This video demonstrates how to power an existing/old UPS using solar energy by evaluating UPS compatibility, preparing a battery bank, installing solar panels and a charge controller, and wiring everything safely with proper fusing. The goal is to create a sustainable backup power setup that reduces grid reliance while reusing an old UPS unit.
Build Sequence
1. Assess UPS compatibility
Check the existing UPS nameplate and internal battery voltage/specs. Confirm the UPS input battery voltage (commonly 12 V, 24 V, or 48 V) and whether the inverter is suitable for continuous use. Verify battery chemistry and that replacement battery voltage matches UPS requirements.
2. Test and prepare battery / replace if needed
Load-test the existing battery or install a properly sized deep-cycle battery bank that matches the UPS voltage. Ensure terminals are clean and capacity is sufficient for your desired runtime. Install a dedicated fuse/isolator close to the battery positive terminal.
3. Select and mount solar panels
Choose panel wattage based on required charging power and available sun. Physically mount panels in a location with good sun exposure, secure mounting hardware, and route the PV cables toward the location of the charge controller.
4. Install MPPT charge controller and wire PV to battery
Mount the MPPT controller near the battery/UPS. Connect panel outputs to the charge controller (observe polarity), then connect the controller's battery output to the battery bank through the DC fuse. Use appropriate cable gauge and connectors.
5. Connect UPS to battery and configure
Disconnect mains/grid input to the UPS if testing off-grid. Connect UPS battery input to the prepared battery bank (through fuse) and verify correct voltage. If the UPS has configurable settings, adjust charge settings or low-voltage cutoffs to match battery chemistry.
6. Test system under load and monitor
With panels producing power, run the UPS on battery+solar and apply a controlled load to verify runtime and charging behavior. Monitor battery voltage, charge controller indicators, and UPS inverter performance for stability and overheating.
Frequently Asked Questions
Can any UPS be run off solar?
Not every UPS is plug-and-play with solar. The UPS battery voltage and inverter type must match your battery bank and intended use. Many UPS units only accept battery input and will work if you can supply the correct DC voltage from a battery charged by solar, but internal chargers and control electronics vary.
VIEW FULL ARTICLE →How do I size the solar panels and battery?
Estimate your AC load (watts) and desired runtime to determine battery capacity (Ah at the UPS battery voltage). Size solar panels and the MPPT controller to provide adequate charging current given your location's sun hours — panels should replenish what you consume daily plus losses.
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Panel size is example; actual wattage depends on load and runtime targets. Multiple panels may be needed in parallel/series for higher voltage or power.
Existing UPS being repurposed; important to check battery voltage and inverter type (pure sine vs modified).
An MPPT controller maximizes power harvest and is preferred for efficiency. Size current rating to panel array and battery bank.
Battery bank must match UPS battery voltage and chemistry considerations. Optionally replace with LiFePO4 for longer life (higher cost).
Fuse between battery and UPS/charge controller sized for expected current; protects wiring and equipment.
Proper gauge cable for panel-to-controller runs and weatherproof connectors.
Helpful for observing state of charge and diagnosing issues.
Brackets, rails, or clamps to secure panels to mounting surface.