NEMA TT-30

http://cosmacelf.net/Home Made Adapters.pdf

Page 7.

You can get the adapter that goes directly from NEMA 14-50 to TT-30 at Wal-Mart, local cost here in Milwaukee is $14.99, They then also have another to go from TT-30 to standard 120v plug. I did try going from 14-50 to the TT-30, then down again to the 120v standard, to see if I could get 16a charge from a 20amp 120v outlet, though, the UMC would not turn on.

rpavlicek said:

But is the walmart one designed properly to work with the model S? evseadapters.com says:

Is the wiring the same in the walmart version? Have you tested it?

I also saw this one on amazon: Amazon.com: Camco 55185 RV Powergrip 30M/50F AMP 18 Dogbone Electrical Adapter with Handles 3750W/125V: Automotive

Click to expand...

The off-the-shelve adapters are not the same. They connect both L1 and L2 to live, with the result is the UMC gets 0V out of them. It's really just meant for RV's with 2 x 110V legs.

deonb said:

The off-the-shelve adapters are not the same. They connect both L1 and L2 to live, with the result is the UMC gets 0V out of them. It's really just meant for RV's with 2 x 110V legs.

Click to expand...

Right. In RV parlance, I believe they are called 'dogbones' usually available for loan at RV parks, but will not power the UMC. To the best of my knowledge, the only way to use the TT30 is to fabricate an adapter as explained in the referenced pdf.

Also, note that 20 Amps is the most the car will allow when the voltage is 120. OK if spending the night, but painfully slow otherwise.

There are RV Park locater apps that allow filtering for 50 Amp sites.

Puyallup Bill said:

Right. In RV parlance, I believe they are called 'dogbones' usually available for loan at RV parks, but will not power the UMC. To the best of my knowledge, the only way to use the TT30 is to fabricate an adapter as explained in the referenced pdf.

Also, note that 20 Amps is the most the car will allow when the voltage is 120. OK if spending the night, but painfully slow otherwise.

There are RV Park locater apps that allow filtering for 50 Amp sites.

Click to expand...

Basically it's barely better than plugging into a normal 120 outlet because these outlets are NOT 240. Not really worth it. You really want 50 amp service or don't bother (unless you happen to want to camp there anyway, but even then I'm not sure I'd bother with the trouble of a special adaptor rather than finding a normal plug).

Hey Rpavlicek,

Just to be sure that it's clear what others are saying; Even with the most ideal adapter, (say a home made J1772 charger) you would only be able to charge at 120V @ 20 Amps from a TT-30 (current limited by the car). This means that charging from a TT-30 would yield about 8 mph, where as charging from a 50A hookup would yield 31 mph.

Peter

bluetinc said:

Hey Rpavlicek,

Just to be sure that it's clear what others are saying; Even with the most ideal adapter, (say a home made J1772 charger) you would only be able to charge at 120V @ 20 Amps from a TT-30 (current limited by the car). This means that charging from a TT-30 would yield about 8 mph, where as charging from a 50A hookup would yield 31 mph.

Peter

Click to expand...

And in real life nobody's ever got close to 8mph from 120 (it's much less efficient). My guess is that you'd get more like 4-5 miles per hour of charging.

we are really talking about two different things here: on the go charging vs destination charging. Certainly a tt30 adapter is useless for on the go charging but if modified properly for the S has the potential to double the rate of charge compared to 12A at 120 when parked at your destination for several days, which has been surprisingly common this summer. On several occasions so far this summer, tt30's have been the only option other than 12A/120 and there is a huge difference in speed. it's a matter of staying a couple of nights in one spot vs having to stay nearly a week to get a full charge!

the wall mart/amazon/RV version will not work at all on the S, I've tried it! there is a simple tt30 to 15-5 (standard 110 wall outlet) that will work with the UMC but only allow 12A... useful to have if tt30's are all you have access to, which is surprisingly more common that I would have thought.

gregincal said:

Basically it's barely better than plugging into a normal 120 outlet because these outlets are NOT really 240. Not really worth it. You really want 50 amp service or don't bother (unless you happen to want to camp there anyway, but even then I'm not sure I'd bother with the trouble of a special adaptor rather than finding a normal plug).

Click to expand...

- - - Updated - - -

Even 5 miles an hour would be a welcome improvement over 2-3 mph, when you are parked for days on end.

gregincal said:

And in real life nobody's ever got close to 8mph from 120 (it's much less efficient). My guess is that you'd get more like 4-5 miles per hour of charging.

Click to expand...

The NEMA TT-30P RV Plug to 14-50R Adapter shown on the following page is the only one I've seen made for the S that is commercially available (and I'm glad to see one, Phill at EVSE upgrade didn't see the point, I'm glad these people did!): http://evseadapters.com/adapters-for-tesla-model-s.php

I've used my home made TT-30 adapter and it worked great giving me about 7 mph. For all day or overnight charging it is definitely better than the regular 120v plug. I also built myself a dual TT-30 adapter that allows me to plug into 2 TT-30 plugs if they happen to be on different legs. This would enable me to charge at 240v 24 amps which is the same charge rate as a 14-30 plug. Building such an adapter is much more involved.

- - - Updated - - -

rpavlicek said:

Thank you!

I assume the "NEMA TT-30P RV Plug to 14-50R Adapter" from the evseadapters.com website would do the trick?

Click to expand...

It is indeed supposed to be wired correctly for the tesla, although some people recently bought one and found them wired incorrectly. Evseadapters knows they made a mistake and presumably new orders will be correct.

Cosmacelf said:

I've used my home made TT-30 adapter and it worked great giving me about 7 mph. For all day or overnight charging it is definitely better than the regular 120v plug.

Click to expand...

OK, if you're doing a camping trip I can definitely see how it would be useful. Two nights would give you a pretty good charge even if you did a bit of driving during the day.

I have now visited two friends home's this summer where a tt30 was the only other option... surprised to see tt30's at people's homes, in both cases they were apparently installed by previous owners who had RV's. I really wish Tesla would come out with a tt30 adapter that would allow 30A charging. If you are traveling out of town to a friends house and want to use the S for a few daily trips and still get it charged up all the way for the trip home, every little bit counts. being behind the 8-ball the whole trip is stressful, BTDT...

gregincal said:

OK, if you're doing a camping trip I can definitely see how it would be useful. Two nights would give you a pretty good charge even if you did a bit of driving during the day.

Click to expand...

100thMonkey said:

I have now visited two friends home's this summer where a tt30 was the only other option... surprised to see tt30's at people's homes, in both cases they were apparently installed by previous owners who had RV's. I really wish Tesla would come out with a tt30 adapter that would allow 30A charging. If you are traveling out of town to a friends house and want to use the S for a few daily trips and still get it charged up all the way for the trip home, every little bit counts. being behind the 8-ball the whole trip is stressful, BTDT...

Click to expand...

Actually, just like you can only draw 40 amps from a 14-50, you could only draw 24 amps from a TT-30 (continuous load can only be 80% of max load). So if 20 amps gives you 7 miles per hour, 24 would give you 8.5 miles per hour. I'm not sure why Tesla limits 120v charging to 20 amps.

I doubt there is a good reason to limit 120v charging to 20 amps. My guess is its a software imposed limitation and the software engineer never knew about TT-30s.

that's a good point, and I'd still be happier with an extra 4A.

gregincal said:

Actually, just like you can only draw 40 amps from a 14-50, you could only draw 24 amps from a TT-30 (continuous load can only be 80% of max load). So if 20 amps gives you 7 miles per hour, 24 would give you 8.5 miles per hour. I'm not sure why Tesla limits 120v charging to 20 amps.

Click to expand...

Cosmacelf said:

I doubt there is a good reason to limit 120v charging to 20 amps. My guess is its a software imposed limitation and the software engineer never knew about TT-30s.

Click to expand...

I suspect otherwise. Every other production EV I am aware of limits 120V to 12A even when it's capable of charging at up to 30A on 240V... There's probably a good reason - an EE could tell us...

I am not an EE but most 120VAC outlets are on 15A breakers. I wouldn't be surprised if the logic was about the futility of slow charging and difficulty of determining if a random outlet was on a higher amp breaker.

Two things:

First, using that adapter above on an RV or other appliance that requires 240V will likely harm or destroy some appliances, so label the thing very very clearly.

I am not an EE but most 120VAC outlets are on 15A breakers

Click to expand...

Not true. Appliance circuits are required to be 20A in some areas (kitchens) and I know plenty of homes that use 20A circuits and 12 AWG throughout the entire structure just to minimize nuisance tripping for power-hungry homes.