Charging from a generator, 2 red blinks

[timk225]

I just picked up a Coleman Powermate 2500 generator for the price of free.

I cleaned it up and got it running. It powered an electric drill with no problems. But when I went to plug in my Gen 2 Tesla charging adapter with a 5-15 plug, the adapter would just go to 2 red blinks of the T, pause a few seconds, 2 red blinks, and over and over like that.

Is the adapter very sensitive, or does the generator just make "dirty" power? I noticed the generator had a grounding tab on its frame, is it supposed to be connected to a metal rod pushed into the ground or connected to a water pipe or something like that?

I don't have to charge the car from the generator, but I wanted to load test it, as it'll be used for backup power to run the furnace if the power goes out this coming winter.

 

[JPP]

Yes, you must ground the generator. Like a wire from the ground pin/stud on the generator to a good earth ground (cold water pipe). The UMC does not like a 'floating' ground.

 

[compu85]

Check and see if the N and Ground are bonded - they probably are.

Also check the voltage and Hz output of the generator.

 

[miimura]

In addition to the grounding and neutral bonding mentioned above, the power waveform will probably not be steady enough for charging a Tesla. They are notoriously picky about the frequency stability. Generally, only inverter generators work. Even then, you need to disable any Eco mode until the car has stabilized the charging current.

 

[eprosenx]

I just picked up a Coleman Powermate 2500 generator for the price of free.

I cleaned it up and got it running. It powered an electric drill with no problems. But when I went to plug in my Gen 2 Tesla charging adapter with a 5-15 plug, the adapter would just go to 2 red blinks of the T, pause a few seconds, 2 red blinks, and over and over like that.

Is the adapter very sensitive, or does the generator just make "dirty" power? I noticed the generator had a grounding tab on its frame, is it supposed to be connected to a metal rod pushed into the ground or connected to a water pipe or something like that?

I don't have to charge the car from the generator, but I wanted to load test it, as it'll be used for backup power to run the furnace if the power goes out this coming winter.

Here is the manual. The UMC Gen 2 is trying to tell you it can't detect ground. What this really means is that it does not detect 120v voltage potential from the hot to the ground pin. (it is really checking for the ground wire being connected and bonded to the neutral)
https://www.tesla.com/sites/default...bile_connector_owners_manual_32_amp_en_US.pdf

Yes, you must ground the generator. Like a wire from the ground pin/stud on the generator to a good earth ground (cold water pipe). The UMC does not like a 'floating' ground.

This has nothing to do with what the Tesla is testing for. While it is technically a good idea to ground your generator to earth ground, almost nobody does it when using portable generators (it probably also is a code requirement - though I am not sure what code applies - I have heard it is an OSHA requirement to have GFCI in some cases). The Tesla is just testing to make sure there is the expected voltage potential between hot and ground. It is really testing for "bonding" of the neutral and ground.

Check and see if the N and Ground are bonded - they probably are.

Also check the voltage and Hz output of the generator.

They are almost certainly *not* bonded together since he is getting that error. Some generators have these bonded together, others do not. My Honda EU2000i does not. I believe this is because if you use a generator with some kind of transfer panel, you want them separate since the main electrical panel is where they will be bonded. But if you use it stand-alone then you do want them bonded at the generator so that a short from hot to ground will blow the breaker. I think some generators may have a bonding strap you can install to tie them together.

I personally built a plug end that has neutral and ground bonded together. When powering things that want to see the bonding I just tie the two together by plugging in my magic plug (I need to go find a picture of that to post here).

In addition to the grounding and neutral bonding mentioned above, the power waveform will probably not be steady enough for charging a Tesla. They are notoriously picky about the frequency stability. Generally, only inverter generators work. Even then, you need to disable any Eco mode until the car has stabilized the charging current.

Hrm, I don't know how true this is. I have not extensively tried a Tesla on a generator. I have only used mine on a generator once and it was a 30kW natural gas powered generator.

But I will say this: Car chargers are just simple rectifiers that take AC to DC. Rectifiers are all around us and they can be built to tolerate pretty *sugar* power. The little wall wart your router came with is likely rated for between 100v and 240v and can handle 50 or 60hz power. I think the concept of electronics needing good power supplies more applies to things that don't have batteries. Since the rectifiers are just providing power to batteries in the car it is not really the end of the world if the power is not perfect. I think typically the issue is if you don't provide consistent DC power to things like computer chips they freak out, but in charging a car (which also has many microcontrollers running) those chips are buffered by the battery.

I also disagree on the Eco Mode comment as well. Disabling Eco Mode is a solution for dealing with thinks with high surge start currents like electric motors. The generator engine does not have time to react to the huge draw. If you have ever watched a Tesla ramp its current draw on a graph it clearly does it really slowly (it can do this since it is all digitally controlled anyway). I have not tried my Tesla with my EU2000i inverter generator, but I am pretty positive that even in Eco Mode it would have no issues since the generator would just ramp the throttle to compensate.

Now Tesla does say you should not charge off a generator. I don't know why. I used my Tesla as a load bank on a 30kW generator (with all the seat heaters turned on to bleed off energy as I approached a full charge on my battery) and it worked great.

I would love if Tesla would provide more details on why they don't want us using generators. I wonder if there are any technical reasons for it? Or are they more safety/liability related? (or they did not want to bother testing / supporting it?)

 

[timk225]

I did notice that when I'd turn on the electric drill, the generator would bog slightly for a second, then return to its normal speed.

The whole ground sensitivity thing concerns me because I have a high efficiency furnace, a Comfortmaker G9MXT, and I wonder if it'll be as sensitive to generator power as the Tesla Gen 2 charge adapter is. Gas Furnace – G9MXT | Comfortmaker

My original plan was to use a large APC battery backup unit from a data center application to provide battery power to run the furnace for a while if the power goes out during the winter. Or if I can use just the generator, or the generator powering the battery backup, I wonder if that would clean up the power enough to have a steady frequency.

I haven't been able to find specs on this furnace yet, but I think most high efficiency furnaces draw less than 1000 watts when running.

 

[eprosenx]

I did notice that when I'd turn on the electric drill, the generator would bog slightly for a second, then return to its normal speed.

The whole ground sensitivity thing concerns me because I have a high efficiency furnace, a Comfortmaker G9MXT, and I wonder if it'll be as sensitive to generator power as the Tesla Gen 2 charge adapter is. Gas Furnace – G9MXT | Comfortmaker

My original plan was to use a large APC battery backup unit from a data center application to provide battery power to run the furnace for a while if the power goes out during the winter. Or if I can use just the generator, or the generator powering the battery backup, I wonder if that would clean up the power enough to have a steady frequency.

I haven't been able to find specs on this furnace yet, but I think most high efficiency furnaces draw less than 1000 watts when running.

Bogging and then returning to normal is totally normal. That is what we would expect.

Please post pictures of the nameplate (with Model #) of the generator here or at least just the model number in text. It looks like the powermate web site has all the manuals online. We may be able to determine if there is a way to bond neutral and ground built into the generator.

I don’t think your furnace will be as sensitive as the Tesla in the respect that it does not have the safety features of the Tesla that are trying to detect neutral to ground bonding, etc...

You are correct that most furnaces are under 1000w of load.

I would recommend you install a generator transfer panel to hook this thing to the house if that is the plan. That should take care of the neutral to ground bond as it will happen in your main electrical panel.

In the meantime, if you want to test with the Tesla, go get a cord end plug from Home Depot or Amazon and a piece of 10 gauge wire let’s say and jump neutral to ground. Plug it into the generator on one port and the Tesla into the other and let’s see what happens!

Also, we need to know what the continuous running watts of the generator is (not just peak surge load which is how they always market them).

I would not mess with a UPS for the furnace or Tesla.

Depending on the kind of UPS it could filter the power (if double online conversion), but it is likely setup for 208v not 240v, and the energy loss is pretty big. It is not really intended for residential use for backup power.

 

[ewoodrick]

The one thing that you are assured of, especially with a generator of that size, is that the voltage will never be right and the frequency will never be, as well. UPSs hate the things. As you mentioned, a drill turning on will change both the frequency and voltage. Anytime that you hear it "bog down" that's exactly what is happening.

Getting the grounding right is probably going to help. I believe that others have mentioned that there is some leeway accepted, especially at 220V. If it kicks out when starting, you may want to lower the charging current to the minimum and slowly increase it. Also remember that you should allow the generator to run for a few minutes before applying any load, and you may want to test with a portable space heater to assure that it accepting load well.

Good luck with the testing and playing, as well as the extremely high probability that you will never use it. Also, don't forget that gas will go bad, you need to either drain and/or add stabilizer.

 

[ewoodrick]

I did notice that when I'd turn on the electric drill, the generator would bog slightly for a second, then return to its normal speed.

The whole ground sensitivity thing concerns me because I have a high efficiency furnace, a Comfortmaker G9MXT, and I wonder if it'll be as sensitive to generator power as the Tesla Gen 2 charge adapter is. Gas Furnace – G9MXT | Comfortmaker

My original plan was to use a large APC battery backup unit from a data center application to provide battery power to run the furnace for a while if the power goes out during the winter. Or if I can use just the generator, or the generator powering the battery backup, I wonder if that would clean up the power enough to have a steady frequency.

I haven't been able to find specs on this furnace yet, but I think most high efficiency furnaces draw less than 1000 watts when running.

When you talk about running the furnace, it will require a lot of planning and you will have a significant safety issue to contend with. IT is against code, and very dangerous to plug a generator into a house plug. If not done correctly, it can create fire, severely damage the generator, and kill people. The only correct way to do it is to have transfer switch to switch the load from the utility to the generator.
If your furnace is gas, then you will only be running the fans, but the fans draw a fair amount of current, 2KW may be marginal.
A UPS may get a little upset with the fan motors and it will probably get really upset with the generator. I've got a 30kW generator and many UPSs hate it.

 

[timk225]

As far as the generator running the furnace goes, the generator will not be plugged into the normal house power system anywhere. When my furnace was installed last year, they ran a new power line to the furnace, into a small metal box with an on/off switch and 2 normal 5-20 outlets in it. The furnace and its condensate pump plug into those 2 5-20 power plugs. That switch controls the off/on for those 2 outlets.

So if I ever did want to use the generator to run the furnace and its condensate pump, they would be unplugged from the house power completely, and plugged into the generator with a 40 foot extension cord (so the generator isn't running in the basement).

It is a gas furnace.

The Coleman Powermate Ultra generator says 2500 peak watts and 2000 running watts. It has 2 5-20 outlets for me to plug into. I didn't see a model number anywhere but its engine is a VLV50 5 horsepower Tecumseh model. And yes, I'm aware of today's poor excuse for gas and its ethanol sucking moisture out of the air. I had some fun with my lawn mower this summer with gas that had been sitting for 2 months, and it was amazing how well it ran after I went and got a gallon of fresh gas.

 

[Sophias_dad]

That furnace needs between 8.2 and 12.3 amps at 120V, depending on the max heat output. If the generator can reliably drive that, it may well work. I'd >definitely< try it before you need it.

http://www.yorktechsupply.com/download/ICP/G9MXT/Product/44056432106.pdf is a link to one version of the spec sheet of that furnace.... it shows a different range of amps(7.5-13.5), so you'd really want to look up your exact model.

A UPS. even a big one, won't have the capacity to drive that unit for very long... probably measured in minutes, at best. If you want hours, get a Powerwall(I'm not real familiar with those, so others will surely correct me).

I have toyed with using sine wave inverter connected to one of my ICE vehicles to drive my oil furnace(~700W continuous), but the inverter(said 1000W, 2000W peak) I had which admittedly was a big name, but probably cheap copy, was absolutely max-loaded at about 150W, and could barely run my fish tank aerator and heater. A typical automotive alternator can provide around 130Amps, so the max you can hope to continuously get out of an inverter connected to it is 1560W, and that's definitely optimistic. That 12.3 amp gas furnace will be asking for 1476W(max). But the good news is a furnace doesn't really run nonstop, and the car battery can help out for occasional overloads, presuming the inverter asks for more than the alternator can supply. BTW, I also tried a giant APC UPS with this furnace, and it couldn't even start the load, which sort of surprised me.

 

[miimura]

Hrm, I don't know how true this is. I have not extensively tried a Tesla on a generator. I have only used mine on a generator once and it was a 30kW natural gas powered generator.

But I will say this: Car chargers are just simple rectifiers that take AC to DC. Rectifiers are all around us and they can be built to tolerate pretty *sugar* power. The little wall wart your router came with is likely rated for between 100v and 240v and can handle 50 or 60hz power. I think the concept of electronics needing good power supplies more applies to things that don't have batteries. Since the rectifiers are just providing power to batteries in the car it is not really the end of the world if the power is not perfect. I think typically the issue is if you don't provide consistent DC power to things like computer chips they freak out, but in charging a car (which also has many microcontrollers running) those chips are buffered by the battery.

I also disagree on the Eco Mode comment as well. Disabling Eco Mode is a solution for dealing with thinks with high surge start currents like electric motors. The generator engine does not have time to react to the huge draw. If you have ever watched a Tesla ramp its current draw on a graph it clearly does it really slowly (it can do this since it is all digitally controlled anyway). I have not tried my Tesla with my EU2000i inverter generator, but I am pretty positive that even in Eco Mode it would have no issues since the generator would just ramp the throttle to compensate.

Now Tesla does say you should not charge off a generator. I don't know why. I used my Tesla as a load bank on a 30kW generator (with all the seat heaters turned on to bleed off energy as I approached a full charge on my battery) and it worked great.

I would love if Tesla would provide more details on why they don't want us using generators. I wonder if there are any technical reasons for it? Or are they more safety/liability related? (or they did not want to bother testing / supporting it?)

I'm not making this stuff up. I am simply relaying the experience of others over the years.
Here is one older video on the subject. You will notice that he is using only inverter generators.

I'm pretty sure the Tesla is picky about generator power quality because they are using power quality in order to detect abnormalities in grid connections so that people don't burn their house down because of a bad plug or other problem.

 

[eprosenx]

I'm not making this stuff up. I am simply relaying the experience of others over the years.
Here is one older video on the subject. You will notice that he is using only inverter generators.

I'm pretty sure the Tesla is picky about generator power quality because they are using power quality in order to detect abnormalities in grid connections so that people don't burn their house down because of a bad plug or other problem.

I would be curious to see tests with non inverter generators. My guess is they would work fine, but we need someone to test!

The Honda in this case simply did not work since it does not have neutral and ground bonded by default. That is easy to fix.

I also think this guy was too conservative ramping the charge current. Perhaps Tesla has moderated this function in software after that video was produced, but watching my Model 3 ramp load using my Sense monitor it is very smooth.

Tesla is using voltage to detect bad things happening power wise (to avoid fires). As long as the voltage is not too crazy far off I think the Tesla will be OK with it. Frequency is the other thing they could detect, but since the failure modes they are trying to look for don’t result in frequency instability I suspect they don’t look at it in the slightest. And also, for the voltage issues they are looking for it is not instantaneous voltage issues but instead ones that develop over a charging session as the wire heats up (so if they have tuned things right, they may have done so to avoid “tripping” due to really short voltage deviations).

 

[timk225]

That furnace needs between 8.2 and 12.3 amps at 120V, depending on the max heat output. If the generator can reliably drive that, it may well work. I'd >definitely< try it before you need it.

http://www.yorktechsupply.com/download/ICP/G9MXT/Product/44056432106.pdf is a link to one version of the spec sheet of that furnace.... it shows a different range of amps(7.5-13.5), so you'd really want to look up your exact model.

My furnace is the 120,000 BTU version, the G9MXT1202422A2 model.

I'll fire up the generator today and test its voltages with a multimeter and see what it shows.

 

[GWord]

No trouble with my Honda inverter generator but I did have to make a special pigtail that allows me to bond neutral to the external ground screw. I wanted it that way so that I can also float the neutral for when I use the generator as a home backup.

 

[eprosenx]

No trouble with my Honda inverter generator but I did have to make a special pigtail that allows me to bond neutral to the external ground screw. I wanted it that way so that I can also float the neutral for when I use the generator as a home backup.

I wish I had a picture handy. I just took a NEMA 5-15P and jumpered the neutral to ground. No need to tie to external ground screw. Can plug and unplug when needed to bond neutral to ground.

I labeled it really really well. (not the safest thing to leave laying around, but also not the most dangerous)

 

[GWord]

I wish I had a picture handy. I just took a NEMA 5-15P and jumpered the neutral to ground. No need to tie to external ground screw. Can plug and unplug when needed to bond neutral to ground.

I labeled it really really well. (not the safest thing to leave laying around, but also not the most dangerous)

I wanted the external jumper for that exact reason honestly (i.e. I wanted it to be obvious it was in use). I did initially think about just making an internal one with 120v pass through. In the end I decided to go with the unelegant external solution which also has extrinsic benefit because I’m a dumbass and would probably have lost it. Now I don’t ever unscrew the ground jumper/wire; I simply unplug it and attach it to the genset case with a bit of Velcro.

 

[Rasputin]

I have a 20K whole house generator. Was told not to add the Tesla to the generator, and that it must be on a separate circuit. As I understand it, it has something to do with fluctuating voltage from the generator and potential damage to the Tesla battery. In the event of a power outage, the generator will work, but power will be cut off to the Tesla. Was not able to simply add an additional meter because it required new wiring from the street to the house at an exorbitant cost and a wait time of 4 to 5 months from the electric company. A master electrician came up with a solution that did not require a new meter, but the total cost is $3500, still below what it would have cost with new meter installation. Have no knowledge of electrical issues and have no idea of whether, or how much, I am being ripped off. On the positive side, I'm assured that the installation is guaranteed to work without any risk to the Tesla. Combined with the crazy delivery process and the non-responsive customer service, my initial enthusiasm is being sorely tested.

 

[David99]

I have charged on a generator. Ground and Neutral need to be connected (that's normal in a main panel in any house in the USA). Always start wit the lowest Amp setting in your car. Start the generator before you plug in.
It is a good idea to use both phases of the generator. For that you need to make an adapter that combines both phases and has a plug that the UMC expects 240 Volt on. For example a 14-50.

 

[eprosenx]

I have charged on a generator. Ground and Neutral need to be connected (that's normal in a main panel in any house in the USA). Always start wit the lowest Amp setting in your car. Start the generator before you plug in.
It is a good idea to use both phases of the generator. For that you need to make an adapter that combines both phases and has a plug that the UMC expects 240 Volt on. For example a 14-50.

So has anyone tried plugging into a generator and letting the car ramp into its charging on its own? I suspect the ramp is slow enough that the generator would ramp fast enough to not lug badly. Does anyone have any first hand experience with this?