Is it safe to charge a stranger's battery on their behalf?

[fp3UK]

A stranger has contacted me to ask if they could charge their FP battery using my phone. Their message:

I have a Fairphone 3 and it suddenly decided to stop charging. I’ve ordered the bottom module but it takes 2-5 days to arrive; in the meantime, if you still have a FP3, I was wondering if I could leave you my battery to charge once? It would be really helpful as it’s much easier to temporarily migrate all my 2FA apps to another phone if the original phone is still available.

They found me on a city-specific subreddit.

I like to help people when I can, but this seems like an unusual request. Does their request make sense?

[Lidwien]

Yes, this makes sense. I can only hope for the other user that the phone doesn’t suffer from sudden death.

[AnotherElk]

@fp3UK

They found me on a city-specific subreddit.

Depending on your city there might be electronic stores or stores selling travel necessities which offer external universal smartphone battery chargers.

For the Fairphone 3/3+ battery the charging contacts have to be thin enough to be able to reach the battery contacts, this is not a given with all universal chargers.

If such a charger can be bought directly in your city, then this would be a fast way for the user to charge the battery, and for a device with a removable battery an external charger is good to have around anyway (as can be learned from this case).

Here’s a topic with some mentions … External universal chargers for Fairphone batteries

[mde]

As for the original question: If the battery is not obviously broken, then I don’t see big chances for harm to your phone by simply swapping the battery and charging it.
The request itself also sounds at least plausible to me.
But of course strangers being strangers you can never know for sure in advance…