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Externally powering the Sonoff Basic

Ok, so I've got a sonoff basic and was planning to use it to control my heating unit, by connecting the line to the thermostat leads and just running a null back to the socket. 

Issue I encountered is the heating unit is varying the voltage from 12v to 70v AC constantly, seemingly not enough to power on the sonoff.

What I was thinking was to get a 5v charger and connect it, as mentioned in the FAQ to D5, however, in my newbness, I am wondering if I need to cut something or disconnect, in order for it to work properly.

Any ideas how I should go about it?

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I don’t know what electromechanical relay the basic has but I would have a search and check it goes as low as 12V AC. The Sonoff SV is designed already to allow an input of 5-24V DC and if you remove a couple of resistors it can switch AC, but the minimum AC is 90V. I don’t know why. Probably worth looking up the specs before putting effort in. I wouldn’t be surprised if they used the same relay on the different PCB. The basic might already have an exposed pin, which you could yourself attach to an appropriate relay, but then you’d have to use your own firmware (unless you just replaced, if needed, the relay that is there)

Ok, so I managed to do it by connecting 5v to D5 and running just the live wire through it and switching that on and off. DIdn't need to remove any rezistors or anything and works just fine now 

Hello.  I tried to make the same that you did, but without success, could you please tell me ,when you connect the 5V power to the D5, does the green LED (used to know if the sonoff basic is in pairing mode or not) is ON? and are you using the eWelink app to configure it with the wifi router?

WHen I connect my 5V adpater to the D5, anything happens (I'm using the little box currently sold and used to power a telephone) so I think that maybe, the current isn't enough... what is the 5V power supply recommended?  Thanks for your help.

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