Start inverter only after SOC reached full charge ?

[Philippe Damour]

Hello

Is there a way to force the inverter not to start before the SOC reaches 100% ?

Configuration of EXTIO3 ?

Thanks

[Dacian Todea (electrodacus)]

Can you provide more details on what you want to achieve ?

In a normal system the EXT IO3 will never be OFF so your inverter if controlled by this will always be ON unless the battery is fully discharged (should never happen) or if there is a fault with the battery.

You can set an SOC limit to say 80% SOC if you do not want the inverter to discharge your battery below 80%. If the SOC drops to 80% the inverter will turn OFF and only turn back on when it gets to 83% SOC

You can increase this to say 97% then inverter will only turn ON when SOC is at 100% and turn OFF when SOC drops to 97% but not sure how will that be useful for any application.

[Philippe Damour]

My system consits of 1.8kW of PV on various faces of my roof, SBMS0 V0.2, LFP 24V 240Ah and an Edecoa 2400W inverter.

Quite a limited power installation and not large enough to full load the battery every day !!

Such, I splitted my electric panel in two: 

Panel 1: high consumption loads, as electric heating, cooking oven, heat pump, etc.. 
Panel 2: moderate consumers, as Controlled Mecanical Ventilation, Thermal panels Solar circulating pump, lights and power outlets for fridges, routers, computers, TV etc..

Panel 1 is permanently connected at the electrical public network (grid).

Panel 2 is hooked , through an ATS (Automatic Transfer Switch), on solar supply if enough power available. If not, battery empty or demand above 2400W, typically if water kettle or toaster ON, then the ATS will return Panel 2 to public network.

With this arrangment, I fully use what the sun is providing, without returning any energy to the public network, which is a reglementary requirement in France.

Since, I acquired an electric vehicle, for which a socket, for the charger, has been installed at the parking place.

Just recently, I build a small carport with 680W PV with a grid-tied 800W micro-inverter, connected to the EV charger power line ( unfortunatly only two-conductor cable !).

This power line was supplied through Panel 1, as such, most PV production returned for free to the public provider!

To avoid this, the EV charger line has been moved to Panel 2. But a problem arrised. If house electrical demand is below production power of the microinverter (typicaly high up to 500W to 700W ) then the Edecoa inverter regulation is lost and turn into FAULT: Bus voltage too high !!

 

That is why I am looking at a way to turn around this problem. 

1- Force the initial system to reach full SOC, usually end afternoon, leaving the Edecoa inverter OFF, and Panel 2 switched to public network and carport PV supplying what it can to Panel 1 and Panel 2.

Other ways:

2- Find a device able to compare house demand versus microinveter production to pilot EXTIO3.

3- Install a programmer timer (end afternoon) to pilot EXTIO3, but one should adjust time over year seasons !!

Thanks in advance for your recommandations.

[Dacian Todea (electrodacus)]

Are you fully discharge the battery each night ?

If so you may be able to use Under voltage recovery default set at 3.20V and increasing that to maybe 3.35V or similar allows the EXT IO3 thus Edecoa inverter to remain OFF for much of the morning.

Keep in mind that if you set this Under-voltage recovery to high the inverter may never turn ON as all cells need to exceed that limit not just the highest cell. You may need to fine tune this number by observing what is the minimum cell voltage when SOC is above 80 or 90%

For the Under voltage recovery limit to take effect you will need to power cycle the SBMS0 so before making that change monitor for a few days what is the lowest cell voltage in your pack when you get close to battery fully charged then say that lowest cell is 3.38V above 90% in most days you can set 3.37V as the limit to make sure inverter will turn ON before full charge but also not turn ON to soon in the day. Like the default 3.20V will turn on the inverter at 5 to 10% SOC.

[Philippe Damour]

Thanks for the clever advice, I would have never thought of that.

Yes, I fully discharge the battery each night.

My battery pack is from 2018 and from the last 2 days, the lowest cell voltage is just above 3.31V when SOC> 90%.
Consequently, I will try to set UVR to 3.30V for the coming days to watch what is going on.

My SBMS0 v02 was delivered with UV set at 2.80V, but I wondered if this limit should not be increased to said 2.85V or 2.90V, as the battery is fully discharged every day, in order to protect battery life?

Regards

[Dacian Todea (electrodacus)]

It depends at what rate you discharge the battery and how low is the internal resistance of the battery. But for low discharge rate you could increase that UV to 2.90V even 3V if you do not have high power loads that can trigger UV to early.