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Marina Charging - NEMA L5-30P to NEMA 14-50

LoudMusic

Active Member
Jul 21, 2020
1,412
1,644
Arkansas
My car is going to be spending time in marinas the next several months and it would be nice to charge the car while it's parked there. I have a NEMA 14-50 adapter for my mobile connector, but those plugs are definitely not common at marinas. They typically have the 125v/30A "L5-30R twist lock" outlet and the 125/250v/50A "SS2-50R twist lock" outlet. Unfortunately the 50A outlets are almost exclusively at the far ends of the dock. But often times the 30A outlets are next to or even IN the parking lots. Often times there are NEMA 5-15 outlets around as well, and I've actually used them at marinas before, but that's awful slow.

I'm curious what's the best way to get the most power from the 125v/30A that is available. My first thought is to adapt from NEMA L5-30P to NEMA 14-50 and use my existing Tesla adapter and set the car to the recommended 24A. But does the mobile connector fail if it only gets one leg of the power when the NEMA 14-50 adapter is plugged in? If it does fail on single leg then I'd assume all the others do as well and my biggest possible would be NEMA 5-20, which is an insignificant upgrade from NEMA 5-15.

If it doesn't fail, AC WORKS® [EVL530MS-018] 1.5FT EV Adapter 30A 125V L5-30P Plug to 50A EV Adapter Cord for Tesla

Alternatively, this thing is SO CLOSE but it's an L5-20 not an L5-30. ***flips table*** Which curiously isn't even listed in the standards charts that I'm looking at.


Older Posts (2015, 2013)

Well I typed all that up so I'm posting this new thread. But I also just found this, which didn't come up in a search on their site but did come up in a search on Google.


Problem solved. Have a nice day ;)
 
On road trips, I always carry a 5-20 UMC adapter. I've used it several times in hotel and motel parking lots instead of the 5-15 UMC adapter. Gives a couple extra mph of overnight charging. If you need L5-20, off the shelf L5-20P to 5-20R adapters are available from any number of places.

For L5-30, it might be a better plan to buy an off the shelf L5-30P to TT-30R adapter - again from any of a number of places. Then buy the TT-30 UMC adapter from evseadapters. (I see they are on backorder right now. But given how popular a product it is, I'd think they'll have more in Real Soon.) The nice thing about TT-30 is that there are quite a number of off-the-shelf extension cords, adapters, and repair parts available at reasonable cost due to its widespread use in the RV community.

If Tesla were to ask me which one additional UMC adapter they should offer, I would easily vote for TT-30.
 
The nice part of EVSE Adapters is they properly/automatically set the max amperage. That is (IMHO) the best option. Otherwise, you have to manually set/verify the amperage on the MCU before each time you connect. When you're in a shared/public space, you might not have easy access to the breaker panel should you forget or set it incorrectly. (i.e. Often people forget about the 80% rule, and end up with frequent breaker trips; or worse...)
 

mociaf9

Active Member
Oct 18, 2018
3,203
6,685
CA
Well I typed all that up so I'm posting this new thread. But I also just found this, which didn't come up in a search on their site but did come up in a search on Google.

Problem solved. Have a nice day
I agree with wws, unless you're really going to be making regular usage of the L5-30 outlet, in the long run the more useful move would be to buy (or make) a normal L5-30 to TT-30R adapter and then get a TT-30 plug for the Tesla UMC from EVSE Adapters. It would be a bit more expensive as you're paying for 2 items, but you have the added benefit that the TT-30 adapter has waaaay more potential utility because it's such a common outlet type to run into at campgrounds/RV Parks/etc. If I was going to live at the marina and be charging there every day, I would go with the L5-30 UMC adapter alone. But that's the only situation I'd do that for.
 
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LoudMusic

Active Member
Jul 21, 2020
1,412
1,644
Arkansas
I agree with wws, unless you're really going to be making regular usage of the L5-30 outlet, in the long run the more useful move would be to buy (or make) a normal L5-30 to TT-30R adapter and then get a TT-30 plug for the Tesla UMC from EVSE Adapters. It would be a bit more expensive as you're paying for 2 items, but you have the added benefit that the TT-30 adapter has waaaay more potential utility because it's such a common outlet type to run into at campgrounds/RV Parks/etc. If I was going to live at the marina and be charging there every day, I would go with the L5-30 UMC adapter alone. But that's the only situation I'd do that for.

That definitely makes sense, but I also have the NEMA 14-50 UMC adapter, which can be used at nearly as many campgrounds as a TT-30, and to significantly greater advantage.

I think there's also some value in not having to daisy chain adapters. Performance, safety, personal ease of use, and the way other people perceive "EV life" are all improved by eliminating that one part.
 
While the 14-50 is definitely much faster, the TT-30 is much more common at campgrounds in Ontario. The Ontario Provincial Parks at their electrical sites usually have a 5-15 and a TT-30 but no 14-50. At marinas the L5-30R is also much more common than any other plug. It is best to set up your adapters that the maximum safe current is automatically set so you do not have to remember to turn down you current draw. If you are daisy chaining adapters I suggest turning the current draw down a further ~10-20% than the auto selected maximum. (eg at a L5-30 where you have a daisy chain the max short term draw is 30a, continuous draw is 24a so you set the draw still lower at 20-21a. Yes it s a bit slower but you decrease the chances of overheating etc If you have any worry you may also sleep a little sounder. This is still faster than a 5-15!)
 

LoudMusic

Active Member
Jul 21, 2020
1,412
1,644
Arkansas
While the 14-50 is definitely much faster, the TT-30 is much more common at campgrounds in Ontario. The Ontario Provincial Parks at their electrical sites usually have a 5-15 and a TT-30 but no 14-50. At marinas the L5-30R is also much more common than any other plug. It is best to set up your adapters that the maximum safe current is automatically set so you do not have to remember to turn down you current draw. If you are daisy chaining adapters I suggest turning the current draw down a further ~10-20% than the auto selected maximum. (eg at a L5-30 where you have a daisy chain the max short term draw is 30a, continuous draw is 24a so you set the draw still lower at 20-21a. Yes it s a bit slower but you decrease the chances of overheating etc If you have any worry you may also sleep a little sounder. This is still faster than a 5-15!)

The very limited exposure I have to US campgrounds, city/state/national, the 14-50 has always been available. Maybe we run air conditioners more in our RVs?

I've used my EVSE L5-30 a few times now and it's been great. Charging at 3kw is way better than 0kw or even 1.5kw (which I've done previously for more than a month as my primary).

Unfortunately these additional adapters are kind of expensive, so choosing carefully is probably the best route. And with Supercharger locations becoming so much more common, simply having a trickle charge on 5-15 might be enough and fill up at the nearest Supercharger when needed.
 
The marina where I kept my boat has pedestals very near the parking lot so I worked out an agreement where they let me charge my MS from whichever pedestal was idle. I made up an L14-50 adapter and an L5-30 adapter using the guide from @Cosmacelf and cost me very little. An unexpected side benefit occurred while traveling the Oregon coast when a marina manager let me charge for free if we had dinner at his restaurant.

F5EED033-3164-4DCD-A500-03D37F642233.jpeg
 

LoudMusic

Active Member
Jul 21, 2020
1,412
1,644
Arkansas
Ok this is now the second time this has happened. I've plugged my car in using my handy-dandy L5-30, checked the car to see 24A going in and a time remaining of like ~16 hours or something, and walked away. A couple hours later I pop open the app to check on the car because I'm neurotic and discover it's showing 12/12A. The previous time it did this I simply unplugged from the car and plugged back in and it went back to 24A until it reached the set limit. I don't recall the outside conditions last time, but it's mildly warm today, upper 80s here in South Portland, Maine. But the car is showing that the MAX is 12, not just that it's adjusted down to 12 on a 24A available adapter. Has anyone had this happen with Tesla branded adapters or 3rd party adapters? I'll need to check the manufacturer's site for references to this. I've only used my Tesla NEMA 14-50 at home and I'm fairly certain that's never happened with that adapter.

I'm about to walk out there and do the unplug/plug (turn it off and back on again) routine since I'll be wanting a full charge for another countryside road trip tomorrow but it's no joke a quarter mile walk from my boat to the car. We get stuck out on the end of marinas because our catamaran is too wide to fit in normal boat slips :(
 
A couple hours later I pop open the app to check on the car because I'm neurotic and discover it's showing 12/12A.
Just a guess, but did you check the receptacle for heat? It’s possible you plugged into an old, corroded receptacle that heated up to the point where your Tesla dropped the amperage. I would have expected the max amperage to keep showing 24 and the actual 12 (12/24) but perhaps the software limits the amperage by dropping the max. And while you’re at it, check your L5-30 adapter to be certain that’s not the issue.
 

LoudMusic

Active Member
Jul 21, 2020
1,412
1,644
Arkansas
Just a guess, but did you check the receptacle for heat? It’s possible you plugged into an old, corroded receptacle that heated up to the point where your Tesla dropped the amperage. I would have expected the max amperage to keep showing 24 and the actual 12 (12/24) but perhaps the software limits the amperage by dropping the max. And while you’re at it, check your L5-30 adapter to be certain that’s not the issue.

I suspect it has something to do with the outlet I was using. Later last night I ended up moving the car to another spot after all the cars had left and it charged overnight at 24A. In fact it's still charging at 24A this morning with several hours to go because it only got 12A for so long :(

How does the UMC detect temperature at the outlet? I didn't notice any unusual heat when I unplugged and moved it, but again it had already been reduced to 12A for quite a while.
 
I suspect it has something to do with the outlet I was using. Later last night I ended up moving the car to another spot after all the cars had left and it charged overnight at 24A. In fact it's still charging at 24A this morning with several hours to go because it only got 12A for so long :(

How does the UMC detect temperature at the outlet? I didn't notice any unusual heat when I unplugged and moved it, but again it had already been reduced to 12A for quite a while.

There is a temperature sensor in the adapters plug. It makes sense that the max current gets dropped, since the UMC would only have the J1772 mechanism for telling the car the max safe current.
 
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How does the UMC detect temperature at the outlet?
My knowledge is sketchy here — hopefully someone with more knowledge will weigh in here — but I believe that as the receptacle heats up there is a corresponding voltage drop which the car treats as an overheated receptacle or wiring. It then drops the amperage draw until the voltage rises to an acceptable level.
 

Rocky_H

Well-Known Member
Feb 19, 2015
7,830
9,851
Boise, ID
My knowledge is sketchy here — hopefully someone with more knowledge will weigh in here — but I believe that as the receptacle heats up there is a corresponding voltage drop which the car treats as an overheated receptacle or wiring. It then drops the amperage draw until the voltage rises to an acceptable level.
Yes, that mechanism is also there to look at potential resistive points causing voltage drop in the circuit as a whole, and it also has the temperature sensor in the plug head as @wws mentioned.
 

LoudMusic

Active Member
Jul 21, 2020
1,412
1,644
Arkansas
I was up until about 3 AM and checked the car in the app and it was still making 24/24A. This morning when I got up around 9 it was showing 18/24A.

I think this marina's power grid might suck! :D

It's plugged back in after today's adventure (TWO covered bridges in ONE day!). We'll see how long it holds 24A.
 

Rocky_H

Well-Known Member
Feb 19, 2015
7,830
9,851
Boise, ID
I was up until about 3 AM and checked the car in the app and it was still making 24/24A. This morning when I got up around 9 it was showing 18/24A.

I think this marina's power grid might suck!
Ah, yes, I think that is the reduction because of sensed voltage drop. When that gets triggered, it will try again with three fourths of the current it was trying before. Using 18 instead of 24 seems to indicate that.
 

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