Off-Grid Inverter and Battery Matching: A B2B Load and Daily-Energy Specification
For an off-grid equipment package, match the inverter to both the AC load schedule and the battery system’s usable energy, voltage window and discharge capability. A watt rating is an instantaneous power limit; it does not tell an OEM how long the equipment can run or how much solar generation is needed to recover the consumed energy.
The photographed WHM-300-C is a 12 V modified-sine inverter. Its matched C-series sheet lists 300 W rated power and 600 W peak power, without a peak-duration curve. Treat those figures as starting information for qualification, not a guarantee that any 300 W appliance or motor will operate correctly.
Separate the functions in the purchased system
A battery-fed inverter converts DC energy to AC for the connected loads. The photovoltaic array, charge controller and battery perform different jobs. The WHM-300-C evidence used here does not identify a solar charge-controller function, battery charger, grid-export function or automatic transfer arrangement. Specify those functions as separate parts of the system rather than assuming they are included in the inverter enclosure.
The US Department of Energy’s PV system overview explains the distinct roles of generation, conversion and storage. That general overview is not a certification or performance report for this WHM sample.
Ask for a load schedule, not only a total wattage
| Required load information | Why procurement needs it |
|---|---|
| AC voltage, frequency and waveform acceptance | The supplied output version and modified waveform must suit the receiver |
| Simultaneous continuous power | Separate the operating combination from a sum of unrelated nameplates |
| Starting power, duration and restart sequence | A peak watt figure without duration cannot establish startup compatibility |
| Hours per day and standby periods | These determine daily energy demand and idle-loss exposure |
| Required autonomy and recovery time | The battery and charging design must cover the specified operating period |
Calculate daily energy with declared assumptions
Suppose an auxiliary AC device consumes 60 W for four hours each day: its load energy is 240 Wh. If planning efficiency is assumed to be 85%, the inverter input energy for that load is approximately 282 Wh. Add applicable inverter idle energy, other DC loads, distribution losses and the battery’s permitted usable-energy limit. These are illustrative assumptions, not measured WHM efficiency or a battery-size recommendation.
Separately estimate the solar energy that can actually reach the battery under the site’s irradiation, shading, temperature and charging limits. Do not compare a panel’s nameplate watts directly with daily load watt-hours. The system must also recover the chosen battery reserve under the specified seasonal conditions.
Check the battery voltage at the inverter terminals
The matched 12 V C-series column lists a 10–15.5 V input range. Confirm the battery’s complete charge and discharge operating window, including charging peaks, protection behavior and voltage loss along the DC circuit. Nominal “12 V” is not the complete compatibility statement.
Use the actual delivered input version; the same sheet also describes 24 V and 48 V variants with different windows. The original sample’s top strip says 12 V, so it must not be relabeled as a higher-voltage unit to fit an existing battery bank. Cable protection, fault interruption and earthing require the completed system design and applicable installation rules.
Qualify the complete load/battery combination
Agree on a sample test covering the minimum available battery voltage, permitted maximum AC load, required starts, thermal conditions and autonomy target. Record the input voltage at the inverter, the battery protection state and the receiving equipment’s behavior. Check whether the actual receiver manufacturer permits a modified-sine source before approving the arrangement.
For recurring OEM orders, bind the approved output voltage/frequency, plug arrangement, input version and C-series mechanical revision to the purchase specification. The supplied C sheet lists a 162 × 106 × 63 mm WHM-300-C body; dimensions from a different WHM revision should not be used to approve the same equipment space.
Information for a system-level quotation
Provide the battery chemistry and voltage limits, charging architecture, AC load list and waveform requirements, simultaneous power, daily duty, autonomy, enclosure conditions, target market and expected production quantities. Use the WEHO product catalogue to compare families and request a version-specific inverter review. Confirm commercial terms and any project approval documents in the quotation.
Buyer questions
Does a 600 W peak rating guarantee motor startup?
No. The supplied evidence does not establish peak duration or the particular motor’s starting demand. Both the inverter and battery/distribution path need a defined test.
Can photovoltaic modules connect directly to this inverter?
The source identifies a battery-voltage DC input, not a qualified photovoltaic input with charging or tracking functions. Specify the correct charging and storage architecture first.
