I leave my phone on and in the car 99% of the time. One problem I have is keeping the phone charged at all times. If I only take a few short trips, then the phone completely drains. What I want is some sort of external battery which sits between my cell phone and cigarette lighter. This would allow extra power to be stored from longer trips which would then keep the phone charged longer.
There are many external USB batteries, but none of them are hands-off fully automated. I have tried out several and they all require user intervention. Either they need to be turned on to charge, turned on to charge the phone, or automatically turn off once the cell phone is fully charged. What I want is something which will automatically handle everything. I should be able to just plug my phone in and the battery takes care of charging itself and the external device.
The difficulty I’m having is that product descriptions are rarely detailed enough for me to figure out if they will do what I need. Even when I can find the documentation, it’s not always clear how they operate.
Does anyone know of such a device? Bonus if it also has solar charging. One thing I was thinking of was hooking up a charger to a motorcycle battery and then installing a cigarette lighter on it. I know I could wire to an always-on circuit, but I wouldn’t want to risk the phone killing the car’s battery if my car was not used for a while.
Why not just use your car’s battery? I’ve left my phone charging in my truck for many hours, even overnight. Such a small amount of current will not drain your battery.
Some vehicles’ lighter sockets are not live when the ignition is off, but this is easily fixed with a jumper in the relay box. If you don’t know which relay to bypass, ask on a forum devoted to your particular car. I’m sure someone will help you, since this is a very popular mod.
I agree. My phone (an old LG 420G) draws about 280 milliamps during charging, then about 27 mA afterwards sitting in rest mode. That’s on a par with normal parasitic drain for modern cars. Unless the car sits for weeks rather than days, I don’t see it being a problem.
That means that if you charge phones from your car battery, the battery will be dead in 3.5 days.
However you’re charging one phone with a capacity of typically no more than 5 Wh (iPhone 5) so you’d need 200 phones to drain your car battery.(assuming no losses)
Keep in mind that the phone is being charged at the full rate only a small percentage of the time. Once it reaches full charge it draws only a nominal of power if it’s sitting at rest.
I would say that charging your phone from your car battery when the car is off is going to lead to a dead battery (well not “dead”, but discharged enough not to start the car) sooner or later, especially if you don’t drive the car a few days and/or the battery is getting old. Also the cars themselves seem to pull battery current now even when off, I know I hear my 2008 Mazda do some things 5 or 10 minutes after I turn it off. It also seems like manufacturers stopped having the 12V port energized when the vehicle is off, my 1995 F-150 has a 12V port that’s always energized but several new cars I’ve been in the 12V only works when the key is turned on.
If you’re really worried about it, most inverters have an auto-shutdown function that will turn them off before your battery gets so depleted the car won’t start. Some of them even have USB ports now, so you wouldn’t even need an AC adapter. Of course, running the inverter will drain your battery a bit faster than just using a car charger. They have auto shutoff switches that do the same thing, but they attach directly to the battery and are expensive.
Of course, the main reason why they don’t have cigarette lighter DC power shutoff devices is that, as the others said, it would take a really really long time to deplete your car battery with any device you would normally run off a cigarette lighter.
What’s the difference in draw between a phone that’s charging while on and one while off? Presuming you’re not getting phone calls constantly and you’re in a strong signal area. Too many unknowns?
Also, if you have a car with multiple power ports (as many do these days), often one is switched and the other is always on. They’re not always clear about labeling them though.
Some cars allow for the sockets to be continuously powered by moving the fuse to a different position. That is, plug it in to contacts A+B, it’s switched; contacts B+C, it’s continuous. Check your owner’s manual or with a dealer.