Specify a LiFePO4 battery and inverter as one power system. Matching nominal voltage and comparing Ah with inverter watts is not enough. Procurement needs an agreed operating range, current envelope, protection behavior and acceptance test for the exact combination.
The distinction matters for distributors selling battery-and-inverter bundles, RV equipment suppliers and integrators commissioning off-grid loads. A pairing may power light equipment successfully yet fail at the advertised application load.
1. Define the load before choosing the bundle
Start with the application's simultaneous running power, startup behavior and required operating time. Record AC voltage, frequency and socket or connection requirements. Separate the inverter's rated output from the load the bundle is actually intended to support.
A quotation for a "2000W inverter with a 100Ah lithium battery" is incomplete unless the battery voltage and discharge specification are included. It should also say whether 2000W describes inverter capability or validated continuous system output.
2. Translate the AC requirement into a DC current budget
For preliminary steady-load sizing, use DC current ≈ AC watts ÷ (DC input voltage × overall inverter efficiency). Then add simultaneous loads outside the inverter. Use the intended operating range rather than assuming nominal voltage remains constant.
The following values use an assumed 2000W steady AC load and 90% overall inverter efficiency. They are engineering illustrations, not WZRELB test data. The voltage in each row is an assumed voltage at the inverter terminals; each configuration requires a matching inverter.
| Assumed DC input voltage | Calculated inverter input current | Procurement implication |
|---|---|---|
| 12.8V | 173.6A | A 100A continuous battery limit is insufficient for this load |
| 25.6V | 86.8A | Validate the complete current budget and peak requirements |
| 51.2V | 43.4A | Still requires the correct input range and protection coordination |
Higher voltage reduces current for this assumed load; it does not establish compatibility on its own. For example, at 12.0V the first configuration would need approximately 185.2A. Include this variation when selecting battery, cable and switching components.
3. Put continuous and peak limits in separate specification fields
Request the complete battery pack discharge rating, the BMS continuous limit, peak-current value, permitted peak duration and applicable temperature conditions. The accepted system current must remain within all relevant component ratings; a single large peak number is inadequate.
A BMS can interrupt output when protection limits are exceeded. Battery-manufacturer documentation illustrates why continuous and timed peak ratings must be read separately. Use the datasheet for the battery being purchased.
For parallel banks, agree the permitted configuration and current-sharing arrangement with the battery supplier. Do not publish a bundle rating by simply adding individual BMS labels. The common cables, busbars and protection also need to carry the intended bank current.
4. Document the protection interface
Record the inverter's input limits, low-voltage shutdown and restart behavior, and the battery's charge/discharge restrictions. Define what should happen when the battery requests a stop and how the system recovers. Some battery systems require an external BMS or a control interface; others provide internal protection. Victron's BMS selection guide shows different architectures rather than one universal arrangement.
If communication is required, specify the protocol, supported messages, connector pinout and validated firmware combination. An RS485 or CAN connector alone does not establish interoperability. If the design relies on a remote shutdown input instead, confirm the electrical interface and intended behavior with both suppliers.
For WZRELB procurement, confirm those functions against the exact inverter configuration. Include charging equipment in a separate compatibility review when the inverter itself has no charger.
5. Agree the sample test before placing a bulk order
Turn the application requirements into a written test plan. Set numerical pass criteria for the project before testing, rather than treating the following checklist as a set of universal limits.
| Test | Record | Agree before testing |
|---|---|---|
| Steady application load | AC load, DC voltage/current, ambient temperature and duration | Required continuous output, allowable conditions and thermal criteria |
| Actual appliance startup | Starting equipment, simultaneous loads and BMS/inverter events | Successful starts and an agreed repeat sequence |
| Lower permitted operating voltage | Voltage at inverter terminals, current and shutdown behavior | Usable operating range and required shutdown/restart sequence |
| Inverter enable and recovery | Enable sequence, BMS response and any documented inrush control | Manufacturer-approved connection and recovery procedures |
| Required runtime | Starting condition, load profile, delivered energy and stopping point | Service duration and reserve requirement |
Testing must stay within manufacturer limits. Do not create a short circuit, bypass protection or force an unsupported deep discharge to complete a checklist. Have the installer confirm DC protection, cable selection and connection requirements using the component manuals; battery installation guidance covers why current ratings and fuse selection belong together.
A state-of-charge percentage alone is insufficient test evidence. Include measured current and voltage and retain BMS events where available. A correctly configured battery monitor estimates charge state from measured battery use; see the SmartShunt operating explanation.
6. Send an RFQ that can be checked
- Battery manufacturer, model, datasheet, chemistry and proposed series/parallel arrangement.
- Nominal and permitted operating voltage; continuous and timed peak discharge ratings.
- Required AC output voltage, frequency, phase and socket or connection type.
- Simultaneous running loads, startup equipment, load schedule and target runtime.
- Required shutdown/control interface and any battery communication requirement.
- Installation temperature, enclosure, cable run and charging arrangement.
- Sample quantity, order quantity, destination and proposed acceptance criteria.
Send the application information to Sales@powerreliable.com for a WZRELB inverter configuration review. Keep the final bundle specification tied to the tested battery, inverter and installation conditions. A change in battery BMS, firmware or wiring may require the combination to be checked again.