Some (Battery) Questions

[Birdman325]

Long time lurker, first time poster. Even though I have never considered purchasing a car anywhere near this price point, I am becoming obsessed with a Model X. I have a couple of battery questions- I have done a fair bit of searching but have not been able to come up with a satisfactory answer.

At least here in Canada, the Tesla web site shows the 75D with a 381 KM range, and the 100D with a 475 KM range. The previous iterations, at least in the X, seems to have been primarily the 90 with about a 402 km range (and most of the MS in the CPO are 85) - is this simply a matter of Tesla being able to unlock more efficiency out of the same technology but the current discrepancy between the 2 models (75 to 100) seems more pronounced than in some of the older cars.

The price difference (again, here in Canada) between the MX 75D and the 100D is about $25,000. That is a hefty premium and while I have read lots of different "theories" (you only need the longer range if you will do road trips, for city use, save the money etc etc) - is it fair to say that "battery size" is akin to computer hard drive size? You can never have too much space? When you buy a new laptop / phone, sometimes the tendency is to try and save some money and get a smaller hard drive because you can't imagine how you will ever fill up so much space - but over time, somehow that seems to happen. On the same theory, that you can never have too much memory, space, etc, (subject to affordability of coursE) is the "better approach" to take a similar view and if one can afford it, just get the bigger battery?

Thanx in advance for helping me on this journey. (Wow, these cars are expensive!) - sorry, couldn't resist.

 

[Rocky_H]

is this simply a matter of Tesla being able to unlock more efficiency out of the same technology but the current discrepancy between the 2 models (75 to 100) seems more pronounced than in some of the older cars.

Those aren't just nicknames. Those numbers mean the amounts of kilowatt hours of energy the battery pack holds. So they definitely are different sized packs, not just advances in getting more out of them.

is it fair to say that "battery size" is akin to computer hard drive size? You can never have too much space? When you buy a new laptop / phone, sometimes the tendency is to try and save some money and get a smaller hard drive because you can't imagine how you will ever fill up so much space - but over time, somehow that seems to happen. On the same theory, that you can never have too much memory, space, etc, (subject to affordability of coursE) is the "better approach" to take a similar view and if one can afford it, just get the bigger battery?

Yes, that's basically about right. I would also add a bit more to it. People who drive gas cars sometimes ask me how much using the air conditioning affects the range of my electric car. It is totally foreign to their minds that heating actually has a FAR bigger impact on range than air conditioning does. In a gas car, it's busy wasting two thirds of the gasoline's energy as heat out the tailpipe and the radiator, so it's no biggie to divert some into the cabin--heating is always free. In a gas car, not so. They are so efficient, there is very little excess heat--certainly not enough to warm the inside of the car noticeably--so it needs to use a regular coil heater, which is drawing from the same pool of "miles" in your main battery and takes away from your range. On a worst case, that can be near 25% efficiency loss, or even worse if there is some short drives with sitting in between with the battery getting cold again.

With living in such a cold area, I just wouldn't want that to be a frequent nervous worrisome thing for you, where you are on the edge of being able to make some drive or are irritated at having to turn down your heating a lot to do the driving you want to do. Also, you're talking about a Model X. The X is already less aerodynamic and uses more energy, so I consider the 75kwh to be kind of borderline for longer distance use, especially in Canada, where there aren't that many Superchargers.

 

[Rocky_H]

and while I have read lots of different "theories" (you only need the longer range if you will do road trips, for city use, save the money etc etc)

Well, I will probably speak against my own earlier point a little bit. Yes, this part is generally true. If you aren't going to use it for long trips, and/or you have a gas vehicle that you intend to use for trips, then sure, save the money and the 75 will be great for mostly local use. It's not quite like the phone or computer example, where later apps need more computing resources. The amount of kilometers you drive is the amount of kilometers you drive. The distance from your house to work doesn't gradually get longer and longer 5-10-15 years from now, so you don't need excess room for that to "grow into". Although some people do find they like a Tesla so much, they end up doing more driving than they used to. Same with power of charging at home. If you can recharge at 30 or 40 km per hour overnight, that fills your vehicle. Future cars possibly having larger and larger batteries don't mean you need to have greater and greater charging speeds at home, where it needs future proofing.

 

[Rocky_H]

You mentioned long time lurker, so you may have seen this already. If you want to check the effect of temperature on longer trips, go to www.evtripplanner.com. Put in some routes and set the inside and outside temperatures for some different levels and see what that does to the amount of energy it takes. That may be eye-opening if you put in some below freezing temperatures in there.

 

[Birdman325]

Those aren't just nicknames. Those numbers mean the amounts of kilowatt hours of energy the battery pack holds. So they definitely are different sized packs, not just advances in getting more out of them..

Thx. For your detailed replies. I get the point about the different kw/h ratings. The point I was trying to make (although not well) is based on what I have read, I get the impression that the range and performance of some of the newer packs (75 ) may actually be longer / better than some of the older (85) for example. Is that accurate?

 

[chillaban]

I went from a 75 to a 100, and honestly the biggest difference I appreciate is that supercharging curve improvements result in much less time spent charging on road trips. Being able to charge to 200-210 rated miles is pretty useful for a lot of road trip legs. On a 100D you’re still charging at nearly full speed throughout that range, but on a 75D you will start hitting the taper past 175 miles and that might cost you 15-20 minutes extra which would’ve easily filled your 100D to 250 miles.

That difference adds up to a nontrivial amount of time on road trips. But you would be paying a hefty premium for that!

 

[Rocky_H]

Thx. For your detailed replies. I get the point about the different kw/h ratings. The point I was trying to make (although not well) is based on what I have read, I get the impression that the range and performance of some of the newer packs (75 ) may actually be longer / better than some of the older (85) for example. Is that accurate?

Take a closer look. It's probably not 75 over 85. It's much more likely dual motor being better efficiency than single motor. A lot of the older 85 cars were before the D version came out. Now almost every Tesla is with the D. There basically aren't any downsides to the D--more traction, more power, and more efficiency--except for a few thousand dollars in cost if those aren't worth it to you.