I recently bought an external power pack for that classic first world problem – running out of phone power when on longer trips for which it works admirably. So , will it work to charge lights that run through a usb connector? Not talking massive 1000 lumens types but the normal smaller lights that I often struggle to charge when on a multi day trip. I am always worried about using wrong charge rates and cooking batteries but I am a profound electrical ignoramus!

Will work just fine

I’m no electrical expert but would think a phone battery would take at least the same amount of volts to charge as some bike lights. Can’t think there would be an issue.

I’ve used one to charge a Garmin and it didn’t blow up.

Yup, should be fine, most USB devices are limited to 500mA. Those that aren’t have some way of communicating with the charger to confirm that they’re both good for 2000mA or whatever (Samsung for example have some terminals shorted together in the charger, if the phone senses that (and that the cable is shielded) it uses the data wires to get another 500mA each and the shield is used as the 0V wire.

So if the lights won’t overload the battery.

Or there’s always a dynamo.

No problem, crack on!