Jesla or Leviton EVB40-PST

[miimura]

Tony, please explain how JESLA can do this. By "automatic" are saying there is no operator intervention required, no firmware changes, no switches to set, no cal pots to readjust, etc, that the JESLA simply self-adjusts all by itself? Is this a pre-existing function of JESLA's firmware?

For example, If a JESLA is plugged in to a 230V, 30A NEMA 10-30R outlet (normally used by an old style electric drier), does it automatically current limit to 24A?

My guess is how it works:
The (imho) expensive conversion plugs have some kind of (inductive) transmitter that is read by the main plug of the jesla. The chip inside the conversion plug is set to 80% of the rated amps and that is what the jesla switches down to as a maximum pwm on the j1772 signal instructing the car charger not to pull more than the intended amps

How did I do Tony ? ;-)

Close. The plug adapters are coded with a resistor to tell the EVSE which adapter is connected. It then sets the pilot signal so that the car will only pull 80% of the plug rating. This is a standard feature of the Tesla Mobile Connector that the Jesla is based on.

 

[miimura]

Or, if you plug it in to a 250V, 50A NEMA 14-50R outlet that only has infrastructure wiring and circuit breaker protection to support 40 amps max, that the JESLA will automatically current limit to 32A? My understanding is the J1772 pilot signal normally tells the connected EVSE how much charging current is allowed, but I am unaware of anything on the AC input side to the EVSE that interprets infrastructure amperage limitations.

A NEMA 14-50 socket should be installed to support 50A. I don't know if the configuration you laid out above is a code violation or not since there is no standard outlet specifically rated for 40A. The Jesla has no way to know what wire and breaker you are using. Since a NEMA 14-50 should be on a 50A circuit, it will signal the car for 40A charging. A 40A breaker should trip after 5 or 10 minutes of 40A draw.

 

[fromport]

The plug adapters are coded with a resistor to tell the EVSE which adapter is connected. It then sets the pilot signal so that the car will only pull 80% of the plug rating. This is a standard feature of the Tesla Mobile Connector that the Jesla is based on.

Could some one with those adapters measure and post the different resistor values for the different adapters ?

 

[Dsinned]

That's what I thought with respect to that scenario . . . e.g. plugging in to a 250V/50A rated outlet (NEMA 14-50R) with infrastructure wiring/protection only good for 40A max. The JESLA has no way to "encode" this AC power source situation and thereby reduce its output current to 32A (i.e. 80% of 40A, not 50A). I have this L2 EVSE AC power situation myself, and I'm sure others may as well. However, Tony's JESLA feature list above implied it can "automatically" current limit appropriately in any situation (using a standard 14-50R to plug in the JESA for its AC power source). He went on to say, this is something that "no other EVSE can do", and that's certainly true. Hopefully, Tony will clarify this for us.

 

[fromport]

That's what I thought with respect to that scenario . . . e.g. plugging in to a 250V/50A rated outlet (NEMA 14-50R) with infrastructure wiring/protection only good for 40A max. The JESLA has no way to "encode" this AC power source situation and thereby reduce its output current to 32A (i.e. 80% of 40A, not 50A). I have this L2 EVSE AC power situation myself, and I'm sure others may as well. However, Tony's JESLA feature list above implied it can "automatically" current limit appropriately in any situation (using a standard 14-50R to plug in the JESA for its AC power source). He went on to say, this is something that "no other EVSE can do", and that's certainly true. Hopefully, Tony will clarify this for us..

Let me try and explain it
When it uses the plain nema 14-50 it will go up to 40 amps.
When use the included nema 5-15 adapter, it measures the resistor that is mounted in the adapter, and "knows" it should limit to 80% of 15 amp = 12 amp and adjust the PWM signal accordingly.
When you buy the additional available plugs:
10-30, 14-30 : they both have another resistor which means the charger will be limited to 24 amps
and the 5-20 which has another resistor value that is limited to 16 amps.
The resistors in the adapter determine the amount of amps drawn.

Hope to have explained it clear enough

 

[Dsinned]

In the case of a JuiceBox, I leave the built-in (firmware based) current limit set to 32A. It is plugged in to a NEMA 14-50R with infrastructure wiring and CB protection rated for 40A max. The car "tries" to pull more amperage, but the JB won't allow it to exceed 32A. This seems like a safer (and cheaper) approach to me. Of course, even that can be defeated, which would then rely on the circuit breaker protection external to the JB. However, if I ever have the occasion to opportunity charge my RAV4 EV from a NEMA 10-30R outlet, (which I have yet to ever do), I have to remember to lower the JB's default current limiter to 24A. That can easily be done with the LCD+Remote Key Fob options, which I had the good sense to purchase from eMW. If I ever lose the key fob or forget to have it with me while driving my RAV4 to a friend or relative's house, then I'd be screwed and not able to charge without removing the JB cover plate and re-adjusting the H/W based current limiter trim pot. That would be my "last resort", but still allow me to charge at 24A by overriding the 32A default set in firmware. I have only ever OC'd my VOLT, and even with the JB still set to 32A, (default for my normal routine charging at home), the output current drawn is still limited to ~14A by the car itself.

 

[fooljoe]

A NEMA 14-50 socket should be installed to support 50A. I don't know if the configuration you laid out above is a code violation or not since there is no standard outlet specifically rated for 40A. The Jesla has no way to know what wire and breaker you are using. Since a NEMA 14-50 should be on a 50A circuit, it will signal the car for 40A charging. A 40A breaker should trip after 5 or 10 minutes of 40A draw.

It's allowed to put a 50 amp receptacle on a 40 amp circuit, which is one of the reasons that to me the UMC's (and by extension Jesla's) "automatic" adjustability is a bit of a disadvantage - you can't set it to anything in between 24 and 40 amps, and you have to have a different $45 adapter for each setting your want.

Getting back to the original question, go with an openEVSE! GlennD has one for sale for $325 right now, to which you can add a 40A cord from Tony for $155 and you'll have the total package for $480! That's half the price of either the Jesla or the Leviton, and it gives you 40A capability, full and simple push-button adjustability at either L1 or L2, great portability, a built-in timer, and an awesome display that shows you a real-time measurement of the line voltage and current.

 

[miimura]

That's what I thought with respect to that scenario . . . e.g. plugging in to a 250V/50A rated outlet (NEMA 14-50R) with infrastructure wiring/protection only good for 40A max. The JESLA has no way to "encode" this AC power source situation and thereby reduce its output current to 32A (i.e. 80% of 40A, not 50A). I have this L2 EVSE AC power situation myself, and I'm sure others may as well. However, Tony's JESLA feature list above implied it can "automatically" current limit appropriately in any situation (using a standard 14-50R to plug in the JESA for its AC power source). He went on to say, this is something that "no other EVSE can do", and that's certainly true. Hopefully, Tony will clarify this for us.

There is nothing to clarify. Each adapter has a corresponding pilot signal. Since there is no unique plug and socket for 40A, there is no adapter to cover your situation. In theory, Tesla could provide a different 14-50 adapter that was coded to 32A charging. However, it does not exist, so the Jesla cannot handle this situation. Actually, there is no need for Tesla to make such an adapter because their cars can manually override and lower the charge current from the center screen.

 

[ppartekim]

Actually, there is no need for Tesla to make such an adapter because their cars can manually override and lower the charge current from the center screen.

Hmm.. Sounds like an Entune upgrade to bring feature parity....

 

[fooljoe]

Hmm.. Sounds like an Entune upgrade to bring feature parity....

:lol: Good luck with that! I do wonder if it might be possible to do some CAN-hacking to command the charger, however. Clearly it has the ability to set current from the dash, since the Model S can do it with the same piece of hardware. We'd just need somebody with a Model S to log the commands sent while adjusting charge current and use a device to send the same commands to the Rav. One can dream...

Anyway, we're getting way off topic here. OP did you buy the openEVSE yet?

 

[ppartekim]

No purchase yet... Waiting to see if I win a Jesla at the EV event this weekend... fingers-crossed...

 

[Dsinned]

I believe Tony's company, Quick Charge Power, is also giving away a JLong Extention Cord (which lists for $299) as well at this upcoming event in Silicon Valley this Saturday. I believe, this is mentioned somewhere on QCP's website.

 

[TonyWilliams]

That's what I thought with respect to that scenario . . . e.g. plugging in to a 250V/50A rated outlet (NEMA 14-50R) with infrastructure wiring/protection only good for 40A max. The JESLA has no way to "encode" this AC power source situation and thereby reduce its output current to 32A (i.e. 80% of 40A, not 50A). I have this L2 EVSE AC power situation myself, and I'm sure others may as well. However, Tony's JESLA feature list above implied it can "automatically" current limit appropriately in any situation (using a standard 14-50R to plug in the JESA for its AC power source). He went on to say, this is something that "no other EVSE can do", and that's certainly true. Hopefully, Tony will clarify this for us..

Let me try and explain it
When it uses the plain nema 14-50 it will go up to 40 amps.
When use the included nema 5-15 adapter, it measures the resistor that is mounted in the adapter, and "knows" it should limit to 80% of 15 amp = 12 amp and adjust the PWM signal accordingly.
When you buy the additional available plugs:
10-30, 14-30 : they both have another resistor which means the charger will be limited to 24 amps
and the 5-20 which has another resistor value that is limited to 16 amps.
The resistors in the adapter determine the amount of amps drawn.

Hope to have explained it clear enough

Perfectly explained. The resistance values are as follows:

40 amps - 9.08k ohms

24 amps - 33.16k ohms

16 amps - 75k ohms

12 amps - 140k ohms

 

[TonyWilliams]

I believe Tony's company, Quick Charge Power, is also giving away a JLong Extention Cord (which lists for $299) as well at this upcoming event in Silicon Valley this Saturday. I believe, this is mentioned somewhere on QCP's website.

Yes, we are giving away both a JESLA and a JLong on Saturday in Cupertino, California. Must be present to win WITH YOUR ELECTRIC VEHICLE. They need every car that can be there for the world record attempt at 7am.

Heres a link:

http://www.myrav4ev.com/forum/viewtopic.php?f=2&t=1295

http://www.myrav4ev.com/forum/viewtopic.php?p=15982#p15982

 

[TonyWilliams]

That's what I thought with respect to that scenario . . . e.g. plugging in to a 250V/50A rated outlet (NEMA 14-50R) with infrastructure wiring/protection only good for 40A max. The JESLA has no way to "encode" this AC power source situation and thereby reduce its output current to 32A (i.e. 80% of 40A, not 50A). I have this L2 EVSE AC power situation myself, and I'm sure others may as well. However, Tony's JESLA feature list above implied it can "automatically" current limit appropriately in any situation (using a standard 14-50R to plug in the JESA for its AC power source). He went on to say, this is something that "no other EVSE can do", and that's certainly true. Hopefully, Tony will clarify this for us.

If you have a circuit that isn't to code, like putting a NEMA 14-50R on a less than 50 amp circuit breaker and capable wiring, no, there is no way that any product can compensate for that.

Tesla tries, by watching the frequency change from 50/60Hz to whatever might change as the circuit gets hot, and then downward adjusts the amperage. Also, we have actually built JESLA's with temperature limiting switches, so that when your poor quality outlet gets hot, we can shut off the current. This is not a normal feature, however.

 

[fooljoe]

If you have a circuit that isn't to code, like putting a NEMA 14-50R on a less than 50 amp circuit breaker and capable wiring

Table 210.24 of the NEC specifically permits 50A receptacles on 40A circuits:

Of course it would be quite foolish to do this if you're installing a new circuit for the purposes of charging at 40A, but it would be not at all surprising to encounter properly-installed 50A receptacles on 40A circuits when charging "in the wild", for example range outlets or even outlets installed for 30A EVSEs.

 

[Dsinned]

Thanks "fooljoe" for the feedback.

Although a bit unorthodox, a 50A outlet such as a NEMA 14-50R, serviced by a circuit breaker and dedicated wiring rated up to 40A, would likely be somewhat "common" indeed, as there is no NEMA standard for a 250V, 40A receptacle. Yet, there are many possible "plug-in" loads slightly greater than 30A, but well under 40. Future proofing aside, a L2 EVSE with a rated output of 32A would be a "natural" for a 40A receptacle. Since there isn't one, the next best alternative would be one with a 50A rating, provided the infrastructure wiring and circuit protection is as least rated for 40A.

Curiously, the NEMA 14-50R is referred to a "RV Park" outlet, not a residential outlet. Its original purpose must have been for commercial properties. However, most homes have at least one 50A rated outlet to provide a plug-in power source for an electric range. Likewise, in older homes anyways, there will typically be one 30A outlet (NEMA 10-30R) for plugging in electric driers. So why don't we have any 40A outlets for other, in-between, load rated, plug-in appliances?

It does indeed seem like an oversight that there is no standard for 40A outlets. To wit, when I had a professional installation for a new central HVAC unit in my home two years ago, they wired the compressor to an existing (spare) 40A protected circuit in my main power panel. Several years before that, the same thing was done to connect a hot tub in my back yard, so there must be many applications for 240V AC power with a maximum rating of 40 amps. Not surprisingly, there are standardized, double pole, 40A rated circuit breakers commonly sold in most hardware stores. It is a very popular rating for residential use, but circuit breakers for 50 amps are a bit harder to find.

A property owner with such an "overrated" 50A outlet would be well advised to label it, "Do NOT use for loads exceeding 40A (or 32A continuous)". Although labeling may not actually be a legal requirement, it still is a good idea, especially in RV Parks, to avoid nuisance circuit breaker trips.

Anyway, I am quite content with my JuiceBox having it plugged in to a dedicated 50A outlet in my garage, which is overload protected at 40A, and pre-programmed to current limit at 32A wile charging my RAV4 EV. I also use my JB to charge my VOLT from the same outlet and it "automatically" current limits to <15A, because that is the maximum allowed by the car itself.

 

[TonyWilliams]

If you have a circuit that isn't to code, like putting a NEMA 14-50R on a less than 50 amp circuit breaker and capable wiring

Table 210.24 of the NEC specifically permits 50A receptacles on 40A circuits

Yes, I'm actually aware of that provision. It's dumb.

Blink, of course, used that provision when they installed their garbage EVSE's, which was a perfect complement to their business model.

 

[ehelmholtz]

If you have a circuit that isn't to code, like putting a NEMA 14-50R on a less than 50 amp circuit breaker and capable wiring

Table 210.24 of the NEC specifically permits 50A receptacles on 40A circuits

Yes, I'm actually aware of that provision. It's dumb.

One can choose not to install a 50A rated outlet on a 40A circuit in ones own garage but there's no way to stop someone else from doing it if it's allowed under code. It's not smart for an EVSE to automatically assume that it can pull 40A from this circuit because this limits versatility. This is the problem with the Tesla UMC used on the Rav4 and hence openEVSE builds like this one: portable OpenEVSE allow for more flexibility.

 

[Dsinned]

To repeat what was previously stated about the virtues of the JESLA:

So, there are numerous major advantages of JESLA:

a) truly portable and light weight with a carrying bag

b) automatic amperage adjustment (absolutely no other charge station has this... NONE) depending on which plug is used

c) automatic voltage capability, 100 to 250 volts

d) able to fully charge any Tesla powered vehicle (Rav4 EV, Mercedes B-Class ED, Tesla Model S/X/3 and Roadster) at 40 amps * 250 volts = 10kW

e) charges far quicker than typical public J1772 stations

f) comes with a warranty

I agree with all these statements in general, but statement "b)" is a bit misleading with respect to the seemingly "oddball" 32A EVSE charging situation. It turns out that there are certainly other commercially available L2 EVSE, including all other L2 capable, open source EVSEs, that are completely "compatible" with 32A charging situations. The JESLA is a noteable exception because of the way it depends on specialized (and quite costly at $50 each) plug adapters. The JESLA's is a versatile EVSE, just not so much for 32A charging unless the EV itself can be set up to current limit for this particular infrastructure limitation.

As a suggestion, Tony's company could offer a "pass thru" adapter for their standard equipped 14-50P AC input power cord, with a special resistor value that could be encoded as connected to a 250V, 40A maximum power source and thereby current limit JESLA's output to 32A. That would be a bargain at $50, considering the alternatives! :mrgreen: