Stupid Question: Emergency Charging on a Gas Generator

Vince Cobelo · Nov 23, 2015

This is a curiosity question as much as anything. I did a search on this and not much came up beyond very early threads about Roadsters.

I understand that the problem with using any electrical source it has to be clean for the MS to accept charging. With today's inverter generators that generate very clean energy why couldn't one be used in a pinch. Say my wife runs out of power and is stuck a few miles from the house. Put the inverter generator in my pickup and plug the car into it for a hour or two to get the car home. Probably very slow charging...I get that. But like I said....in a pinch.

jeffro01 · Nov 23, 2015

If you can clean up the power sufficiently enough before it hits the UMC then depending on voltage and amperage it could work. The problem though, is getting the electricity signal cleaned up enough before you get to the UMC...

Jeff

cinergi · Nov 23, 2015

I've done it.

That said, I was never able to get the UMC to work by directly hooking it up -- it didn't like the grounding situation.

FlasherZ · Nov 23, 2015

cinergi said:
I've done it.

That said, I was never able to get the UMC to work by directly hooking it up -- it didn't like the grounding situation.

Generators have always been an interesting item to deal with when it comes to bonding and grounding.

If run completely standalone with plug-connected loads only, in theory the generator's neutral and ground should be bonded together to the generator's frame, and a ground rod should be driven into the earth. In many generator sets, however, the ground is left floating from the neutral and has no defined relationship to the ungrounded conductors. The reason it works for most appliances is that they frankly don't care whether ground is present and/or stable. The Tesla does care - and as a result it doesn't like when it can't detect a stable relationship / steady voltage between a line conductor and ground.

The reason many generators don't have this bonding done by default is that occasionally they are used to feed a home electrical system where the bonding is already done, and having multiple points where EGC and neutral are bonded can create undesired current return paths.

If you do use a generator to charge Model S, look in its instructions for a way to bond neutral and ground together. In some cases, generator manufacturers will sell a dummy plug and/or an adapter that will provide the necessary bonding (and therefore voltage stability).

EDIT: I should also note that there are certain types of inverter generators that use floating-neutral configurations where you cannot bond ground to neutral. It is reported the Honda 2000 & 3000 models are this way -- for 120V, their inverters generate +/- 60V from ground for the "hot" and "neutral" of the 120V outlets, so it's not really a "neutral". Bonding neutral to ground here will cause problems for the generator (it's like shorting hot to neutral). Be sure your generator manual or its manufacturer contemplate bonding ground and neutral together.

samcarney · Nov 23, 2015

cinergi said:
I've done it.

That said, I was never able to get the UMC to work by directly hooking it up -- it didn't like the grounding situation.

I have charged my Roadster and MS 85 with a portable generator. It works best when the generator is plugged into the house and I plug the car into a NEMA 14-50 outlet.
This confirms the grounding issues previously discussed.

Tree95 · Nov 24, 2015

I've done it with a cable adapter from Amazon from the locking generator connector to NEMA 14-50. I plugged the UMC into that, and it worked fine on my Honda 6500W generator.

Amazon.com: Conntek RV Generator Adapter with 30 Amp 4 Prong Locking Male Plug To RV 50 Amp Female Connector: Automotive

The car charged fine for 20 minutes at 240V / 20A.

supratachophobia · Nov 27, 2015

Basically, if the UMC doesn't complain, it should be fine. The UMC knows what the car should and should not have plugged into it, and will refuse to charge or sacrifice itself to save the on-board charger.

modelx007 · Jan 5, 2016

I have a generac 22kw generator. For emergency purposes what is best way to charge model s 90d? Someone told me to just use my dryer outlet? I'd say the run would be about 20 ft.

FlasherZ · Jan 6, 2016

modelx007 said:
I have a generac 22kw generator. For emergency purposes what is best way to charge model s 90d? Someone told me to just use my dryer outlet? I'd say the run would be about 20 ft.

Assuming your Generac is a whole-house genset connected via a transfer switch and your dryer receptacle is on the panel getting backup power, then that's probably the best option you have in an emergency. Also assuming - just because you asked the question - that your 14-50 is not on the backup panel.

modelx007 · Jan 6, 2016

FlasherZ said:
Assuming your Generac is a whole-house genset connected via a transfer switch and your dryer receptacle is on the panel getting backup power, then that's probably the best option you have in an emergency. Also assuming - just because you asked the question - that your 14-50 is not on the backup panel.

Correct on your assumptions. What can I run with charging the model s in emegency? Ac?
Also what cord do I use that I would run from the dryer outlet? I've seen a few and not sure which is the best?

Vince Cobelo · Jan 6, 2016

I was talking portable generators. A whole home backup generator naturally would do the trick no problem.

I'm going to pickup a 1600 watt inverter generator and give it a try. I know it will be a very slow charge but if it is clean it should do just fine with a 110 adapter. If not, I'll have to have plan B.

FlasherZ · Jan 6, 2016

modelx007 said:
Correct on your assumptions. What can I run with charging the model s in emegency? Ac?
Also what cord do I use that I would run from the dryer outlet? I've seen a few and not sure which is the best?

There are two types of dryer receptacles, 10-30 and 14-30, depending upon when your home was built. There are some Tesla adapters available for the UMC plugging into these receptacles, but you noted 20 feet which is beyond the 18 ft of the UMC. Your best bet, for emergency use only, is to create an emergency cable, about 6 feet long, appropriately wired and labeled "for emergency Tesla charging only" (or purchase from a place like EVSE adapters). See my FAQ for more details.

As for what you could run with the Model S charging, a 22 kW genset can run about 90A of load. With Model S charging at the full 24A off a 30A dryer receptacle (the continuous limit of that receptacle), you'd still have quite a bit of room for other loads - certainly your A/C and many other appliances.

- - - Updated - - -

Vince Cobelo said:
I was talking portable generators. A whole home backup generator naturally would do the trick no problem.

I'm going to pickup a 1600 watt inverter generator and give it a try. I know it will be a very slow charge but if it is clean it should do just fine with a 110 adapter. If not, I'll have to have plan B.

Some inverter generators won't work, depending upon how their grounding is set up. If it's a "floating neutral" generator, the Tesla UMC will flash red four times because ground won't be stable relative to the line voltage. Some generators can use a special plug to bond ground to neutral to make it work, but in others it will not work (and will destroy the generator).

miimura · Jan 6, 2016

Vince Cobelo said:
I was talking portable generators. A whole home backup generator naturally would do the trick no problem.

I'm going to pickup a 1600 watt inverter generator and give it a try. I know it will be a very slow charge but if it is clean it should do just fine with a 110 adapter. If not, I'll have to have plan B.

In addition to what FlasherZ said, you should check the continuous rating of that generator. 1600W is not very much. At the most, you should pull 80% of 1,600W, which would be dialing down the amps on the main screen to 10 amps from 12 amps.

modelx007 · Jan 6, 2016

FlasherZ said:
There are two types of dryer receptacles, 10-30 and 14-30, depending upon when your home was built. There are some Tesla adapters available for the UMC plugging into these receptacles, but you noted 20 feet which is beyond the 18 ft of the UMC. Your best bet, for emergency use only, is to create an emergency cable, about 6 feet long, appropriately wired and labeled "for emergency Tesla charging only" (or purchase from a place like EVSE adapters). See my FAQ for more details.

As for what you could run with the Model S charging, a 22 kW genset can run about 90A of load. With Model S charging at the full 24A off a 30A dryer receptacle (the continuous limit of that receptacle), you'd still have quite a bit of room for other loads - certainly your A/C and many other appliances.

- - - Updated - - -

Some inverter generators won't work, depending upon how their grounding is set up. If it's a "floating neutral" generator, the Tesla UMC will flash red four times because ground won't be stable relative to the line voltage. Some generators can use a special plug to bond ground to neutral to make it work, but in others it will not work (and will destroy the generator).

Ok I'll take a photo and paste it here tomorrow to confirm which I have.

I found this on amazon and someone in a review said they used it with the umc cable. Camco 55195 50 AMP 30' Extension Cord with PowerGrip Handle
Where would I exactly plug this into?

On a new question what would I use if I park at a hotel or friends house that has only 110? Can you send me to a link? I assume this would plug into the umc cable like the above Camco but need it to be 110.

Thanks for your insight! This is hard stuff to get all straight. Lol

green1 · Jan 6, 2016

modelx007 said:
On a new question what would I use if I park at a hotel or friends house that has only 110? Can you send me to a link? I assume this would plug into the umc cable like the above Camco but need it to be 110.

Use the 110 adapter that comes with the UMC, and a heavy gauge extension cable (not the normal cheap indoor ones) I have one, but I can't for the life of me remember where I got it (was a long time ago) and the car charges just fine on it.

FlasherZ · Jan 6, 2016

modelx007 said:
Ok I'll take a photo and paste it here tomorrow to confirm which I have.

I found this on amazon and someone in a review said they used it with the umc cable. Camco 55195 50 AMP 30' Extension Cord with PowerGrip Handle
Where would I exactly plug this into?

You still need an adapter that will take your 14-50 extension cord and allow you to plug it into the 30-amp dryer outlet. EVSEadapters.com has some cables that should work.

green1 · Jan 6, 2016

FlasherZ said:
You still need an adapter that will take your 14-50 extension cord and allow you to plug it into the 30-amp dryer outlet. EVSEadapters.com has some cables that should work.

I remember hearing somewhere that the UMC didn't actually use the neutral plug, and as a result you could effectively saw the neutral pin off a 14-50 and then it could be used in either 14-50 or 14-30 outlets. EVSEadapters has an extension cord pre-built that way too:
Heavy-duty NEMA 14-50 extension cord for Tesla, 20 ft.
Seems like a simple enough solution to get extra versatility (just remember to dial down those amps on a 14-30!!!)

Lloyd · Jan 6, 2016

Been charging two cars tonight and running my house on my gas (diesel) generator. Power out for 10 hours now.

http://www.teslamotorsclub.com/showthread.php/48977-Ready-for-Zombie-Apocalypse%21?highlight=Zombie

FlasherZ · Jan 6, 2016

green1 said:
I remember hearing somewhere that the UMC didn't actually use the neutral plug, and as a result you could effectively saw the neutral pin off a 14-50 and then it could be used in either 14-50 or 14-30 outlets. EVSEadapters has an extension cord pre-built that way too:
Heavy-duty NEMA 14-50 extension cord for Tesla, 20 ft.
Seems like a simple enough solution to get extra versatility (just remember to dial down those amps on a 14-30!!!)

Correct. Someone had even surgically removed only half of the neutral blade so it could fit in either as well. Not really needed, but helped stabilize the plug a bit.

green1 · Jan 6, 2016

FlasherZ said:
Correct. Someone had even surgically removed only half of the neutral blade so it could fit in either as well. Not really needed, but helped stabilize the plug a bit.

Any reason not to do that on the UMC adapter itself vs an extension cord (assuming length isn't an issue?)

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