Zephyr Vent Fan


Zephyr Vent Fan, 12/24/48 Volt battery box ventilator & back draft damper, DC brushless fan, 3 – 6 Watt

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The Zephyr Vent Fan is meant to provide power-venting of battery boxes. In many locations electrical code requires a power vent (the NEC and CEC both do), though especially for regular flooded lead-acid battery banks it is a very good idea to vent them with a power vent regardless of code requirements. Without good venting the battery tops tend to get grimy much more quickly, a Zephyr Fan can help to keep the air inside your battery box much more agreeable!

Zephyr Vent Fan - made by Solacity Inc.

Zephyr Vent Fans are made in-house by Solacity in Canada. Before Solacity took over Zephyr Vent manufacturing in 2022 they were created and made by Zephyr Industries in the USA for the past 25 years. Solacity continues that tradition, and today’s fans are made with the same quality and care as before!

Zephyr Fans are sold by Solacity in three formats: We sell box quantities at distributor pricing (with minimum order quantities). If you are looking to buy vent fans to distribute them, including for countries other than Canada, please contact us for bulk pricing.

For solar installers and the trades that have a dealer account with us and that need just a few vent fans we have dealer pricing. Lastly, for individuals or businesses that just need single fans you can order them right here at retail pricing.

The Zephyr Vent has a gravity operated damper that keeps the vent pipe closed to prevent back-drafting when the fan is not in running. This prevents the batteries from getting unnecessarily cold during winter, preventing a temperature-induced capacity loss. The battery Voltage is an easy way to determine if the fan should be running, and many inverters and charge controllers include a build-in relay that can be used for this purpose.

The Power Vent is designed around typical home power systems with battery banks under 2,200 amp hours and charge rates under 150 DC Amperes. Systems larger than this can produce more hydrogen gas than the expel rate of the Power Vent which operates in the 5 to 8 cubic foot per minute range. Two vents may be used for higher volume.

The hydrogen gas produced by charging lead-acid batteries will set off a carbon monoxide detector in case the battery bank is located indoors (carbon monoxide detectors are actually much more sensitive to hydrogen than they are to carbon monoxide!). The Zephyr Vent Fan has been successfully used to prevent nuisance tripping of this sort when there is a carbon monoxide detector near the battery box.

Power Vents have also been used for other applications where low power ventilation is required. These include methane gas extraction from landfills, sewage sump tanks, outhouses, modest crawl space ventilation, beer tap line cooling and more.


  • Available for 12, 24, and 48 Volt
  • Positive venting of hydrogen gas
  • Stops back drafting
  • Puts the smell outside
  • Keeps batteries warmer in cold climates
  • Keeps the battery tops and terminals cleaner
  • Uses very little power
  • Excellent results for over 25 years!
  • 2 years warranty

Installation Instructions

The Power Vent must be placed vertically with the label right side up in order for the backdraft damper to function properly.

Place the Power Vent higher than the top of the battery box and indoors, especially in cold climates. If placed outdoors or in a very cold location the damper could freeze shut due to the condensing battery gasses (mostly water vapour!).

Use no more than four 90º bends including one at the exterior terminus facing down. Put a screen on the outside pipe terminus to keep insects and debris out. If installed in a dusty or construction environment put a porous foam or paper filter on the battery box inlet. DO NOT glue the Power Vents in place. Friction fit is adequate. DO NOT drip glue onto the fan blades. Use 2″ PVC DWV pipe on 12 and 24 volt systems. Use 2″ intake and 3″ output PVC DWV pipe on 48 volt systems.

Place a 1 Amp fuse at the start of the positive circuit wire. Thermostat wire and phone splice/tap connectors (ULG or UG)) work well to connect the Power Vent. Use a cable tie around the base of the Power Vent and wires to provide strain relief and create a neat wire job

A controller is usually used in the circuit to cycle the fan OutBack inverters and charge controllers may have a 12 volt powered auxiliary relay available. Other inverters may or may not have a voltage controlled auxiliary relay. Please refer to the appropriate manual for hook up and programming instructions. If no relay is available, a Voltage Monitoring Relay be used. The voltage set points for turning the fan on and off are above the full state of charge voltage of the battery but below the battery gassing voltage. In the case of grid tied systems where the batteries are kept at float voltage 24 hours/day it may be necessary to run the fan full time as the batteries are always gassing. An alternative is to remove the backdraft damper to allow passive venting and only switch fan on when batteries are above float voltage.

For the inquisitive, please note that the 48 volt Power Vents are built with two 24 volt fans wired in series.

Recommended Set Points for Flooded Lead Acid Batteries

Battery Voltage Fan On Fan Off
12 Volt 13.2 Volt 13.0 Volt
24 Volt 26.4 Volt 26.1 Volt
48 Volt 52.8 Volt 52.2 Volt
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