Charger inside the frame?

Is there any reason why I should not install the ebike charger inside the ebike frame? There is a plenty of room inside the frame and it would be cool you use any standard plug to charge my bike.

Is it safe to drive by bike if the charger connector is always connected to battery pack? Or do I have to use some external switch between them?

Leaving the charger connected may cause a small drain on the battery that could eventually over-discharge it. You'd have to check.

The more imminent problem is most chargers won't survive the vibration found on a bike for long at all. A waterproof/potted charger will, but most chargers are not potted (cheaper and higher-powered). You might be able to beef one up to survive by using blobs of silicone junk to physically support the large/heavy components on the PCB (transformers, capacitors).

When using BMS it would help for the drain problem. That's true that the vibration problem would be a more challenging.

Only if the bms cut the connection between charge input and charger at all times, not just when it gets full. Really simple to just put a switch on that charger input though.

Should be no worries if you are riding daily, but for sure, disconnect the battery from everything for longer storage, a week or more.

One of the great features of the Grin Technology satiator charger is that it is specifically made to be mounted on the bike or other vehicle, even in the weather.

Most chargers though, would not last so long frame mounted. This is something you can fix though, just adding some support to the larger components so they don't vibrate enough to break the legs off them at the board.

my two winter and summer ebikes have chargers mounted on them.
Of course not in original shape,
chargers have been modified and mounted into Pelican cases.
electronics, boards inside needed securing and reinforcement .
I am close to 24500 kilometers on my summer ebike , never had a problem with charger mounted on ebike.
You cannot just take typical China charger and bolt it into the frame

my standard solution is to use a mean well ELG or HLG (potted), fanless)
have a main voltage relay directly on the mean well output side and it switches on the connection between the battery and the charger only when mains voltage is present. as soon as you pull the mains the relay swiches off and the charger disconnects from the battery. simple but effective.

when you reinforce electronics you must make sure primary is isolated really good from secondary in SMPS circuity.
China brands chargers are sometimes poorly isolated sec from prim