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UMC Charging Rate Drop

Discussion in 'Model S: Battery & Charging' started by clx, Apr 6, 2015.

  1. clx

    clx Member

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    #1 clx, Apr 6, 2015
    Last edited: Apr 6, 2015
    Hi,

    Does anyone know if the UMC charges the car in constant rate? When I first plugged it my 240v outlet, my car had 140miles left (I have 85kwh) it start charging at 40Amp, and it said the estimated charge time was 3 hours 20 mins (set to charge 90% full). When I checked again 3 hours later, the battery was at about 80% and it shows I still have more than 1 hr left to charge; the dashboard is showing the warning message "Weak Power or Ext Cable Used", and the car is being charged at 30amp.

    My garage has another EVSE charger for the Nissan Leaf, that charger plugs into a 6-50 outlet that I had an electrician installed last year. During the installation, I asked the electrician to put in the correct wiring to support up to 80AMP circuit since I was thinking getting a model s with dual charger at the time. When I took delivery, I bought a 14-50 -> 6-50 adapter from Tesla SC, when I need to charge, I unplug the Leaf charger and plugged my UMC into the same outlet. Could that be the culprit?


    Thanks!
     
  2. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    The drop in amps is because the car thought that there was a potential electrical safety problem. First thing to do is to check the various connection places, UMC, and breaker to see if any are overly warm (after a couple of hours of charging). Because you unplug and plug frequently, the receptacle may be wearing or need to have the connections tightened.
     
  3. supratachophobia

    supratachophobia Active Member

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    It's the car thinking there is an issue when there most likely isnt. The severity or how often it occurs seems related to what firmware you are on. I will say that after 4 on-board chargers, two UMC's, and three charge ports it hasn't happened in two weeks. And no, it's not an electricity issue at the site.
     
  4. FlasherZ

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

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    This is not true, and you can't rule out an electricity issue at the site based on your experience.

    For some people, it's the UMC. For some people, a component in the car (charger). For others, it's a larger than normal voltage drop due to long conductors or undersized conductors. For others, it's a misbehaving appliance or a load-related condition (transformer too small, etc.)

    It is unlikely to be the wiring to your HPWC outlet, if indeed they used #3 wire to supply the outlet as you asked. However, it could be due to an overloaded transformer, long run from transformer to your panel on undersized conductors, etc. Can you start by giving us the voltage that the Tesla displays at 0A charging, and when it reaches 40A?
     
  5. clx

    clx Member

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    Is there a quick way to find out if it's the electrical wiring issue without getting another UMC?
     
  6. FlasherZ

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

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    We'll need some information. When you first plug the car in, look on the display and tell us what voltage it reports while charging at 0A and at 40A... that'll be a good first start.
     

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