any thoughts on a battery for a Sonoff SV?

[Christopher Smith]

I have several LED decorative light fixtures that each run on 3 AA batteries

I want to control them from my OpenHAB server

The Sonoff SV looks like the best option

since the the existing setup is running at 4.5 volts, i'm thinking I should setup the SV with the WiFi and Relay circuits isolated.

You think running the LED lights at 5 volts would be a problem?

If I run in isolated mode

1. What voltage would best run the SV?
2. What kind battery setup? 
3. Any battery brands/suppliers offer the longest operations

If I run in non-isolated 5 volt mode

1. What kind of battery setup?
2. Any battery brands/suppliers offer the longest operations

Non-isolated looks like the easiest setup

Wisdom is welcome 

[Phil]

looked at this and after a bit of back of fag packet maths decided the batteries in my price range would require too frequent an exchange/recharge, also my dcv devices being powered were more than led lights..  so i invested in a few 3m and 5m usb power leads and wall chargers..  

But at full pelt the sonoff sv can draw up to 80 ma( 20-40ma average usage??)..  and published battery capacities are not the most reliable of metrics (many batteries boast well beyond real life capacity)

I looked at 5v lipo battery bank/packs as @ a common voltage of 5v i can do the simple usage maths ;)   for example  a 1000 mah 5v battery bank should be able to supply upto 12.5 hours of power to a device drawing 80 ma (1000/80 =12.5)  or if real life draw is closer to 40ma, a days use??

hope thats usefull

[Philip Knowles]

We're now in a world where you can buy a USB wall charger cheaper than a pack of batteries. Many of them are capable of supplying 2A. It may be worthwhile replacing the batteries with wall chargers and, if you have few fixtures close to each other, you could 'daisy chain' from one charger. The devices would almost certainly survive 5V as most actually run on 3.6V and have simple voltage regulation to cope with the change in battery voltage over the battery life. If you're worried a dropping resistor calculated from R = V/I (1.5/x) will give you protection (something like 1k would be ok).
Regards
The other Phil

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[Daryl Sargent]

I have looked at this as well, I have done some measurements of the Sonoff SV with relay triggered and just wifi running and no load connected, running of a 4xAA battery pack:

Running Tasmota, no sensors, in 'standby" mode: approx 70 mA

Running with relay triggered: approx 150 mA

Typical usaeable capacity for AA cells at 70 mA is about 2300 mAh, so in standby it would be:

                                               2300 / 70 = about 24 hrs.

With the relay trigger it not only draws more current, but doe to alkaline battery chemistry the available mAh drops the more current you draw, so with a draw of 150 mAh there is probably less than 2000 mAh capacity, say for arguments sake:

                                              1900 / 140 = about 13 hrs.

Add the draw of your load and things start looking even worse.  a string of decorative LEDs can draw up to 800 mA, so depending on your duty cycle you may not get too much life out of your batteries. 

[Christopher Smith]

Thank you all

Sounds like a battery is a non-starter idea.

This is really too bad.

I have successfully used a "wall warts" to power an Inching switch and another decorative light

But I want to place the light fixtures where a wall wart is not practical and running a wire is aesthetically undesirable.

3 AA batteries are "good enough" to power the lights for 4 hours a day for about 3 weeks.

I was wondering if some sort of replacement rechargeable battery kit could be used that would power the Sonoff for months, not hours.

[Christopher Smith]

I posted a question on ITEAD Studio about if they could recommend a type of battery that would last 6 to 12 months running a SV in isolated mode

Other than an automated confirmation response, no reply in 27 hours.

What is the expected response time?

[Phil]

Give 48 hours for someone in china to read and respond, tho the itead forum contributions are mostly from users..  

You probably already have as good an answer as you can get without running your own tests which sound inevitable ;) 

Daryls tests above reveal a requirement for circa 2300mah for 24 hours run time, so for 12 months running the Mah required would be 365 X 2300mah

so 10 x of these should do the job ebay example

for a really low power solution look at some of the esp32 boards the esp32 can go into a deep sleep cycle which can run on ua (micro amps) 

Best thing you can do tho is wire up a few test boards with all the h/w your project needs and run some actual power useage tests yourself

however with such a long duty cycle between battery charge/changes i would question the validity of using tasmota as is as its 'sleep' features and abilities may not be upto the demands your gonna put on them. 

[Christopher Smith]

Got a response from ITEAD

"We don't have recommendation" 

[Christopher Smith]

Well... I was in Costco and they had this 2 Pack of "iPhone power banks" for emergency phone recharging. 

Li batteries exactly the same size as my regular sized iPhone

5v 6000 mAh, what the box sez...

< 20$

So 4 batteries for < $40

I got my first test running right now.  Stock firmware.  No other load other than running wifi.

I will update just how long a fully charged battery runs the Sonoff SV

Costco has a single 10,000 mAh kit for $30 https://www.costco.com/Ubio-Labs-10%2c000-mAh-Power-Bank-Kit.product.100413724.html

[Phil]

Hope the following link is useful,  

u-tube regarding esp8266 battery life

i think a more barebones board solution than an itead/sonoff sv may be more economical/efficient to run