Path-Q Solar
How can I tell whether a proposed backup battery can handle the combined starting surges of several large motor-driven appliances?
Answer
Compare the battery inverter's surge capability and duration with the simultaneous starting demand of the motors, while also checking the continuous output for their running loads. Do not rely only on battery energy capacity or the appliances' running wattage.
Key points
- List each motor load's running current, locked-rotor or starting current, starting duration, and control sequence.
- Determine whether pumps, compressors, fans, and other motors can start simultaneously or can be staged.
- Check inverter continuous output, short-duration surge output, phase configuration, and transfer behavior.
- Include non-motor loads operating at the same time and account for voltage drop or starting failure.
What it depends on
- Actual appliance nameplate and measured starting characteristics
- Inverter surge rating and duration
- Whether loads can be shed or sequenced
- Electrical service and backup-panel configuration
Risks and trade-offs
- An undersized inverter may trip, fail to start a motor, or shut down other critical loads.
- A larger battery may provide more energy without providing sufficient instantaneous power.
- Motor-start capability can vary with temperature, voltage, mechanical load, and appliance condition.
Information you may need
- Appliance list and nameplate data
- Measured or manufacturer-provided starting current
- Proposed inverter continuous and surge ratings
- Backup-load sequence and load-shedding plan
Your next step
What to do next
Ask the designer to provide a written starting-load calculation and commissioning test plan that covers the worst credible combination of motor starts.
Path-Q
Find the right next step
Answer a few questions and we’ll narrow your options.
Loading…
SQ02886