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Hello everyone. I just realized i'm getting really slow charging time when i plug in my smart. the other day I was at about 15% battery and the charge time was 17 hours, today i was at about 50% and the charge time says 9.5 hours, and that's if it's set to speed 2, on speed 1 its 11 hours. Has anyone had this issue, or knows what the problem might be? I use a new 10 gauge extension cord which runs about 75ft. Any help is appreciated!
 

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Max charge speed from the internal charger is 3.3kA/hour, meaning 5.3 hours, or about 20% per hour on an L2 charger at 14A or better. With the L1 EVSE (like the one that comes with the car), you're only pulling [email protected] tops, or about 7% per hour. At 8A, it's just under 5% per hour.

Both of the times you note come out to just about 5%/hour, so my bet is you're only charging at 8A. That could be the L1 EVSE is set to 8A, or the car itself is limiting to 8A due to the setting on the in-dash menu. The latter is my bet.

Also keep in mind that the "predicted" time is based on the previous charge cycle and what it was hooked up to then. (Still broken in V9.) So if you plug in a L2 charger after an L1, it will still say 11+ hours, despite the real EVSE capacity.
 

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Also keep in mind that the "predicted" time is based on the previous charge cycle and what it was hooked up to then. (Still broken in V9.) So if you plug in a L2 charger after an L1, it will still say 11+ hours, despite the real EVSE capacity.
This is true, but if you check again about 1-2 minutes after you've plugged in and set the OEM charger to the max charging setting (you may have to press the lock button on the key to turn on the dash display and show the updated est. charge time), it will have the correct (re-calculated) charge time estimate. This is assuming you've set the in-car dash settings to always accept the Max Charge Rate. It's recommend to leave it on this setting and control the charge rate externally via the charge adapter or charge station.
 

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Also, the ambient temperature plays a big role in actual charge times vs. the car's estimated charge times.

When the ambient temperature is hot (>80 degF) or cold (<32 degF) the charge time is negatively affected. The charge controller is designed to charge the battery without overheating it. In hotter weather, the battery has to run the coolant system and the charge controller has to throttle charging power to maintain optimal battery/charge-controller temperatures. The same is true for heating the battery in colder temperatures.

I've noticed that on a nice day (ambient temperatures between 70 and 80 degF) that the car will charge faster (between 1-2 hours faster on the OEM charger) compared to a hot day (ambient temperatures between 80-100+ degF).

If the ambient temperature is above ~90 degF and you are in the "Charge Now" mode vs. the "Departure Time" mode while using a 3.3kW (240V, Level 2) charge station, the charge controller can potentially overheat and prematurely terminate the charging process. When this has happened to me, I am usually left with about 94-96% SOC. To avoid a premature termination of the charging process, change the charging mode to a specific "Departure Time".

Set your departure time using these general suggestions:
7+hrs after your plug-in time if you have a SOC between 0-10%
6+hrs after your plug-in time if you have a SOC between 20-40%
4+hrs after your plug-in time if you have a SOC between 50-60%
2+hrs after your plug-in time if you have a SOC between 70-80%
(Note: it is not recommended to plug-in the charge adapter if you're above 80% due to increased stress on the battery.)

The basic concept is to set the Departure Time far enough in advance that the charge controller can adequately regulate the charging process in order to get a full 100% SOC upon completion. I usually set my Departure Time to 6:00am which is when I leave for work; however, the battery is usually charged to 100% by 7-8pm (using a Level 2 charger) with an initial 50-60% SOC at my 4:30pm plug-in time.
 

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I once accidentally left the Amps setting on 8A, and was connected to 110V over night. Sadly, 10 hours later I had only recovered 70% of the battery.

That was the kicker for me, I immediately upgraded to a 220V circuit with a ClipperCreek 20A EVSE. Now it never takes more than 4-5 hours to recharge. And most of the time I get back to full in < 2 hours (because I rarely use more than 50% of the pack).

Admittedly, I wish that M-B would sell us the 22 kWh DCQC in the US, even if we can't connect it anywhere. That won't be the case forever.
 
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