28-07-2020, 05:21 PM
(This post was last modified: 28-07-2020, 05:25 PM by Ian McGowan.)
Urgent, not withstanding what others have said, it all depends on exactly what is inside the large plug on the car end of the charging lead. Almost certainly there will be a 3 leg voltage regulator of the 7805 ilk which takes any input between about 10v and 35v and delivers 5 volts to the phone or GPS on charge. Now, the problem is that various devices that fulfil this function come with what is generally known as different drop out voltages. The most convenient will accept 6.5v and deliver 5v. however, they are constructed to a spec. that requires they perform between 11v and 28v input to deliver a reliable 5v output. My TomTom worked splendidly on the 6v system until I required it to perform at the same time as over rated headlight bulbs for 3 hours. After one hour the TomTom failed miserably as the headlights dragged down the voltage available at the battery. So, like Reckers, I fitted a DC-DC up convertor (AKA as a "Buck convertor" to our US cousins) to convert the 5 to 7.8v battery voltage to a reliable 11 or more volts to drive the charging lead under virtually all conditions likely to prevail, since when I have had no problem. Better safe than sorry!!