Yeah, i successfully re-firmed 6 shelly 1 gen3 last week, no issues at all.
I used mgos32-to-tasmota32-mini1g3.zip
I tried this with the Shelly Mini Gen3 and while it worked, OTA afterwards results in the “ERROR Error binary size: Unknown error from ESP” message, just like @baerrs reported.
Sorry…i misread the complaint…i suffer from the same 
Just ran into the same issue. Did you find a solution or a workaround?
(I went through the full Tasmota based migration and am on the latest esphome build)
I’ve been successfully using the code on this PR when converting from Tasmota (as per the above instructions) to ESPhome. I’m not sure if this related to the “Error binary size” message above. It used to be the case that if you didn’t use the above PR, the initial ESPhome conversion would work, but then all subsequent updates would fail silently.
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Thanks for confirming it is fixed…but…the esp’s flashed before this PR can still only be updated by serial; OTA will not work on them…
I don’t think it is “fixed” - that PR hasn’t been merged, so if you want to OTA convert newer Shellys you need to check out that branch of esphome to do the initial conversion. And yes, if you do the initial esphome conversion without this, serial is the only way out.
Hi there,
Maybe a warning on top of this Guide, that OTA doesn’t work when you use this guide at the moment, would be nice.
Just used your guide today (HA is up to date) and I forgot one option in my config. After trying an OTA I get the error : ERROR Error binary size: Unknown error from ESP. Only then I read the comments 
But thanks for the guide anyway … Although I hate the idea of using serial on the next ESPHome update, also because I built-in the Shelly in floodlight unit 
Done so (you could have done yourself; this is a wiki topic 
)
I didn’t find it necessary, as it is mentioned in the 6th or 7th post
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I’m still a bit confused… if i understand correctly there are two options: either option explained above or option from mentioned PR… or not?
Please correct me if i’m wrong, but as i understand it’s so that if i convert according to first post here i’m stuck without OTA, but if i follow PR it’s ok ?
If you use an esphome repository that includes the mentioned PR (pull request), you will not have any issues.
So you could fork your own version, insert the PR, and then use that to flash…
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…or just go the solder-and-serial-flash route. With all the steps needed for the migration, I found the traditional way easier. Especially after running into the mentioned problems and as I wanted to flash multiple devices.
Given, this requires the soldering skills to deal with the tiny PCB.
So, are you saying that doing via uart none of above steps are necessary and it “just goes” with standard flashing from esphome web?
I always do first flashing via serial anyway. (Ok, the problem would be module like shelly plug, which is a pain to disassemble, as I’ve read).
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Yeah, it’s a nightmare, agreed,if you’re not familiar with smd’s. Those pads fall off pretty quickly.
I do a lot with smd’s, though, so it’s no problem for me (i do that under a microscope). But i still wouldn’t do that each time - only first conversion shelly -->esphome, all later updates must be over OTA.
I guess i’ll have to buy and sacrifice one shelly for science…
Just for the avoidance of doubt, you need to have that PR and carefully follow the instructions described there. In particular, the first esphome firmware you flash onto the device from Tasmota must have unprotected_writes: True in the ota config. If it doesn’t it’s bricked and needs serial to recover.
You then need to do the upload-factory-ota step to complete the conversion. After that, you can switch back to latest esphome and use OTA as normal.
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Very smart remark…thanks!
So your ESP-Home version must not only have the PR, but also this in the yaml:
ota:
unprotected_writes: True # This is mandatory if you want to flash the partition table or bootloader!
As soon as the PR made it in I’ll update the thread
For people that don’t exactly know what to do here, can someone document steps to actually use this PR? I will admit I didn’t read every message in the thread but I didn’t see where someone said here’s how to setup an ESPHome environment with this PR baked in to do your first flash.
So, let me get this straight:
I have new Shelly PlugS and I want to flash Tasmota on it. Do I follow the steps and that’s it?
About a year ago I could just flash OTA in 1 step and they were done. That has changed I guess.