Solution to avoid range anxiety - Carry a generator

[fooljoe]

Sounds like it'll work out ok for you then. I'd recommend looking into getting a hitch and a basket (something like this) to carry the thing outside of your car though. Gas/oil fumes in the cabin can be quite unpleasant, plus if you're at all like me then you use all the cargo space available in the back of the Rav when taking a trip even without a big generator in there.

And don't forget to make a "ground-spoofer" in case an earth ground isn't available:

The easy way to make this work is take a screw-on plug (NEMA 5-15P) and install two 1/2 watt 100k ohm resistors. One from neutral (silver screw) to ground (green), and the other from hot (gold screw) to ground (green). Then simply plug this into one outlet on the generator, and your EVSE into the other. This will safely pass the ground detect on the Nissan (and our upgraded) EVSE, while not being a hazard in any other way.

 

[Dsinned]

Sounds like it'll work out ok for you then. I'd recommend looking into getting a hitch and a basket (something like this) to carry the thing outside of your car though. Gas/oil fumes in the cabin can be quite unpleasant, plus if you're at all like me then you use all the cargo space available in the back of the Rav when taking a trip even without a big generator in there.

And don't forget to make a "ground-spoofer" in case an earth ground isn't available:

The easy way to make this work is take a screw-on plug (NEMA 5-15P) and install two 1/2 watt 100k ohm resistors. One from neutral (silver screw) to ground (green), and the other from hot (gold screw) to ground (green). Then simply plug this into one outlet on the generator, and your EVSE into the other. This will safely pass the ground detect on the Nissan (and our upgraded) EVSE, while not being a hazard in any other way.

Thanks for both suggestions. The first would also solve the problem of thwarting a would-be generator theft, and the second would gets around the lack of an Earth ground to the generator. I have a question about that ground "spoofing" scheme. Would using a dual resistors to ground, grounding plug in one of two unused 120V outlets (both NEMA 5-15R) be sufficient while operating the generator (and L2 EVSE) from a single 240V outlet (NEMA L14-30R)? There are only these three outlet on the generator. Thus, this operating mode requires the generator's Voltage Selector Switch to be in 120/240V (vs. 120V Only) position, but all three outlets will be powered up.

 

[fooljoe]

From what I've read in the Leaf forum (haven't tried it myself), it's perfectly sufficient to put the resistor'd plug in one of the unused 120v outlets. I think you could also add the resistors directly to the adapter you'd be using (L14-30p?) to plug into the generator. I'd just try either approach out first to make sure it'll work.

EDIT: In this thread of the Leaf forum, Phil says:

If you have a 240v capable generator and you intend on charging @ 240v, then barring a proper bonded ground with ground rod, a 100k resistor from neutral to ground should suffice.

So it sounds like you just need 1 resistor bonding ground to neutral in your L14-30 adapter. I'd buy 3 anyway just in case...

EDIT 2: Ok a few posts later in the same thread he says you should instead connect resistors from each hot to ground in your L14-30p, so now I'm confused. I posted over there for clarification.

 

[Dsinned]

The 240V plug method sounds harmless enough, putting a 100k resistor between neutral and ground, but I don't have an easy way to modify a "molded" L14-30P to 14-50R AC adapter and there is only one of these type of outlets on the generator. So, I will probably have to add dual 100k resistors into a dummy plug (5-15P) for one of two unused 120Vac outlets, or do you think just one 100k resistor from neutral to ground in that same 120V outlet should suffice?

 

[fooljoe]

Hmm another good question. Your adapter is molded on both ends? Of course you could just chop one end off and put on a screw-on type plug or receptacle with the resistors added. Otherwise I guess if Phil's answer is bonding both hots to ground you might need 2 of the dummy 120v plugs, one on each leg. Can you verify that your generator has the 120v receptacles on different legs when in 240v mode?

 

[Dsinned]

In 120/240V mode, I believe the 120V outlets are in parallel, but in the 120V ONLY mode they must be in series. I came to that conclusion the other day when I was testing the generator while charging my VOLT via the OEM level 1 charge cord. I was using just one of two 120V outlets, and I noticed the voltage at each outlet was significantly unbalanced. This imples those outlets were in series in this mode. But, if I switched the generator to the 120/240V mode, I "think" the voltages would have been equalized suggesting they are in parallel. However, I did not try that yet, so I am not certain.

To tell you the truth, the generator's wiring scheme in these two modes is confusing, and the owner's manual is rather vague as well. Here is a direct quote from the manual.

VOLTAGE SELECTOR SWITCH
THe voltage selector switches the main power carryig windings of the generator to produce "120V ONLY" or "120/240V". If a 240V appliance is connected to the 4-prong receptacle (NEMA L14-30R), the switch must be in the "120/240V" position. If only a 120V appliance is being connected, select the "120V ONLY" position.

I have read elsewhere (online reviews) that the generator windings are being "swtiched" from series to parallel depending on the position of this switch, but exactly which one is which, still remains unclear. Logically, it seems to me, that the switching scheme with respect to these 120 vs. 240V outlets, would be reversed, but I really don't know. :?

 

[pchilds]

You could put the resistors inside the EVSE, with a switch if you want to test for ground. If you have an OpenEVSE you can turn off the ground check in the setup menu.

 

[Dsinned]

That would work since the ONLY purpose of this generator is for charging my RAV4 at 240V in a roadside emergency.

With 100k resistors from either hot side to ground, the induced current flow would be very small at only about 2.4mA (120/100k * 2), simulating a detectable current path to ground . Is that the purpose of these "bleeder" resistors? With zero leakage current, the GFCI protection in the EVSE cannot detect any current flow so it thinks there is an open circuit to ground, and will not operate, correct? Is that the idea of a fault detector for "GFCI", which acts like a circuit breaker to turn off the AC input?

 

[fooljoe]

I like the in-the-EVSE idea! As far as that voltage selector switch, I believe what it does is switch whether the two 120v outlets are on the same leg or not. If you aren't using 240v, it makes sense to leave the switch on 120v, so both outlets are on the same leg and you don't have to worry about balancing loads.

As far as the point of the resistors, they just serve to pass the EVSE's ground detection test - so as mentioned they're not needed if you can disable that in other ways. I think GFCI should work regardless of the grounding situation, as all it does is check to make sure both hots (or hot and neutral if 120v) are carrying the same current.

 

[Dsinned]

In the JuiceBox's EVSE design, there are two AC load side "hot" leads that pass thru a current sensor. I believe the way GFCI works is to detect a current imbalance between these two conductors by sensing the strength of the magnetic field created by these two wires. Normally, with no appreciable leakage current from either side of the line via these load leads, the electrically created field will be essentially nill. However, when the field strength increases above a certain threshold, (20mA?) that means there must have been an increase in leakage current to ground, which is an abnormal (potentially unsafe) condition. The placement of these wires thru the current sensor is quite critical and there is a way to calibrate this current imbalance sensor's circuit to eliminate spurious GFCI ground faults. Is this how GFCI actually works in most EVSEs that have this safety feature enabled?

 

[fooljoe]

Yes that's the way GFCI is generally implemented in an EVSE, but again discussion of GFCI is immaterial to the subject of getting your EVSE to pass its ground detection test when charging from a generator.

The ground detection test you have to worry about is a check by the EVSE to determine if a voltage potential exists between either or both lines and ground. This is also the way an (U.S.) EVSE determines if it's connected to a 120v or 240v supply: if 240v both lines will show a 120v potential to ground, and if 120v only one will. But if there's a floating ground neither will show a potential to ground, in which case most EVSEs will refuse to operate. The idea is to electrically bond the lines to ground so the check for a potential to ground will show the potential between the two lines, thereby passing the test.

https://code.google.com/p/open-evse/wiki/theory_of_operation

 

[buickanddeere]

As previously stated it depends if the genset has a bonded or floating neutral. Small portable units tend to be of the bonded variety.
I just can't get comfortable will a smelly gassy generator strapped into the passenger compartment. How about one of those trailer hitch carriers ?

 

[swogee]

I figured I would mention this fuel cell generator as it is higher tech but likely higher cost as well. It also has the disadvantage of running off of hydrogen which is not as readily available as gasoline but it is compact and lighter weight. Check it the link out below:

http://www.upssystems.co.uk/wp-content/uploads/2011/08/Mobixane-UPSS.pdf


The unit referenced in the link above would only half fill the RAV4 battery in about 8 hours.

They do make some fuel cells that run off of methanol and water which would be preferable but I think the energy density is less on those fuel sources so more volume would be required.

 

[fooljoe]

Last weekend "as a test" I had the generator charging my VOLT (via the JuiceBox) successfully. It definitely works and I did not have to use any resistors in a 120V "dummy" plug either. The only issue I uncovered with the generator was that about every 2 minutes it would appear to become overloaded and struggle to stay running; almost like it was running out of gas. However, each time this happened, after a few seconds, it would recover and resume charging my VOLT all by itself. Of course, the VOLT would drop out of charging mode briefly, which allowed the generator to recover automatically.

When I reduced the JB current limiter to ~10A (while still sourcing at 240V), this problem simply went away. Could it be the generator was beginning to overheat and has some sort of overload protection that behaves this way? Doubtful . . . The CB (rated at 14.8A) never tripped, even though I was running close to its maximum allowable amperage (3300W / 225V = 14.67A).

I was measuring the output voltage and freq of the generator before (and after) this problem occurred to determine how well it was regulating. The voltage was within specs at ~225 to 230V, but the frequency was down around 58hz (3420 rpm), while the output load was ~14.5A. With the load down to 10A, the frequency was closer to nominal (60hz or 3600rpm). It must of been too much load for the generator, although the manufacturer's "rating" is 3500W continuous. With the load reduced to ~2400W, there were no further issues, and the generator's output parameter were well within spec. Of course, this resulted in charging my VOLT at about 2/3rd of its maximum charging rate.

Of course, I tried charging my VOLT with the JB plugged in to a 240V wall outlet in my garage. This worked flawlessly at the full charging rate of the VOLT's onboard charger (3.3kW). I did the same with my RAV4 EV and it also charged equally well up to its full power rating of 10kW.

I could have a defective generator, or maybe there was something strange going on in the VOLT's onboard charger, or the J1772 pilot circuit between the car and the JB. I saw a similar problem on the generator with either cars' OEM charge cords at 120V, without the JB involved, when the output load on the generator exceeded 12A.

Do you still think this has something to do with the "grounding"?

No, I don't think this has anything to do with grounding. If the Juicebox worked ok without the ground-spoofer I guess that means it just doesn't do the ground check. :/

Sounds like you were just stretching the capability of your generator charging at the Volt's full 14ish amps. I would try every setting in between 10 and 14 amps to see precisely how much power you can get out of it. And what about the big question? Does it work on the Rav???? (at 10 amps or more?)

 

[Dsinned]

Yes, it does! I thought I mentioned that, i.e. if you mean without the generator as the 240V AC power source, which I have yet to test. I tested my RAV4 EV with the JB (standalone) up to full power, ie. 240V at 40A, and it worked like a champ!

Note, while testing the JB with my VOLT, I had a temporary Earth ground connection to the generator.

GFCI in the JB can be disabled in the Ardunio firmware, but it is enabled by default. It can be a very tempermental circuit, however. Both AC output power conductors go thru a GFCI sensor (CT) and these conductors have to be precisely routed thru the center of the coil to avoid false GFCI trips. There is also a pot on the main PCB to "calibrate" the GFCI sensor circuitry.

 

[fooljoe]

I mean can you charge the Rav off the generator. That's the whole point of this thread, right??? :lol:

I know that you got the Volt charging, and you had said before that when you got the Juicebox you'd test the Rav off the generator, since you needed it to limit the current draw. So now that you have the Juicebox when's the big test? The suspense is killing me!

 

[Dsinned]

As you can imagine, running a gas generator in a residential neighborhood early mornings or evenings on weekdays is a precarious event. I have been doing all my generator tests on weekends, when the sound of gas powered lawn mowers is fairly common. I have also been using weekends to slowly break-in the engine. The next test (with my RAV4 EV) will probably be sometime this Saturday morning. I have every reason to believe it will work, but while charging my VOLT, I found a problem operating the generator over 2400W, or just under 70% of its continuous power rating. The voltage and frequency regulation at that power level was nominal, but not at higher sustainable loads. I will repeat testing at higher load to see what happens with charging my RAV4, using the JB to limit current to <15A (at 230V). I may imit the current to even less to get it to work, just like I did for my VOLT. However, this time I will put a big circular cooling fan on the generator to see if keeping it cooler while operating has any effect on the problem. Stay tuned . . .

 

[Dsinned]

This morning I did the long awaited generator based EVSE l2 charging test on my RAV4 EV. After numerous attempts, I was not successful. Every time the charge initiated, the generator immediately bogged down and the charge aborted. Of course, I limiting charging current on each atttempt. First, I set the JuiceBox limiter to 12A, and that failed. Then I tried limiting to 10A and then 8A. Both failed as well. I even tried limiting to 4A, but at that ridculously low current limit, I could not even get a charge to initiate in the first place. Below 8A, I think the pilot circuit to the RAV4 was disabling the J1772 for some reason. With the limiter set between 8 to 12A, the J1772 would enable an active charging mode, but each time the JB tried to respond by switching on the power, the generator would bog and active charging immediately aborted.

During these tests, I had a temporary Earth ground connection to the generator, but no "spoofer".

As I mentioned in a previous post, this same test setup worked on my VOLT (with JB current limiter set to 10A). Higher currents (up to 14A) worked as well, but for only 2 minutes or so, when the generator temporarily bogged, but after only a few seconds, charging resumed automatically. Another couple minutes later, the same thing happened. This pattern of behavior kept repeating every couople minutes thereafter. When I lowered the current limiter to 10A, the "bogging" problem went away.

Of course, I have no intention (other than out of curiosity) to ever charge my VOLT with a portable generator. The idea was to take a generator along to charge my RAV4 during a road trip if it ever ran out of battery power in between public charging stations or there was no available 240V outlets in-route. This no longer looks feasible; at least not with a relatively low cost portable gas generator. A "better quality" generator could still possibly work.

I don't know why THIS generator did not work with my RAV4, but it did on the VOLT. There is a difference, but I guess it should not come as any big surprise the RAV4 did not work, in lieu of some of the other "quirky" issues with its onboard charger.

 

[fooljoe]

Well that's too bad. Thanks for reporting back. You did say earlier that the same generator did work on the Rav @ 120v with the stock Panasonic EVSE @ 12 amps though, right? It seems quite strange that it would work on 120v but not 240v. I guess our Tesla chargers are just a bit more "sensitive" than whatever GM uses in the Volt. It'd be interesting to try a Leaf out on the same generator as well...

 

[JasonA]

Like I've said earlier in this thread as has others... you are using an incorrect power source and the Tesla charger only wants a PURE SINE WAVE or utility quality voltage..

Plain and simple.. don't know why that's hard to understand? :roll:

Use an inverter generator next time.. no issues.

***************

This is TonyWilliams speaking now.... unfortunately, the software has locked me out as a spammer, and won't allow new posts from me, but apparently as a moderator, I can edit others posts:


The "4 amp" setting isn't a J1772 standard. If your EVSE has that setting, it's wrong.

The lowest duty cycle of the Pulse Wave Modulation (below 6 amps) is the signal for "digital communication"... in other words, DC charging instead of supplying AC power to an onboard charger.