A battery supplies direct current, or DC, while household appliances usually expect alternating current, or AC. A pure sine wave inverter makes this change through several coordinated stages.
The PCB shown here is a 3000W RBQ sample configured for 36V DC input and 120V AC, 60Hz output. Other RBQ versions follow the same basic path, but component counts and layouts may vary.
A real RBQ sample board showing the battery-side switching, transformers, capacitors, cooling, control, and output-filter sections.
Why use a 36V battery bank?
A 36V inverter needs a nominal 36V battery bank and compatible charging equipment. It is not an automatic input that can be connected to one 12V battery or a 48V bank.
Higher battery voltage can reduce the current required for the same output power. For a simple 3000W example:
3000W / 36V = about 83A
Real current is higher because efficiency is below 100% and battery voltage changes under load. Use the exact model instructions when choosing battery capacity, cables, fuse or breaker, terminals, and disconnects.
Stage 1: Protect and stabilize the DC input
Power enters through the battery terminals. Input fuses help protect against excessive current or short circuits, while low-voltage capacitors support fast current changes.
A battery can look charged at rest but drop under load. Long cables, loose terminals, corrosion, or an undersized battery can cause low-voltage alarms.
Stage 2: MOSFETs switch the battery power
A battery provides steady DC, but a transformer needs a changing signal. MOSFETs turn the battery current on and off rapidly, creating high-frequency pulses that can drive the transformer sections.
The 3000W sample shows nine visible input MOSFET positions. This is a detail from the video sample, not a specification that applies to every RBQ model.
Stage 3: Transformers raise the voltage
The high-frequency pulses enter the yellow transformer sections, which change the voltage level needed by the AC output stage. The sample has three visible transformer sections. The battery remains the energy source.
Stage 4: Rectifiers and capacitors build a DC bus
The transformer output is not finished AC. Rectifiers convert it into higher-voltage DC, and high-voltage capacitors smooth and store it on an internal DC bus. These parts can remain dangerous after shutdown, so customers should not open the case.
Stage 5: IGBTs form the AC pattern
Four IGBTs in the sample switch the high-voltage DC bus in a controlled pattern. Pulse-width modulation, or PWM, shapes the pulses into an AC waveform. IGBTs control the pattern; they do not create extra power or replace the transformer.
Stage 6: The output filter smooths the waveform
The raw switching pattern contains high-frequency content. Copper inductors and CBB film capacitors filter it into a smoother AC waveform. Current RBQ pages list THD below 3% and efficiency of 90%.
The control system monitors voltage, load, and temperature and supports alarms, protective shutdowns, the display, and wired remote control.
Introduction Video
What to match before buying
RBQ models use fixed ordering choices for 12V, 24V, 36V, or 48V DC input; 110V or 120V AC output; and 50Hz or 60Hz frequency. These are not automatic modes.
Before choosing, check:
- The battery-bank voltage
- Total continuous appliance wattage
- Startup demand from motors, pumps, refrigerators, or compressors
- Battery capacity and charging method
- DC cable length, cable gauge, and external fuse
- Ventilation space and ambient temperature
Compare the four RBQ power levels
| Model | Continuous / surge power | Current listed price* | A practical starting point |
|---|---|---|---|
| RBQ 1500W | 1500W / 3000W | From $179.00 | Smaller appliance groups and backup loads |
| RBQ 2000W | 2000W / 4000W | From $225.00 | RV, vehicle, or backup systems needing more margin |
| RBQ 2500W | 2500W / 5000W | $279.00 | Higher mixed loads and moderate startup demand |
| RBQ 3000W | 3000W / 6000W | From $335.00 | The highest total demand in the current RBQ range |
Prices checked August 10, 2026. "From" means the selected configuration can change the price. These are public website reference prices, not volume quotations. Confirm current price and availability on the product page.
Frequently asked questions
Can I connect a 36V inverter to a 12V battery?
No. The battery bank must match the inverter's selected DC input voltage.
Is 6000W surge the same as 6000W continuous power?
No. Surge is short-duration startup capability. The RBQ 3000W model is rated for 3000W continuous output and up to 6000W surge.
Why does the inverter show low voltage when the battery looks full?
Battery condition, cable resistance, terminal quality, and load current can all cause voltage to drop under load.
The path from 36V DC to 120V AC is a coordinated sequence: protect the input, switch the battery power, raise the voltage, build a DC bus, form the AC pattern, and filter the output. Correct battery matching and installation are just as important as the inverter's wattage rating.