Why I Ordered My MS With 2nd Charger

[Scotty]

I test drove a MS, talked with a friend about it, and ultimately, we both ordered S85's a day apart. My house electrical service is a 300 AMP service, but my friend only has a 90 Amp service. As a result, he decided to not order the 2nd on board charger. I did, but not for the obvious reason. I thought I'd post my reason, but it's not just because I have a 300 Amp service.
Looking down the road, it's apparent that superchargers will continue to be rolled out. We are already seeing them being installed in metropolitan areas; Las Vegas, San Mateo, Mountain View, Fremont and increasingly in Southern California. As more Tesla's are sold and delivered, the usage of these Superchargers will continue to rise. Queue's are inevitable.
In the next few years, battery pack capacity will increase, perhaps by as much as 50%. I can easily envision a 125kW pack, and charging it will become more of an issue. If you're spending 25 minutes to get 75% range, you will be spending a bit more. The time spent will be much longer, and since everyone will probably be spending longer plugged in at the Supercharger, the queue time will become more of a n issue.
Now, if I'm plugged in at home or opportunity charging, particularly with the appearance of more 80 Amp HPWC's at hotels, etc, regardless of your home service, you'll want to take advantage of the higher power and shorter charging time. Only having 1 on-board charger will limit the charging rate and increase the charging time. It might take 8 hours (at 28 miles range per hour charging) to get to ~ 80%. However, if the pack capacity is increased to 125 kW, that charging time will take quite a bit longer. Now, having the 2nd on board charger will allow charging at 80 Amps, and getting the pack recharged overnight will still be achievable.

Scotty

 

[ohmman]

Fine reasoning. I've used my dual chargers a number of times on road trips and have been thankful for them. Especially in the Pacific NW, there are plenty of 80A public chargers, which provide a reasonable top-up to get between a SC and your desired off-the-path location.

 

[Barry]

I don't see the point of a 125 Kwh pack, given Supercharger spacing. To me, it makes more sense to make a physically smaller pack, as energy density increases, to lighten the weight of the vehicle. That, my itself, will increase efficiency and range.

 

[Xenoilphobe]

I think we need both. Having just driven from Chincoteague Island to my house 208 miles away with two bikes on my hitch and the AC maxed out and the car loaded to the gills with beach gear and two teen agers with all their toys. I had to stop twice to charge (speed played a role - 70 to 80 most of the way). The Salisbury SC helped but so did my CHADeMO that I used at Queenstown "Premium" Outlets. 30 minutes on that got me home. I avoid Bethesda SC like the Plague, but could have risked it and attempt to use that site (every time I go there someone has their Tesla camped out there like its there own personal parking spot. I know it has something to do with the store there but move the car once charging is complete...

I probably could have done a nail biter at 55 MPH and gotten rear ended, but chose to keep pace with traffic - the trip took longer but the boys enjoyed long boarding at Salisbury and Queenstown Outlets..

 

[TexasEV]

To the OP, I'm all for dual chargers, but I don't agree with your logic about superchargers. Bigger battery sizes does not mean longer supercharging times or longer waits at superchargers. 85s don't take longer at a supercharger than 60s. Bigger batteries can sustain a higher charge rate.

 

[gaswalla]

Agree w Texasev, bigger battery sizes allow Max charging rates at superchargers for a longer period of time if you look at rated miles as a marker for battery charged. Also you may need less supercharges because of the increased range.

 

[ItsNotAboutTheMoney]

I don't see the point of a 125 Kwh pack, given Supercharger spacing. To me, it makes more sense to make a physciall smaller pack, as energy density increases, to lighten the weight of the cehcile. That, my itself, will increse efficiency and range.

125/85 ~= 1.47 => 125kWh could charge in 32% less time than an 85kWh pack. Even allowing for higher consumption, owners would still save time on longer trips, and spend less time at Superchargers. So, if technically possible, and people want to spend the (hopefully, by 2025) $4k-$5k extra, Tesla would be mad not to sell them. Especially, if it's only available in the full-size Model S/X.

 

[mwulff]

I didn't order dual-chargers for my car. But that is mainly because we have great supercharger coverage in my country and public chargers are about 80 cents pr kWh.

So home charging at 51 km/hours and supercharging. So far I haven't missed a dual charger. But at least it can be had later if I need it.

 

[jerry33]

1. The larger the batter the quicker it will be to reach any given number of miles of range. This is because the charge rate tapers as the SOC gets higher. In practice, the first 50% SOC is really fast, The next 30% is reasonably fast, and the last 20% takes as long as the first 80%. Larger is certainly better in charge times.

2. There are now and will be for the foreseeable future many routes that have zero Supercharger coverage. When all state and interstate highways are covered, then there will be a case that larger batteries aren't required but not until then.

3. The shallower the cycle, the longer the battery will last. For daily charging, charge as much as you need (I suggest three days of normal travel to allow for the unforeseen). A larger battery will just last longer because the percentage of SOC used in a daily cycle will be lower.

4. Twin chargers allow you a greater degree of flexibility when on trips. I have them on mine and although they aren't needed often, when they are I'm sure glad I have them.

5. The HPWC allows you to be a good samaritan for other Tesla owners. It also provides more robust charging than the UMC.

 

[Matteo]

The time spent will be much longer, and since everyone will probably be spending longer plugged in at the Supercharger

It is the opposite. Jerry33 is right. Larger battery supercharges faster. This has to do with the fact that supercharging slows down at higher percentages (known as tapering curve). In the table below you can see that 200 rated miles equals to 96.15% in 60 kWh battery but only 69.93% in 90 kWh battery. With larger batteries you don't need to supercharge to high percentages to acquire the same rated miles. Therefore it is faster. Here is a comparison between 60,70,85 and 90 kWh batteries supercharging from 30 to 200 rated miles:

Model S 60	Model S 70D	Model S 85D	Model S 90D
max 208 miles EPA rated range	max 240 miles EPA rated range	max 270 miles EPA rated range	max 286 miles EPA rated range
Step 4: Supercharge From	Step 4: Supercharge From	Step 4: Supercharge From	Step 4: Supercharge From
30	30	30	30
charge level 14.42%	charge level 12.50%	charge level 11.11%	charge level 10.49%
charge time to this percentage	charge time to this percentage	charge time to this percentage	charge time to this percentage
06 min 36 sec	05 min 48 sec	05 min 12 sec	04 min 54 sec
Step 5: Supercharge To	Step 5: Supercharge To	Step 5: Supercharge To	Step 5: Supercharge To
Enter miles (max 208)	Enter miles (max 240)	Enter miles (max 270)	Enter miles (max 286)
200	200	200	200
charge level 96.15%	charge level 83.33%	charge level 74.07%	charge level 69.93%
charge time to this percentage	charge time to this percentage	charge time to this percentage	charge time to this percentage
1 hour 19 min 06 sec	56 min 36 sec	46 min 18 sec	42 min 18 sec
1 hour 12 min 30 sec	50 min 48 sec	41 min 06 sec	37 min 24 sec

The data is from this spreadsheet: Tesla Supercharge Time Calculator - Google Sheets

However, dual chargers is still a good idea because of the destination charging program. Not all destination chargers are at hotels where you stay overnight.

 

[deonb]

Why does a hypothetical future 125kWh pack impact any kind of buying decision today?

In Elon's most optimistic opinion, a 125kWh pack is 7 years away. Adding a standard Elon fudge, would put it at 14 years out. Extrapolating recent history puts it at 21 years out.

You're not going to want to put a new $25'000 battery in a 14 year old car.


I have dual chargers. I live in the most dual-charger rich area in the country - heck even contributed to building that network. Over 2.5 years:
* Number of times I've used dual chargers: 2
* Amount of time spent waiting less due to dual chargers: Uhh. It has yet to happen.

Thing is, even though there's a lot of dual chargers here, there's also a lot of Chademo's. I'll take Chademo over dual charging any day.

If you have to bet on a hypothetical future abundant dual charger rollout, you'd also have to simultaneously bet against a hypothetical future abundant Chademo rollout, otherwise it's still pointless.


To anybody who is unsure about buying a dual charger, my advice is this: Wait until you've been in a situation where you can say, hey, if I had a dual charger now it would have been nice. Then only go and install one. Chances are better than average you would never be in that situation, and then you saved yourself $2500.

 

[Xenoilphobe]

I actually buy your Chademo argument,u nfortunately when I bought my car Chademo wasn't an option. Either way if I bought a new one today it would get dual chargers as well. I like having redundant systems and have twin HPWC's at home has been great. (no fiddling with the onboard cable - just plug in). Also getting taken advantage of by the EVGO isn't fun... they now require a monthly plan - which I might use once or twice a year..

 

[deonb]

Also getting taken advantage of by the EVGO isn't fun... they now require a monthly plan - which I might use once or twice a year..

Their FLEX monthly plan is free. Just pay per kWh. They just require a $5 setup.

 

[jerry33]

To anybody who is unsure about buying a dual charger, my advice is this: Wait until you've been in a situation where you can say, hey, if I had a dual charger now it would have been nice. Then only go and install one. Chances are better than average you would never be in that situation, and then you saved yourself $2500.

I've been in that situation several times. I'm glad I bought mine. Haven't yet been in a situation where CHAdeMO would have helped. It totally depends on where you live.

 

[m6bigdog]

1....

4. Twin chargers allow you a greater degree of flexibility when on trips. I have them on mine and although they aren't needed often, when they are I'm sure glad I have them.

5. The HPWC allows you to be a good samaritan for other Tesla owners. It also provides more robust charging than the UMC.

I like that kind of thinking!
Yep, on the road Superchargers are great but everyone wants to charge at the end of a day...
I have mine and if I were to never use it, it would have still been worth the expense. Nobody that buys a MS saves money!!
It is more about being prepared, being efficient, saving time, than trying to save money (second charger after build is $2k not $2.5k).

IMHO, if you could have used a dual charger and didn't have one, the opportunity was lost.

Nothing worse than entering a new transportation technology with a handy cap or waiting behind someone that thinks they understand the economy of the technology by making other wait because they are too frugal to understand the reality of wasting the time of others in the community!!
At any destination with HPWC and +40amps, if a queue exists, all the dual charger cars should be allowed to charge first!!

In the big scheme of things dual chargers are inexpensive, more efficient and would be even less expensive if they were factory installed in every MS.

FWIW, the time saved is invaluable because it wouldn't take many single charger cars to bottle neck charging to a stand still!!

 

[David99]

If anything, a larger battery decreases charge time. Others have already pointed out how larger batteries are charged faster at Superchargers.
But even for your daily driving, a larger battery will decrease or even eliminate the need to charge at all. Let's say you have an 85. If you need to drive 300 miles a day, you need to charge maybe 50-100 miles extra some time during the day. If you have a 125 kWh battery, you don't need to charge at all because you have 380 miles of range. Ok let's say you need 400 miles a day. In an 85 you need to charge 150 miles extra. That takes maybe 3 hours on a dual charger. With a 125 pack you only need to charge maybe 80 miles. That would take only 1.5 hours.

Dual or single charger has nothing to do with battery size. Your daily driving needs determine how fast you need to charge. And of course if you can find 80 Amp chargers out and about.

 

[mwulff]

Why does a hypothetical future 125kWh pack impact any kind of buying decision today?

In Elon's most optimistic opinion, a 125kWh pack is 7 years away. Adding a standard Elon fudge, would put it at 14 years out. Extrapolating recent history puts it at 21 years out.

You're not going to want to put a new $25'000 battery in a 14 year old car.

To anybody who is unsure about buying a dual charger, my advice is this: Wait until you've been in a situation where you can say, hey, if I had a dual charger now it would have been nice. Then only go and install one. Chances are better than average you would never be in that situation, and then you saved yourself $2500.

@Deonb: I completely agree with your sentiment of "go ahead and wait" with regards to dual-chargers. But for my little corner of the world where cars are heavily taxed and extremely expensive due to 180% import tax, 25% sales tax and so on. Currently electric cars are exempt from the 180% import tax and that means that a standard 85 RWD costs about $96.500. Add the tax (the tax break runs out this year) and a Model S will cost around $150k (tax break for high mpg).

My Model S is hopefully that last car I ever buy simply due to our tax structure. So I expect to buy not just 1 battery over the lifetime of my car, but probably 2 or maybe even 3.

 

[WarpedOne]

I don't see the point of a 125 Kwh pack, given Supercharger spacing.

Au contraire. Given current SC spacings, I'd need 300kWh pack to really feel free.
SC's are cool, what is even more cool is not thinking about charging on your daytrip and routing your way to visit each one the way (adopting the way to actualy go near them).
It is dead easy to do 300m roundtrip without any SC nearby.

If one does not see the point of it, just don't buy it. Options, options, ...

 

[Scotty]

To all. I know that Superchargers don't use the on-board charger(s), as you all know. However, Since 95% of my charging (10 months and almost 36,000 miles) has been on Superchargers, there is a limiting factor with SC's. The limiting factor is the current capability of the SC. If you're down to 20%, and want to go to 80%, you will have to put a significant amount of energy back into the battery pack, no matter what energy charging system you use.
Sure, if you're only looking to add a few miles, the size of the pack won't matter. The most charging current I have seen at a SC is 329 Amps, before it tapers down as charging continues. That, of course, is when the other side of the charger is not being shared....ie 1A and 1B). If you need to charge the 'future' pack up to 80%, it will take longer, given the current limit of the SC. Now, a 60 kW pack might take the same or very similar time to charge, but going from 80% to 20% of a 60kW pack will not deliver the miles that an 85 kW pack will give, for the same percentages. Also, the current limit of the SC in use today does limit how fast a larger pack will charge, not for the rated miles, but for the percentage. Again 10 miles of driving in a similar fashion and conditions will use a similar amount of energy, whether from a 60 kW or 85 kW pack.
Gelled electrolyte batteries are used in my business, and a 12 Volt 100 A/Hr deep cycle rating refers generally to a 20 hr rate. Theoretically, assuming a perfect and efficient battery, a 100 A/Hr batter can discharge down to 20% at 1 Amp/Hr for 80 hours, or 4 hours at 20 Amp/Hr. All batteries have rating in this format, but I have not seen the rating for the Tesla. It could be calculated or extrapolated, but my point r5emains at a set charging rate, a larger capacity battery pack will take longer to charge to the same SOC than a smaller capacity one.
Now, my original post was about the 2nd on-board charger. On my recent trip to the NW, and particularly for the SC gap between Baker City and the Utah SC, having the 2nd charger did not help me, as I was limited to 32 Amps maximum. However, there are 80 Amp HPWC's out there that would have helped, and I would have been charging for substantially less time.
I don't know and can't predict future battery prices and the possible resizing of the packs. I will tell you, though, I'd rather have a 125 kW pack and keep it between 30% and 70% charged. (Less charge cycles per 100 miles driven equates to longer life).
Summing up, no matter what size of battery pack you have now or in the future, Fast DC Charging makes it easier or more acceptable to go on trips without worrying about charging when away from home. Whether you SC, CHAdemo, single or dual charge, you need to put the energy into the battery pack in order to get it out.
If you want 5 miles of range, you'll need 200 to 500 Whr/mile, all things considered.

Scotty

 

[jerry33]

But even for your daily driving, a larger battery will decrease or even eliminate the need to charge at all. Let's say you have an 85. If you need to drive 300 miles a day, you need to charge maybe 50-100 miles extra some time during the day. If you have a 125 kWh battery, you don't need to charge at all because you have 380 miles of range.

Regardless of battery size, you should charge daily because the smaller the charge cycle the longer the battery will last. Skipping is not a good plan for battery life.