ozak
Have you considered to flash custom firmware?
That way you don't to have to depend on the cloud and just pair with home automation apps like home assistant

After conduct a test on the sonoff, which

1) Power OFF the main to sonoff. Power OFF the router/modem. Wait till the sonoff schedule timer ON coming out.
2) Power ON the sonoff after the schedule timer ON function. Sonoff doesn't turn ON the light.
3) Power ON the router/modem. iphone detect the network and the apps alive. But sonoff remain OFF. It is on the timer ON schedule.
4) Power OFF the sonoff for a while and ON back. Sonoff remain OFF. Even on schedule timer ON and detect the network.
5) Finally using the apps to ON it.

Conclusion, sonoff require cloud to run. Without network detect, it cannot function on it own. No memory in the device.

"WiFi Pairing and Device Addition
eWeLink obtains device status and controls devices by sending commands through cloud server. This means all devices must first connect to WiFi router and connect to our Amazon AWS server. So every new device must be paired with user's home WiFi and added to eWeLink account."

Why so complicated?
Just turn off your wifi just before a schedule timer is due to test.

Your test I feel something is wrong. You cannot expect it to work when it is already passed it's schedule. For example - you set for it to turn on at 9am. If you turn on power to the Sonoff at 9.15am, it is already passed its schedule. You must turn it on before 9am to test

I create a few scenario to see how it run. Without wifi and without power.

I thought it will function like a mechanical timer. Where it will ON even pass the schedule timer ON. When the power OFF and ON back.

It should behave in this way. Cause the timer ON schedule is already set when the power coming back. It is like your main power trip and coming back later on. Than the sonoff detect back the setting and resume the function. Without your intervene.

mechanical is different from electronic mah....
in electronic - you need to trigger it to make it switch state
actually it does resume back its function after you turn it back on but you cannot expect it to look for something that has already passed. Even my LIFX works the same way.

Btw there is a setting inside -
Power On State
> on
> off
> Keep

I think what this does is if you manually turn it off - then what is the condition it will go to when you turn it back on? Try these three setting.

I thought they prg the sonoff behave like mechanical timer. Since programming is much more easier to do.

Wonder what reason not to resume the function after main power back. Safety ?

For this "power ON state", I have try it out. It is when the main power ON back, what state it in position. Turn ON or in OFF state. But don't understand it "keep" state.

So talking about this "power ON state". Since it have such function, why not create a "resume" state and "Default" state. When choose resume, it will run back and the prg have been execute. Like timer.

* suddenly have an idea to try this. What happen if the main power OFF and ON back during,
1) light ON
2) Timer ON

I think that "keep" state got to do with this.

maybe Keep means Resume ?

Will try it out tonight.

also try this -

example -
1. Set timer to Turn On at 9pm
2. before 9pm, turn off Wifi
3. see if Sonoff keep to its schedule to turn on lights at 9.00pm

If you want to locate at your DB, forget it. The size and shape doesn't DB friendly.

If you want to place hide it away near your device, should be ok.

DIY replacing is easy. Cut the wire between and joint this unit in. The rest is hook up with your HP with few instruction.

You can check back here. idoblu got picture how to join.

Or search in youtube. Plenty of instruction.

Aiseh, so bulky huh.
But my DB is not that pack if i remember correctly. Will have a look on it.
BTW, this Sonoff can only purchase online from overseas now?

also try this -

example -
1. Set timer to Turn On at 9pm
2. before 9pm, turn off Wifi
3. see if Sonoff keep to its schedule to turn on lights at 9.00pm

Aiseh, so bulky huh.
But my DB is not that pack if i remember correctly. Will have a look on it.
BTW, this Sonoff can only purchase online from overseas now?

Boss, good news.

I tried out liau. You need to set to "Keep" state in the setting. Than it will memorise the last setting before main power OFF. When ON back, it will run back the last setting.

2 test I tried yesterday.
1) I set the timer ON at 9pm. Before 9pm, OFF the wifi. At 9pm, the light ON without the wifi.
2) Set to "Keep" in Apps. Turn ON the sonoff. Than main power OFF. Wait for a while and ON back. Sonoff ON back the light.

So my early conclusion testing is wrong. Sonoff do have memory set inside the device.

Aiseh, so bulky huh.
But my DB is not that pack if i remember correctly. Will have a look on it.
BTW, this Sonoff can only purchase online from overseas now?

Some sellers selling them at lelong
Cheapest is probably in taobao shop.

It is not bulky. The size is about same as hager timer or smaller.

But the shape and the design is not suit to the DB. Hence, not DB friendly. Hager timer is design suit according to DB.

You still can put into the DB. But it doesn't look nice and be prepare to take out some space.

So far no local sell this. Just get it online. It take 2weeks to arrive. Not difficult and cheaper too.

Some sellers selling them at lelong
Cheapest is probably in taobao shop.

I think its not suitable for DB. One thing the DB wires are too thick to enter the Sonoff terminal block which to me is the most "weakest" in the whole device

Thanks sifu, I have to set mine to KEEP then 
I never tested mine....lucky you did....

DB never look nice ba  . Anyhow, it is covered, so aesthetic shouldn't be an issue to me.
Thanks for the info.
Ow....this might be a problem then.