Is it possible to upgrade firmware and MAPS on Sync3 without engine running ?
Can a battery charger connected to the battery be useful without getting message car is running on battery power and is shutting down in few minutes ?
Moved to Ford Support
If it’s on charge it will still trigger battery warnings, just run the engine, go for a drive or something.
I sense english is not your first language and that there’s some kind of language barrier, but be very careful about translations 
Firmware is one very specific thing, a Sync3 version/build IS NOT firmware.
Having said that, updating firmware REQUIRES the battery on a charger. Upgrading Sync3 version does not but it’s highly recommended to keep the engine running during the process (in a very VERY well ventilated space if stationary).
As @SaNdMaN said, firmware and sync3 version updating are very different, though I believe you are after Sync3 update and yes you can do this without the engine running if using a battery charger. That said you need to connect the charger correctly. Most think its simple enough (and it used to be) but if your vehicle is equipped with a BMS (Battery Management System) you need to connect the negative of the charger (in most cases) to a good chasis ground or on the other side of the sensor if it is post mounted like on an F150. NOT directly to the battery negative terminal. Connecting this way will allow the vehicle regonize that you are charging and keep the battery charge updated in the BMS. Connecting it directly to the negative post will not, though it will charge the battery the vehicle will not know that it is charged and may shutdown to preserve the battery. Hope this info helps.
It doesn’t but it would be extremely highly recommended
FYI - There is a warning in the FORScan firmware update process that the vehicle should be placed on a battery charger.
Ucds doesn’t make this same claim, I drove to a friend’s house had some firmware flashed and drove back no issue. Bcm and stuff definitely wouldn’t do it without charger but APIM is fine imo.
Can you update directly from 3.0.20204 F10 to 3.4.23088 F12 or must you do an extra upgrade step in between ?
You can do it directly.
I’ve merged your question into this thread, if you have issues create a new thread using this template → New SYNC 3 Issue - CyanLabs , providing all the information the template requests.
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