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What factors to consider when choosing a battery pack?

All,

I've just received my invitation to build my Model S but I'm having trouble deciding on which battery pack to get. I originally thought 230 miles was enough but seeing how $10k in savings will be realized I chose the 160 mile one, I'm having second thoughts. Below are some facts:

- Live in downtown Washington DC
- Use the car about 3 days/week at approximately 20 miles roundtrip.
- About 5 times a month, I'll go visit family in the suburbs or have business there. On average, the DC suburbs are 10-20 miles away so assume 50 miles roundtrip.
- I would also like the ability to occasionally make a road to Baltimore, Philadelphia, Richmond, etc. all of which are within 200 miles. Obviously the 160 won't cover NYC but I haven't heard much of charging stations on the East Coast.

Any thoughts/ideas on this from you guys would be much appreciated. Hope you're all enjoying your Model S's as I'm quite excited to get mine soon.

Thanks,

A

For city driving and suburbs only you would probably be ok with the 40kwh pack. If, however, you are planning any road trips like you describe I would go with the 60kwh battery. Remember, the 160 and 230 stated ranges are "rated". That is based on 300Wh/mile (55 mph, no ac, heat, etc). Especially in the winter you will be using significantly more energy. You also use a lot of energy by just parking your car in the cold, especially when not plugged in (I have seen a loss of 50 miles in a 24h period).

Now, the 160 and 230 and 300 mile range is not only derived from "rated miles" but also based on a range charge which is not recommended for daily driving because it degrades the battery faster. That means you will not get the stated range with a regular charge.

My commute is 70 miles round trip. I start out with approx. 230 miles in the morning. While at work I cannot plug in. Pulling in my garage at night leaves me with a range somewhere around 120-130 miles. That is with a 85kwh battery.

My recommendation: Get the largest pack you can afford. Skip all options if you have to.

PS Also, you cannot use superchargers on the I95 corridor with the 40kwh pack

adahagam - I was debating the same issue. I live in St. Louis and have a 40 mile round trip each day that occasionally goes to 75 if I run a few errands or stop somewhere after work. My wife has an AWD ICE SUV that we take on longer trips to visit family etc (200-300 miles away with few charging options in the midwest). I have decided to go with the 40kwh battery because I just will not use it beyond my daily commute or trips around town. If I was single and did not also have an ICE, I would choose the 60kwh battery and the supercharger option to increase my range.

Thanks for the great comments guys. I'm single and live in a city so I use cabs/metro a lot. Also Tesla just opened up recharging centers between DC and Boston so I should be good to go on that end, but unfortunately they don't allow 40kwh batteries to be recharged. I've read that Tesla expects to make supercharging available for ALL batteries but I'm not sure when and if they'll do it for previous purchases. Do you guys have any information on this?

I'm leaning towards the 40kwh but if they decide to allow previous 40kwh purchases to be supercharged then I'm sold on the 160 mile range battery pack.

Tesla has said pretty clearly that the 40 will not (ever) support supercharging. (Does anybody have good refs saying otherwise?) The 60 does for an extra fee of $1K. I drive round trip to Richmond on the 85. With the 40 it would be one way and nearly a full charge needed. Draw a 120 mile radius circle on the map and thats your range roughly. Sounds like you are really deciding if you want a commuter only, or not. (Note also they are roughly laying out SC stations for 150-200 miles between each, at least for the first four years.)

That's correct bfranks273, I'm not really doing long-distance road trips anymore as I fly mostly. So for NYC, I'll rarely, if ever, drive there since I'll take the train to Penn Station or fly one of the shuttles out of DCA. Most drives will occur for the DC suburbs and as far as Va. Beach, Raleigh, etc.

I also figured that 10k buys a lot of plane ticketes and rents a lot of ICE cars. I purchased the 60kWh battery because I expected cold snowy days to cut my range down significantly and looking at the reports it does. I am also figuring my driving habits will remain at least the same in 5 years so I need enough battery to cover a 10-15% loss from aging batteries plus bad weather driving. I concluded if there is an over 100 mile round trip then the 60 kWh is required unless you want to stop and charge for a few hours. Anything under and you should be good.

I was in a similar position as you b/w the 40 & 60kWh. My overall recommendation is buy the biggest battery you can afford.

The 40kWh would have been sufficient for most of my driving but after factoring in battery degradation and length of time I expect to keep the car, I went with the 60kWh.

SC capability must be built-in to the original order. Do not kid yourself otherwise. Dual chargers may offer some future-proofing, and will be particularly useful with the Sun network in Canada.

Do NOT try and finesse the 40 kWh into a distance car. Tears will result. Unless you trade it in for a GenIII in a few years.

@ChrisDC - that is ideal miles, not rated -- rated is based on EPA ratings and is 265 for the 80kWh battery pack.

Note also that if you want supercharger access in the 60kWh battery, that costs $2k extra, so the delta to 85kWh is only $8k in that case and it is $12k more than the 40kWh.

I agree with @BrianH - if you get the 40kWh, think of it just as a car for driving around town and plan on using (or renting) another car for the out-of-town trips.

@ adahagam@gmail
@ bfranks273

Correct, no supercharing for the 40kWh, but the upcharge for enabling supercharing for the 60kWh battery is $2,000, not $1,000.

I originally was going to get a 40 kWh battery. I am getting the 85 kWh battery. I have not test driven the car, but based on test driver comments, I think that I will want to use the MS to explore my province (Quebec) as well as Ontario and possibly New Brunswick. The battery will degrade over time and I do not want to have to replace it any time soon.

You may enjoy the car so much that you will want to go "exploring". Get the biggest battery pack that you can afford.

"supercharging", not supercharing.

60 Kwh Pack here, But I WANT a 170 kwh Pack and Quad chargers!! I'll tow the extra pack behind the car built in the floor of a small one person pop up camper. Hey what the heck!! It will make sitting in the Campgrounds waiting for charge completion a whole new adventure and might get me up to near 450 - 500 mile range "optimal"

I know ... Dream on lol!!

Agree with the sentiment that the 40kWh is a commuter car - rent an ICE for long trips.

In my case, it makes sense. My daily commute is approx 30 miles, weekends 75 miles, occassionally
in-town, 1 day travel of about 100 miles...all with a standard range charge for the 40kwh. Since the 100+ mile trips are only occassional, a range charge would boost my effective range up over 140 miles. Travel more than that happens at most twice a year. As said before, you can rent a lot of ICE for the extra $10K - $12K.

Given this, I really don't understand the logic behind 'get the biggest battery you can afford'. Seems you would just be leaving money on the table. So much batter would remain largely unused which translates to $ wasted, IMO. Especially since EV batteries are so expensive right now.

correction: "So much battery..."

The mantra should be 'buy the most battery you will need'.

You want to select the battery that will still meet your needs at the end of the time you plan to own the car. Therefore, estimated battery degradation must be taken into account.

Multiple other threads have discussed estimated battery degradation. Bottom line is no one knows for sure what it will be and Tesla is not warrantying any specific capacity after a given period of time.

However, in order to figure what battery size to buy the consensus rule of thumb is to assume about 70% of original capacity remaining after 8 years of normal driving. Roadster data suggest you will likely have more than this so it is probably a reasonably conservative figure to use.

@ChasF - there is also the convenience issue. Until the supercharger is built out on the east coast, I will have one trip a year that the 85kWh Model S will not be sufficient for. Having to rent a car every other month vs once a year is a big difference in convenience, and you have to drive a crappy gas-powered car that trip. It isn't always about the financial side of things, or I would have just kept driving my LEAF.

If range is already a concern at the outset, the recommendation remains "get the biggest battery you can afford." If you can afford $12k to upgrade to the 60 then you should. The lack of logic is the unnecessary hassle of renting a car anytime you need to go over 100 or so miles...particularly on a Sunday when most rental car companies are closed.

Between 40 and 60 for me too. You may want to track your mileage closely - I've been doing this for the past month and haven't driven more than 80 miles in a day. My wife will keep her ICE car for now so if ever needed I could use that. I do want to see the 40's EPA rating so hoping that comes out soon.

I've considered all three battery options and at different times had good rationales for each. I have now decided on the 85kWh - as I agree with the sentiment to get the biggest you can afford. It is not only future degradation to consider, but other driving factors such as weather (cold, headwinds, etc.), hills, daytime parking outside without a charger (and in the cold, which apparently really hurts range).

Also, you have to decide how much you are willing to adjust your driving habits (extra slow, or keeping the cabin at an uncomfortable temperature) because you may be worried about range. Finally, Tesla says the biggest thing affecting the life of the battery is how often you do a full charge - so getting a larger battery if you can afford it could be in part so you do not have to charge it to full too often.

I agree with Vinprof. Go big if you can. There is tremendous value in having more range.

It's also the fastest, and by default has full S/C access, free forever!

My contrib. to your rationale-ization.

sage;
Also remember that $2K must be paid up front. ??I think technically you could buy just the $1K h/w SC upgrade for the 60, and buy the SW enabling later. Don't know if that's still on the table.

@jat

I don't understand your point about renting an ICE "every other month". I never said that would be acceptable. I think renting for a trip once a year is a good compromise unless you have so much money that the one trip a year is worth the extra $12K to $20K.

@Lou

If "range is a concern", as you put it, then you obviously need more than the (insert applicable battery size here), so buy what you need is still a valid approach.

I can afford to buy the 85kWh but I choose not to spend for the extra capacity that will almost never be used. It comes down to what your particular travel patterns are. In my case, 40kWh will work for 95% of my needs easily. The extra range is not worth it to me for the current cost.

If I find in 3, 4, o4 5 years that I am traveling more, or that I underestimated my needs, I will sell the car and buy one with more appropriate range - most likely at a much lower cost by that time.

All I'm saying is, I understand everything is not a financial decision, but if we aren't considering it, they why are we even discussing this?

@ChasF - if I were to buy the 60kWh model, I could not use it for some of my out-of-town trips, which I take about 6 times a year. The 40kWh is basically just an in-town car, so you need another car for every out-of-town trip. I already have a LEAF, which is also only an in-town vehicle, so if my wife and I both had only in-town cars, that means lots more rental car trips which are inconvenient besides the expense (which surely you can pay for from the battery savings). Even with the 85kWh battery, I will have about one trip a year that it won't be sufficient for until the Supercharger network is built out around here, and renting a car once a year is the level of hassle I am willing to put up with.

Thanks for the great conversations everyone. While I can afford the 60kwh, I really don't need it based on my commuter travel style. My farthest trip I've made is PHL/Atl. City, which is about 140 miles away from DC and I do this very rarely as I take the train/fly to NYC and beyond. This combined with still the ability to publicly charge, albeit longer than supercharging, and the 240volt outlet I'll have at home, I'm comfortable with the 160. Thanks again guys your help!!

@adahagam - note that 160 is ideal miles, not rated miles (which haven't been computed yet, but I would estimate around 145) - you won't get the ideal miles driving normally, and you may not get rated miles depending on your driving style. Also, in the northeast, I would expect you need to consider cold weather's impact on the battery itself and on your need to run the heater. I think you will be very hard-pressed to make a 140mi trip with the 40kWh battery without charging. If you are planning on charging half-way, then that will be fine.

Based on the arc of rated vs ideal in the 85kWh and 60kWh, I would expect the 40kWh to be rated at 145-150 miles by the EPA. Assuming you do a standard charge, you should have 89% of that for actual use (129-133 miles). Assuming normal driving habits (including heat/cold outside temps) drop a standard charge rated range by 20%, you should have 103-106 miles of actual driving. Assuming time/use degrade the battery by another 20% over the next 7-10 years, you would have 82-85 miles.

If the vast majority of your travel is under 75 miles in a day, then you should be fine with the 40kWh battery for the next decade (maybe longer).

Good breakdown.


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