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Unread 03-18-2015, 12:36 PM   #1
cwein23
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hardwired phone charger

I got to thinking last night, theres no reason I couldnt hardwire a charger for my phone straight from the battery, right? I wouldnt have to worry about losing it and itd free up my 12V cig lighter for a different application.

My phone charger says its 2A 5.3V on the sticker, so Id wanted a resistor to drop the voltage 6.7V at a 2 A current so that would mean I add an inline 3.35 ohm resistor with a 6 V fuse along the way?
Would it be that simple, just adding wire, a resistor, a fuse and splicing it to my charger?

Thanks for any input!

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Unread 03-18-2015, 12:47 PM   #2
mike134
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You shouldn't use a resistor to drop the voltage in this case. The current rating is for Max current of 2A. The phone charger will draw whatever it needs up to 2A. So while your calculation may work when the phone is drawing the maximum current of 2A, it will not work when the phone is nearly charged and drawing less current. In that case, you will over volt the phone. For example, as the phone reaches maximum charge, the current goes to zero. This means the voltage drop across your resistor is 0. Then the telephone sees 12.4-12.6VDC from the battery instead of the 5VDC.

You would need to use a voltage regulator like the LM7805 to drop from 12VDC to 5VDC. This will maintain 5 volts no matter what current the phone wants to draw. The 7805 actually only goes to 1.5 Amps, but any USB compliant device must be ok with .5-5 Amps.

The USB protocol specifies capacitance on the power line, so you need a Vout filter capacitor. You probably don't need a input voltage filter capacitor, but should use one anyway while you're at it. 0.1 microFarad filter capacitor on the Vout side, and .33 microFarad capacitor on the Vin side. If you mount the voltage regulator against a metal backing plate, then it will act as a heat sink for you. You also want a 2A fuse in there.

With all of that said above, it is usually cheaper and easier to just grab a cigarette lighter to USB converter from the dollar store and harvest the circuit board that is already in there (it is usually in the plastic plug section). Just remove the cigarette plug casing and hook the +12VDC and Gnd wire into your vehicle power directly. It should already be regulated, filtered, and fused for your convenience.

This may be pretty good as well. 12 volts goes directly into this box, so there doesn't seem to be any electronics hidden in the cigarette lighter plug section. http://www.amazon.com/DiGiYes%C2%AE-...lt+usb+adapter Just mount this baby right under the dashboard and wire it right into 12VDC (i'd use an inline fuse just for safety). Everyone in the vehicle can charge their iphones! Or 3 people can charge their iphones, and one person can plug in their USB powered fish tank.

12 VDC input, 5VDC USB output


You must have the added ports for your USB fish tank clock!!!!!!!!!
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Unread 03-18-2015, 01:43 PM   #3
Anticanman
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This one is kind of neat

Dual USB Charger Socket 12 Volt Outlet Plug Jack Panel Mount Boat Sea Marine Car Truck Blue Rv ATV Auto #Ygd by 12vtechnology LLC http://www.amazon.com/dp/B00I3Q2YC0/..._BvDcvb1090CFE
http://www.amazon.com/dp/B00I3Q2YC0/..._BvDcvb1090CFE
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Unread 03-18-2015, 02:06 PM   #4
Chrisnvegas
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Too much work, not enough payoff.

Try multi-gang 12 volt outlet in or under dash.
Pick up the usb adapters anywhere. Wire so they work without key on.

Multiple uses, just like a Jeep. Charge the phone and use a hand held spotlight.


Oh, and thanks, Mike. Now I want a fish tank clock.
Problem is, i want it for the Jeep.
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Unread 03-18-2015, 02:09 PM   #5
T800
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Used one of these in my camper. Works well.

http://www.amazon.com/Blue-Sea-Syste...bxgy_sg_text_y
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Unread 03-18-2015, 04:04 PM   #6
JeeperDon
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^^ Yup, have two in vehicles.
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Unread 03-18-2015, 05:03 PM   #7
cwein23
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wow mike, good info! Thank you, and that makes sense, I didnt think of the voltage needing regulation based on the draw, duh. I thought of this at work last night so I figured it had its flaws
Chris may be right that its way more work than its worth lol

The four port one would be nice, but I wouldnt want something non mounted, plus then I cant use my seat heater that uses the cig lighter.. Then again, maybe I could directly wire THAT to the battery?!

Anticanman/T800/JeeperDon, that looks like itd work well, I need to find a spot on my dash though, because Im planning on using the under gauge location for switches, but it doesnt look too big.

What gauge wire would work best?
Thanks for everyones help!
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Unread 03-18-2015, 05:16 PM   #8
cwein23
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Oh another question,
I have the Samsung note 4, which has a "fast charger". I believe typical chargers are 5V 2A, but when I use a "fast charger" compatible charger, I believe it goes to 9V 1.67A
To solve that, could I take apart a "fast charge" compatible wall/car charger and use the circuit from that like Mike was saying, and solder the board to the dual charger sockets that you guys linked to?

That way, I could have two charger ports and still have the fast charge. Im not sure if itd work though, because if I had two phones plugged in, wouldnt that overload it since the circuit board was designed for single output?

EDIT: found this: http://www.mobilefun.com/51153-dual-...rger-black.htm
Maybe wire the circuit board of that into this: http://www.amazon.com/Blue-Sea-Syste...iglink20314-20 ?
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Unread 03-18-2015, 05:31 PM   #9
T800
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Quote:
Originally Posted by cwein23 View Post
What gauge wire would work best?
16ga would be plenty.

On the fast charge, you maybe be able to rig something up, but why not just get a regular car quick charge and use this guy ...?

http://www.amazon.com/Blue-Sea-Syste..._bxgy_sg_img_y
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Unread 03-18-2015, 06:01 PM   #10
mike134
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oh, I meant that you would open up the box, drill holes through it then mount it below the dash that way. Or even a good quality hook and loop would be acceptable. You would cut the 12Volt plug off and attach the wires directly to 12 volts and gnd or wire 12volts and gnd directly into the USB chassis.

If you want a fast charge capable USB port, you should definitely find the same sort of box in a fast charge version. You really don't want to mess with building that circuit since I think it actually needs to communicate with the phone as well.

And please... don't forget to pick up your USB mini fridge... While I don't suggest drinking while driving. It will keep your beer cold until you get to your favorite fishing spot. "But officer, I only had one beer... my mini fridge can only hold the one."
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Unread 03-18-2015, 06:28 PM   #11
Chrisnvegas
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Collin, add a few 12 volt sockets. Cheap and they work for anything. What will you do next year when you drop your phone and get the new note 5 and it had a different charging system? Be ready for anything. The only constant is the 12 volt outlet.

Then pick this up.
http://www.amazon.com/Getwow-Adaptiv...+quick+charger

3 switches will fit in that space to the bottom right of the steering column. use your under dash space wisely and you can fit plenty of switches/ outlets under there.
If you need more space, run wires to the console.

And Mike, cut that out. I also like that mini fridge.
I'm a sucker for stupid gadgets. My house and garage are loaded already. Soon I'll be starring in a new hoarder show.
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Unread 03-18-2015, 06:47 PM   #12
beakerbload
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Quote:
Originally Posted by mike134 View Post
.

12 VDC input, 5VDC USB output

I like this. I was considering putting in something similar myself. My idea was to wire it into the old radio bay since I relocated my radio to the center console. An inline fuse is a must IMO.

If I don't I may just install a CB there, or an old 8-track deck to screw with my friends and/or thieves.
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Unread 03-18-2015, 07:40 PM   #13
bergovoy
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http://www.newegg.com/Product/Produc...B&gclsrc=aw.ds

I was thinking of doing something like this....as I have a couple already onhand...Im guessing that is what the other suggestions have inside their cases... 'more or less'...

3s-8s ratings are different voltages.... we use LIPO lithium polymer batteries in the RC world and each cell, (S) is about 3.5v so 3s is 3 X 3.5v or 10.5v and 6s is 6 X 3.5v or 21v

so, if my car battery were to die, and if I had my modeling equipment, I could power my fone...

I could also build a little box to put the voltage gauge to add to the 'coolness' factor?
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Unread 03-18-2015, 08:44 PM   #14
mike134
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Quote:
Originally Posted by beakerbload View Post
I like this. I was considering putting in something similar myself. My idea was to wire it into the old radio bay since I relocated my radio to the center console. An inline fuse is a must IMO.

If I don't I may just install a CB there, or an old 8-track deck to screw with my friends and/or thieves.

... You mean you'll mount an 8 track so you can listen to some van halen?!
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Unread 03-20-2015, 12:18 PM   #15
fishadventure
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Quote:
Originally Posted by beakerbload
I like this. I was considering putting in something similar myself. My idea was to wire it into the old radio bay since I relocated my radio to the center console. An inline fuse is a must IMO. If I don't I may just install a CB there, or an old 8-track deck to screw with my friends and/or thieves.
Nobody under 35 years old knows what an 8 track is anyway...
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