EV 914's Options

[raynekat]

Whether you like 'em or not....they are definitely a wave of the future.
Not sure what I think about the whole idea myself.

Still have the rear luggage boot which is nice.

It's pretty slick the bolt in rear cradle that holds some of the batteries, Tesla motor, cooling, etc.

The "custom" look is pretty bad as to me.

https://www.youtube.com/watch?v=hJTNsH-SIqk

[emerygt350]

Batteries will get lighter.

And you can put the electric on the transmission. It doesn't help with range but I would definitely do it for fun.

[Superhawk996]

Batteries will get lighter.

Keep drinking the Kool-Aid. (IMG:style_emoticons/default/lol-2.gif) The promised land of battery technology is always 10 years away . . . as it has been for the last 20 year or more.

It's always a trade off between range and weight.

[bbrock]

Batteries will get lighter.

Keep drinking the Kool-Aid. (IMG:style_emoticons/default/lol-2.gif) The promised land of battery technology is always 10 years away . . . as it has been for the last 20 year or more.

It's always a trade off between range and weight.

What the heck are you talking about (IMG:style_emoticons/default/confused24.gif)

Sure it's a compromise between range and weight, but the range batteries get for the same volume/weight today is many times more than just a decade ago. Maybe the weight of the battery hasn't changed so much, but the amount of juice inside it certainly has. Remember that 30 years ago these cars would have been crammed full of lead acid batteries that just "might" get you to the grocery store and back.

(IMG:https://www.energy.gov/sites/default/files/styles/full_article_width/public/2022-04/FOTW_1234.png)

https://www.energy.gov/eere/vehicles/articl...m-ion-batteries

[Superhawk996]

Batteries will get lighter.

Keep drinking the Kool-Aid. (IMG:style_emoticons/default/lol-2.gif) The promised land of battery technology is always 10 years away . . . as it has been for the last 20 year or more.

It's always a trade off between range and weight.

Maybe the weight of the battery hasn't changed so much . . .

Agreed. Point being Lithium is the lightest metal (and 3rd lightest element) so not likely to find a new metal to replace it anytime “soon”.

Yes, battery energy density is increasing but it is still a long way from the energy density of gasoline.

Always fun to (IMG:style_emoticons/default/stirthepot.gif) on the EV topic (IMG:style_emoticons/default/happy11.gif)

My end point being that the weight of the batteries is what destroys the handling - especially with a 914 conversion. That’s OK if you only drive in a straight line to go get ice cream as your fun drive. I prefer something that handles better than that.

[bbrock]

My end point being that the weight of the batteries is what destroys the handling - especially with a 914 conversion. That’s OK if you only drive in a straight line to go get ice cream as your fun drive. I prefer something that handles better than that.

Well, let's consider these two examples. They said the rear battery pack plus Tesla drive train weighs about the same as a Six engine and trans. Okay, I've heard people argue even the extra weight of a six takes away some of the nimbleness of a four, but people seem to be pretty happy with the handling of their sixes.

Let's just consider that if they dropped the front battery pack, the weight has been held about the same. It's hard to know how the distribution of weight between battery pack and motors affects moment of inertia compared with a stock ICE. It looks like maybe it would be moved toward the axles a bit more, but seems it would be close(ish). Seems like you should be allowed at least a small battery pack in the fuel tank compartment to make up the weight of a full tank. Overall, some range would be lost but how much? The point being that even with current tech, you should be able to EV a 914 without destroying the handling if that were the priority.

It's all good because I know that you secretly fantasize about your own 914 EV (IMG:style_emoticons/default/lol-2.gif)

[Superhawk996]

Well, let's consider these two examples. They said the rear battery pack plus Tesla drive train weighs about the same as a Six engine and trans. Okay, I've heard people argue even the extra weight of a six takes away some of the nimbleness of a four, but people seem to be pretty happy with the handling of their sixes.

Let's just consider that if they dropped the front battery pack, the weight has been held about the same. It's hard to know how the distribution of weight between battery pack and motors affects moment of inertia compared with a stock ICE. It looks like maybe it would be moved toward the axles a bit more, but seems it would be close(ish). Seems like you should be allowed at least a small battery pack in the fuel tank compartment to make up the weight of a full tank. Overall, some range would be lost but how much? The point being that even with current tech, you should be able to EV a 914 without destroying the handling if that were the priority.

It's all good because I know that you secretly fantasize about your own 914 EV (IMG:style_emoticons/default/lol-2.gif)

What flavor is the Kool-Aid? (IMG:style_emoticons/default/happy11.gif)

We don't have to guess blindly at what the range might be with your proposal.

Let's presume that you are correct and that the powertrain approximates the mass and inertia of the /6.

So to preserve handling, now let's replace the fuel tank with batteries. Luckily we already know the volume of the 914 tank. 62 liters.

For simplicity let's assume we can package the batteries with perfect efficiency and use all 62 liters of space for the batteries.

Using 914e's specification of 412 Wh per liter we get 62 liters * 412 Wh/liter = 25,544 Wh. Likewise, 25,544 Wh / 259 Wh/Kg = 98.6 kg. This is extremely generous since 100% volumetric efficiency won't be achieved with packaging of the batteries in that "tank" space. Tesla model 3 battery packs are on the order of 300 Kg - 400 Kg depending on size so 98.6 Kg 914 battery is very generous indeed. Notice, in the video that the reality is that the 26 KWh battery they have occupies the entire Frunk in front of the gas tank. The reality is that you cannot package 26 KWh of battery in that gas tank package space. I'll ignore this for now.

So let's say gasoline weighs 6.0 lb/gallon, after conversions this is 0.719 kg/liter. So gasoline would weigh --> 62 liters * 0.719 kg/liter = 44.6 kg. Hmm . . . so those batteries are double the weight up there vs. gasoline. I can guarantee you that I can feel the degradation from an extra 44.6 kg of weight up in the gas tank area which is now increasing moment of inertia in a big way.

But wait, we don't even have the weight of the power electronics yet. (IMG:style_emoticons/default/sad.gif) I guess whatever they weigh - they would have to go in the Frunk and will continue to degrade handling even further since that added Frunk mass is no longer centralized. I'll ignore them for now to work in your favor.

Now how about range? That 62 liters of gas would normally get us 410 miles of range at 25 mpg. It can also be refueled in less than 5 minutes.

So what might we expect for range from a 25 kilowatt hour battery pack? Might be a bit harder to guesstimate. Let's work off a Tesla Model 3. The Model 3 gets about 165 miles off the 50KWh battery. Only about 40Kwh (of the 50 KWh) is usable since we can't discharge Li-ion to zero SOC (keeping 20% reserve - using 80%).

https://ev-database.uk/car/1060/Tesla-Model-3-Standard-Range

So let's do that with our 914 battery pack. 25 KWh * 0.8 = 20 KWh usable capacity.

So now let's scale and say that if the Tesla Model 3 gets 165 miles of real world range off that 40 KWh usable battery - simple scaling would give us 1/2 of that off the 914 20 Kwh (usable0 battery = 82.5 miles. I'll even grant you that the 914 is lighter than the Model 3 and will have less rolling resistance as a result. I'll guesstimate it might be 30% more efficient due to that weight delta (3600 lbs vs 2000 ish). So we'll call it 107 mile range which will be more than generous for that tiny 25 KWh battery.

So I guess I won't be road tripping in a 914 anytime soon. Sounding a lot more like an ice cream getter to me.

It's not that I am completely against EV's. What I do oppose is all the wishful thinking and boundless optimism that ignores the physics that degrades a conversion as well as the range assumptions that assume the conversion would still usable for real world purposes like a long road trip.

[bbrock]

Well, let's consider these two examples. They said the rear battery pack plus Tesla drive train weighs about the same as a Six engine and trans. Okay, I've heard people argue even the extra weight of a six takes away some of the nimbleness of a four, but people seem to be pretty happy with the handling of their sixes.

I think you missed my point - or more likely chose to ignore it because, yes, I know how you are (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/poke.gif)

There's no disagreement that batteries have not come close to the energy density of gasoline, so yes, any 914 EV conversion will be a compromise as the 914 (or any car) has been since first conception. I'm just saying it is now possible to match the weight distribution of a stock 914 with an EV package that gets a respectable amount of range, keeps the fantastic handling, gains a (IMG:style_emoticons/default/stromberg.gif) ton of torque and power, and sound damn cool while beating the pants off any stock 914. Yes, that's right, EVs sound cool (IMG:style_emoticons/default/happy11.gif) That would not be easily accomplished just a decade ago.

No, the car is not going to be a long hauler. If you want that, you have to pay the weight and handling penalty like you say. Can't deny that the energy density of liquid petrol has its perks. I'm just saying that if you constrain the conversion to matching the weight distribution of a stock ICE, you can still have a fun car. 100 mile range really isn't bad for a pleasure ride. You don't have to have "boundless optimism." Even if you are realistic about trade-offs and limitations, there is a lot to like about EVs and they just keep getting better.

Love the info card on that bug. Very cool!