Vauxhall Astra solar battery charger

My focus is always live, but try plugging something in like a phone charger of satnav, they mostly have a little red or green light on, lock the car and see if the light is still on,

Tony

Forgot to add, I had a couple of cheap solar chargers I used to put on my tractors over the winter, trouble is some drain the battery at night so b carefully what you buy,or buy a blocking diode,they are only a few pounds on eBay or such and will only let power flow one way, is charge in daylight but block at night