Dual Chargers

Dual Chargers

I am unsure on whether to get the dual charger option. My expected driving pattern from home is not enough to justify getting this option with the High Power Connector for home use, but I am unsure about longer road trips to places that may not have the Supercharger access. As I understand it, many J-1772 charging stations are set up with relatively low current circuits that are fine for the Nissan Leaf, but would not support the full 20 kW dual chargers for the Model S using the proper connector. I have checked all the online sites (Recaro, Plug Share & Car Station) and can find no details on which J-1772 charging stations would support an 80 to 100 amp circuit necessary for medium fast (60 mile per hour of connection) charging.

Does anybody have thoughts on this? The core question is how to find out where the high current J-1772 stations are located to make the decision on dual chargers for someone like me who only needs this function on the road and not at home.

Mark E | 18. Juli 2012

I'm 99% sure that I wont bother with dual chargers. Since they are not a requirement for supercharging and I drive on average less than 60km (35miles) per day it's pointless.

Here in Australia the standard wall sockets are 230V, 10A. This will give about 2kW, so around 12-15km/h charging rate. With the car being parked for at least 12 hours overnight every day it would recharge more than double what I use.

I'm looking at putting a 20A or 32A (230V) outlet in the garage that would give me up to 7.2kW. Still less than the 10kW single charger but enough to recharge the car from empty overnight.

The only consideration that would change this is if there were a lot of 20kW chargers on the open road where there weren't superchargers. At the moment its a moot point as there aren't even many 32A 230V chargers around.

ggr | 18. Juli 2012

Given your apparent requirements, I wouldn't get the dual chargers. Even if you plug into a high amperage charger, the negotiation between the charger and the car would just limit the current automatically anyway. The only worry would be someone who comes along and wants to use the full current.

Peter7 | 18. Juli 2012

I'll add that everyone at Tesla that I've talked to feels that the second charger can be added after you purchase the car for about the same cost as purchasing it with the car. Just about all also suggest waiting. That being said I am going to get both initially because the of the road trips I do and the ability to charge off of 70/80 Amp Tesla HPC's along the way. I don't have much hope of finding many if any J1772 chargers greater than 30A.


brianman | 18. Juli 2012

"about the same cost as purchasing it with the car"
From a materials perspective, I believe we've heard that stated officially from Tesla.

From a labor perspective, installing it after *has* to cost Tesla more .. so I'll presume they'll charge a bit more, accordingly.

Vawlkus | 19. Juli 2012

If you have the money: get it.

If you don't, then don't.

It's a simple question really.

bsimoes | 19. Juli 2012

I'm thinking that I'll get them for two reasons: resale/trade-in value, and I think that the car will be such a pleasure to drive that I will want to do many more "day trips." With the money I save in gas, I can drive a few hours, go out to lunch while charging, and then make my way home.

Teoatawki | 19. Juli 2012

Resale value may be the best reason to have the dual chargers. By the time you're ready to part with your car, assuming BEVs really take off, high power J1772 chargers will be much more common. If your car cannot take full advantage of those chargers, that reduces its value relative to other cars on the market.

EFusco | 19. Juli 2012

Here's my thoughts and how I made my decision to get the dual chargers.

#1--the cost differential was fairly minimal
#2--I've never owned an EV before and have some range anxiety/concerns
#3--I do hope to use my Model S for some longer highway trips that will almost certainly require at least a partial top-up prior to getting to my destination or home.
#4--I think we are in some rapidly changing times and that there will be more and more higher capacity chargers available over the next several years. I intend to keep this car for at least the next 7 years and probably closer to 10 yrs. The ability to recharge 62 miles in an hour is significantly greater than 31 when you're traveling and using a charger.
#5--At times I need to make quick turn arounds...perhaps commuting to work, home and immediately needing to leave for a more remote destination. The ability to top up the charge in a very short period of time will be handy at those times.

I was very close to not going with the HPC and twin chargers and I think that for most people they won't be "necessary". But I also suspect there may be a time or two for everyone where you wish you had it.

pilotSteve | 19. Juli 2012

+1 @EFusco. I am already wired with a 100A/230V outlet in my garage, and had decided to go dual chargers when Tesla called me re Sig waiting list. That made the premium for sig more reasonable to me since dual chargers etc. are of course included.

I don't have that many long trips planned, but home to/from the beach is a 220 mile trip, which I fully intend to drive in a 'spirited' fashion.... and it will be comforting to know that the car will be fully recharged always the next morning even after a long weekend.

stephen.kamichik | 19. Juli 2012

The charge adapters supplied with the model S are 10k capable. The dual chargers are only necessary if you get the home charger unit which is 20k capable. Third level charging does not require dual chargers because the DC voltage is fed directly to the batteries.

pilotSteve | 19. Juli 2012

@stephen.kamichi - correct, when I said "outlet in my garage" I mean wires to connect my HPWC. Yes, my order includes the HP wall connector.

Twin charges (even without HPWC in your garage) is for "future proofing", resale value, and best available technology access while traveling reasons as others have posted.

murraypetera | 29. Juli 2012

I am looking at the 40kwh battery and in my mind this almost requires the twin charger for that just incase time when you have to wait to top off to get home. This would 1/2 the wait time.

This in mind I am now confused when I look at the web site and after speaking with a Tesla badged gentleman who was at the NY test drive and said he was hired to install the DC quick charge stations.

First the web site states two conflicting specs for the mobile charger:
The Mobile Connector is included with every Model S and allows you to charge almost anywhere.

2. 10 kW capable Universal Mobile Connector with 110 V, 240 V, and J1772 adapters
3. Public charging station adapter (J1772, 80 amp capable)

Then the Tesla gentleman also said 40 amp only. He also did not think the DC stations were going to have the standard tesla chargers to let us twin-chargers top off. This would be a great disappointment and rather shocking if they did not have 2-3 twin-chargers at each.

So this makes me think:
1. it does not support more than 40 amp
2. it does support 80 amp
3. it does but with a separate 80 amp adapter

It would be nice to know.

jkirkebo | 29. Juli 2012

The mobile connector only supports 40A (9.6kW). To get the full 20kW you need the HPWC or a public 80A J1772 EVSE. I don't think finding >40A public connectors would be very easy anyway.

The DC quick chargers have nothing to do with single or twin chargers. It bypasses them entirely. Teslas quick charger ("Supercharger") is basically 9 10kW chargers in a big box, feeding DC to your battery. The quick charger has the proper cable attached already, nothing else needed.

But a 40kWh battery will not allow DC quick charging.

Thumper | 29. Juli 2012

I had a thought about the twin charger after driving the S. I commented that the car's regen didn't seem very strong, the Tesla employee said at higher speeds, the car couldn't convert the kinetic energy back to electricity fast enough to slow the car at the same rate as it does at lower speeds. Does it follow then that with the twin charger, regen has the potential to be twice as agressive?

jerry3 | 29. Juli 2012

I don't think that follows. It's unlikely that the regeneration path goes through the chargers.

Bear in mind that regeneration throws aways some of the kinetic energy as heat so while it's better than throwing all of the energy aways as heat (the way friction brakes do) it's not as good as gliding to a lower speed (or stop) where a larger portion of the kinetic energy gets converted into forward motion.

Teoatawki | 29. Juli 2012

I don't know if that follows, but seems worth asking. I think regeneration has to go through the charger(s), since the AC motor running ias a generator (regen mode) produces alternating current, which must be converted to DC to charge the batteries.

Brian H | 29. Juli 2012

I suspect the 85kwh battery can accept charge faster than the 40kwh, so would have stronger regen, too. In Doug's (?) video, the car was slowed to 45mph, and dropping going downhill with just regen. And all the cars made so far are 85kwh.

pilotSteve | 29. Juli 2012

I believe the "inverter" is what converts DC (battery) to AC (3 phase for the motor) and also converts AC (3 phase from the motor when acting as a generator) to DC back into the battery.

Think of the single or twin chargers simply as the "wall bug" that comes with your computer or phone: it exists only to convert house current (be that 110VAC or 240VAC, at 10-80A depending on your configuration) to DC strictly for the purpose of charging the battery.

jkirkebo | 29. Juli 2012

Yep, the charger(s) have nothing to do with regen.

At higher speeds, much more energy needs to be dissipated to slow the car down. Regen is simply limited by how fast the battery can accept the charge and the grip of the rear wheels.

Leofingal | 29. Juli 2012

Regen should theoretically be limited in around the same scale as the energy transfer the other direction (i.e. Acceleration). Currently this is incredibly higher than the "high" regen setting. I would not want 60-0 when releasing my foot from the accelerator in 4.4 seconds however, so "full" regen is probably not practical.

Brian H | 29. Juli 2012

You'd need a VERY heavily padded steering wheel. And strong shoulders. ;)

Michael23 | 29. Juli 2012

I opted for no dual or charging station. These are pretty much the only options I didn't get. I will use supercharger on the road and saved 3k. I'm leaving my car plugged in all night anyway so who cares if it charges a bit faster.

jkirkebo | 29. Juli 2012

Leofingal: Nope. Most batteries can deliver way more energy than they can accept from a charger. 4C discharge/1C charge is fairly common.

And with braking comes weight transfer forward. Too high regen and the rear wheels will lose their grip.

jerry3 | 29. Juli 2012

- And with braking comes weight transfer forward

In the Model S the center of gravity is about the same height as the centre of the axle. Weight transfer is close to zero--it might even be negative. Note that the rear brakes on the Model S are are larger diameter than the front brakes.

Agreed about the rate of charge vs. discharge. Charging is much lower.

Leofingal | 29. Juli 2012

Ok, I'll accept a factor of 4, but that is still a lot faster than current settings, so it is a software limit.

Teoatawki | 29. Juli 2012

@pilotSteve (et. al.) - Thanks for clearing up the regen functionality not using the charger!

Just when I think I really have a handle on how this car works, I find out how wrong I am. I guess it doesn't pay to get cocky.

@Leofingal - Since you can essentially drain your battery in an hour or a little less (at 100+mph), and full power charging from the HPWC takes 4:43 according to Tesla's calculator, it probably closer to a factor of 5.

Brian H | 29. Juli 2012

I think that's about right; the max from an HPWC is a touch over 60 miles of range per hour charging. Not a straight line, though; the last 20% takes a lot longer than the first 20%!

ewtriplett | 18. Oktober 2015

Does the dual charger double the speed of charging from a 110-volt line?

flyjeffva | 18. Oktober 2015

@ewtriplett, NO.

dortor | 18. Oktober 2015

@ewtriplett- charger is a poorly chosen term IMHO - they are "converters" - they convert AC to DC to charge the batteries - these converters have a capacity - how much AC can they convert to DC…

1 converter can convert 10,000 watts of AC to DC
2 converters can convert another 10,000 watts of AC to DC

watts = volts * amps

typical house hold current is 110-120 volte and 15 AMPS

for conversion proposes you de-rate the circuit by 20% - a 15 AMP house hold current is actually 15 * .8 which is 12 AMP continuous load

120 volts * 12 amps = 1440 watts

1440 watts is way under the the 10,000 watt limit of a single converter/charger…

so dual chargers make no difference until you have are talking about having an electrical source > 10,000 watts

moving to a 220/240 volt circuit if you have an 50 AMP source the math is:

240 * (50 * 0.8) = 9600 watts

so dual chargers _ONLY_ make a difference when you're talking about charging from a source that is more than 50 AMPS (some J1772 and HPWC installation are greater than 50 AMP)

the maximum currently disclosed AC charging capabilities is a Tesla HPWC @ 100 amps

220/240 volts * (100 amps * 0.8) = 19,200 watts which nicely fits under the 20,000 watt limit of dual converts/chargers.

Linus | 18. Oktober 2015

@Brian H
>>> Not a straight line, though; the last 20% takes a lot longer than the first 20%!

This may be true for supercharging, but not for home charging. I had the dual charger installed a few weeks ago. Charging speed doubled, as was expected and is constant from the beginning to the end. Here in Austria we have 240 V three phases. At 32 amps I can now charge with 240 V x 3 phases x 32 Amps = 23 kW, which gives me about 102 km of range per hour. This remains constant all the way to 90% where I usually stop.

sule | 18. Oktober 2015

@dortor: They are more than (AC to DC) "converters" (rectifiers). They also have logic and meters that monitors battery state and adjusts that conversion to be what it should be. At the very least they have the ability to be controlled by the system outside.

@Chess2: It is fairly constant but not entirely. There is a ramp-up at the beginning. If you charge to 100% you will also notice that it slows down (even though it may indicate otherwise; it can stay at a certain range for 15 minutes even though it says it is charging at around 100 km/h, for example).

Otherwise, it *can* MORE than double the charging speed. Extreme case scenario: cold winter, you need (pre)heating and charging at the same time. Without charging this will draw up to 30A at 240V (observed!), or 7.2kW.

With a single charger you have 10A or 2.4kW left for actual charging.

With dual chargers you have 50A or 12kW left for charging.

johncrab | 18. Oktober 2015

Evaluate your needs. I bought dual chargers because of a lack of superchargers where I travel mostly. Some of that gap has been plugged nicely and some never will. I travel to Hermosillo, Sonora and have my own charging net along the way to get me there and back. I'll take all the speed I can get which is 80A @ 216V or 17.3KW. Once I'm there a single charger would certainly suffice

oldenfield | 07. November 2015

Now I Have a headache.

sule | 07. November 2015

@oldenfield: Many doctors and engineers here. How can we help? :)

allRedP85 | 08. November 2015

+1 @EFusco - read what he/she has to say
+1 @sule

I ordered mine with the 2nd charger last year - cheaper. Was very nice on a recent trip to Yosemite. I was able to get twice as much juice (a top-off) during lunch at Groveland - no waiting. Then again, twice as much juice at the Ahwahnee.

More and more "destinations" will be installing the HPWCs. And I'm seeing more 80-ampers. I'm keeping an eye on CHAdeMO and CCS.

As an older person, I have time, but I don't want to waste time. Sitting in the Tesla is nice, but driving is really nice.

Is it true? I heard that Tesla uses the same "chargers", same box/circuitry at the Superchargers. A rack of the same boxes that we have in the car - smart!

allRedP85 | 08. November 2015

I like options. Not having a 2nd charger is kind of like going on a trip without the UMC, now MC. That leaves you with Superchargers and J-1772 (bummer).

I'm thinking seriously about buying a CHAdeMO adapter - one more option. If I do, I'll let fellow, South Bay, Tesla owners borrow the CHAdeMO for trips.

PTP | 08. November 2015

good idea, a community CHAdeMO adapter. makes sense. I don't take a lot of trips so buying one just for me doesn't make sense.

sule | 08. November 2015

Maybe this can help:

I also recently posted this on Model X forums again, after posting it here long time ago, but can't find it any more:

(a) You don't need the faster charging rate ever. Until you do. It may not apply to everyone and it may not apply to you ever. But I have benefited from having 80A-capable HPWC charging in a few unplanned situations (winter, long commutes and unexpected needs to cross the city after that). Not everything can be planned. I am happy I have dual chargers.

(b) "Fast" L2 charging stations may not be available near you but they are plentiful in Canada. In Europe there are standard three phase outlets that can deliver the power, without the need for HPWC or J1772 stations.

(c) Tesla's "Destination Charging" program included sending HPWC to many institutions that could have immediately, or could in the future, enable full 80A charging.

(d) Supercharging is the answer only in between the cities. It is much more convenient and easier to rely on destination charging. You go to a hotel, a restaurant or an attraction and you charge there. You don't have to drive to a Supercharger location and spend time there. Even if the Supercharger is in the same city, it is, on average, inconveniently far away. If it is half your range away it is entirely pointless. In cold winter that is further reduced.

(e) Now, if you envision destination charging as success (or condominium parking charging) you must accept that the charging stations will be shared. You should not assume to be the only guest with a Tesla or that there are as many HPWCs as Teslas. An 80A HPWC can charge "reasonably empty" Teslas to about 90% within about 3 hours. Yes, it can take more in extremes, but you don't really arrive truly empty and you don't really charge more than 90%. If the hotel has two guests needing a charge, one needing 3 hours and another needing 6 hours to charge, what do you think will happen? The 3 hours one should get the charge first, not because s/he deserves it, but because that minimizes the total wait. Waiting 3 hours more on top of 6 hours is a lot less trouble than tripling tour 3 hours charge by having to wait 6 hours to start it. Of course, there may be no choice. The "6 hours guy" may already be there. Point is, it isn't good sharing. And because of that point, my opinion has always been, that the charging rate should not be a thing you choose when buying a car. Everyone should get the fastest charging possible at the time, not because of himself/herself, but because of the other drivers they may have to share the charging spot with. Furthermore, the cars have "lives" after first owners - and those are a lot less likely to pay for any/charger upgrades.

allRedP85 | 08. November 2015


Well said.

In the future, we'll need to share HPWCs at the hotel (destination). When I check-in and plug-in at the hotel, I leave my name on the dash.
With my 2nd charger, I don't need to be plugged in all night. My note, on the dash, says "Call before 10, and you can have the charger."

I just hope that you, with a single charger, don't get there before me and block access all night.

Please leave your name on the dash.

P.Dolby | 09. November 2015

Basically well covered here.
I got the dual charger to quickky charge my car for use folowing a weekly 100+ mile commute.
I Would say, though, that if you dont need the charge you should not leave your car plugged in at a destination charger ever.
The person arriving exhaused at midnight needs that charger.