Charging mobile devices on board
QHow can I recharge my Pixelbook and mobile phone from my boat’s 12V electrical system? Maurice Williams Longtime subscriber
ANDY HAINES REPLIES:
If the boat has a cigar lighter socket (most do), the easiest solution is to purchase a ‘cigar lighter socket to a USB socket adaptor’. This effectively converts the existing cigar lighter socket to a USB charger.
A better solution, however, is to wire in a separate USB charge socket as this takes out the vulnerability of the connection of the USB adaptor coming loose in the cigar lighter socket. If installing one yourself, care must be taken to get the positive/ negative power connections the correct way round.
Something else you’ll need to consider is the ‘charge rate’. USB sockets are 5V, but the speed the device charges at will depend on the amperage capability of the charge source. Your phone’s AC mains charger could have a 2A charging capability, which means that charging a completely flat 1500mAh phone battery at home would take about 45 minutes. If the charger had a 1A capability then it would take twice that time, ie 1½ hours.
The same flat phone battery connected to the USB port on your PC would take at least three hours to charge. This is because the output on a USB 2.0 socket is 0.5A (500mA). A USB 3.00 socket will provide up to 900mA, so the same flat phone connected to that would take approx 1.7 hours. These figures are based on 100% charge efficiency, which is never the case, so in reality the times will be slightly longer.
Many wired-in sockets have both 1A and one at 2.1A outlets, so theoretically, you could connect your phone to the 2.1A output to charge your phone in just under half the time than if connected to the 1A socket. However, generally speaking you should use the output that corresponds the AC charge adaptor you use at home (it’ll have the output printed on it). If it’s a 2A adaptor then you’d be OK to use the 2.1A output, but if it only states 1A then it would be wise and safer to use only the 1A output.