Allowable voltage of external power supply

If I look at the schematics I get the impression that I can use the “solar power” input also to connect another power supply (which would then charge the LiPo whenever power is available).

Does anyone know whether this is safe? And what the maximum voltage is I should supply?

I’m thinking of using the car cigarette lighter socket to charge the LiPo, and I’m wondering whether I can connect directly or whether I should add a car usb or phone charger or some such.

According to the datasheet: http://support.sodaq.com/sodaq-one/schema-sodaq-one/
The charge regulator is a MCP73831.

According to its datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/20001984g.pdf
The maximum input voltage is 6V.

Silly me, I could have looked that up myself:-)

Thanks!

If i look at the specs of the supplied solarpanel, ists 8.4V open circuit voltage. wont this blow up the regulator when the battery gets full?