will either fail to match the power drawn, resulting in dropping charge level, just match it (no change in charge level) or will exceed it (car keeps adding charge, albeit more slowly). I know this. The only thing I'm not certain of is whether or not the coolant loop systems in the 2011-2012 cars have the heat-limiting feature you mention. I know that 2013+ Leafs do not.
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2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
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dmacarthur
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Re: Resistance heater actual amperage draw?

Thu Feb 21, 2019 5:38 am

Thanks all, this is great info. I do not seem to have a KW meter on-screen, the model S is the base model, unless I am missing something? That info would be really helpful.......
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SalisburySam
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Re: Resistance heater actual amperage draw?

Thu Feb 21, 2019 6:16 am

dmacarthur wrote:Thanks all, this is great info. I do not seem to have a KW meter on-screen, the model S is the base model, unless I am missing something? That info would be really helpful.......
Don’t feel bad about this...from this thread and all the posters you now know what the actual behavior is even if you don’t have a display to show you. And like any vehicle, you’ll quickly get used to what happens without thinking about it. Enjoy your car, and the knowledge that you know how it works.
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Lothsahn
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Re: Resistance heater actual amperage draw?

Thu Feb 21, 2019 7:02 am

LeftieBiker wrote: Hmmm... My understanding is that the car will draw full heating power, because all Leafs power their heaters and A/C or heat pumps directly from the battery pack. The power provided by the EVSE will either fail to match the power drawn, resulting in dropping charge level, just match it (no change in charge level) or will exceed it (car keeps adding charge, albeit more slowly). I know this. The only thing I'm not certain of is whether or not the coolant loop systems in the 2011-2012 cars have the heat-limiting feature you mention. I know that 2013+ Leafs do not.
Interesting. I can confirm on my 2011 that when on L1 charging, heat output is limited to approximately 1000-1200W when the car is ON (but not in ready mode) and connected to L1 charging. This roughly matches the input power from the L1 charger. It will maintain this power output basically indefinitely to warm the car in the morning, until I unplug the car and put it in ready to drive mode. In Ready to drive, it will provide full heat output (as much as is necessary based on internal/outside temperatures, etc).

It's interesting to hear that this behavior doesn't exist on the 2013+ Leaf's. This feature is really nice for L1, because it won't discharge my battery during pre-heating, even if I pre-heat for 15-30 minutes.
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