I have a system running properly with ESS. I’m now wondering if I even need ESS?
A bit about my system and setup:
15 Kw of PV
30 kWh of BYD managed lithium batteries
15k quattro
Cerbo MK2
Two 450/100 chargers
- All loads are on AC out 1. AC out 2 can’t be used for technical reasons.
- ESS is in operation (ditch this?) with a grid setpoint of 0. However, as expected, the system injects and draws a small amount of power to/from the grid.
What I would like to achieve:
Draw from grid only when battery SOC falls below 20%
Switch to grid passthrough when loads are high (rise above 9200W)
PotentialApproach
Ditch ESS
Use programmable relay assistant with a high power relay (I have some such relays lying around) with 2 conditions: 1. Switch on grid when SOC is below 20% 2. Switch on grid when loads exceed 9200W for 1 minute
Constantly switching the relays isn’t great for lifespan of a system.
Accepting mains takes time, depending on the grid code, it also has ramp times.
You could use more grid doing this than the setpoint would.
You seem to be trying to reinvent the wheel when ESS and its features does this fine. It also exposes more points of control for custom automation than a vanilla system has.
I don’t see what the benefit of removing it and adding a more rudimentary control system would be.
Utility metering cycles tend to average out most of the push/pull that the setpoint creates.
In my system I use ESS and AC ignore via the GX and reconnect when the weather is poor and the system cannot sufficiently recharge. The system is sized sufficiently from a power and battery perspective to fully run the property as long as the sun mostly shines, so there is no need to switch on size of load. This means I only have to switch relays on/off infrequently - personal best was 3 months.
I can see the point there. I hadn’t thought about that.
I don’t see what the benefit of removing it and adding a more rudimentary control system would be.
I was thinking of the ability to switch to passthrough when loads are high. Designing the system to take care of big loads is generally better. Except that in my situation it’s impossible to predict or specify types or size of loads. This changes frequently. Not ideal but I’m looking for ways to mitigate it with limited resources.
In my system I use ESS and AC ignore via the GX and reconnect when the weather is poor and the system cannot sufficiently recharge. The system is sized sufficiently from a power and battery perspective to fully run the property as long as the sun mostly shines, so there is no need to switch on size of load. This means I only have to switch relays on off infrequently - personal best was 3 months
I was thinking of getting an additional 10 kWh of batteries. Otherwise I get plenty of sunshine through out the year. Batteries are normally charged to 100% by midday and discharged to around 40% overnight.
I am doing just that but with the hardware of the Multi RS.
I am using conditional AC-IN connection when the SOC is below 30%
And I am also using connect AC-IN when the load is above about 80% of the inverter’s max output power and disconnect when load is below 50%.
All this because you have such controls on Multi RS and also because it’s internal transfer switch is capable of 50A.
I believe that on Quattro you can achive the same with the VE Configure and its Virtual Switch - dedicated ignore AC input - with its load and battery conditions.
And you also don’t need the external power relay, because, as it says on the Quattro datatsheet:
You have an internal transfer switch capable of 100A, which is about 23kVA, way bigger than 15kVA of the Quattro.
If you want zero grid charge maybe disable the internal charger on the inverter or use the one charge control assistant to be able to manipulate if you would like the option to do so at some point
Did I misunderstand something? Yes, I’m aiming to achieve exactly what you are doing with your system, albeit with different hardware. My transfer switch should be fine. It is the Quattro relays, such as the alarm relay, that I’m worried about. Since given my hardware I need such a relay to switch on conditions I provide, I don’t see a way for grid to bypass it. Basically, I was thinking that I have to use the low power Victron relay to control my big relay to then switch the substantial grid power?
AC 2 out has a relay already in built into the inverters (except the Multi RS)
AC1 out is designed for essential loads, so really loads you don’t ever want off (like lights), it doesn’t make sense for that to have a relay when the inverter will shut down in the end it will all be off anyway
True, but I was thinking switching AC Out 1 via an external relay forces the inverter to run off-grid (not shut down completely) most times and on-grid only when the relays switch on the grid. In my specific circumstances, I can’t use AC Out 2 for this.
To run off-grid you disconnect ac in and both ac inputs on a quattro have a relay- see the block diagram. In other word you are off the grid (not on it)
Or by running off grid you mean running the loads using grid in other words powering off the grid source (removing it from the inverter?)
A 15kva can easily run this load inverting.
Everything you are talking about in your post is like using the grid as a generator -only as needed.
The idea is to normally switch off grid going to AC in but leave inverter running in off-grid mode via AC out 1 so that it doesn’t use grid at all.
When battery SOC drops below my conservative minimum or when unexpected loads come on line, switch grid back on via AC in and charge batteries if needed and continue to run loads on AC out 1 in passthrough mode (because my grid and quattro transfer switch should be able to handle unexpected loads as opposed to inverter only in off-grid mode).
My 15k Quattro should normally cover 9200W; I’m just being conservative here. Unfortunately, I often deal with people who come with all sorts of loads. It’s impossible to predict them but my grid, quattro transfer switches and the relay I’m proposing to place on AC in should cover them. I might even increase on 9200W but the concept is the same.
Generally, my smart meter IHD reads about -40W and this gives the system a few moments to react to change of load without registering any import on the smart meter.
It’s not an issue for me to have a trickle of export because my tariff pays me for it more than the off-peak energy that later replaces it.
Regarding the Quattro max output, you can probably set this in the Cerbo and clamp the output at a value. Not exactly what you suggest, but maybe close enough?f
