EG4 6500, Why is there 150v ac on the dc solar input terminals?

[Mielectric1]

So while testing voltages and other things on the terminals I noticed this a while back. Even with nothing connected to the dc solar inut terminals, when the inverter is on there is approx 150v ac on those terminals. I find that very strange.

 

[Ampster]

I have heard that described as backfeed EMF, but I am not sure that is the correct term. The current is very small and some inverters use ferrite cores to reduce that. It was enough to screw up the current measurments on my BMS when I had an Outback Radian. I did not notice it on my Outback Skybox or my SolArk.

 

[Mielectric1]

Someone shared the basic diagram for inverters like this and I think I understand it, maybe kinda, since the transistors are used for ac outpput are also used for ac charging, the ac output goes both directions from the transistors, both to ac out, and solar in

 

[AntronX]

In these AIO inverters PV terminals are connected to AC output at all times.

 

[zanydroid]

This is a well known phenomena on forum thread. I don’t call it an issue because this is allowed by code. If you have non isolated (EDIT: and ungrounded) MPPTs, which is the current standard for string inverters, all bets are off.

If you don’t like this, you can specifically shop for isolated MPPTs, Victron might have some. Though in that case this marketing is a bit silly because AC cannot couple through a setup like this because the inverter and SCC anyway interact via a 48VDC bus which is typically isolated from AC to respect max voltage safety limits

On the AIO there likely not a step down to 48V bus between the components, since that is inefficient when your final output is ~350V peak to peak

 

[Mielectric1]

It just struck me strange more than considering it an issue.
And Thanks Zanydroid for shwing me the diagram in the other thread. I searched for an answer and could not find one, but it seems this is common enough knowledge. I will probably delete this thread to avoid clutter.

 

[zanydroid]

It just struck me strange more than considering it an issue.
And Thanks Zanydroid for shwing me the diagram in the other thread. I searched for an answer and could not find one, but it seems this is common enough knowledge. I will probably delete this thread to avoid clutter.

No you should keep this around because it needs to be bashed into people’s heads as a safety matter ?

It is very counterintuitive

 

[Adam De Lay]

I bookmarked this thread for this very reason

EG4 6500 voltage on PV terminals?

Hi, Is the EG4 6500 supposed to have voltage on the PV input (with no panel attached). I just noticed that if I put my multimeter on either the PV neg or PV positive and stick the neg wire of the multimeter in the ground I’m getting over 100 volts! Is that normal?

diysolarforum.com

 

[zanydroid]

An interesting question might be, will future standards add a safety requirement where PV conductors are disconnected within the MPPT/AIO in certain "powered off" states.

I imagine it's pretty low on the priority list for design / implementation. It might be difficult to get value out of this b/c you have to figure out which modes are "intuitive" for the PV conductors to be dead/floating. And the PV conductors are already dangerous in many states, IE after you connect them to the array, anyway.

 

[MrStimpy]

It would be interesting to see if it is a nuisance AC either thru circuit or induction OR a actual AC power of some type. I would place a 1500 ohm 20W or more resistor on the terminal with no PV connected and see if the 150V is still present or greatly reduced. If it goes away its nuisance, if it has current , it's not. Of course be careful with voltages at this level....