I need to substitute a 12v battery for a 12v usb cigarette lighter adaptor to power my satnav, as my car only has 6v electrics. If I wire a cig lighter outlet direct to a small sealed 12 battery in the glovebox, what size battery do I need to run a satnav on 12v for say 8 hours? I would recharge the battery overnight using a mains 12v charger connected to the battery via the cig lighter socket.
Thanks, Patrick
A small 12 v Motor Cycle battery will do the job or a battery designed for a UPS. You can get 9Ah battery that will fit nicely in a glove box. A 9Ah battery will provide 9 AMps for one hour or 1 amp for 9 hours. As the SatNav is unlikely to draw more than 500 Ma this will provide power for up to 18 hours. You could even gt a 4Ah battery but that would be leaving little in reserve.
Stuart
Thanks Stuart, that's really helpful. I was looking at a 7AH 12v sealed battery for fire alarms, so this might be enough for my needs. I might be able to recharge my iPhone as well!
Patrick
Yes, 7Ah at 500Ma should give you 14 hours. Plenty with a bit left over for your iPhone. Stuart
Rather than installing a bulky 12V battery in the glovebox I'd investigate a 6V/12V transformer so you could step up the ciggy lighter socket to 12V. No battery recharge issues then. http://www.jaycar.com.au/productVie... Goin' Fishin' (Some day)
