I have a Motorola navigation dock that has the custom audio cable (audio + charge in one). When I use this cable, the audio gets messed up by the charging due apparently to a shared ground in the phone. I could probably fix this by rewiring my truck to have the cigarette lighter pull 12V from the same source as the radio, but I thought it might be worth a try using an isolated DC-DC adapter first. I'm not aware of any of the premade chargers that offer isolation, so I'm planning on using an isolated buck converter. Non-isolated ones are available for cheap with 500mA and above for a reasonable price ($5-15USD). Isolated converters are reasonable for lower current (400mA or less) but get very expensive over 500mA ($80+).
Is it possible to charge with 200-400mA, or do I really need more current? If I provide less current, I understand that the phone could be charging and still kill the battery depending on demand (music + GPS + 3G + etc). The only spec I have found to date is that the phone requires 500mA or more to charge, but that's simply based on the USB spec, isn't it?
Is it possible to charge with 200-400mA, or do I really need more current? If I provide less current, I understand that the phone could be charging and still kill the battery depending on demand (music + GPS + 3G + etc). The only spec I have found to date is that the phone requires 500mA or more to charge, but that's simply based on the USB spec, isn't it?
