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Old 12-01-2014, 15:16   #1
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Hard wire ipad to 12v?

I want to be able to charge my ipad at the helm. I could install a 12v outlet and use a bullet charger to charge my ipad, but this leaves a lot of connections exposed to spray. I found a nice 2 prong outlet that comes with the male end to wire something of your choice. The plug screws into the outlet, making a fairly weather resistant connection.
I believe the ipad requires 5v for charging. How do I step down the voltage from 12 to 5v at the outlet?
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Old 12-01-2014, 17:24   #2
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Re: Hard wire ipad to 12v?

Could you use a small solar charger?
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Old 12-01-2014, 17:29   #3
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Re: Hard wire ipad to 12v?

you can buy 12v/USB converter plugs. they are a small plug that plugs into your 12v socket, outlet is a USB socket at 5v. few dollars, on ebay, etc.
lee
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Old 12-01-2014, 17:29   #4
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Re: Hard wire ipad to 12v?

Two prongs is not enough. The IPad also needs a voltage reference which tells it the charge source is a high current USB connection.

Blue seas make a dash mounted USB connection.
http://www.bluesea.com/products/1016...Charger_Socket
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Old 12-01-2014, 17:32   #5
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Re: Hard wire ipad to 12v?

Changing the voltage to 5 volts is really quite easy and cheap. The auto parts shop will have a cigarette lighter plug with USB slots. Not all work with iPad for some weird reason so check it says it will charge iPads.

Anyway, just take the plug apart and inside you will see the curcuit board for the step down

Cut the wires and solder or connect to your 12 volt system. Keep the usb socket.

Voila!

I have a nice, neat one, in my cabin too.
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Old 13-01-2014, 08:40   #6
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Re: Hard wire ipad to 12v?

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Originally Posted by noelex 77 View Post
Two prongs is not enough. The IPad also needs a voltage reference which tells it the charge source is a high current USB connection.
The official Apple 12v adaptor for ipads is only $21. I assume it satisfies the ipad's current requirements.

Anyway, I sure wouldn't be leaving an ipad for long periods at an outdoor helm position, so a standard 12v USB adaptor at the helm should be more than sufficient to maintain charge.
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Old 13-01-2014, 09:07   #7
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pirate Re: Hard wire ipad to 12v?

Correcto. I'm running my chart plotter (aka ipad Mini) on one.
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Old 13-01-2014, 09:18   #8
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Re: Hard wire ipad to 12v?

If you want to charge with any speed you will want a 5v USB product capable of at least 2 - 2.1A. The wall chargers that ship with the current iPad Air's is 2.4A and the last version was 2.1A.... If you have a NavPod at the helm a 12V USB outlet can be hidden inside and stay pretty dry...

The problem will be that when charging your iPad, above deck, the charge port will be exposed to the elements. Not real good.. Best bet is to charge below and then run 10 hours on battery above deck in a waterproof case...
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Old 13-01-2014, 10:49   #9
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Re: Hard wire ipad to 12v?

With so many devices using USB as a power source I've found it useful to install a single 12V-5V DC/DC converter and then install USB outlets in various places nearby (voltage drop is killer at 5V). I look for the most efficient converter I can find and then install it out of the way on a 12V circuit that I can shut off when I don't want the 5V (so that the converter isn't consuming idle power). The last one I used was this one:

Digi-Key

which gives about 90% efficiency at reasonable loads. You can also find similar supplies with 5.1 or 5.2V outputs, I use those when I know my wiring run will be more than a few feet.

Then I install "waterproof" USB connectors at various places (look here: USB 2.0 Waterproof Connectors or here: USB 3.0 Waterproof Connector - A Female to Solder Pins - Panel Mount). The devices themselves aren't waterproof, but sealing up everything in between just seems like a good idea. I don't have a recent iPad around, but assume it needs a 3.0 connector for the higher power requirements.
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Old 13-01-2014, 15:51   #10
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Re: Hard wire ipad to 12v?

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Originally Posted by Lake-Effect View Post
The official Apple 12v adaptor for ipads is only $21. I assume it satisfies the ipad's current requirements.
There is no need to buy the official apple product. There are many cheap suitable adaptors available from ebay etc.
They need an output of 2.1A (or more). Some 12v adapters only have an output of 0.5A or 1.0A. This is sufficient for phones etc, but not the larger demands of the iPad. The 2.1A models can be also be used with phones etc.

The adaptor also needs to have a special voltage reference over some of the other pins. This tells the ipad that it is connected to high power (2.1A) plug. Without this reference the adaptor will not work with an iPad. Most adapters incorporate this voltage reference, but check it says "ipad suitable"
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Old 13-01-2014, 15:56   #11
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Re: Hard wire ipad to 12v?

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Originally Posted by Dsanduril View Post

which gives about 90% efficiency at reasonable loads. You can also find similar supplies with 5.1 or 5.2V outputs, I use those when I know my wiring run will be more than a few feet.
If you make your own USB 5v supply you need to also incorporate a voltage reference across some of the other pins if you want to use it with an iPad or some other tablets (I think Samsung has the same requirements).
It is not difficult to do. A simple resistive voltage divider is sufficient.
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Old 13-01-2014, 23:26   #12
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Re: Hard wire ipad to 12v?

just for the avoidance of doubt , heres what you must apply to the D+, D- lines to enable high power charging


D+ 2.8v / D- 2.0v allows high current charging (2A)
D+ 2.0v / D- 2.8v allows high current charging (1A)
D+ 2.0v / D- 2.0v 500ma ( standard if no voltage on D lines)

simple resistive dividers will do on a well regulated power supply

Note the charge voltage must not drop below 5.0v under load or the device will step down its charging current. nor will it charge at below 4.5v or above 5.5v.

you really don't want to recharge iPads at 500mA!

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Old 14-01-2014, 17:01   #13
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Re: Hard wire ipad to 12v?

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Originally Posted by noelex 77 View Post
There is no need to buy the official apple product.
Of course not, but by the time you source a cheaper 12v-USB adaptor, take it apart, whip up that hi-current trigger resistive divider (including the drive to Radio Shack because you're short on the right resistors), put it back together, curse when it doesn't work, take it apart again and fix a short, put it back together... the $21 for the official Apple adapter starts to look reasonable.
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Old 14-01-2014, 17:28   #14
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Re: Hard wire ipad to 12v?

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Originally Posted by Lake-Effect View Post
Of course not, but by the time you source a cheaper 12v-USB adaptor, take it apart, whip up that hi-current trigger resistive divider (including the drive to Radio Shack because you're short on the right resistors), put it back together, curse when it doesn't work, take it apart again and fix a short, put it back together... the $21 for the official Apple adapter starts to look reasonable.
Most of the third party 12v-USB adaptors have the high current trigger voltages so providing they have a 2.1A output they will will charge the ipad successfully.

You only a need to play around with the electronics if you make your own using a simple 5v power source.

I have found the commercial adaptors slightly unreliable. Six months seems about their average life in my hands. I don't think the manufactures design them for use every day in hot conditions. The slightly lower and variable boat battery voltage (verses the constant 13.8v when used in a car) is also probably a factor.

They are cheap enough that buying a few spare adaptors seems like the best option, and is my solution. The genuine Apple products may be a bit more durable ? so could be worth the extra cost. I have not tried them.

The other option is some adaptors are appearing with 3+ Amp output. The iPad has a lower maximium charge current so these will not charge quicker, but the greater peak output may enable these higher power units to run a bit cooler and therefore be a bit more reliable at the lower currents.

The other factor is electrical efficiency. One of the main advantages of the iPad for boat use is the low power consumption. I suspect the 12v adaptors are reasonably similar, but it would be great if someone could do some measurments.
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Old 14-01-2014, 17:38   #15
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Re: Hard wire ipad to 12v?

Quote:
Originally Posted by Lake-Effect View Post
Of course not, but by the time you source a cheaper 12v-USB adaptor, take it apart, whip up that hi-current trigger resistive divider (including the drive to Radio Shack because you're short on the right resistors), put it back together, curse when it doesn't work, take it apart again and fix a short, put it back together... the $21 for the official Apple adapter starts to look reasonable.
I was not aware that Apple made an Apple branded 12V adapter? They make 120V wall-worts but Apple sells Belkin, Incase and others for those of us who need 12V adapters..

Amazon has piles of 12V USB chargers. Just pick one that has 2.1A and it should work fine with an iPad...

Amazon Car Charger USB
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