Inverter/Charger Passthrough & Shore Coordinator
Coordinate shore power pedestal limits with inverter transfer relays and battery charging. See when your charger automatically throttles and when the inverter provides battery boost power.
Enter the values above and click Calculate to view recommendations and engineering specifications.
How Hybrid Inverter/Charger Passthrough Works
Calculation Assumptions
- Internal transfer switch relay rated for full shore passthrough current (e.g. 30A or 50A).
- Evaluates combined shore power plus battery inverter assist wattage.
Engineering Limitations
- Shore breaker curves trip on prolonged overload even if the inverter attempts current-limiting power assist.
Connecting an RV to a 15A household outlet limits shore draw to 1,800W; when a 2,200W A/C kicks in, the hybrid inverter supplements 400W from the lithium battery, preventing the house breaker from tripping.
Modern marine and mobile inverter/chargers (such as Victron MultiPlus, Mastervolt, and Magnum Energy) integrate a high-speed automatic transfer switch (ATS) with bidirectional power flow:
- Dynamic Current Limiting: When plugged into a limited shore source (like a 15A household receptacle), you set the inverter's shore limit to 12A or 14A. The inverter continuously measures incoming current.
- Automatic Charger Throttling: As cabin AC appliances (coffee maker, microwave) turn on, the unit automatically reduces its internal battery charging current to prioritize AC appliances without tripping the pedestal breaker.
- PowerAssist (Inverter Boost): If AC loads exceed the shore limit (e.g. 2400W load on a 15A / 1800W supply), the inverter synchronizes with the shore AC sine wave and draws battery power to inject the difference ($600\text{W}$), allowing you to run heavy equipment seamlessly.
Frequently Asked Questions
What is inverter charger AC passthrough capacity?
Inverter chargers feature an internal automatic transfer switch that passes AC shore or generator power directly through to sub-panel branch circuits while simultaneously charging the battery bank. The transfer relay has a maximum continuous current limit (typically 30A or 50A) that must never be exceeded by downstream loads.
What is Victron PowerAssist / hybrid inverter boost?
Hybrid inverter chargers (such as Victron MultiPlus or Outback FXR) can synchronize with a limited AC source (like a 15A household outlet or 2,000W generator) and seamlessly inject battery power in parallel to meet peak appliance surges, allowing a 15A shore feed plus a 25A inverter boost to deliver 40A of combined power to appliances.
What wire gauge is needed for a 50A inverter charger transfer switch?
For a 50A AC passthrough transfer switch, 6 AWG copper conductor with 75°C or 90°C insulation is standard under NEC Table 310.16. Ground and neutral conductors must also be sized to carry full rated 50A return current.
Why does neutral switching matter on mobile inverter chargers?
When connected to shore power, the neutral-to-ground bond must occur at the shore supply panel, with the inverter's internal neutral-to-ground relay OPEN. When disconnected from shore power (inverting mode), the inverter must automatically close its internal ground relay to establish a safe local neutral-to-ground bond to ensure GFCI breakers function properly.