Autonomous wifi bridge

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Power needs estimation

  • 2 Ubiquiti Nano LocoM5 24v, 5,5W each, so approx 12W
  • 1 Ubiquiti ToughSwitch 5PoE 24v, 2,5W, so approx 3W or Ubiquiti NanoSwitch N-SW (1.5W)
  • TOTAL => 15w under 24v

The estimation is voluntary "high". If we assume that the setup is used 24 hours a day at 100% of its capacity, it means 15*24=360Wh per day. We're not rich, so we assume that we will get lead-acid batteries. Because of the low yield of lead-acid batteries (10%), the capacity of the battery must be at least 150Ah. Finally, the solar panel have to produce at least 360Wh per day (this value depends of its size,yield, and the sun exposition). The maximum debited current from the batteries is 24/15 = 1.1A.

Solar panel

At the Goutailloux, the solar power is 1,46kWh/m**2/d, so we can take large : 1,40. If we take a 300Wc (nominal power) solar pnnel, the average power delivered a day is 300*1,4=440Wh per day, for the worst case, the December month. : 305€


The setup has to be robust, with low temperature and humidity. So we have to take great hardware. The MPPT 100/15 seems to be great, it can take 400w under 24v solar panels. : 91.80€

Battery setup

We want to have native 24v because we don't need DC/DC converter for the PoE. We can take 4 batteries of 80Ah each. We can assemble 2 batteries in series to make a pack of 24v/80Ah, then do the same with the 2 others. Finally, we can assemble this 2 packs (connected in series) in parallel to obtain 24v/160Ah. We hope that comrades provide batteries :)

WiFi relay prices


What do we need

We can buy some stuff, but we would like to recover as mush as possible from motivated people :)