Dual PV max charge current

[Anže Košir]

i have been playing around with the dual PV, specifically setting the current limit to switch between L1, L2 and L3 charging, but the switching does not seem to be based on battery charge current, but on total PV current instead. So if production is high enough to trigger a diversion of 1/3 of the array, and i start a bigger load on the inverter, it does not switch back to using full array to charge the battery even though it might be discharging at that point.

[Dacian Todea (electrodacus)]

Yes that is correct.  The dual PV array can only react slowly up to around 2 seconds and Load could react much faster so it will not be a good idea to have the dual PV array switch based on battery current.

Using PV current ensures that charging will not exceed your set limit no matter what your load is.  Not quite sure what your intention was for that extra PV energy is. If it is to heat the house or large volume of water then you can use diversion for that so the array that is not needed for battery charging can be diverted to a heating element directly.

[Anže Košir]

I was mostly just trying to confirm my suspicion.

I understand that the dual PV array functionality is not the quickest, but i would think that a 2 second response time would't really matter though. as it is really only sustained fast charging that could be detrimental to the battery.

an actually, i am using diversion for heating a hot water tank, and i was wondering about this because of the following scenarios:

3.7 kWp, and 10 kWh usable battery.

hot water tank has a 800w DC element and a 2 kW AC heating element controlled by home assistant with some additional logic to operate differently based on battery SOC, diversion status, water temerature, forecast...

anyway, the two scenarios:

if there are very little loads on a good day, i could produce more total kWh, if some solar got diverted to water heating when battery is still charging, as the ac element on its own can't keep discharging the battery fast enough.

if there are bigger loads, (like an ev charging which i often do with excess production), i would prefer all the solar to ho towards the battery/inverter.

not a big deal at all, and i assume not a common thing to do, i just see a small possible optimisation opportunity here.

[Dacian Todea (electrodacus)]

There are multiple type of loads and some switch ON/OFF every few seconds (electric ovens or hotplates) to regulate temperature.

Say your 3.7kWp array is split in about 1.2kWp small PV array and 2.5kW the large PV array and you set the limit to 1.2kW (not sure why you will do that but that is how the dual PV array was designed) then you have a limit set at around 1 to 1.2kW or maybe you set the limit to 2.4kW then you mostly have to levels.

If your battery can charge at 2.4kW then is fairly likely it can also charge at 3.7kW and so there will be no reason for a dual PV array.

Not quite sure what your setup is like so I can not provide good advice but the dual PV array will need to be controlled based on PV shunt current and not based on battery current for many reasons.

With a 10kWh battery the typical dual PV array will be 6 to 9kWp example 7.5kWp (split in 2.5kWp and 5kWp) with charge limit set at 2.5kWp

If your limit is set at 2.5kWp and you have that configuration with 1.2kW + 2.5kW array then the 2.5kWp array will always be connected and when it is not in full sun the 1.2kWp will also be connected. So maybe 2 to max 3 hours per day the small 1.2kWp array will not be connected and during those 2 to 3 hours it can be diverted to a DC heating element a 1200W (2x600W) element.

My setup is not that different as I have a 13kWh battery  and a 9kWp PV array setup as dual PV array 3kWp + 6kWp

I have a 120A circuit breaker both for Load and PV so max Load is around 3000W (3500W inverter).

The PV limit is set to 80A so while sunny small PV array is sufficient and it may get to even 100A in winter maybe even 110A still OK for the 120A circuit breaker.

You can imagine if I use the battery current for limit and have say a 2000W load the large PV array will be connected and I will have 160A from PV array that will easily trip the 120A circuit breaker.  Of course I could use a 200A or larger circuit breaker but the batteries may not be able to handle that and the inverter can not accept cables that thick to handle 200A thus I'm forced to use 120A circuit breaker to protect the cables going to inverter.

I have a total of 9kW of DC heating elements so during winter all PV array energy is used but of course during summer maybe 10  to 20% of total PV array energy will be used since I just do not need it.

I will say that you likely do not need a dual PV array in your case if you can ensure about a 1kW load during the afternoon.