During force charge, why is the KH10 inverter limited to 10kW from AC and 1kW from PV (max 11kW total)?
According to the EQ4800 specifications, the nominal operating voltage is 403.2V, and the recommended charging current is 30A (max 50A). A simple P=VA calculation means the recomended charging power is 12.1kW (max 20.2kW).
During force charge, why is the KH10 inverter limited to 10kW from AC and 1kW from PV (max 11kW total)?
During force charge, why is the KH10 inverter limited to 10kW from AC and 1kW from PV (max 11kW total)?
Because it is a KH10 with a maximum AC power of 10kw, a KH7 would be 7kW, the limit is set by the inverters power limit or the (BMS maximum charge current * battery volts) whichever is the smallest.
The AC output is used to provide power to the house load when discharging from the battery. AC output is not used to charge the battery.
The inverter is connected to the battery by DC not AC. The Datasheet for the inverter specifically contains the DC specifications of the battery for charging and discharging.
As previously provided, the EQ4800-L9 operates at a voltage of 400V and the inverter has a maximum charge current of 50A (battery recommended is 30A). This shows the KH10 is capable of charging the battery at 20kW (battery recommended 12kW).
The AC Input specifications are what determines how much power can be used to charge the battery (allowing for AC to DC efficiency which is 97%).
As shown, for Australia, the max AC Input power is 14.5kW.
The inverter is connected to the battery by DC not AC. The Datasheet for the inverter specifically contains the DC specifications of the battery for charging and discharging.
The AC Input specifications are what determines how much power can be used to charge the battery (allowing for AC to DC efficiency which is 97%).
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Apologies, I guess I'm making some incorrect assumptions (that make sense to me) based on the data available to me in the datasheets. I'd very much like to understand how the inverter works (I was promised I'd be able to fully charge the battery during the free 3 hour period). Is there any more detailed reference material available for the inverter? The AC Input power specs are higher than the AC Output. Besides charging the battery, what else is the AC Input used for?
Also why can't the combined available PV + AC be used to maximise the battery charging. If it can only use 10kW from AC, when the PV is producing 2kW or more, why can't the inverter charge the battrey at above 11kW? Where does the 11kW limit come from?
Also why can't the combined available PV + AC be used to maximise the battery charging. If it can only use 10kW from AC, when the PV is producing 2kW or more, why can't the inverter charge the battrey at above 11kW? Where does the 11kW limit come from?
Unlike the traditional modular inverter with distinct MPPT and charger, the hybrid inverter has the added challenge with the charge controller being both DC and AC coupled so it can charge from either source or blend the two sources to get maximum charging whilst still meeting the anti-islanding protection requirement; I suspect this is what sets the charge controllers power to the inverter AC maximum power limit.
The inverter internally can handle more power on the vbus than its AC limit, up to the maximum power limits for the combined strings. Where the MPPT's are generating more power than the rated AC output, surplus power will be diverted to charge the batteries. Equally when charging batteries from PV, if there is more DC power being generated than the batteries charge controller can handle, the inverter will export the surplus up to the maximum AC power limit. If the MPPT's don't have a consumer for all the power they are generating they will derate.
In practice what that means is that your battery maximum charge power will be limited to the AC rating of the inverter, which for most batteries isn't a problem as the BMS sets the maximum charge current and that will be the limiting power factor, however with the higher voltage stacks such as EQxxxx and EPxx it is possible the inverter rating could be lower.
Also worth noting the BMS (BMU) is constantly managing the charge current and will ramp up or down depending on temperature, and soc.
A colleague of mine has done a high level schematic block diagram which helpfully details the system losses in the various stages and indicates where a Fox sensor is measuring it’s feed. https://github.com/TonyM1958/HA-FoxESS ... it-work%3F
Sadly Fox haven't shared the direct schematics for their hybrid but over the years a few people have opened them up and reverse engineered them, and they are very similar to the reference diagrams you can find on the internet for other hybrid inverters (Solax).
The inverter internally can handle more power on the vbus than its AC limit, up to the maximum power limits for the combined strings. Where the MPPT's are generating more power than the rated AC output, surplus power will be diverted to charge the batteries. Equally when charging batteries from PV, if there is more DC power being generated than the batteries charge controller can handle, the inverter will export the surplus up to the maximum AC power limit. If the MPPT's don't have a consumer for all the power they are generating they will derate.
In practice what that means is that your battery maximum charge power will be limited to the AC rating of the inverter, which for most batteries isn't a problem as the BMS sets the maximum charge current and that will be the limiting power factor, however with the higher voltage stacks such as EQxxxx and EPxx it is possible the inverter rating could be lower.
Also worth noting the BMS (BMU) is constantly managing the charge current and will ramp up or down depending on temperature, and soc.
A colleague of mine has done a high level schematic block diagram which helpfully details the system losses in the various stages and indicates where a Fox sensor is measuring it’s feed. https://github.com/TonyM1958/HA-FoxESS ... it-work%3F
Sadly Fox haven't shared the direct schematics for their hybrid but over the years a few people have opened them up and reverse engineered them, and they are very similar to the reference diagrams you can find on the internet for other hybrid inverters (Solax).