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Lowest Charge Current @ 110V

Discussion in 'Model S: Battery & Charging' started by aarossig, Dec 24, 2015.

  1. aarossig

    aarossig Member

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    I am looking forward to purchasing an S70D sometime over the next couple of months and have been going through the research phase of my big purchase :)

    I live in an apartment complex and have a private garage with a 110V outlet. I was told by office staff that the outlet is not suitable for EV charging. I can imagine that the garages are on a shared circuit.

    Given this constraint: what is the minimum charge current allowable from a 110V supply? I think it is a good idea to keep it plugged in to avoid self-discharge and possibly charge at 0-1mph. I have free charging at my office so it is not critical that I be able to charge.

    Any thoughts?
     
  2. islandbayy

    islandbayy Active Member

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    5 amps at 110/120v. so in other words, about 600 watts. If you plug in at 0 rated miles remaining, it would take roughly 140-150 hours for a 100% charge at that rate, if the ambient tempetature stays above 32*F. Below 32*F, you mileage may vary, as once the pack temp drops below freezing, it will need to heat the pack to be able to actually charge. Then, it would basically, be drawing just enough power to keep the pack warm. The closer to 0*F, the less charging and more heating it will do. You could potentially go backwards in range. but you will have a warm pack. Given you have a private garage, this is unlikely. While the garage may initially be at or below freezing (I ave no idea where your located), the lack of Wind Chill, and the insulating effects of the car being in a relitively sealed room, and the heat in the pack from being used should allow it to stay at a reasonable charging temp.

    What I would do, is see what amp breaker that your 110/120v circuit is on. If it is a 20 amp, given the power for a garage door opener, I'd say you'd be fine at 8-10 amps on a 15 amp circuit, and a solid 10 amps on a 20 amp circuit, maybe 12. Thats the best I can give ya without seeing the setup, and knowing if you have a dedicated breaker to your garage or if it is shared with multiple other garages. If it is a dedicated circuit to your specific garage, then you may be able to get away with more.

    Heres a Idea, get yourself a Kill-A-Watt meter, and a space heater (or hair dryer should work too). Plug in the kill-a-watt meter, then turn the heater on low setting, a $15 heater from Wal-Mart has 2 heat settings that I saw, 700 watt and 1200 watt. This should be good enough for the test.

    Record first the starting voltage of the outlet/circuit (The meter will show you!)
    Next, turn the space heater on 700 watt. Note the voltage again after the heater has been running for about 10 minutes.
    Finally, crank her up to max heat, and let it run for about 20-30 minutes (So if the line is heating up, it will reflect in the voltage due to the higher resistance) and then record the voltage once again.
    Please report back here, I can give you a much better opinion on "safer" charge rate once I see what kind of voltage drop you get.

    And if your feeling daring, while the heater is on max, close and open your garage door, noting the voltage on the line as the door is going up. Make sure you or someone else with you can activate the manual garage door lever if the breaker trips, or that you have a second way out of the garage if the breaker trips so you can reset it.


    Please report back. Kill-A-Watt meters can be had for $20 at Menards, Home Depot and Lowes, space heaters around $15 just about anywyere. Get the dual voltage one though, better for testing.
     
  3. aarossig

    aarossig Member

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    This is great. I thought I read 600W somewhere. Thanks for confirming!

    I was planning to do exactly as you say: test the circuit. I will likely experiment with it after the car arrives. I have an AC clamp meter as well so it should be a fun exercise. I don't have access to the panel so I probably don't want to push my luck too much. If the circuit breaker trips, I would likely need to contact building maintenance.

    As I mentioned, charging fast is not a priority but maintaining the battery state and keeping the car warm (if necessary) would be nice. It will also be nice to play with the various features of the car without draining the battery. The temperature rarely goes below 0C, I live in the Bay Area in California.

    Thanks for the lengthy reply, much appreciated.
     
  4. islandbayy

    islandbayy Active Member

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    Your Welcome! Please report back with your findings. The Max on the standard 120v adapter that comes with the car is 12 amps (for a 15 amp circuit) and a optional plug is available from Tesla (I HIGHLY recommend it!) for 20 amp circuits with a max draw of 16 amps.
     
  5. Firewired

    Firewired Member

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    We are at South Padre Island for the holidays renting a condo. There are no great local charging options nearby. Nearest is a destination charger HPWC 76 miles away. I had thought I might need to charge at the 14-50 at an RV park prior to making the return trip to San Antonio. I thought I would give the 110 outlet in the condo's garage a try, and had pretty pessimistic preconceptions, I was not sure if it would even keep up with the vampiric loss of the car. I have been presently surprised to get 4mi/hr (12A showing in the Tesla app.) We are not driving much being everything is closed and charging 96 miles a day will be ultimately be fine for us to only need one stop to get back to San Antonio.
     
  6. islandbayy

    islandbayy Active Member

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    My disabled son has been in the hospital since Saturday with Pneumonia. Just came home today though.

    The parking structure at the Hospital has a 20 amp outlet at each staircase and then again at the crosswalk entrance. Saturday, after the days running around, I plugged in. Each day I've had a lot of running around to do in the 2 hrs that my parents came to the hospital to watch Vinny so I could get at least a little work done. Each day, before I left, I ended up with a full charge. While 120v is slow, over time, it really does add up. Since I was at the hospital 22hrs/day, sure enough, each day I ended up with a full charge no problem. I will say, it was a 20 amp outlet, so 16 amp charge rate at 120v (110 after voltage drop, but given the distances of the wire runs in the structure, expected). I was supersized no issues though.
    Now if it was a 15 amp outlet, at 120v, so 12 amp charge speed, I think It would have taken the first couple days before I hit the 100% (When it's a emergency, or someone is in the hospital, I don't hesitate to use 100% and keep it at that. Never know if you will need the extra, and that is more important!).
     
  7. Cosmacelf

    Cosmacelf Active Member

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    120v charging works great if you have the time.

    If you can find a 20A outlet (and have the Tesla 20A adapter), that'll give you about 42% faster charge rate over the included 15A adapter due to less overhead losses.
     
  8. Atebit

    Atebit Member

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    Last summer I had to keep my S in storage in a 1 bay garage with an outlet in the ceiling for a garage door opener. The garages were in banks of 5 each and I just assumed they were probably all on a shared breaker. I dialed my charge rate down to 7A and didn't have any issues. I checked the outlet, surrounding ceiling and charging cord frequently for overheating at the beginning just to be doubly sure. Now I did not drive the car at all during this time, so a driveable SOC and how long it took to get there wasn't a concern for me. Every 3-5 days it would charge for a few hours to top the battery back up to 50%
     
  9. linkster

    linkster Member

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    +1

    I get ~100miles/day @12a and ~125miles/day @16a.



    @island

    So glad your son is home for Christmas!
     
  10. aarossig

    aarossig Member

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    Glad to hear things are better!

    Agreed. That is mostly the plan. I think even at 5 - 8A, I can probably keep the car full enough or at least recover some of the mileage from the previous day (30 miles typical).

    I have access to free ChargePoint at the office but have heard it is generally crowded. I usually work 11-8pm so I can likely move my car at dinner time and get a couple of hours of faster charging in after everyone else has gone home and before I leave.
     
  11. scottm

    scottm Active Member

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    I think the question should be what's the highest charging current you can get from a 110 outlet?

    This is something I routinely try to figure out by doing some experiments using the Tesla 5-20 adapter, and a cheater cord that adapts that to a 5-15 plug, which then gets inserted into the test subject outlet. I dial down the amperage on the center console to 12 and keep an eye on the voltage, then over time of several minutes punch up amperage by one amp at a time... if voltage drops (to below 109) I know the onboard computer will kick down the amps automatically to try and keep charging. But in performing this experiment I often find it's possible to pull 16A continously (the maximum the 5-20 adapter will allow) and stay at or above 116V.. in parking lots where there are rows and rows of outlets meant for block heaters. I think they're overbuilt sometimes with 20A breakers and wiring and just have 5-15 outlets installed instead of 5-20. Just a guess.
     
  12. aarossig

    aarossig Member

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    I plan to answer that question when visiting my parents up in Canada and have access to the breaker panel. My Dad is a carpenter so I'm sure he would love to fiddle with this sort of thing and see what kind of power we can pull from the plug that he installed himself.
     
  13. brkaus

    brkaus Member

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    Low current or not, the apartment may not want to pay for your electricity out of the common budget (or set the precedent).
     
  14. tga

    tga Active Member

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    Old cars had a hard limit at 20A when charging on 120V. This did not depend on single/double chargers or firmware version; it was a limitation in the charging hardware. Later cars removed this limit, and have been charged at [email protected], using TT-30P -> 10-30R/14-30R/14-50R adapters (TT-30 is a [email protected] outlet often found in RV parks):

    It IS possible to charge at 24A from a 120V TT-30 plug...

    NEMA does define 5-30 and 5-50 outlets (30A and 50A, respectively at 120V), but your chances of encountering them in the wild is pretty much 0.
     
  15. aarossig

    aarossig Member

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    That is very possible and another reason that I don't want to use this as my primary means of charging.
     
  16. scottm

    scottm Active Member

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    Yes, you can get 16A out of a 5-20 adapter on the mobile charger.

    And I've done better than 24A on 120V!

    Using a 15-40 adapter with a cheater cord to a TT-30 plug... at an RV park. I started with 24A then dialed up and found I could get 30A @ 120V out of that TT-30 receptacle. No circuits blown, but I didn't want to push it further.
     
  17. brkaus

    brkaus Member

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    Assuming your units are individually metered, and it's near your unit, you might consider turning off all the breakers in your unit and see if the power is coming from there.

    If it is, your probably safe charging with the standard current for the plug type and using it as much as you like. It's your dime.

    If not, it's probably on a string with ~6-12 other garages. The risk then isn't what it handles steady state, it's what happens when some other garage plugs in a vacuum or heater and trips the breaker. You have no control of the other loads (which you likely understand and is why your asking about lowest possible charge rate setting rate to minimize risk).
     

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