Off Grid Solar Charging - MYP won't charge using UMC?

[arorgan]

Hello all.

I am stumped on what to do next with my solar system and getting it to charge my MYP.

I have a 12V 300Ah Li Battery being charged by 2kW of solar, and 12V to 240V single phase Pure sinewave inverter. I'm running the Inverter through a transformer to create a split rail 120V-N-120V to give me L1 and L2 240V. I've put the scope on the inverter output and see the waveform, and checked the transformer outputs, and all seems good.

When i connect my wife's Ford mobile charger for her Mach E to this solar system, and connect to her car, all is fine and her car starts charging with no error messages.

When i connect the tesla UMC to the same power system (that works with the Ford) and plug in to my Tesla that's when things go wrong. The MYP sees the 230-240V. I've reduce the charge current to 5A just to make sure I'm not maxing anything out. The UMC relays are engaging but the car does not start to charge at all. I've connected the UMC to my home power supply to make sure the UMC is working. it works on the 110V and the 230V supplies in the home.

I've tried neutral/Ground bonding on the output of the inverter (the input to the transformer) and this makes no difference to the UMC or Ford charger operation.

I've purchased a second charger that is not a tesla charger to see if the UMC is the issue and the same thing occurs with that other charger when connecting to the Tesla from the solar system. The car sees the 240V system but won't charge. When i put this other charger into an outlet of my home, the MYP sees it and starts charging at the max charge level i've set. This other charger works fine with the Mach E also from the solar system and also from my home.

The upshot of all this is that my tesla doesn't seem to be able to charge from my solar system with any type of charger, but the Mach E can. I've tried simulating the grounding my home has, and made sure the system is doing what i think my home is doing. I've tried everything i can think off and done quite a bit of research, but just can't see to solve this.

Has anyone else has an issue with their UMC's not working on Solar but ok on their home power system?

Thanks in advance.

 

[Bp25]

Does the inverter have an 120v option that you can try?
Also, when you put scope on the transformer, can you observe both outputs to see the phase relationship and make sure you truly have a 120-N-120?

 

[arorgan]

Does the inverter have an 120v option that you can try?
Also, when you put scope on the transformer, can you observe both outputs to see the phase relationship and make sure you truly have a 120-N-120?

hello Bp25 - thanks for getting back to me. After the transformer i have the split rail and can see the waveforms on both legs. They are 180* out of phase and aligned in the time domain. However the waveform from the inverter is a mess.

The waveform from the inverter is the issue for the tesla specifically i believe. It is a weird combination of a triangle wave overlaid onto to pseudo sine wave with some sharp dv/dt transitions. I wish i had a storage scope that i could add the waveforms here, but i don't have one.

I've purchased (Arriving today) a Low pass 30A LC filter to put on the output of the inverter and before the single phase to split phase transformer to clean up the hard edges (Harmonics) to see if that will solve the issue. I know the peak to peak might be affected with this and putting this on the single phase going into the transformer i'm hopping the Phase shift of the L and C cancel out and there is no shift in phase.

When i run from a generator and neutral bond, all is fine with the UMC, so i'm very certain the waveform is not what the Tesla is expecting or wanting.

I'll add to the thread when the filter arrives.

 

[arorgan]

So i put the filter in and the weird waveform remains "but it looks a lot cleaner!" lol!

There is no doubt the type of waveform is somehow not liked by the Tesla. I put the Ford mobile charger onto the system and it works ok with the Mach E. I used the Mach E charger on the Tesla - didn't work. Plugged the Mach E charger into the home power supply at 240 with the Tesla - worked fine!.

It totally seems to me that the waveform generated by the Inverter is not suitable for the tesla at all. The UMC seems like it is simply passing the waveform through to the car and the car simply can't take it.

The only thing i can't try because i don't have an adapter is the Tesla UMC charger on the Mach E to rule out the UMC and a waveform conflict.

I tried a generator today and this worked fine with the Ford charger and the UMC on the Tesla. So this is my off grid back up plan for when i'm remote. Was hoping to use the solar energy, but i think i'll need a different inverter for the Tesla.

Any other pointers on inverters would be gratefully received.

Thansk

 

[Bp25]

So i put the filter in and the weird waveform remains "but it looks a lot cleaner!" lol!

There is no doubt the type of waveform is somehow not liked by the Tesla. I put the Ford mobile charger onto the system and it works ok with the Mach E. I used the Mach E charger on the Tesla - didn't work. Plugged the Mach E charger into the home power supply at 240 with the Tesla - worked fine!.

It totally seems to me that the waveform generated by the Inverter is not suitable for the tesla at all. The UMC seems like it is simply passing the waveform through to the car and the car simply can't take it.

The only thing i can't try because i don't have an adapter is the Tesla UMC charger on the Mach E to rule out the UMC and a waveform conflict.

I tried a generator today and this worked fine with the Ford charger and the UMC on the Tesla. So this is my off grid back up plan for when i'm remote. Was hoping to use the solar energy, but i think i'll need a different inverter for the Tesla.

Any other pointers on inverters would be gratefully received.

Thansk

It’s true that the “charger” that we plug in to the car is really just a glorified connector. The real charger is in the car. So it’s possible that the Mach-e tolerates irregular waveforms better than Tesla.

 

[Sophias_dad]

However the waveform from the inverter is a mess.

That doesn't sound very 'pure sinewavy' to me. A different charger(actually connector) won't fix this issue, but a better inverter should.

 

[GuruByNature]

Hello all.

I am stumped on what to do next with my solar system and getting it to charge my MYP.

I have a 12V 300Ah Li Battery being charged by 2kW of solar, and 12V to 240V single phase Pure sinewave inverter. I'm running the Inverter through a transformer to create a split rail 120V-N-120V to give me L1 and L2 240V. I've put the scope on the inverter output and see the waveform, and checked the transformer outputs, and all seems good.

When i connect my wife's Ford mobile charger for her Mach E to this solar system, and connect to her car, all is fine and her car starts charging with no error messages.

When i connect the tesla UMC to the same power system (that works with the Ford) and plug in to my Tesla that's when things go wrong. The MYP sees the 230-240V. I've reduce the charge current to 5A just to make sure I'm not maxing anything out. The UMC relays are engaging but the car does not start to charge at all. I've connected the UMC to my home power supply to make sure the UMC is working. it works on the 110V and the 230V supplies in the home.

I've tried neutral/Ground bonding on the output of the inverter (the input to the transformer) and this makes no difference to the UMC or Ford charger operation.

I've purchased a second charger that is not a tesla charger to see if the UMC is the issue and the same thing occurs with that other charger when connecting to the Tesla from the solar system. The car sees the 240V system but won't charge. When i put this other charger into an outlet of my home, the MYP sees it and starts charging at the max charge level i've set. This other charger works fine with the Mach E also from the solar system and also from my home.

The upshot of all this is that my tesla doesn't seem to be able to charge from my solar system with any type of charger, but the Mach E can. I've tried simulating the grounding my home has, and made sure the system is doing what i think my home is doing. I've tried everything i can think off and done quite a bit of research, but just can't see to solve this.

Has anyone else has an issue with their UMC's not working on Solar but ok on their home power system?

Thanks

Try running a #8 pure copper wire from the nema 14/50 receptical earth ground (round prong) directly into the earth. Also keep the existing earth ground that goes to the pure sinewave inverter frame/to earth ground. So basically you will have two earth grounds and I believe this will resolve your issue. At last try disconnecting the inverter to ground, tricking the UMC with the single #8 from nema to earth.

 

[Rocky_H]

Try running a #8 pure copper wire from the nema 14/50 receptical earth ground (round prong) directly into the earth.

I was thinking of that idea too. Pushing in a real physical ground rod would ensure that the ground is correct in case it's the "ground faking" methods that aren't working. That would at least check if it is that variable or not first, and if that doesn't fix it, then it would seem it has to be a problem with the wave of the power pins.

 

[GuruByNature]

I was thinking of that idea too. Pushing in a real physical ground rod would ensure that the ground is correct in case it's the "ground faking" methods that aren't working. That would at least check if it is that variable or not first, and if that doesn't fix it, then it would seem it has to be a problem with the wave of the power pins.

I’ve actually made it work that way!

 

[Electric700]

Is this resolved? I agree that a new inverter is needed as Sophias_Dad said, unless the grounding rod idea works first, and return the existing one if it says pure sine wave but the output is not that. Here is one option:

AIMS Power 3000 Watt Pure Sine Inverter Charger

AIMS Power 3000 Watt Pure Sine Inverter Charger. Ships in One Business Day. Buy it and Save at GlobalIndustrial.com

www.globalindustrial.com

This company got good reviews too.

 

[fiveangle]

The only way you can be creating 240v split-phase power ( +/-120v, ground-referenced) from a 240v single-phase inverter is by using a 1:1 transformer with a center-tap. The center-tap output potential of the split-phase transformer would need to be ground-referenced for the Tesla to accept it but it is not in your current setup. If you've connected earth-ground to the input of the inverter then bonded one side of it's output to this ground, then you are sending a -240v potential from the EVSE ground to one of the power leads going into your transformer and so the Tesla on-board charger would see about double the voltage it expects. It may be triggering an over-voltage condition and shutting off because this would indicate 480v AC in a split-phase system ( +/-240v). The Tesla on-board charger would also see its ground at 0v potential and not -120v as expected. Either of these facts could be why the Tesla is likely not accepting this since it officially supports only up to 240v 50/60Hz split-phase AC in North America. The Mach-E may simply not be designed with that extra safety check for North America. An EVSE + charger designed specifically for the 240v AC single-phase market like in Europe would not have these possible safety checks, but would also work in North America, which may be what Ford has done.

To test this theory, you could configure your existing equipment as the Tesla expects by connect the EVSE earth ground input to the center-tapped output of your transformer while leaving the ground lug on the inveter left floating (or else you blow the fuse (or worse) of your inverter the moment you turn it on). If you connect it in this way and it works, then that indicates one of the safety features I mentioned is being triggered. If the experiment I suggest here still doesn't work, then you know for certain that the Tesla on-board charger is also doing sinewave detection and it doesn't accept the inverter waveform (rather than one of the other safety checks I mentioned).

For my $$$ using a 1:1 center-tap transformer to create 120v split phase power is adding both complication and safety concern unless you enclosed the entire inverter + transformer into a double-insulated single unit so that neither chassis could ever be connected to an earth-ground (or to a human). Plus you do not know if the inverter is designed to safely isolate both of the 12v input leads from the output up to 240v. Not to mention the hysteresis losses of the transformer. Trying what I said would be an interesting exercise to better understand the safety mechanisms built into the Tesla charge components (and understand why it isn't working), but ultimately replacing your 240v inverter with a 240v split-phase pure sinewave inverter is the best and safest long-term solution.