Mobile charger with single phase 240v circuit ground loss

[Baked Billy]

I'm trying to get a mobile charger working with a 240v single phase solar inverter (off grid setup). This is a pure single phase circuit with no 120v neutral to bond to ground. As such, I'm getting a ground loss error (two red "T" flashes). My understanding is that the mobile charger needs to see 120v on ground, which is not possible with this particular inverter.

Is there any way around this? If not, does the more expensive wall charger require 120v on ground or can ground go straight to the grounding rod (via the breaker panel)? Buying a wall charger will be a lot cheaper than a split phase inverter.

 

[Earl]

I'm not sure exactly what your configuration is, however, I made a neutral bond to ground plug myself and plug it into one of the 15 amp outlets on my EcoFlow battery so I can charge my Tesla with the TT-30 outlet and UMC cord from EVSEAdapters.
The plug is easy to make with an off-the-shelf replacement grounded NEMA15-20 plug and a short piece of wire. I won't guarantee the safety of this but it does work.

 

[Rocky_H]

My understanding is that the mobile charger needs to see 120v on ground, which is not possible with this particular inverter.

Is there any way around this? If not, does the more expensive wall charger require 120v on ground

That's not a thing. There better not EVER be 120V on ground on any piece of charging equipment or circuit!
The thing that a lot of charging equipment checks for is that ground better not be floating. It needs to be fairly solidly held to 0V. So what a lot of them do is trickle a little bit of current into the ground pin, and if it easily moves voltage, then it's probably floating, and it will throw an error. If it stays hard at 0V, then it considers that a good tied-down ground.

or can ground go straight to the grounding rod (via the breaker panel)? Buying a wall charger will be a lot cheaper than a split phase inverter.

Yes, grounding rod should be the way to go and should work. If you have 240V and a ground, there is no need for a neutral or a split phase 120V point in the system at all, so there is no need for a split phase inverter.

The thing that @Earl is talking about is with standalone generators that don't have any real grounding connection or ground rod, you can sometimes fool the EVSE's grounding check by a kind of "cheater plug" that ties the neutral and ground pins together, and that will hold them both to 0V, so it doesn't look like either is floating, and that is usually enough to satisfy the charging equipment so it doesn't throw an error.

 

[Baked Billy]

That's not a thing. There better not EVER be 120V on ground on any piece of charging equipment or circuit!
The thing that a lot of charging equipment checks for is that ground better not be floating. It needs to be fairly solidly held to 0V. So what a lot of them do is trickle a little bit of current into the ground pin, and if it easily moves voltage, then it's probably floating, and it will throw an error. If it stays hard at 0V, then it considers that a good tied-down ground.

Sorry, I should have been more clear. I thought that it checks L1 to ground for 120v and L2 to ground for 120v in order to pass the check. If ground and neutral are bonded at the main panel, this would be the case. I have a separate 120v off grid inverter with neutral and ground bonded and the charger works fine with the NEMA 5-15 adapter at 12a current, even without a ground rod.

Yes, grounding rod should be the way to go and should work. If you have 240V and a ground, there is no need for a neutral or a split phase 120V point in the system at all, so there is no need for a split phase inverter.

Something must be wrong with my ground rod setup, then. With the 240v inverter and NEMA 6-50 outlet both tied to the ground rod, I'm measuring 90v on L1 to ground and 200v on L2 to ground (via both the 6-50 outlet and direct breaker panel measurements). If I disconnect the ground rod, both measure 0v but the charger's ground check obviously fails due to the floating ground.

Any ideas what would cause this? How can voltage feed back from the ground rod?

 

[ATPMSD]

What voltage do you see L1 to L2?

 

[ATPMSD]

I'm measuring 90v on L1 to ground

If you do some reading you will find the leading culprit for low voltage is a loose connection. This should be easy to eliminate.

 

[Baked Billy]

What voltage do you see L1 to L2?

L1 to L2 measures a clean 240v and other devices (such as mini-split AC) work fine on the outlet.

If you do some reading you will find the leading culprit for low voltage is a loose connection. This should be easy to eliminate.

There aren't any loose connections on the ground rod connection - that was the first thing I checked. You're saying a loose ground connection can cause two different voltage readings on L1 / L2 to ground?

 

[ATPMSD]

L1 to L2 measures a clean 240v and other devices (such as mini-split AC) work fine on the outlet.



There aren't any loose connections on the ground rod connection - that was the first thing I checked. You're saying a loose ground connection can cause two different voltage readings on L1 / L2 to ground?

What I was suggesting is you check for loose connections on the whole circuit: the inverter, breaker and the outlet. Based on what I have read a loose connection means higher resistance and lower voltage. Since only L1 is low, this seems like a reasonably possibility and, at the very least, it should be easy to rule out as a cause.

 

[Rocky_H]

Something must be wrong with my ground rod setup, then. With the 240v inverter and NEMA 6-50 outlet both tied to the ground rod, I'm measuring 90v on L1 to ground and 200v on L2 to ground (via both the 6-50 outlet and direct breaker panel measurements). If I disconnect the ground rod, both measure 0v but the charger's ground check obviously fails due to the floating ground.

Any ideas what would cause this? How can voltage feed back from the ground rod?

There aren't any loose connections on the ground rod connection - that was the first thing I checked. You're saying a loose ground connection can cause two different voltage readings on L1 / L2 to ground?

Hmm, well that's the kind of symptoms people get with a split phase system in a house but their neutral gets broken and disconnected. It's supposed to maintain a center point between the "positive" 120V side and the "negative" 120V side. If the neutral gets broken and floats, then various 120V circuits around the house can get really unbalanced, where one side drifts low, and the other side drifts high.

But I would expect those symptoms from the opposite cause of what you're saying. If you have your ground rod set in the ground, it should hold pretty solidly at approximately 120V on each side and when you have the rod pulled, it then it might imbalance, but you said you are seeing it the other way around. That's stumping me. I would check all the wire points to see if something is loose somewhere.

 

[Baked Billy]

Hmm, well that's the kind of symptoms people get with a split phase system in a house but their neutral gets broken and disconnected. It's supposed to maintain a center point between the "positive" 120V side and the "negative" 120V side. If the neutral gets broken and floats, then various 120V circuits around the house can get really unbalanced, where one side drifts low, and the other side drifts high.

But I would expect those symptoms from the opposite cause of what you're saying. If you have your ground rod set in the ground, it should hold pretty solidly at approximately 120V on each side and when you have the rod pulled, it then it might imbalance, but you said you are seeing it the other way around. That's stumping me. I would check all the wire points to see if something is loose somewhere.

I'm at a loss at this point. I tried the following with the same result each time (2 red "T" flashes = ground loss):

- Changed the NEMA 6-50 outlet to a different one
- Tried a NEMA 14-50 outlet / UMC connector
- Wired the outlet's ground directly to the ground rod, bypassing the panel entirely
- Disconnected the inverter's ground connection from the panel
- Tightened all connections and tested continuity between everything

At this point I'm fairly convinced that the UMC needs a split phase system with neutral / ground bonded in order to pass the ground check. My system is similar to a European, South African, or other foreign pure 240v system. What do they use in those countries?

Are there any other level 2 chargers on the market that don't have this agressive of a ground check?

 

[Baked Billy]

Apparently, the solution is to bond either L1 or L2 to earth to allow the UMC to pass the ground check. I will be testing this with a resistor and eventually adding a GFCI breaker to the panel.

UPDATE: Bonding L2 to earth put the UMC into an all green with 5 red flashes state (adapter fault / charge limited to 8a).

 

[Baked Billy]

Looks like there's no way around the 5 red flashes of death. I'm going to return the Tesla charger and buy one that actually lets me charge my car (plenty have an option to charge without ground).

Thanks again for the help...

 

[Baked Billy]

My UMC also immediately caps charging at 8a @ 240v with 5 red "T" flashes (unknown fault). I've tested both 14-50 and 6-50 adapters, so I either have a faulty unit or it can't auto detect something properly. Definitely not an overheating issue. Either way, this thing is way too over engineered and problematic and it's going back to Tesla.

I have a Chinesium smart 32a charger arriving today and I'm sure it'll do just fine.

 

[Oil4AsphaultOnly]

My UMC also immediately caps charging at 8a @ 240v with 5 red "T" flashes (unknown fault). I've tested both 14-50 and 6-50 adapters, so I either have a faulty unit or it can't auto detect something properly. Definitely not an overheating issue. Either way, this thing is way too over engineered and problematic and it's going back to Tesla.

I have a Chinesium smart 32a charger arriving today and I'm sure it'll do just fine.

Charging faults are reported in the car. Go into your "notifications" screen to see what the car reported as the reason for the throttling. I find that although the cheapy EVSE's work just fine, the lack of detail about what the actual charging issues are a little unnerving.

 

[Baked Billy]

Charging faults are reported in the car. Go into your "notifications" screen to see what the car reported as the reason for the throttling. I find that although the cheapy EVSE's work just fine, the lack of detail about what the actual charging issues are a little unnerving.

To provide some background info, I'm charging from a single phase 240v solar inverter (fully off grid system). This is a similar power system to that used in Europe or Australia, and not split-phase like in the US. To accomodate US-based customers, the inverter provides a clean 240v / 60hz AC pure sine wave output.

When I first attempted to use the UMC, I was getting a ground loss error (two red "T" flashes). I was able to get past this check by bonding L2 with earth in the panel. In this case, L2 is considered "neutral" (like in the EU / AUS) but not in the same sense as a US split-phase setup.

The UMC error I'm getting states that the adapter can't detect the wall plug type, so charging is reduced to 8a. I tested both 14-50 and 6-50 adapters / outlets with no difference. If I were to use a European or Australian UMC with a foreign plug adapter, I'm sure I could get past the charging limit. I don't want to go that route, though. I should also note that my UMC works fine at 120v / 12a on a separate off-grid inverter I have.

The Chinesium charger arrived earlier today and although it shows a clean 240v input on the screen, it won't charge at all (it just clicks a few times and the car reports a charging error). So much for that idea...

I fully understand that this is an unsupported and ridiculous way of doing things, and I guess I should be grateful that I can even get 8A out of the UMC. The reality is that these US-based chargers need a true split-phase inverter to function properly, but I have no desire to drop $1,500+ on one of them when single-phase 240v inverters can be found for a third of the price (or even less).

 

[Oil4AsphaultOnly]

To provide some background info, I'm charging from a single phase 240v solar inverter (fully off grid system). This is a similar power system to that used in Europe or Australia, and not split-phase like in the US. To accomodate US-based customers, the inverter provides a clean 240v / 60hz AC pure sine wave output.

When I first attempted to use the UMC, I was getting a ground loss error (two red "T" flashes). I was able to get past this check by bonding L2 with earth in the panel. In this case, L2 is considered "neutral" (like in the EU / AUS) but not in the same sense as a US split-phase setup.

The UMC error I'm getting states that the adapter can't detect the wall plug type, so charging is reduced to 8a. I tested both 14-50 and 6-50 adapters / outlets with no difference. If I were to use a European or Australian UMC with a foreign plug adapter, I'm sure I could get past the charging limit. I don't want to go that route, though. I should also note that my UMC works fine at 120v / 12a on a separate off-grid inverter I have.

The Chinesium charger arrived earlier today and although it shows a clean 240v input on the screen, it won't charge at all (it just clicks a few times and the car reports a charging error). So much for that idea...

I fully understand that this is an unsupported and ridiculous way of doing things, and I guess I should be grateful that I can even get 8A out of the UMC. The reality is that these US-based chargers need a true split-phase inverter to function properly, but I have no desire to drop $1,500+ on one of them when single-phase 240v inverters can be found for a third of the price (or even less).

Ah! That makes sense now. And yes, split-phase (two 120v sine waves that are 180-degrees out of phase) is different from single-phase (single sine wave with amplitude 240v), so there's no way to "trick it".

 

[Baked Billy]

Ah! That makes sense now. And yes, split-phase (two 120v sine waves that are 180-degrees out of phase) is different from single-phase (single sine wave with amplitude 240v), so there's no way to "trick it".

The primary use of these (dirt cheap) 240v inverters is for the MPPT solar charge controller and battery charging (30kw solar and 100kwh+ LFP 48v bank). They also run multiple 240v mini-split ACs fine (heat pump / inverter), so I guess some devices are just more picky than others.

This weekend I'll be testing a 5000w 120v to 240v step up transformer that'll hang off one of my 5000w 120v inverters. If I can squeeze 4000w (~16a) out of it, I'll be happier than I am now.

If that doesn't work and the step up transformer only provides a single 240v wave, then I can probably use two transformers in step down mode off the 240v inverter and swap the hot / neutral on one of them to get two 120v waves 180 degrees out of phase.

 

[mongo]

Ah! That makes sense now. And yes, split-phase (two 120v sine waves that are 180-degrees out of phase) is different from single-phase (single sine wave with amplitude 240v), so there's no way to "trick it".

@Baked Billy
Extreme not advice:
Adding a low power 240V center tapped transformer with center tap connected to ground might make it happy. High power autoformer is possibly overkill.

 

[Baked Billy]

@Baked Billy
Extreme not advice:
Adding a low power 240V center tapped transformer with center tap connected to ground might make it happy. High power autoformer is possibly overkill.

One of these auto transformers should work to take the single phase 240v from the inverter or a generator and clean it up for proper split phase, right?

Autotransformer - Victron Energy

Use the Autotransformers for step up, step down and split phase output balancing purposes. Find a Victron Energy dealer near you.

www.victronenergy.com

Do you have a link for one of the low cost devices? Since I have multiple single phase 240v inverters and a couple 240v generators, I'd rather invest in a single device to clean up the legs that I can move around in the event that one inverter fails or I want to charge with a generator. I only need to charge one EV at this point.

 

[stopcrazypp]

To provide some background info, I'm charging from a single phase 240v solar inverter (fully off grid system). This is a similar power system to that used in Europe or Australia, and not split-phase like in the US. To accomodate US-based customers, the inverter provides a clean 240v / 60hz AC pure sine wave output.

When I first attempted to use the UMC, I was getting a ground loss error (two red "T" flashes). I was able to get past this check by bonding L2 with earth in the panel. In this case, L2 is considered "neutral" (like in the EU / AUS) but not in the same sense as a US split-phase setup.

The UMC error I'm getting states that the adapter can't detect the wall plug type, so charging is reduced to 8a. I tested both 14-50 and 6-50 adapters / outlets with no difference. If I were to use a European or Australian UMC with a foreign plug adapter, I'm sure I could get past the charging limit. I don't want to go that route, though. I should also note that my UMC works fine at 120v / 12a on a separate off-grid inverter I have.

The Chinesium charger arrived earlier today and although it shows a clean 240v input on the screen, it won't charge at all (it just clicks a few times and the car reports a charging error). So much for that idea...

I fully understand that this is an unsupported and ridiculous way of doing things, and I guess I should be grateful that I can even get 8A out of the UMC. The reality is that these US-based chargers need a true split-phase inverter to function properly, but I have no desire to drop $1,500+ on one of them when single-phase 240v inverters can be found for a third of the price (or even less).

Not surprised it's not working. L1 or L2 is not supposed to be bounded to ground. In the US, L1 and L2 is 120V vs N (which generally is same potential as G). L1 vs L2 is 240V. In Australia from what I can find, L1 and L2 is 240V vs N.

Note the Tesla UMC when using 240V doesn't even use the neutral at all, so I don't think it cares at all if you have split phase, just that your setup is properly grounded. Have you tried using the UMC on an actual 240V circuit powered by the grid? That would confirm if it's working fine with the 240V setup in your country.

I think your issue is your inverter is either not grounded properly or it was not designed to be grounded in the first place (but rather floating), in which case it's not compatible with EV charging that relies on a ground for protection against electrocution (which is why the later a EVSE you bought doesn't work either).