Surviving on a regular 110v trickle charging

[SSedan]

I would love to see the original reference to this. I'm not saying it is wrong, but it sounds rather excessive to me for an idle current on a charger. I plug my car into a 120 volt outlet through a 15 amp rated remote control switch which also measures current. When not charging the car seems to draw a mere 2 watts. I will say I have never seen my model X charging at 4 mph on a 120 volt outlet. I get 2 or 3 depending.... on what I don't know. I figured the wattage must come to 2.5 mph and it varies a bit making it 2 or 3 mph. But doing a quick calculation shows if all the power were going into the battery it would be 4.14 mph at 115 volts (which I commonly see). Hmmm... 400 watts lost would pretty much put the charging rate around 3 mph.

Still, I'm surprised. I'm an electrical engineer, but high voltage and power switching regulator design is not my area of expertise.

The 400watt number is long accepted and includes things whatever else might be in use to support charging like extra computer activity. I haven't looked into it but I would think the coolant pumps run just to keep temp balanced even if cooling is not needed, going to be some draw for contactors in the car and the UMC/HCWC, some cable resistance heating losses.

I believe part of the justification for this accepted number is the published and observed difference going from 15-20amp outlet.

 

[f-stop]

Two years and counting. I'm a little embarrassed because I'm just lazy about getting a 50 amp line installed. I have a signature wall charger still in the box

I don't have a regular commute anymore but if I had my previous 60 mile per day commute, it would not be a problem plus my previous employer now offers free charging at work. There was only one time where I had to stop at a SC starting out because I couldn't charge enough overnight.

I have a 90kWh pack which supposedly is prone to faster degradation... I've lost maybe 1% (2-3 miles) in 2 years and 19k miles. My charge level is usually between 50-90% and I supercharge about 20-25 times a year. Just sayin' ...

I am in almost exact same situation as @BlueRocket - in a couple weeks it'll be the 3yr anniversary of getting my 70D and charging on 120V at home ever since then. (my signature HPWC is also still in a box, it may finally get installed next year...)

It's perfectly fine for my usage since I don't have a regular commute and maybe drive only ~40km on a typical day, and sometimes make use of one of many public J1772 chargers if there's one at a destination around town and I’m parked there for an hour. I typically charge to 65% overnight, getting +6km/hr of charge at home, 120V/12A. Battery pack health seems excellent, 30,000km mileage after 3 yrs, and my 70D's rated charge is still almost exactly same as on day 1 (90%, 345~347km rated / 100% 384~386km rated).

so in my use case, charging at home on a 120V/15A circuit works well - but If I had a longer daily drive or lived in a colder climate things would be different.

 

[davewill]

To respond to the actual topic of this thread


Does Tesla have an adapter for that connector? My car came with a 120 V NEMA 5-15P adapter and a NEMA 14-50P adapter. When I looked on the web site the only other adapter I recall seeing (at least that I might be interested in) was the Chademo for $500. A friend has a NEMA TT-30 120 volt outlet in her barn intended for her horse trailer. While it would only double my charging rate (but maybe a bit more given the 400 watt PSU loss) I coudn't find an adapter. So no way to plug in and get the higher current.

You can get one here: TT-30 Adapter for Tesla Model S/X/3 Gen 2

 

[davewill]

A 120v outlet will certainly work for a lot of folks, but sometimes, you can find yourself at home, wanting to leave sooner than a 120v outlet can get you ready. Of course, if you have Supercharging nearby, that would do the trick.

 

[xdms]

A 120v outlet will certainly work for a lot of folks, but sometimes, you can find yourself at home, wanting to leave sooner than a 120v outlet can get you ready. Of course, if you have Supercharging nearby, that would do the trick.

This is true. If you need to get out and go in a hurry before the 120v outlet can charge you where you need to go, having chargers nearby really help. Luckily, I have at least 4 supercharger stations all within 30-45 minutes away from where I live and over a dozen destination and 3rd party charging stations (1 chademo charger being 0.2 miles away) near where I live.

 

[follow.johnny]

A 120v outlet will certainly work for a lot of folks, but sometimes, you can find yourself at home, wanting to leave sooner than a 120v outlet can get you ready. Of course, if you have Supercharging nearby, that would do the trick.

Agreed! My commute to work is 20 miles round-trip and been charging on 120v outlet since taking delivery in July. No issue with range anxiety.

• Charging overnight gets me about 50 miles (4-5 miles per hour) and charge to 70-80% for daily commute | 90% for weekends
• 15 minutes away from nearest Supercharger ($0.27/kWh)
• Free 2 hour charging at work using ChargePoint station ($2.50 rate for every additional hour)

 

[BlueRocket]

Some real numbers on charging at 120 volts / 15 amps. Cold weather struck here so it was about 47 degrees in my garage. I'm not sure if any battery heating is done and is not registered by the car in the "number of kWh charged" so efficiency number below may be off somewhat.

I hooked up a Kill-a-Watt device to the charging cable to measure actual kWh delivered versus charge reported by the car. The Kill-a-Watt registered 31kWh used to charge the car 25 kWh. That is 81% efficiency which is in line with what others have quoted.

 

[gnuarm]

You can get one here: TT-30 Adapter for Tesla Model S/X/3 Gen 2

I think my friend will let me put in a NEMA 14-50 outlet in her garage. Then I can charge fast *and* precondition. Woo, hoooooo!

 

[gnuarm]

Some real numbers on charging at 120 volts / 15 amps. Cold weather struck here so it was about 47 degrees in my garage. I'm not sure if any battery heating is done and is not registered by the car in the "number of kWh charged" so efficiency number below may be off somewhat.

I hooked up a Kill-a-Watt device to the charging cable to measure actual kWh delivered versus charge reported by the car. The Kill-a-Watt registered 31kWh used to charge the car 25 kWh. That is 81% efficiency which is in line with what others have quoted.

Yeah, that's actually pretty sad. The AC input charging is limited to about 17 kW if I understand it correctly (72 amps/240 volts) vs 1.4 kW on a regular 120 volt outlet. I suppose 81% efficiency is not so bad.

I have a switch controlling my 120 volt charging which also indicates power (but not energy, maybe, not sure). It regularly displays 1.2 kW when charging the Tesla while the car displays 114 volts and claims 12 amps. I'm not sure the 12 amps is actually a measurement, rather it is a limit.

I may spend a little time on this. I don't have a 20 amp circuit, but can compare 120V 15A to one of the higher current chargers.

 

[ChadFeldheimer]

Some of the 19% energy loss is surely due to losses to heat in the battery cells. It would be quite interesting to see how efficiency scales at higher charging rates.

I have been charging on 120V for the past few months, with a 25 mile round trip work commute and sporadic non-commute use. Zero range anxiety. I still plan to install a 14-50, but it is lower priority than a litany of other home improvement projects.