All is not well in the PW SE multi verse

[SteamyTea]

31 minutes ago, Radian said:

Am I being silly or is it as simple as this

I am not sure if silly is the right word.

 

If each CT is sensing current from each AC circuit, does it not just cancel out and then end up doing nothing?

Take away the CTs and associated wiring, then it is just two batteries banks in parallel.  which is what I have been trying to say, without actually saying it (as the conversation had moved on).

 

[Radian]

1 hour ago, SteamyTea said:

If each CT is sensing current from each AC circuit, does it not just cancel out and then end up doing nothing?

That cancellation is exactly what I think is needed to fix the problem. If the PW can't see the power flowing into the SE then it won't push up its output voltage to try and supply it. And the same is true for the SE.

 

Edited to repost the schematic to make the cables passing through the CTs clearer:

Edited July 31, 2022 by Radian

[SteamyTea]

8 minutes ago, Radian said:

That cancellation is exactly what I think is needed to fix the problem.

I hate NAND and NOR.

 

I have not been following this too closely, apart from the kwh/kw/KW/KWH/kwH/Kw/killawotour.

Is it the software and how it reports that is the main problem?  It may be give a very false impression of what is actually happening, when in reality, PV is being stored when there is excess, when the batteries are low, they can charge at night, sufficient power is being delivered to the house and little is exported.

What @pocster needs it to make one of my energy monitors, then he can see what is really happening.

(I am not developing a crapple version).

[Radian]

5 minutes ago, SteamyTea said:

I have not been following this too closely,

 

Me neither because I'm incredibly jealous of all that luverly kit 🤣

 

Glancing at my schematic again, I realise that I'm taking it for granted that people understand that the house loads come off at the far right of the 'L' cable although not shown. This diagram only shows the relative locations and wiring for the two battery systems. Also, I think the SE system is a hybrid inverter but it should only have the one connection point to the AC so can be considered as a 'self charging battery' for our purposes here.

[MikeSharp01]

6 minutes ago, Radian said:

Glancing at my schematic again, I realise that I'm taking it for granted that people understand that the house loads come off at the far right of the 'L' cable although not shown

Have you shared that somewhere I must have missed it. 

[Radian]

Just now, MikeSharp01 said:

Have you shared that somewhere I must have missed it. 

 

Er, Are my picture attachments not showing up? How about this one...

[MikeSharp01]

That works.

[MikeSharp01]

Sorry it was above I must have missed it - only England beating Germany at football on the telly so not sure why I missed it.

[RobLe]

2 hours ago, Radian said:

 

Er, Are my picture attachments not showing up? How about this one...

That's a very interesting arrangement, but I'm not sure that will do what you want.  As an aside, you may find it difficult to fit 2 thick cables through the clamps.  Anyway - considering the power into B1, B2, and House - I think the schematic above, with knowledge that B1 is trying to null CT1, will create 2 equations:

B1=-House

B2=-House

Thus the overall power from the Live Tail will be the sum of B1, B2, and House:

B1+B2+House = -House. 

The units will each independently compensate the house, but that's unlikely to be what you want, as you've gone too far and are still interacting with the grid.

 

In contrast, the version I intended a while back gives equations:

B1=-House

B2=-House - B1

Thus the overall power from the Live Tail will be:

B1+B2+House = -House-House-B1+House = -House-House+House+House = 0

 

No current at the tail, just what we want I think 🙂

Honest.

 

 

 

[MikeSharp01]

Can I suggest a meet at 12 noon tomorrow at the OK corale to sort this out. @pocster will bring the ammunition

 

I am not sure that the obvious problem here is not more simply seen from the big picture. Whatever the equations you need to be able to act on them / what they tell you, and it isn't obvious, to me, how such interventions might be achieved with these two devices, their associated systems and controls.

[SteamyTea]

7 hours ago, MikeSharp01 said:

Can I suggest a meet at 12 noon tomorrow at the OK corale to sort this out

Can I bring my diodes.

[MikeSharp01]

36 minutes ago, SteamyTea said:

Can I bring my diodes.

Bullet proof vest might be more useful, but you are correct and I, like you, never go far without a pocket full on 1N4001s. 

[Radian]

19 hours ago, RobLe said:

I think if the PW clamp were after PW+House+PV, then SE clamp after PW+House+PV+SE that this stops the PW responding to the SE as it can't "see" that current flow.  The SE can still respond to the PW - but the overall feedback loop is broken, so I think this might fix it 🙂  One of the home batts will be exercised much more than the other doing this - the way around I described it, the PW will do all of the work until it cannot, being full or empty or having too high power flow, then the SE will mop up the rest. 

Hi RobLe, in trying to understand your suggested scheme I couldn't work out what you meant by 'after'. But I suspect the issue is that, as being near-identical generators and consumers of power, no asymmetric arrangement of clamps is going to produce symetrical results. Pocster needs both storage systems to bank-up charge in the narrow off-peak window.

 

9 hours ago, RobLe said:

Anyway - considering the power into B1, B2, and House - I think the schematic above, with knowledge that B1 is trying to null CT1, will create 2 equations

 

 

I don't follow. B1 is not nulling CT1, it would defeat the operation of the composite device. CT1 belongs to B1 and must see everything going in or out of it!

 

What happens in the arrangement I'm proposing is that B1's operation is invisible to B2 and vice-versa.

[Radian]

2 hours ago, SteamyTea said:

Can I bring my diodes.

I know you're being tongue in cheek but if only all this kit was DC then diodes could indeed solve the problem. Unfortunately you can't selectively block the direction of Alternating Current to create a 'one-way road' in the same simple fashion.

[RobLe]

I'm going to have another go at convincing people 🙂  The pic below is in 3 parts, showing a progression of the idea in my mind, and without pesky equations:

 

a) is as the manufacturer intends, batt1 having a CT on the tail before it, so that it can identify the power flow and try to make it zero on average.  It's doing a lot of maths and clever power electronics to achieve this, but we don't need to know about that.  A bit of power sneaks in and out on transients, but otherwise it does a good job.

 

b) is just like (a), but I've put a dashed box around the house+batt, and now we are just going to ignore what's inside - it all just works in isolation - any interactions are inside that box, and ultimately just give or take power from the grid.  Importantly, nothing from outside the box affects the inside (neglecting stuff like the grid is broken etc).

 

c) now we apply another battery, but you can see that box from (b) replaces what was just "house" in (a).  So batt2 should work, just as well as batt1 in (a).  As described before, the 2nd batt won't do much work - the first will preferentially absorb PV and make the tea, 2nd batt only operating when the 1st for some reason cannot.

 

🙂

[SteamyTea]

23 minutes ago, RobLe said:

I'm going to have another go at convincing people

Can see what you are getting at, but does it not assume that all potentials are always equal?

Secondary supplies need to be at a higher potential or nothing happens, and when they are lower, they absorb energy.

 

Maybe the PW and SW are always at the same potential (or try to be), which is slightly higher than grid potential.

Or worse, they fight each other to be the top one.

[SteamyTea]

1 hour ago, Radian said:

know you're being tongue in cheek but if only all this kit was DC then diodes could indeed solve the problem.

Zener diodes, or the much better Zennor, though mythical, ones. 

[RobLe]

1 hour ago, SteamyTea said:

Can see what you are getting at, but does it not assume that all potentials are always equal?

Secondary supplies need to be at a higher potential or nothing happens, and when they are lower, they absorb energy.

 

Maybe the PW and SW are always at the same potential (or try to be), which is slightly higher than grid potential.

Or worse, they fight each other to be the top one.

You don't need to worry about the voltages - the PW and SE will do all of that complicated stuff with their power electronics and control algorithms.  All you need to know is that the PW is trying to minimise the power flow through its CT; it will put out whatever current at whatever voltage is required to achieve this.

 

Imagine that you sublet a room in your house, where you had a single power feed in, and there was a PW battery, and a kettle which somebody turned on and off, maybe even a bit of PV.  The PW battery would effectively power the kettle.  You might not even know that they had done this, inside their sublet room.  Then imagine you fitted an SE battery to your whole house - this would work too, but nothing it does will affect the PW operation.

[Radian]

36 minutes ago, SteamyTea said:

Can see what you are getting at, but does it not assume that all potentials are always equal?

Secondary supplies need to be at a higher potential or nothing happens, and when they are lower, they absorb energy.

 

That's right. I suspect Pocster's install is wired in exactly the way RobLe shows it in (c) although which is batt is PW and which is SE is unclear. But it doesn't matter. It's the job of each battery to supply the power demand in preference to the grid except for when it is set to absorb power at off-peak times. Neither battery system can distinguish the house load from the other battery system if that battery system is being charged - therefore, if not actively charging itself, it will attempt to provide power for the other batteries charge.

 

Again, it's a highly symmetrical problem so is unlikely to yield satisfactorily to an asymmetric solution.

[Radian]

1 hour ago, RobLe said:

Imagine that you sublet a room in your house, where you had a single power feed in, and there was a PW battery, and a kettle which somebody turned on and off, maybe even a bit of PV.  The PW battery would effectively power the kettle.  You might not even know that they had done this, inside their sublet room.  Then imagine you fitted an SE battery to your whole house - this would work too, but nothing it does will affect the PW operation.

Except for it's insistence on charging the PW in the sublet during off-peak tariff time if PW is in need of charge and SE isn't. This is what annoys poor old Pocster so much becuase he doesn't want them exchanging their power reserves - ever!

[Pocster]

19 minutes ago, Radian said:

Except for it's insistence on charging the PW in the sublet during off-peak tariff time if PW is in need of charge and SE isn't. This is what annoys poor old Pocster so much becuase he doesn't want them exchanging their power reserves - ever!

Exactly !

This I have achieved !

The issue is when they both are set to charge from the grid . I’m hoping the PW won’t ‘see’ the SE as SE will be set to charge . Therefore PW will charge from grid . No idea if that will happen !

Frustratingly there’s so much solar I can’t empty the buggers to force a charge at off peak ( caveat being PW will ‘decide’ whether it charges or not ) . Both charging at the same time is my test for winter mode I.e no PV . Best find out now not later …. 

[Pocster]

@Radian a question for you .

Why doesn’t the PW just take from the SE when it’s <100% ?

What I mean is the PW sees the SE as solar ( regardless of whether it’s PV or SE ) . So say PV production is low today ( real sunshine PV ) and PW is <100% . Why doesn’t PW just drain SE until it’s full ? I.e it’s just PV to it after all ….

The answer doesn’t matter ! 😁 - I’m just curious !!

[Radian]

17 minutes ago, pocster said:

Why doesn’t the PW just take from the SE when it’s <100% ?

"Why does/doesn't the PW..." seems to be a very common refrain, featuring greatly in Tesla's own FAQ. The glib answer is because it's got some of Musk's AI baked into it - so nobody, not even Musk himself, knows why it does what it does at times. A great deal will actually depend on what external sensing it has. Is there more than one CT for example? Certainly one for the main incomer but is there another looking at the output from the SE?

[Pocster]

30 minutes ago, Radian said:

"Why does/doesn't the PW..." seems to be a very common refrain, featuring greatly in Tesla's own FAQ. The glib answer is because it's got some of Musk's AI baked into it - so nobody, not even Musk himself, knows why it does what it does at times. A great deal will actually depend on what external sensing it has. Is there more than one CT for example? Certainly one for the main incomer but is there another looking at the output from the SE?

Don’t know will look .

As it just doesn’t take regardless then effectively it can maybe distinguish between PV and power source ( as such ) 

[Radian]

1 hour ago, pocster said:

Don’t know will look .

As it just doesn’t take regardless then effectively it can maybe distinguish between PV and power source ( as such ) 

 

I think I get what you're saying. PW must know when there's free PV to slurp on, and when there isn't, in order for it to be compatible with the off-peak energy scheme it's associated with. Pretty fundamental to the whole idea behind it all. But of course it will never see (or expect to see) PV in the off-peak window.

 

Therefore when it does charge in the off-peak window, the resulting load must be hidden from SE and here we go around the explanation merry-go-round once again. I'm pretty certain You or your installer is going to have to do some nifty CT lacing to fix it. It may be that they did something along these lines but either got the current direction the wrong way around, or only did it for one battery system (or all the other combinatorial fails that are possible).