Featured PHEV Tesla Model 3

almost every new technology is vaporware

 

The bottle in my hand says, "For storage up to 12 months..."

I'll worry about that the next time I get a car with a carburetor in it.

 

Wait what? I thought the appeal of the PHEV was freedom from the tyranny of public charging.

 

Have you used Electrify America recently?

• You can get less but you can't pay more.

Bob Wilson

 

yes - our local Walmart added both DC QC as well as L2 electrify america stations. Big dummy - my reading glasses left at home, it looked like the charge fee was 3¢/minute. So, planning on being in the store for an hour, wanting to support a newer network - & thinking we would pick up roughly 6kWh (after accounting for 6.6kW losses) in the Chrysler Pacifica. BUT, they also tacked on $1 hookup.
So - that meant (after tax added) an hour cost $3 for 6kWh .... 50¢/kWh .... so if we had had an even slower charging 3.6kWh on-board L2 charging system - flat fee per minute - it would have even been even more outrageous!!

 

I don't think public charging is tyranny, but the key advantage of phev over bev

Can fill in all the gas stations so easy to take road trip. I've never had a problem, but I haven't taken a trip past san antonio, approximately 200 miles round trip when including the other driving that day. Drove 75 mph most of the way other than the traffic slowdowns and city with cold blasting air conditioning. Had public chargers available. Started with a full battery in the morning, had 57 miles showing when I came back, high speeds and hot day looks like it dropped my range 53 miles. Many have tougher driving scenarios.

Definitely in towing situations and longer trips some people may want a phev over a bev. Choice has been limited to this date, with the cars either not being optimized for it, or not big segments. Rav4 phev looks like the first good attempt at a high volume phev. Many thought when the volt came out they needed to follow with something like the planed rav4 phev, Of course a lot of the success of that is down to implementation and dealers.

Now oberst is claiming other advantages over a long range bev - weight and price. If we look at the bmw rex it adds 120 kg (265 lbs). When we look at the 250 mile standard plus tesla model 3 versus 325 mile rwd long range, there is a 114 kg (251 lb) so yes if you drop mileage to 200 miles or bellow and put in a lightweight gen set weight will be reduced versus a 300 mile+ phev. As to cost, I'm not so sure it depends on the costs of the engine, gasoline, maintenance, versus battery, electricity, maintenance. I doubt much cost is saved.

 

Well it actually does, if you follow my math ;-) Just take the total power subtract engine power and you get the additional power the electrified drive train can add to the system. Note your own figures 90kw (121 hp) total power - 71 kw (95 hp) = 19 kw (26 hp). Horsepower non rounding errors added from toyota ;-) Now I didn't look at the mg as they don't really act additively. The battery definitely can supply more than 26 hp and the mg2 can use it, but given the electronics and software limitations that's all they can contribute to peak. If the ice is not at max power the battery, mgs, electronics definitely do supply more power to the wheels if it is called upon.

Now in the rav4 there is an additional mg, a bigger battery, and upgraded electronics so electricity can add much more even at max engine hp when it is called upon. If toyota took a lesson from tesla that mg3 will be tuned to be efficient at a different speed range than mg2 adding not only electronic awd but also higher electrical efficiency at higher speeds.

 

And where did 19kW come from when you have a 23kW motor, a 53kW motor and a 68kW battery?

Which is my point - the electric system on its own is far more powerful than the difference between the stated system total and the ICE alone.

 

We'll write the tyranny off to dramatic license.

Either way, if you pay for PHEV gear and gas and taxes, there's little point in also paying for public charging access. For plenty of drivers that's perfect. They'd never want to use public chargers anyway, and they're perfectly capable of driving very electric on home charging only.

The article itself suggests that a $15k battery could be deleted from a Model 3 in exchange for a $3-4k PHEV power system. Even if they're cheating and hiding lots of costs, there's room for a lot of accounting shenanigans before the PHEV setup appears to cost more than the BEV deal.

 

I don't think we are in disagreement here on the technical factors just on the engineering trade offs. On a phev generator set, the trade offs are efficiency, power, weight, size (both volume and packaging), pollution after pollution controls, cost, and nvh.

On point 1 - atkinson cycle absolutely it would help. The bmw i3 rex is rated at 28 kw but rpms are limited so it produces at most 20 kw after losses through the generator. Now you can do a better design taking into account many of the changes in mazda skyactiv or toyota dynamic force and get more hp and better nvh and add to the cost. But if you increase cylinder size to 0.5L that sweet spot of highest efficiency is going to be extended because lower rpms are needed to get to the same power, and the engine does not need to overproduce to charge the battery for later higher loads. The lower rpms will reduce noise and vibration (better nvh) for higher loads compared to an undersized engine. Larger displacement does mean higher minimum efficient power but its not really a problem going from a 0.647 L I2 otto to a 1L I2 atkinson to a 1.5 L I3 atkinson. If you need 2700 rpm to make a I2 run smoothly a I3 can do it @ 1800 rpm if both are designed well. Increasing displacement simply makes it less expensive to get close to high efficiency on a phev load using these small engines.

Of Course if you turbo charge you can go smaller but ... it doesn't save you a lot and it costs more money. The oberst 1L is only 498 mm tall, 577 mm long, and 1.88 mm wide (19.6" x 26.7" x 7.4") including generators and sound deadening. The nissan 1.5L 3 cylinder turbo engine from their experimental race car is even smaller 400 mm tall, 400 mm long, and 200 mm wide weighing 40kg, of course you don't really want the 400 hp and need to add the generator to the size and sound deadening to the car. The oberst engine is claimed to be 40% efficient like the prius. The most efficient mass produced gasoline engine is the toyota dynamic force atkinson @41% efficiency. The most efficient gasoline engine today is the the mercedes 1.6L I6 turbo that is in their f1 cars at 50% efficiency but that costs a lot and can't do low rpm. Skyativ-x is giving higher efficiency in the lab, but not yet in the real world and its going to have worse nvh than toyota's dynamic force engines.

On point 2 - cooled egr helps the prius because the battery is small, on a bigger battery phev that extra power from full load at the rpm can just charge the battery. Of course if you want the rpm to follow the throttle for better traditional connected sound, cooled egr can make it more efficient.

 

Toyota!

Again toyota max power is 90 kw, engine power is 71 kw, which means at max power electronics only add 19 kw.

Well you have to take into account the implementations. In a psd, and follow the story problem, mg1 and mg2 ARE NOT additive. In fact in most situations the power from mg1 flows to mg2 to create the transmision. The numbers are not material to how things work in a ev mode. If that battery is indeed 68 kw perhaps it can drive 53 kw through mg2 in certain situations. Of course rpm of mg2 proportional to mph which means it can't provide full power at lower speeds (I don't really know the power curve). The engine max power is at over 4000 rpm which also can't be had at low speeds given the psd. It appears from total power electronics have not been upgraded to allow mg2 to provide much additional power when the ice is providing full power. Let's face it at only 8.8 kwh and likely using at most 70% state of charge, the battery would be drained to the minimum state of charge in 20 minutes at 19 kw, going 68 kw would drain it in less than 6 minutes. The rav4 phev appears to have upgraded electronics and enough room on mg2 and mg3

So what is your point? The electric system is inadequate on its own. You can analyse it as a bev, but my guess on a bench it peaks bellow 53 kw of power on the out put shaft (sure it can draw a lot more power but we are talking about output not input). The prime works well as a phev but it needs its engine other wise it is badly underpowered and is carrying a fairly heavy paperweight. If mg2 is driven electrically for 53 kw, odds are the ice is providing far less than 37 kw, and I don't know where the ice would be on and the battery would be providing close to that power.

 

Correct as only the Prime had the one-way clutch that allowed MG1 and MG2 to work as a single unit.

Bob Wilson

 

I get 63kW net on my Prime in EV mode.

That's just simply false. I drive my Prime in EV mode 99% of the time and I rarely get to full power even accelerating from zero up a 7% grade. 0 to 40 times are almost the same with or without the engine and even at highway speeds, passing is rarely a problem in either mode.

 

A con of a power-split hybrid is that the motors need to be oversized for proper operation as they also have duties simulating a CVT in addition to providing propulsion.

For a Prime using both motors in EV mode, Toyota likely limits the combined output. Either for efficiency, to keep EV and hybrid mode performance similar for the driver considering the different power curves, or to protect some component.

 

Technical details:

• Power split - 28% follows electrical path and 78% takes the mechanical path
• Prime one-way clutch - allows MG1 and MG2 to work as a single unit.

Bob Wilson

 

• The split is actually of torque.
• They can work together, but that doesn't mean the components in between can bear the full output for the life of the car. Ford derated the 3.5 Ecoboost in the Taurus because its potential output would tear apart the drivetrain over time.

Toyota limiting the output of both motors working together simply could be about traction. The above Taurus was AWD only for that reason.

 

The torque that splits comes in via the same flywheel shaft. It then leaves by a separate, single gear to the differential. In my physics class, power is the cross-product of the rpm and respective 28% and 72% torque.

Bob Wilson

 

yes yes that is true.

Power = pi/30*(MG2rpm*MG2torque + MG1rpm*MG1torque+ ICErpm*ICEtorque) if power is in watts and torque in Nm. Instead of multiplying by pi/30 divide by 5252 if power is in horsepower and torque is ft-lbs. Of course this is power at each shaft and mg1 and the ice must go through the psd and mg2 through a reduction gear so this power gets derated compared to a typical single speed bev, but the psd is very efficient so the power adds more performance than an ice into a typical transmission.

Now if we are only being driven by mg2 which has a peak output power of 53 kw and torque of 163 Nm, then we need to get to 3105 rpm to hit peak hp if torque is max there. A little higher if torque is less than 163 Nm depending on the motor curve. I know in the gen 3 this would be around 30 mph, I don't know the gear ratios in the prime, so perhaps you can fill those in also. Up to that point hp would increase almost linearly with speed.

I do not know the efficiency of the system but assuming 93% efficient electronics and 97% efficient motor (this is the peak efficiency of the tesla model 3 switch reluctance motor). The system from the 68 kw battery to the output shafts of mg1 and mg2 would be at most 68kw x 90% x 97 % or 61.3 kw. Use your own numbers if mine are off. So the one way clutch can definitely let mg1 augment the power especially at lower speeds. I do not have a prime or a bench to test this stuff on but I'd be surprised if it was much higher than this, and assume in most situations it is much lower (lower state of charge or called on power will reduce the draw). I do not know if the 63 kw leejay read was coming from the input of the motor or the electronics. As we see from the simple equations when the motor is running and high power is called upon mg1 will act as a generator and this electrical power will reduce the amount that the battery can provide to mg2.

The prime engine produces peak torque of 142 Nm @3600 rpm (53.5 kw) and peak hp of 71 kw @5200 rpm (130 Nm).

 

wait are they really claiming this hybrid generator just costs just €1200?
"The cost of the Obrist hybrid generator is just ~$1,335 (€1,200) with the battery at ~$2,230 (€2,000)."

in that case couldn't you just get the base model 3 at $35k with its 50kWh battery and tack this on... let's say cost is quadruple for installation mods ($5200), and you're still ahead of getting the Tesla 3 LR at $49k.

fascinating idea, prius prime battery way too small to run primarily as an ev, i3 Rx (and volt too) gasoline mode ~40mpg not all that great either.

i wonder what the ICE mpg would look like lugging an Tesla 3 50kWh- less than their claimed 2.9L/100km, but even if it were only 3.5-4L/100km still ahead of the prius/prime with their ~50mpg 4.7L/100km. if you could get prius like indefinite ICE 50mpg, with tesla 3 short range BEV (even with say a 5-10% range loss for lugging around gas tank and extra generator).

i'd even be OK with the ICE generator a bit underpowered, e.g. at highways speeds >55mph eating into battery range.

 

It would need to get EPA certification first.