I’m trying to plan for an off-grid system that offers the freedom to move my 3.5kW grid-tied system off-grid (if ever needed).
I’m looking at the Conext SW 4048 which supports AC-coupled solar power connected to it’s output port but is limited to 45A or ~2.25kW of charge power.
My 3.5kW Microinverter-based grid-tied array is overpowered by 4kW of solar panels and will often max out at 3.5kW of output during peak hours of the day.
So the SW 4048 cannot absorb full peak ac-coupled solar power by charging a battery.
The battery charger is 92% efficient and if I assume a lowest-possible battery voltage of 50VDC, is can absorb at most 2446W of AC power.
Hence the need for some ‘turbo’ solution to bump max battery charging power from 2400W up over 3500W…
I have a 240VAC to 50VDC rectifier that can be programmed to consume 2kW (like a Chargenectifier) so my ‘turbo’ idea is to use a current switch to turn on the rectifier to divert 2kW into charging the battery whenever AC-coupled current from the Microinverter string exceeds ~8A.
So the idea in phases would be as follows:
-Overnight: SW 4048 depleting battery by offsetting loads of ~300W average.
-Early morning - AC-coupled solar power < 300W: loads partially offset by AC-coupled solar power but battery continuing to be depleted.
-Mid-morning - 300W < AC-coupled solar power < 2000W (< 8A): SW 4048 first offsets loads and then consumes excess AC-coupled solar power by charging battery (with < 2000W of input power or < 37A of DC charge current).
-Mid-day / Peak-Production - >8A of AC-coupled solar power turns on current switch which turns on rectifier / charger. 2000W of AC-coupled power consumed by rectifier to charge battery @ ~38ADC while remaining AC-coupled power of < 1500W consumed by SW 4048 by first offsetting loads and then charging battery with excess of < 1500W with < 30ADC.
-Afternoon - 300W < AC-coupled Solar Power < 2000W (<8A): current switch switches off turning off rectifier so full AC-coupled solar power of < 2000W goes into SW 4048 to offset load and charge battery with < 2000W of input power or < 37A of DC charge current.
-Evening - AC-coupled Solar Power < 300W: loads partially offset by AC-coupled solar power but battery begins to be discharged to offset remaining load.
-Overnight - battery discharged to fully offset load.
In terms of clouds or other occurrences that temporarily reduce AC-coupled solar output, all of these ‘phases’ can transition up or down and can also cycle through multiple cycles without issue, so from what I can see, so I don’t see any issue there.
The idea would be to have a large-enough battery to power easily absorb a full day’s production but the system needs to also work when the battery starts out near full.
Once the SW 4048 enters float, the rectifier will be programmed to also be in CV and so the AC-coupled solar current will drop under 8A so all AC-coupled solar power of under 2000W will again enter the SW 4048 where it can properly throttle solar output to offset load and CV charge power.
So I’m not seeing any reasons this idea would not work to add a ‘turbo’ charging capability to the SW 4048’s modest AC-charge ing power and would appreciate any insight into what I may be missing…
I’m looking at the Conext SW 4048 which supports AC-coupled solar power connected to it’s output port but is limited to 45A or ~2.25kW of charge power.
My 3.5kW Microinverter-based grid-tied array is overpowered by 4kW of solar panels and will often max out at 3.5kW of output during peak hours of the day.
So the SW 4048 cannot absorb full peak ac-coupled solar power by charging a battery.
The battery charger is 92% efficient and if I assume a lowest-possible battery voltage of 50VDC, is can absorb at most 2446W of AC power.
Hence the need for some ‘turbo’ solution to bump max battery charging power from 2400W up over 3500W…
I have a 240VAC to 50VDC rectifier that can be programmed to consume 2kW (like a Chargenectifier) so my ‘turbo’ idea is to use a current switch to turn on the rectifier to divert 2kW into charging the battery whenever AC-coupled current from the Microinverter string exceeds ~8A.
So the idea in phases would be as follows:
-Overnight: SW 4048 depleting battery by offsetting loads of ~300W average.
-Early morning - AC-coupled solar power < 300W: loads partially offset by AC-coupled solar power but battery continuing to be depleted.
-Mid-morning - 300W < AC-coupled solar power < 2000W (< 8A): SW 4048 first offsets loads and then consumes excess AC-coupled solar power by charging battery (with < 2000W of input power or < 37A of DC charge current).
-Mid-day / Peak-Production - >8A of AC-coupled solar power turns on current switch which turns on rectifier / charger. 2000W of AC-coupled power consumed by rectifier to charge battery @ ~38ADC while remaining AC-coupled power of < 1500W consumed by SW 4048 by first offsetting loads and then charging battery with excess of < 1500W with < 30ADC.
-Afternoon - 300W < AC-coupled Solar Power < 2000W (<8A): current switch switches off turning off rectifier so full AC-coupled solar power of < 2000W goes into SW 4048 to offset load and charge battery with < 2000W of input power or < 37A of DC charge current.
-Evening - AC-coupled Solar Power < 300W: loads partially offset by AC-coupled solar power but battery begins to be discharged to offset remaining load.
-Overnight - battery discharged to fully offset load.
In terms of clouds or other occurrences that temporarily reduce AC-coupled solar output, all of these ‘phases’ can transition up or down and can also cycle through multiple cycles without issue, so from what I can see, so I don’t see any issue there.
The idea would be to have a large-enough battery to power easily absorb a full day’s production but the system needs to also work when the battery starts out near full.
Once the SW 4048 enters float, the rectifier will be programmed to also be in CV and so the AC-coupled solar current will drop under 8A so all AC-coupled solar power of under 2000W will again enter the SW 4048 where it can properly throttle solar output to offset load and CV charge power.
So I’m not seeing any reasons this idea would not work to add a ‘turbo’ charging capability to the SW 4048’s modest AC-charge ing power and would appreciate any insight into what I may be missing…