Limit battery charge current without limiting inverter current

[John Sheppard]

Hello i live in Greece and in the process of selecting solar panel equipment due to the electricity cost being tripled in the past 6 months

TL,DR I need a way to limit the charge current to my batteries without it limiting the solar power to the inverters .

Long(er) version : I have long experience with electronic pcbs and have done a lot of electrical installations in my own house and relatives .
I intend to install 7500w worth of solar panels (maybe add more later) and 24x 2v 500ah opzs batteries for a usable capacity of roughly 9kwh. The WAAAY oversized solar panels compared to batteries is because i only need the batteries to get me through the night and with those panels i will likely get 3-4kw of continuous power "worst case scenario" and batteries are quite expensive .
However i have a problem that the in the morning hours when kids are at school and only the wife is at home the full draw of the house can be as low as 300w. At the same time we almost never have even a single cloud until 13:00 so the panels will likely be producing in excess of 6000w which will fry the batteries in short order. I need some way to limit that power to say 2000w or less but still have it available for the oven etc. On the other hand i can't connect only few of the panels to the batteries (through mppts ofc) as i still want all the panels feeding the battery in case of very bad day when they will be producing maybe 3kw or less.

I know Victron ecosystem can do this but that's way too expensive for me . I quite liked Epever but after a few back and forth messages with them they said it's not possible to do this. Their inverter with integrated chargers could do this but they can't be paralleled and each can take only 5kw solar power so i can't have all of my 7500w array connected to batts (again doing this for low light charging guarantee)

My idea was to have 4 Epever Tracer MPPT CCs feeding the inverter (NOT the batteries) then get a small 40a pwm CC taking power from the other 4 and have THAT charge the batteries , which would supply the inverter though a schottky diode to prevent the 4 powerful MPPT CCs from sending full current to the batteries. However when i asked them if it's possible to do this they said that i shouldn't for an unspecified reason. I'm out of options

[Ampster]

The concept in the title is easily done in many All In One inverters. They use separate settings for charge current and discharge current. I think the above plan is overly complex when component systems should each have separate settings for charge current and inverter draw.

[John Sheppard]

Thanks for the reply .
Yes i noticed that they have this option but in that case i need them to be parallelable so all the PVs can feed the same battery pack. I've found a 2 or 3 here (importing is out of the question due to insane customs and taxes which end up more than the product cost unless it's from EU) but they all seem to be identical with very little documentation or none at all or even a website . Coupled with the very short warranty of 1 year , it doesn't seem trustworthy . And if it fails , the whole system fails . That's why i was looking into hammering something together with discrete components that if/when they fail , won't bring the whole system down and will be much cheaper to replace

[solardreamer]

Hello i live in Greece and in the process of selecting solar panel equipment due to the electricity cost being tripled in the past 6 months

TL,DR I need a way to limit the charge current to my batteries without it limiting the solar power to the inverters .

Long(er) version : I have long experience with electronic pcbs and have done a lot of electrical installations in my own house and relatives .
I intend to install 7500w worth of solar panels (maybe add more later) and 24x 2v 500ah opzs batteries for a usable capacity of roughly 9kwh. The WAAAY oversized solar panels compared to batteries is because i only need the batteries to get me through the night and with those panels i will likely get 3-4kw of continuous power "worst case scenario" and batteries are quite expensive .
However i have a problem that the in the morning hours when kids are at school and only the wife is at home the full draw of the house can be as low as 300w. At the same time we almost never have even a single cloud until 13:00 so the panels will likely be producing in excess of 6000w which will fry the batteries in short order. I need some way to limit that power to say 2000w or less but still have it available for the oven etc. On the other hand i can't connect only few of the panels to the batteries (through mppts ofc) as i still want all the panels feeding the battery in case of very bad day when they will be producing maybe 3kw or less.

I know Victron ecosystem can do this but that's way too expensive for me . I quite liked Epever but after a few back and forth messages with them they said it's not possible to do this. Their inverter with integrated chargers could do this but they can't be paralleled and each can take only 5kw solar power so i can't have all of my 7500w array connected to batts (again doing this for low light charging guarantee)

My idea was to have 4 Epever Tracer MPPT CCs feeding the inverter (NOT the batteries) then get a small 40a pwm CC taking power from the other 4 and have THAT charge the batteries , which would supply the inverter though a schottky diode to prevent the 4 powerful MPPT CCs from sending full current to the batteries. However when i asked them if it's possible to do this they said that i shouldn't for an unspecified reason. I'm out of options

You maybe able to solve your problem with one or more diversion loads. You need a controller to monitor the battery voltage and turn on a diversion load when the voltage is above certain threshold and turn off when the voltage is below certain threshold. Depending on your diversion load you may need to adjust the voltage thresholds to avoid frequent switching.

[Mike90250]

Easiest way is with flooded lead acid batteries and a 3 stage charge controller. if the batteries overcharge a bit, add more water the next week and tweak the settings. You WILL have to monitor the system because you have a specific view of how you want it to work.

All parts from the same manufacturer. That way, they have a good chance of talking to each other.
All-In-One systems are clever, but if a section breaks, you have to buy an entire new unit (usually, there are no user serviceable parts inside)

You will need a knowledgeable installer to configure the set-point voltages, because there will be terminology that you ( or I ) don't understand

Are you "back-feeding" the grid or "selling to grid" ? Trying for zero grid use? sell to grid only at specific times ?

More simply, you could build an off grid system, and then use a 48V grid charger only when you need to 3x a month ?