Why isn't my smartphone charging from the boat's 12v socket?

Slightly off-thread but here's a related question to those who have a better notion than I of these things (i.e. 0): I'm a little wary of plugging my iPhone to a cigarette lighter adaptor on board, especially when starting the engine, in case I fry something. Are my fears groundless? Should I put in a filter or fuse between the power source and adaptor?
 
Smart phones and iPhones and iPads (generally speaking) need 2+ amps delivered to the USB lead to charge. When I first got an iPad, all I had on board was an old 'dumb' phone charger which didn't work with the iPad. It turned out to deliver less than .5 of an amp, so of course wouldn't charge the iPad. I now have a collection of 12v chargers designed for the job which variously deliver between 2.1 and 4 amps. All work well on the boat or in the car. As to protecting the thing with a filter, I've started and stopped the engine many times with things plugged charger with no ill effects.
 
My understanding is that recent Apple devices also need specific voltages at the USB data pins in order to start charging and also for deciding how much current to draw.

I made a couple of USB charging sockets for my boat, using first a buck converter to reduce 12v to 5v and then a pair of voltage dividers – two resistors in series – to get the the correct voltages at the D+ and D- pins.
2,75v at D+ and 2,0v at D- signals to the device that it can draw up to 2 amps.

These work with my wife's iPhone and iPad and also charges my old dumb Samsung phone fine.
 
nigelmercier said:
Yes, the charger tells the device what it can deliver. But if that is less than 2A it won't work anyway.
Click to expand...

Exactly, what it CAN deliver, as signaled by the voltages on the data pins.
When I tested the iPad with the charging socket I made, it charged fine at 1.2A, probably because the device was already 70 percent or so charged.
 
duncan99210 said:
I now have a collection of 12v chargers designed for the job which variously deliver between 2.1 and 4 amps. .
Click to expand...
"Can" deliver maybe.. :) Did you ever try checking just how much is actually getting into the devices?

I charged a sony experia for a while using the charging pads on the side bypassing the USB, even pushing the voltage up as high as I dared (5.25v from memory), the xperia still would not accept more than about 1.5A.

Not easy getting power in quickly.
 
I've fitted one of these 2 mine. As you can see the usb connections have different power ratings. My HTC one says that charging is slow if it's plugged into the upper one that says 1A but doesn't record anything wrong with the lower 2.1A one so i suspect that your usb connection hasn't enough oommpphh

http://www.ebay.co.uk/itm/New-Car-Motorcycles-Dual-USB-Charger-Socket-USB-Charger-Boat-With-Cap-/201555628141?hash=item2eeda6d06d:g:R8YAAOSwgApXA1la

$_57.JPG
 
The 12v socket adaptor I bought from Amazon gives 2.5A which charges fine. So the problem was entirely the old 0.5A adaptor - which was too limited to even 'trickle-charge'.
 
Tammany said:
I've fitted one of these 2 mine. As you can see the usb connections have different power ratings.
Click to expand...


I have an identical one that I fitted because I was having problems with a USB charger that used to fit into a cigarette lighter socket.
It works fine and actually charges my iPhone 5 and my Kindle faster than the mains charger at home using the ordinary standard cables.
 
I have discovered that my phone will not charge on any one of 3 USB sockets if the battery voltage is too high - eg if the solar panel or the engine is keeping the voltage above 13.something volts. Switch on the fridge, the voltage drops to upper 12.something v and the phone charges correctly. Nexus 7 is less concerned (though only charges at lower rate - will try different leads). No idea how the USB output varies with the higher input.

There is a USB socket on my inteverter, and all devices charge ok on this regardless of input voltage, though it is a bit like taking a hammer to crack a nut.

Handheld VHF picks up interference when charging with the USB sockets. Main VHF not affected.
 
Babylon said:
The 12v socket adaptor I bought from Amazon gives 2.5A which charges fine. So the problem was entirely the old 0.5A adaptor - which was too limited to even 'trickle-charge'.
Click to expand...

I've yet to find any device that can not trickle from a 500mA supply. That is the USB standard, and so not allowing charge from a PC which is a bad marketing plan IMHO. However, what I suspect is happening is that your phone doesn't realise it's connected to a 500mA supply and tries to draw more power. Belkin may cope with that for a period then some current overload circuit kicks in, shutting down the power. I've seen similar happen on wall chargers.

Sony seem particularly prone to it!!

I'm not sure why - as pointed out the volts on the data wire should tell it it can draw higher power. I suspect Sony default may be to draw full current unless the data wire says it can't rather than draw full power only when data wire says it can.

Sony also have a habit of cracking screen while on charge. I suspect due to overheating.. ..makes you wonder what's designed wrong in the device. . .
 
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