BYOAQ-BAT V: Power

If you haven’t already, please read the previous BYOAQ-BAT articles first – just search for the BYOAQ-BAT tag.


Up to now, the HoG has been powered from the mains, but now it’s time to swap to battery power for the next article. My quad has 2 batteries – the main LiPo powering the motors, and one of those phone charger rechargable battery banks (Lithium Ion under the covers) powering the HoG. That way by using optically isolated ESCs (‘Opto-ESCs’), the HoG is electronically isolated from the power demands of the motors: the phone charger power bank provides the 5V to supply the HoG, and the LiPo powers just the motors. There is not electronic connection between them – just an IR LED and photo-transistor.

One word of warning though: some ESCs may claim to be opto but are not. If the ESC has a (U)BEC, the presence of the (U)BEC is to power the flight controller. But due to ignorance in the market, sometimes the lack of a (U)BEC has incorrectly marketed as “Opto”. I came across this with a set of “The Black Sheep” (TBS) ESCs, where the manufacturers do not mention “Opto” whatsover, but a vendor / distributor made the mistake that a lack of (U)BEC must mean “Opto” and they sold it as such.

I took a gamble and bought a set. First thing I did was attach an ESC to the LiPo via the high power wires and measured the voltage on the 3-wire cable between (brown & red) or (black & red). It should read an unstable voltage close to 0v for “Opto” as you are measuring the voltage across an unpowered IR LED. But with the TBS ESCs they measured a clear and stable 5V. There’s nothing wrong with that in itself other than the ignorance of the distributor / vendor, but I wanted to keep my HoG completely isolated from the high-current surge LiPo and provide it with a stable regulated 5V instead.

So it’s your choice whether you go for 2 batteries and opto-isolation or 1 battery and (U)BEC, but be careful on the choice of ESCs in either case.

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