Does acceleration drop if using AC like in an ICE?

I don't know if this is a silly question, but in most cars I've driven when I turn the AC on the car loses some power. It will slow down a little with the throttle kept the same, and it won't accelerate quite as quickly. I understand why, but I honestly don't know if a similar problem could happen in the Leaf. I was wondering if having the AC on while driving decreases the motor power at all. I guess the bigger concern would actually be the heater, which is not an issue in an ICE since heat is "free".

I would imagine this depends on whether the motor draws the max amount of power that the battery can deliver during hard acceleration. If it does, then the Leaf would either need to limit the power going to the accessories, or not give full power to the motor. If there is some headroom between the max the motor draws and what the battery can deliver though, then there should be no slowdown.

JasonT said:

I don't know if this is a silly question, but in most cars I've driven when I turn the AC on the car loses some power. It will slow down a little with the throttle kept the same, and it won't accelerate quite as quickly. I understand why, but I honestly don't know if a similar problem could happen in the Leaf. I was wondering if having the AC on while driving decreases the motor power at all. I guess the bigger concern would actually be the heater, which is not an issue in an ICE since heat is "free".

I would imagine this depends on whether the motor draws the max amount of power that the battery can deliver during hard acceleration. If it does, then the Leaf would either need to limit the power going to the accessories, or not give full power to the motor. If there is some headroom between the max the motor draws and what the battery can deliver though, then there should be no slowdown.

Click to expand...

Nope. And the a/c doesn't 'warm up' when you floor it, either! I'm impressed with the cooling ability and small energy usage of the a/c. The heater, OTOH, sucks the power down like Gatorade after a marathon!!!

Technically the answer may be yes, the max pack output to the motor is restricted by other loads on the car and will reduce the peak output to the motor so if there are many loads it may reduce the output to the inverter and motor as the loads are managed electronically.

JasonT said:

I don't know if this is a silly question, but in most cars I've driven when I turn the AC on the car loses some power. It will slow down a little with the throttle kept the same, and it won't accelerate quite as quickly. I understand why, but I honestly don't know if a similar problem could happen in the Leaf.

Click to expand...

On a related note, I wonder if Nissan had considered driving the A/C compressor off of one of the reduction gear's output shafts. The compressor would have a clutch, engaging only when the A/C is turned on, just as in an ICE vehicle. That way, regeneration scenarios will also see the car's inertia drive the compressor, giving "free A/C".

Adding the A/C to the mix may muddy the regeneration/braking force logic, maybe by a lot, which might be why Nissan didn't do it...

aqn said:

JasonT said:

I don't know if this is a silly question, but in most cars I've driven when I turn the AC on the car loses some power. It will slow down a little with the throttle kept the same, and it won't accelerate quite as quickly. I understand why, but I honestly don't know if a similar problem could happen in the Leaf.

Click to expand...

On a related note, I wonder if Nissan had considered driving the A/C compressor off of one of the reduction gear's output shafts. The compressor would have a clutch, engaging only when the A/C is turned on, just as in an ICE vehicle. That way, regeneration scenarios will also see the car's inertia drive the compressor, giving "free A/C".

Adding the A/C to the mix may muddy the regeneration/braking force logic, maybe by a lot, which might be why Nissan didn't do it...

Click to expand...

It's not "free", because it would eat into the regen and cost you range. Also, you'd have no A/C unless moving, which would make the system useless.

Or to look at it another way, it already works this way, go down a hill and put out 5kW or regen, if your A/C is on and draining 500w, then you are getting "free" A/C + 4.5kW into the pack. =)

-Phil

EVDRIVER said:

Technically the answer may be yes, the max pack output to the motor is restricted by other loads on the car and will reduce the peak output to the motor so if there are many loads it may reduce the output to the inverter and motor as the loads are managed electronically.

Click to expand...

I don't claim to know anything about how it really works, but if I had been programming that load management I would have given precedence to the motor. After all, both the heater and the A/C are buffered through a liquid intermediary. Turn either down or off for a short time and the driver probably won't even notice [... unless he's trying to see how far he can go at 90+].

Ray

Ingineer said:

aqn said:

JasonT said:

I don't know if this is a silly question, but in most cars I've driven when I turn the AC on the car loses some power. It will slow down a little with the throttle kept the same, and it won't accelerate quite as quickly. I understand why, but I honestly don't know if a similar problem could happen in the Leaf.

Click to expand...

On a related note, I wonder if Nissan had considered driving the A/C compressor off of one of the reduction gear's output shafts. The compressor would have a clutch, engaging only when the A/C is turned on, just as in an ICE vehicle. That way, regeneration scenarios will also see the car's inertia drive the compressor, giving "free A/C".

Adding the A/C to the mix may muddy the regeneration/braking force logic, maybe by a lot, which might be why Nissan didn't do it...

Click to expand...

It's not "free", because it would eat into the regen and cost you range. Also, you'd have no A/C unless moving, which would make the system useless.

Or to look at it another way, it already works this way, go down a hill and put out 5kW or regen, if your A/C is on and draining 500w, then you are getting "free" A/C + 4.5kW into the pack. =)

-Phil

Click to expand...

And actually, there is a fatal flaw in my "design"! If the compressor is driven from the reduction gear set's output then when the LEAF is stopped, there will be no A/C!

aqn said:

Ingineer said:

It's not "free", because it would eat into the regen and cost you range. Also, you'd have no A/C unless moving, which would make the system useless.

Or to look at it another way, it already works this way, go down a hill and put out 5kW or regen, if your A/C is on and draining 500w, then you are getting "free" A/C + 4.5kW into the pack. =)

-Phil

Click to expand...

And actually, there is a fatal flaw in my "design"! If the compressor is driven from the reduction gear set's output then when the LEAF is stopped, there will be no A/C!

Click to expand...

Isn't that what I mentioned? You were one of those kids that copied off everyone else's tests in school, weren't you?

Ingineer said:

aqn said:

Ingineer said:

It's not "free", because it would eat into the regen and cost you range. Also, you'd have no A/C unless moving, which would make the system useless.

Or to look at it another way, it already works this way, go down a hill and put out 5kW or regen, if your A/C is on and draining 500w, then you are getting "free" A/C + 4.5kW into the pack. =)

-Phil

Click to expand...

And actually, there is a fatal flaw in my "design"! If the compressor is driven from the reduction gear set's output then when the LEAF is stopped, there will be no A/C!

Click to expand...

Isn't that what I mentioned?

Click to expand...

So you did. Somehow I never saw that part!!! You could at least have made it red.

Ingineer said:

You were one of those kids that copied off everyone else's tests in school, weren't you?

Click to expand...

I resemble that remark.

I think all vehicles would benefit from removing the accessory belts and drive each item with its own electric motor.
The Leaf is a leader in this area out of necessity but the technology will soon help all vehicles. JMHO.

smkettner said:

I think all vehicles would benefit from removing the accessory belts and drive each item with its own electric motor.
The Leaf is a leader in this area out of necessity but the technology will soon help all vehicles. JMHO.

Click to expand...

Kinda like the Prius?

Prius has no drive belts. I did not know that. Then by all means Prius should have credit for being the early innovator.

smkettner said:

Prius has no drive belts. I did not know that. Then by all means Prius should have credit for being the early innovator.

Click to expand...

I don't know if it has no belts at all, but they've moved some components to all-electric instead of being belt driven.

DarkStar said:

smkettner said:

Prius has no drive belts. I did not know that. Then by all means Prius should have credit for being the early innovator.

Click to expand...

I don't know if it has no belts at all, but they've moved some components to all-electric instead of being belt driven.

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The 2004+ Gen II Prius (NHW20) had only one remaining drive belt, for the ICE water pump. All other ancillaries are electrically driven. I've never seen this belt fail, though the pumps sometimes go at really high mileages.

The 2010+ Gen III Prius (ZVW30) has no belts, all ancillaries are electric.

The biggest improvement I'd like to see on the Leaf is a heat-pump heating system. Adding an $18 reversing valve (my cost) and some software would greatly improve things!

The PHV prius (plug-in) uses a heat-pump system.

-Phil

Wouldn't a heat pump for providing AC and heat have been a more efficient way to provide heat on an electric vehicle, than using solid state resistance heating?
Doesn't anybody manufacturer an automotive application heat pump?

TimLee said:

Wouldn't a heat pump for providing AC and heat have been a more efficient way to provide heat on an electric vehicle, than using solid state resistance heating?
Doesn't anybody manufacturer an automotive application heat pump?

Click to expand...

That's what I just mentioned right before your post.

-Phil

Ingineer said:

It's not "free", because it would eat into the regen and cost you range. Also, you'd have no A/C unless moving, which would make the system useless.

Or to look at it another way, it already works this way, go down a hill and put out 5kW or regen, if your A/C is on and draining 500w, then you are getting "free" A/C + 4.5kW into the pack. =)

-Phil

Click to expand...

So, maybe theoretically you could get *more* benefit from regen with the AC on, under a scenario where the car is limiting the regen input to the traction pack to some chosen value, even though more regen could be generated. If the AC is on, then it would be possible for the car to accept a greater input (AC + battery charging) without exceeding the parameters for pack charging. Kind of a nit though, I suspect.

TimLee said:

Wouldn't a heat pump for providing AC and heat have been a more efficient way to provide heat on an electric vehicle, than using solid state resistance heating?
Doesn't anybody manufacturer an automotive application heat pump?

Click to expand...

I think a heat pump is about 3 to 1 efficient compared to resistance heating.

smkettner said:

I think a heat pump is about 3 to 1 efficient compared to resistance heating.

Click to expand...

Doesn't that only apply when the outside temperature is fairly moderate, well above freezing? I thought heat pumps got much less efficient with large temperature differentials.

Ray

planet4ever said:

smkettner said:

I think a heat pump is about 3 to 1 efficient compared to resistance heating.

Click to expand...

Doesn't that only apply when the outside temperature is fairly moderate, well above freezing? I thought heat pumps got much less efficient with large temperature differentials.

Ray

Click to expand...

Yes, heat pump is 2 to 3 times the efficiency of resistive heating down to moderate temperatures in the 25F to 35F range, at least on home heat pump systems. Below that the strip heating usually has to begin operating some. And below 0F to 10F range your home is pretty much being heated with resistive heating.
Even if a heat pump system for automotive were available, it is not in line with the Nissan design objectives for the Leaf.
Economics is #1 priority on the car.
A heat pump system costs quite a bit more money on the front end due to reversibility of the refrigerant flow using valving, which also adds more weight, plus the car still has to have the solid state resistive heating system anyway in case temperatures are below 10F.
I speculate that on later versions they might offer a heat pump system as an option, and it could be standard equipment on the first Infiniti all electric vehicle.