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Am I overthinking things?

DopeGhoti

Active Member
Aug 28, 2019
1,229
1,391
Phoenix, AZ
My employer offers a few EV charging spots, but the only power outlets available are 5-15/5-20, and 6-20. There is only one of the latter. I plan on going to the nearby service center today to see if they have any 5-20 and/or 6-20 adapters for my mobile charger, but when looking around at various charging rate comparisons, I don't see much difference between charging at 5-15 and 5-20. Should I even bother with the 5-20 connector, or does the extra amperage actually help with any significance in comparison to the standard outlet's trickle charge?
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,043
12,097
San Diego
My employer offers a few EV charging spots, but the only power outlets available are 5-15/5-20, and 6-20. There is only one of the latter. I plan on going to the nearby service center today to see if they have any 5-20 and/or 6-20 adapters for my mobile charger, but when looking around at various charging rate comparisons, I don't see much difference between charging at 5-15 and 5-20. Should I even bother with the 5-20 connector, or does the extra amperage actually help with any significance in comparison to the standard outlet's trickle charge?

If this is your main way to charge it might be worth the 5-20 Connector. It depends on if you’re having a tough time “keeping up” as is.

There is a significant fixed overhead so adding an extra 480W is fairly beneficial. Takes you from ~1150W net to about 1650W.

A lot of recent threads about this here.
 

Tigerkc

Member
May 25, 2019
44
31
SF Bay area
5-20 allows 16A constant load, vs 12A for 5-15, so that is 1/3 more watts per hour.
Before going off to purchase the 5-20 adapter, I would suggest you check out the 5-15 plugs by charging at 12A to see if there is any significant voltage drop. Depending on the installation, if the wires are already long, and if you are seeing a large voltage drop even at 12A, then these plugs may not allow you to charge at higher amperage.
 

DopeGhoti

Active Member
Aug 28, 2019
1,229
1,391
Phoenix, AZ
I lucked out, they had 5-20 and 6-20 adapters, so I went ahead and snagged them both (I've seen other Teslas parked here, and they were using the 5-20 and reporting better charge rates than 5-15), and when I got back from lunch was able to grab the 6-20 connection. As such, by the end of the workday I'll be right around my 90% limit. The voltage doesn't seem to be spectacularly stable; it's drawing 16 amperes, but the voltage fluctuates between 200V and 235V or so. No complaints from the car about the unstable voltage, but should I be concerned about this?
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,043
12,097
San Diego
it's drawing 16 amperes, but the voltage fluctuates between 200V and 235V or so. No complaints from the car about the unstable voltage, but should I be concerned about this?

That seems like a very large variation. I think 5% is generally the acceptable limit. So you're saying you plug in and the voltage drops from 235V to 200V....or it is just randomly changing independent of YOUR current draw? In theory the car could filter out that sort of variation from other sources (in its voltage drop algorithm to check for deficient wiring), but it would not necessarily be a good idea to do so. I'm surprised the car is not reacting.
 
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AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
10,043
12,097
San Diego
5-20 allows 16A constant load, vs 12A for 5-15, so that is 1/3 more watts per hour.

It's more like 40-45% more into the battery due to the overhead. Agreed on checking the voltage drop when using the 5-15 plug to make sure it is adequately wired. Seems like there may be some problems...
 

Bill25cycle

Member
Mar 31, 2011
103
69
I lucked out, they had 5-20 and 6-20 adapters, so I went ahead and snagged them both (I've seen other Teslas parked here, and they were using the 5-20 and reporting better charge rates than 5-15), and when I got back from lunch was able to grab the 6-20 connection. As such, by the end of the workday I'll be right around my 90% limit. The voltage doesn't seem to be spectacularly stable; it's drawing 16 amperes, but the voltage fluctuates between 200V and 235V or so. No complaints from the car about the unstable voltage, but should I be concerned about this?

Wouldn't bother me Ghoti - the juice at my house varies from a high of 245 to a low of around 200 volts (and this is on a nominal 240 volt system) - I've never seen a neighborhood with such lousy juice (there are 5 big brain-dead reasons why my Utility (National Grid) is unintentionally causing this - which I won't bore people here with unless there is interest) as my current sub-division. If your car seems to be working fine you have nothing to worry about.

And if the current is staying at a steady 16 ampere charge rate through the voltage fluctuation of 200-235 you are getting the best you can hope for under the circumstances. Since the charger is not putting out quite as much at 200 as at 235, you are actually giving it and the battery even more of a 'rest'. The vast majority of EV's run cooling fans, pumps, and refrigeration off the High Voltage Battery (even the 12 volt equipment ultimately gets its juice from there), so there is no danger of anything running 'undervoltage'.


I assume almost none of this fluctuation is due to poor connections at the receptacle. If everything seems just luke warm with no hot spots, then everything is cool.
 
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mswlogo

Well-Known Member
Aug 27, 2018
6,069
4,696
MA, NH
I lucked out, they had 5-20 and 6-20 adapters, so I went ahead and snagged them both (I've seen other Teslas parked here, and they were using the 5-20 and reporting better charge rates than 5-15), and when I got back from lunch was able to grab the 6-20 connection. As such, by the end of the workday I'll be right around my 90% limit. The voltage doesn't seem to be spectacularly stable; it's drawing 16 amperes, but the voltage fluctuates between 200V and 235V or so. No complaints from the car about the unstable voltage, but should I be concerned about this?

If it's long run and other cars on the circuit, it might sag. If it swings to much the Tesla / UMC might back off on charge rate.
 

DopeGhoti

Active Member
Aug 28, 2019
1,229
1,391
Phoenix, AZ
I assume almost none of this fluctuation is due to poor connections at the receptacle. If everything seems just luke warm with no hot spots, then everything is cool.
I checked after it'd been charging for about an hour. Nothing seemed unusually hot, though "unusually hot" is a rather high bar in Phoenix generally. That said, nothing on the mobile charger assembly seemed more than vaguely warm to the touch when I poked around.

Is the other plug a 5-20, or 6-20? A 6-20 is a 240 V outlet, and will charge about 2.5x faster than a 5-15.
There is one 5-15, some 5-20s which also accept 1-15 plugs (T shaped rather than - shaped on one side), and one 6-20. I've not yet attempted to connect the 5-20 to see if it can actually get more power than the 1-15.
 

Bill25cycle

Member
Mar 31, 2011
103
69
I checked after it'd been charging for about an hour. Nothing seemed unusually hot, though "unusually hot" is a rather high bar in Phoenix generally. That said, nothing on the mobile charger assembly seemed more than vaguely warm to the touch when I poked around.


There is one 5-15, some 5-20s which also accept 1-15 plugs (T shaped rather than - shaped on one side), and one 6-20. I've not yet attempted to connect the 5-20 to see if it can actually get more power than the 1-15.

Wouldn't you just rather use the 6-20 to get 3200 watts or more to charge your tesla, even at the 200 volt time?
 

DopeGhoti

Active Member
Aug 28, 2019
1,229
1,391
Phoenix, AZ
Wouldn't you just rather use the 6-20 to get 3200 watts or more to charge your tesla, even at the 200 volt time?
As I mentioned, I was on the 6-20 earlier; charged without incident and further monitoring showed that it didn't bounce the voltage so much as it started at 240 and dropped to 200 and generally stayed there. If I have my pick when I park (and I'm lower on charge than I'd like to be) I'll probably opt for the 6-20 connection, but I don't want to hog it from the other EV drivers who might have a more dire need than I. Supercharger near the office notwithstanding, this will be my primary place to charge the car, so it's nice to have a quiver of connectors so that I can hook up to whatever option might be available to me.

Naturally, all things being equal, yes, I would prefer the higher-voltage connection :)
 
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user212_nr

Active Member
Aug 26, 2019
1,407
744
US
My employer offers a few EV charging spots, but the only power outlets available are 5-15/5-20, and 6-20. There is only one of the latter. I plan on going to the nearby service center today to see if they have any 5-20 and/or 6-20 adapters for my mobile charger, but when looking around at various charging rate comparisons, I don't see much difference between charging at 5-15 and 5-20. Should I even bother with the 5-20 connector, or does the extra amperage actually help with any significance in comparison to the standard outlet's trickle charge?

I suppose you can't charge at home? The connector is only $35 so maybe you are overthinking things.
 

DopeGhoti

Active Member
Aug 28, 2019
1,229
1,391
Phoenix, AZ
I suppose you can't charge at home? The connector is only $35 so maybe you are overthinking things.
I cannot. My apartment manager did inquire with their overseers whether I'd be permitted to pay for an electrician to open and install an outlet at the junction at my carport (and I did offer to pay the the electrical usage also), but they were not willing to accommodate facilitating EV charging on their premises. And so my primary charging locations will be the free outlet at my place of employ, or, at need, the Supercharger a few blocks from there.
 

user212_nr

Active Member
Aug 26, 2019
1,407
744
US
I cannot. My apartment manager did inquire with their overseers whether I'd be permitted to pay for an electrician to open and install an outlet at the junction at my carport (and I did offer to pay the the electrical usage also), but they were not willing to accommodate facilitating EV charging on their premises. And so my primary charging locations will be the free outlet at my place of employ, or, at need, the Supercharger a few blocks from there.

Maybe your employer can allow you to pay for the upgrade? Assuming that you plan to stay with them long enough to make that worthwhile.

Another solution is to re-think your apartment situation. Some other building may accommodate.
 

DopeGhoti

Active Member
Aug 28, 2019
1,229
1,391
Phoenix, AZ
Maybe your employer can allow you to pay for the upgrade?

It can't hurt to ask, but as I found today, the 6-20 charger is plenty to get my car topped up, I'm just curious to see what I'll get out of the 5-20 at this point. I'm not going to look a gift horse in the mouth, though.

Another solution is to re-think your apartment situation.

When my lease expires, this is certainly something to consider, but the time, effort, and cost of moving is much more burdensome to me than charging up my car in locations extrinsic to my domicile.
 
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user212_nr

Active Member
Aug 26, 2019
1,407
744
US
It can't hurt to ask, but as I found today, the 6-20 charger is plenty to get my car topped up, I'm just curious to see what I'll get out of the 5-20 at this point. I'm not going to look a gift horse in the mouth, though.
.

If you can get the 6-20 "some of the time" then you should be perfectly fine if your commute is less than 60 miles round trip. Showing up early gets you the 6-20 without fail, but you might just want to talk to whoever else is using it.
 

ewoodrick

Well-Known Member
Apr 13, 2018
5,285
3,732
Buford, GA
My employer offers a few EV charging spots, but the only power outlets available are 5-15/5-20, and 6-20. There is only one of the latter. I plan on going to the nearby service center today to see if they have any 5-20 and/or 6-20 adapters for my mobile charger, but when looking around at various charging rate comparisons, I don't see much difference between charging at 5-15 and 5-20. Should I even bother with the 5-20 connector, or does the extra amperage actually help with any significance in comparison to the standard outlet's trickle charge?
If a 5-15 is sufficient, then no need for the 5-20. If the 5-15 is just not quite enough, then go with the 5-20.
You can order the connectors online.
 

DopeGhoti

Active Member
Aug 28, 2019
1,229
1,391
Phoenix, AZ
If a 5-15 is sufficient, then no need for the 5-20. If the 5-15 is just not quite enough, then go with the 5-20.
You can order the connectors online.

As I mentioned, I picked up the 5-20 and 6-20 already at a nearby service center on a lunch break, so now I can charge just about anywhere I am likely to need to.

I had a good SoC when I arrived this morning, so I went with the 5-20 outlet just so that I could have a read on the charging rate for future reference (and also to leave the 6-20 outlet for one of the other Tesla drivers- I don't want to be rude and claim it for myself every day). My anectodal results so far:

5-15 - ~3mi/hr
5-20 - ~6 mi/hr
6-20 ` ~15mi/hr

Given that my one-way commute is only about twenty miles, I doubt that, road trips notwithstanding, I'll be biting into my supercharging credit a lot before it expires.
 

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