TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker or making a Paypal contribution here: paypal.me/SupportTMC

Can I use a dual charger if I do not have that option?

Discussion in 'Model S: Battery & Charging' started by ElectricAvenue, Apr 27, 2014.

  1. ElectricAvenue

    Joined:
    Jun 11, 2013
    Messages:
    60
    Location:
    Nashua NH
    I have only the supercharger option installed not the dual charger.
    If I visit a mall is a high power wall charger (which I believe is the dual charger) can I use it to charge?
    Will it just operate at a single charger lever 10KW?
     
  2. djp

    djp Roadster 2.0 VIN939

    Joined:
    Aug 28, 2011
    Messages:
    1,108
    Location:
    Toronto, Canada
    Yes, you can still use high amp charge stations but they'll be limited to 40A.
     
  3. dsm363

    dsm363 Roadster + Sig Model S

    Joined:
    May 17, 2009
    Messages:
    18,235
    Location:
    Las Vegas, NV
    djp is correct. Also note more than likely the charging stations are lower than 10kW and are 208V 30A stations so around 6.2kW.
     
  4. David99

    David99 Active Member

    Joined:
    Jan 31, 2014
    Messages:
    2,057
    Location:
    Brea, Orange County
    A charger is a transformer and some electronics that convert the 208/240 Volt AC into the 350-400 Volt DC that the battery needs. In the Model S tt has a limit of 10 kW. The high power wall connector is a 'source' that is capable of delivering up to 20 kW. The dual charger option is not in the HPWC, it's an extra option in the car. Basically it's a second charger in the car. Each charger can do 10 kW so both together will do 20 kW if there is enough power from the source.

    The Supercharger is basically a giant transformer/charger that converts the grid power into the 350-400 Volt that the battery needs. It bypasses the small chargers in the car and directly feeds into the battery. So on a Supercharger it doesn't matter if you have a single or dual charger in the car. They don't do anything at this point.
     
  5. simonog

    simonog Member

    Joined:
    Jan 9, 2014
    Messages:
    350
    Location:
    United Kingdom
    @David99 Does the double charger handle a single phase of 20 KW or need feeding two separate 10 KW signals on different connector pins?

    the reason I ask is that in the UK we are all likely to be limited in home charging options at least in the short term.
     
  6. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

    Joined:
    Jun 21, 2012
    Messages:
    7,019
    #6 FlasherZ, Apr 27, 2014
    Last edited: Apr 27, 2014
    Each charger is limited by current (amps), not by power (kW). If all you have is 100V, a single charger car is limited to 4 kW (40A x 100V) and a dual charger is limited to 8 kW (80A x 100V). European cars are different; while not confirmed, the behavior suggests each of their "single" chargers consists of three individual 16A "sub-chargers" that share a common neutral connection and "dual" charger models consist of 2 of these, for a maximum of 32A per phase. EDIT: I incorrectly said that maximum single-phase charging was limited to 32A on dual-chargers, this is incorrect as the cord / adapter design could deal with paralleling single-phase inputs to L1-3 using a single-phase cord. It is maximum 32A on dual chargers where you have non-wye 3 phase, though, because only a single L-L phase can be used across the chargers due to shared neutral.

    See this post for speculation on the EU car chargers. (I say speculation because it's not confirmed but all reported behavior so far, and limitations such as single-phase-only on Norway's IT grid.
     
  7. Cottonwood

    Cottonwood Roadster#433, Model S#S37

    Joined:
    Feb 27, 2009
    Messages:
    5,062
    Location:
    Colorado
    Another choice is to have a modified charging module design that uses a 3-phase input, rather than multiple, single-phase sub-chargers. This sort of design has been used for years in high power DC power supplies with 3-Phase AC available. Taking the best of 3 phases and rectifying that to DC, gets you to signal that has much less variation (ripple) than rectifying a single phase source which goes to zero. See the third paragraph in Three-phase electric loads - Wikipedia, the free encyclopedia.

    This added efficiency may be why the European single charger is rated at 11 kW instead of 10 kW.
     
  8. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

    Joined:
    Jun 21, 2012
    Messages:
    7,019
    The European single charger is rated at 11 kW because 230V nominal * 16A * 3 (sub-chargers) = 11.04 kW.

    - - - Updated - - -

    Take a look at my post referenced above. That's basically what they're already doing - they take L1-N, L2-N, and L3-N voltages, attach them each to the "sub-chargers" that feed a common DC bus.
     
  9. Cottonwood

    Cottonwood Roadster#433, Model S#S37

    Joined:
    Feb 27, 2009
    Messages:
    5,062
    Location:
    Colorado
    We are talking semantics here. I agree that the 3 phases are combined into a common DC bus, but is that bus the output to the battery, or is it an internal bus in the charger? Because 50/60 Hz transformers are large and expensive compared to high frequency transformers, combined with the fact that high frequency power transistors have become common and cost-effective, almost all modern power supply/charger designs use a flow that is similar to:

    AC Input -> DC Rectifier -> Filter -> Unregulated DC -> High Frequency Inverter ->
    High Frequency Transformer -> Rectifier -> Filter -> Regulated DC Output

    The regulation/current control is done at the High Frequency Inverter. High Frequency here for power conversion is usually in the range of 40 kHz to 1,000 kHz (1 MHz). Because the frequencies in the second stage are so much higher than 50/60 Hz, the transformers and filters are much, much smaller.

    If I were designing the 3-phase charger for Europe, the most likely choice would be to keep most of the charger the same as the single phase North American model, and only change the DC Rectifier and Input Filter. A secondary advantage is that the filtering needed for the Unregulated DC intermediate bus is much less with a 3-phase input. See Diode bridge - Wikipedia, the free encyclopedia for a comparison of full-wave single phase and poly phase rectification. Using most of an existing design, replacing part of it with a simpler, more-efficient alternative, seems much more attractive than designing a new, 1/3 power design, and stuffing 3 of those into the same space.

    Of course, an argument for multiple sub-chargers would be that it is easier to create a charger that minimizes input current harmonic distortion. As Tesla goes to 10 and 20 kW level AC input in residential locations, THD on the AC power lines becomes a big concern. See "Harmonic Distortion of the AC Power Line" for reference. Given the the battery itself is a big filter, perhaps Tesla have gone out of its way to build chargers that appear as a resistive load to minimize THD issues on the grid. Given that we have heard few complaints in this area, that may be very likely.

    Until someone dissects a European charger or Tesla publishes something, we won't know the details of their design, and can only speculate.
     
  10. pilotSteve

    pilotSteve Member

    Joined:
    Jul 14, 2012
    Messages:
    586
    Location:
    Vancouver WA
    Thanks for the interesting white paper Cottonwood. Good explanation of the design challenges. Not directly relevant but there is also A lot of engineering ( SW and HW) to minimize the vehicle inverter noise from the battery at high current AC output. Makes Tesla engineering even more impressive.
     
  11. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

    Joined:
    Jun 21, 2012
    Messages:
    7,019
    #11 FlasherZ, Apr 27, 2014
    Last edited: Apr 27, 2014
    Yes, and the semantics all fall within that speculation area. I don't necessarily care what's behind the rectifier when we're considering how we can connect to the grid. :)

    The reason I can speculate it's a sub-charger system with common neutral bus is that the Norwegian 230V IT grid (similar to US ungrounded Delta system) isn't supported at 3-phase and Tesla has a habit of using wye-based 3-phase designs targeting the 230-240V range (where L-N works). A true 3-phase charger design would use L-L voltage (400V in EU) and wouldn't care delta or wye as long as it could handle L-L voltages of 230V, 400V, etc.

    The speculation is also supported in that (I believe) you can get single-phase charging at more than 16A on a single charger by paralleling the single-phase line input across L1, L2, and L3 to get up to 48A across all three subchargers. Would a polyphase rectification design allow for paralleling a single phase across all three inputs for full power?

    (I'm not an expert once we get past the rectifier and to be honest, my brain still lives in linear power supply worlds. :) )
     
  12. mgboyes

    mgboyes Member

    Joined:
    Apr 16, 2014
    Messages:
    811
    Location:
    United Kingdom
    A few relevant points:

    1. Yes the EU charger supports 3 phase but it does not require it, so the design cannot rely on there being 3 phases present in terms of managing distortion etc, and must be able to operate properly with power only on L1.
    2. As noted, user testing has shown that if you connect the same phase to all three power inputs the car charges fine, drawing power equally from each, which again suggests that no part of the charging circuitry relies on L-L voltage or any particular L-L-L phase relationship.

    Agree a common DC bus scenario sounds most likely.
     
  13. arg

    arg Member

    Joined:
    Aug 22, 2012
    Messages:
    741
    Location:
    Cambridge, UK
    They don't have much choice in Europe, since they need to meet the EMC directive (and hence EN 61000, which prescribes limits on harmonic currents).

    My understanding (which may well be wrong since I don't have experience building stuff this big) is that you can't get away with a simple polyphase rectifier, and so get forced into active power-factor correction. Active PFC on a 3-phase input then forces you into a 3-channel design.
     
  14. Cottonwood

    Cottonwood Roadster#433, Model S#S37

    Joined:
    Feb 27, 2009
    Messages:
    5,062
    Location:
    Colorado
    #14 Cottonwood, Apr 28, 2014
    Last edited: Apr 28, 2014
    The appropriate standard is IEC 61000-3-4, but the IEC wants 60 Euro for a 180k PDF :mad:: Buy IEC/TS 61000-3-4 ed1.0 - Electromagnetic compatibility (EMC) - Part 3-4: Limits - Limitation of emission of harmonic currents in low-voltage power supply systems for equipment with rated current greater than 16 A.

    In doing more research, I found this paper which is very useful and references most of the key limits in the spec: Electrical network and power converters, H.U. Boksberger, Paul Scherrer Institute, Villigen, Switzerland. In particular see sections 7-3 to 7-5. There is a lot of detail about allowable distortion per harmonic, etc, but it looks like the car chargers best fit "Class 2" which allows a total harmonic distortion (THD) of the current waveform of 8%. There are also limits on power factor.

    To reach these levels, and I hope Tesla meets these limits with lots of margin, Tesla is probably using an active AC to DC converter that creates a current draw that closely emulates a resistive load. BTW, this is much more sophisticated than a "rectifier" as some have called it. By doing this active, resistor emulation, they greatly reduce the requirements on filters that must deal with large currents and power at low frequencies (large, heavy, and expensive). In today's age of efficient, relatively-inexpensive, high-frequency, power transistors, this is pretty straight forward. For the single phase systems, there will be a power into the battery that is an offset sinusoid at twice the power line frequency which is probably acceptable, and for the 3-phase systems, the charging power will be almost constant.

    The great advantage of simulating a resistive load is its lack of stress on the utility grid, besides meeting standards!

    I now agree, the 3-phase chargers, probably use three, parallel sub-chargers, one per phase. I also learned a lot about what Tesla needed to do to design the charger from this discussion. I continue to be impressed!
     
  15. Chipper

    Chipper Active Member

    Joined:
    Sep 23, 2013
    Messages:
    1,182
    Location:
    Chattanooga, TN
    Did you get the answer you were looking for? Your question is worded in such a way I am not sure if you got the correct answer. If you need further clarification there are many here that would be willing to assist. The chargers are actually in the car. If you got a single charger, you can charge on any HPWC at up to 40 Amps. You can charge at any J1772 at up to 40 Amps. If you got supercharger enabled in your build, you can charge at any supercharger as high as it will go since the superchargers charge directly and do not use the on board charger(s).
     

Share This Page