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 and becoming a Supporting Member. For more info: Support TMC
Start a Discussionhttps://teslamotorsclub.com/tmc/tags/

20amp/120v charging vs. 15 amp/240v

Discussion in 'Model X: Battery & Charging' started by Cellsaver, Jan 9, 2017.

  1. Cellsaver

    Cellsaver Member

    Joined:
    Dec 25, 2016
    Messages:
    48
    Location:
    Cincinnati Ohio
    Let me say in advance that I am not an electrician by any means lol...

    I have a NEMA 5-20 outlet in my garage. From what I am reading, since I have an open slot on the panel next to this breaker and nothing else on the circuit, I could convert it to a 240V NEMA 6-15. Seems like the charge rate is not a whole lot different but everyone says 240V is more efficient so I just don't want to be wasting electricity that isn't getting funneled into my battery.

    I have a wall charger going in at work so I won't need to do a ton of charging at home.

    Tx,
    Trace
     
  2. Hammer@OR.US

    Joined:
    Feb 1, 2016
    Messages:
    235
    Location:
    Wren, Oregon
    Seems like a no brainer to me as long as that is the only outlet on that circuit. Charge rate will almost double. If any other outlet is on that circuit they would need to be changed as well.
     
  3. SageBrush

    SageBrush Active Member

    Joined:
    May 7, 2015
    Messages:
    4,171
    Location:
    Colorado
  4. TexasEV

    TexasEV Well-Known Member

    Joined:
    Jun 5, 2013
    Messages:
    5,213
    Location:
    Austin, TX
    By my calculation it increases by 50% (2.4kW to 3.6kW), not double. I think it's still worthwhile doing.
     
  5. Hammer@OR.US

    Joined:
    Feb 1, 2016
    Messages:
    235
    Location:
    Wren, Oregon
    OK, I excessivly rounded but it's more like a 70% increase 2kW to 2.9kW
     
  6. Cellsaver

    Cellsaver Member

    Joined:
    Dec 25, 2016
    Messages:
    48
    Location:
    Cincinnati Ohio
    4-5 mph charging is plenty for me, I'm worried more about the decreased "efficiency" that others talk about with a 120V system. If I leave it at 20amp/120V I can still plug other things into it if I need to, but if I'm somehow mysteriously losing 20% of my electrons I'd rather change it to 240.

     
  7. BestRadar

    BestRadar Member

    Joined:
    Nov 14, 2013
    Messages:
    420
    Location:
    NJ
    For a 220v outlet you really should have an extra wire. There should be a ground and neutral for 220v lines.
     
    • Disagree x 1
  8. Hammer@OR.US

    Joined:
    Feb 1, 2016
    Messages:
    235
    Location:
    Wren, Oregon
    Not true. A 240v only like the 6-15 only requires two hots and a ground. A 120/240 like a 15-40 should have a neutral.
     
    • Informative x 3
    • Like x 1
  9. AB4EJ

    AB4EJ Member

    Joined:
    Feb 25, 2015
    Messages:
    751
    Location:
    Tuscaloosa, AL
    Right. The Tesla does not require a neutral.

    On capacity, you should pull max 80% sustained from a circuit. So at 120v, you can pull 16 A = 1920 W, or at 240v (with 15 A breaker) you can pull 12 A = 2880 W, which is 50% more than the 120v.

    In either case, you have a relatively slow charge rate. My advice would be to save your nickels & dimes and eventually (hire someone to) put in a NEMA 14-50. This gives much more flexibility for being able to get a good charge at home in cases where you need this without having run somewhere else
     
    • Like x 1
  10. Hammer@OR.US

    Joined:
    Feb 1, 2016
    Messages:
    235
    Location:
    Wren, Oregon
    DOH, must have been before my coffee this morning. :confused:
     
  11. Rocky_H

    Rocky_H Active Member

    Joined:
    Feb 19, 2015
    Messages:
    1,423
    Location:
    Boise, ID
    Others have given good advice addressing making the change, but I don't see checking on this yet. Is it really just one single 5-20 outlet on the circuit all by itself? That would be really unusual. Usually those 120V outlets have several along the circuit running around a room, or on both sides of a wall. If you make the breaker change to switch it to 240V, you will be making ALL of the outlets on that circuit 240V, and that could be a nasty unexpected surprise POP if someone plugs a regular 120V device into one of the other outlets on that circuit.
    So if it is just that one, then yeah, go for it. If it is multiple outlets on that circuit, then you should do something about those others so you don't have false/dangerous 5-20 outlets with double the voltage out there waiting to surprise someone. If you can do without them, I would unhook the others and put blank cover plates over them so nothing gets accidentally plugged in there.
     
    • Like x 2
  12. Cyclone

    Cyclone Cyclonic Member ((.oO))

    Joined:
    Jan 12, 2015
    Messages:
    4,910
    Location:
    Charlotte, NC
    If that is indeed the only plug on the circuit and you have to buy a new double-pole breaker to get to 240 V, I would just change it out to a NEMA 14-50 or leave it alone.

    The inefficiency of charging on 120v is simply b/c of the wasted energy running the charging system and associated components. At 120v, they are a decent percentage of what is used. I know the numbers are on TMC, but I don't recall them offhand. Let us just say they are 500 W for the BMS, charger, charging losses, etc. At 16a/120v for 1920 W, that is just over 26% "wasted". At 12a/240v for 2880 W, that is over 17% "wasted". However, you also have to keep in mind that b/c of the slower charging on 120v (4 - 6 mph in warm weather), that 500 W load "wasting" energy will run longer since it takes longer to charge. So ultimately, the best efficiency is to install a 14-50 where possible and just charge at 32a-40a/240v for 7680 W - 9600 W of juice.
     
  13. Pwdr Extreme

    Pwdr Extreme Member

    Joined:
    Nov 30, 2016
    Messages:
    164
    Location:
    Bozeman, MT
    You absolutely do not need a neutral line for a 240v outlet. Two hots and a ground is all that is required. There is a very good chance that you do have a dedicated single outlet in your garage, most new houses will install this dedicated outlet for the purpose of putting a freezer in the garage. If this truly is the case, you can essentially double your charging rate for a few minutes time and about a $10 outlet. I would recommend it myself if it truly is a dedicated outlet. Although you may not ever think you will "need" it, I think It's absolutely worth it considering how easy and cheap it is to convert.
     
  14. davewill

    davewill Member

    Joined:
    Feb 5, 2014
    Messages:
    534
    Location:
    San Diego, CA, US
    #14 davewill, Jan 11, 2017
    Last edited: Jan 11, 2017
    You can have your cake and eat it, too. Re-purpose the line for 240v 20a and put in a 6-20. Use the Tesla 5-20 adapter on your UMC and make yourself a 5-20r to 6-20p adapter. This will give you 240v 16a charging for 3.8kW. Be sure to follow code for the work which usually includes marking each end of the white wire with red so that it's clear that it's now a hot.

    If you don't like using an adapter this way, you can purchase a J1772 EVSE like the 16A Level 2 EVSE LCS-20 | ClipperCreek (which is designed for a 20a 240v circuit) or a JuiceBox which can be configured for one. Neither one comes with a 6-20 plug, so you'll either have to put one on it, or hard wire the unit...or you can get an HPWC and configure it for a 20a circuit and consider yourself future proofed.
     
    • Like x 1
    • Disagree x 1
  15. Cellsaver

    Cellsaver Member

    Joined:
    Dec 25, 2016
    Messages:
    48
    Location:
    Cincinnati Ohio
    Awesome, thanks!
     
  16. Cellsaver

    Cellsaver Member

    Joined:
    Dec 25, 2016
    Messages:
    48
    Location:
    Cincinnati Ohio
    So just to make sure I follow you, even though the circuit can't support 50 amps, install the NEMA 14-50 and dial back amps on my X. Do I have to dial back the amps every time, or will it remember by location?
     
  17. mspohr

    mspohr Active Member

    Joined:
    Jul 27, 2014
    Messages:
    2,629
    Location:
    California
    I wouldn't install a 14-50 since the car will try to charge at 40 amps from this socket. (You can dial it back but it might reset itself).
    The wire to this socket is 12 gauge which is max 20 amps (16 continuous) so charging at 40 amps will burn your house down.
    As suggested above by @davewill, install a 6-20 socket. This will give you 3.8kw which will be faster and much more efficient than charging at 120v.
     
    • Helpful x 1
    • Like x 1
  18. Rocky_H

    Rocky_H Active Member

    Joined:
    Feb 19, 2015
    Messages:
    1,423
    Location:
    Boise, ID
    I'm not @Cyclone , but someone needs to step in and say, "I hope that's not what he was suggesting, since that is a violation of electric code and a terrible idea."
    I am pretty sure by "change it out", he meant replace the whole thing, by pulling new thicker wire, new breaker and new outlet. You really shouldn't put a 50 amp outlet type on a 20 or 30 amp breaker with 20 or 30 amp sized wire.
    But yeah, my own suggestion lines up with a couple of other people here. If it's a dedicated 5-20 outlet, go ahead and change it over to either a 6-20 outlet or hard wired wall connector for a 240V 20A circuit.
     
    • Like x 2
  19. Cyclone

    Cyclone Cyclonic Member ((.oO))

    Joined:
    Jan 12, 2015
    Messages:
    4,910
    Location:
    Charlotte, NC
    Nope. This...
     
    • Like x 1
  20. Cellsaver

    Cellsaver Member

    Joined:
    Dec 25, 2016
    Messages:
    48
    Location:
    Cincinnati Ohio
    Ok great, thanks for all the advice guys.
     

Share This Page