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How do I hardwire a car charger?

H

Heywood

Hard-core CEG'er
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Jan 24, 2006
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I want to make a car charger for my mp3 player so that I can charge it when I go on long trips. At the moment I just take it out and charge it at home which is OK but a little annoying.

I know V = I.R and that good stuff but if I have a 15V source and want to supply 5 volts at 2 amps, how do I make up the circuit?

I was also thinking of hard wiring my belkin fm transmitter at the same time. Would it be possible/good idea to put that on the same circuit or would that draw too much current (or do other bad things)?

All input appreciated, thanks. :)
 
SVTC1136 said:
I want to make a car charger for my mp3 player so that I can charge it when I go on long trips. At the moment I just take it out and charge it at home which is OK but a little annoying.

I know V = I.R and that good stuff but if I have a 15V source and want to supply 5 volts at 2 amps, how do I make up the circuit?

I was also thinking of hard wiring my belkin fm transmitter at the same time. Would it be possible/good idea to put that on the same circuit or would that draw too much current (or do other bad things)?

All input appreciated, thanks. :)
Click to expand...


This may be a bit bulky, but you can install a power inverter and then plug in your home charger right into it. This is the idiot's way to do it :laugh:
 
SVTC1136 said:
I want to make a car charger for my mp3 player so that I can charge it when I go on long trips. At the moment I just take it out and charge it at home which is OK but a little annoying.

I know V = I.R and that good stuff but if I have a 15V source and want to supply 5 volts at 2 amps, how do I make up the circuit?

I was also thinking of hard wiring my belkin fm transmitter at the same time. Would it be possible/good idea to put that on the same circuit or would that draw too much current (or do other bad things)?

All input appreciated, thanks. :)
Click to expand...

You could buy a car charger for your MP3 player an then hardwire that..
 
OK, so I did a bit of research today. I know that I can get a charger to charge my unit from a usb cable, and usb cigarette lighter plugs a super cheap, so I'm going to get one of those and use the insides to reduce the voltage. Then I can just wire up a plug from the output to my unit and voila.

Can someone confirm that the power to the radio is a good source. Thanks.
 
iBrent said:
http://www.tss-radio.com/cigarette-lighter-hardwire-adapter-p-4057.html

You can hide this behind the dash. Hardwire it into the radio's wire harness (you should probably ad an inline fuse), plug in your usb->cig. cable, also hidden behind the dash, and string the usb cable to wherever you need it.
Click to expand...

They sell these at the install bays of Best Buy for $10... its the real way to go if you know how to wire it once its able to have 12 volts going to it w/o screwing iit up...
 
ConcepTrs913 said:
They sell these at the install bays of Best Buy for $10... its the real way to go if you know how to wire it once its able to have 12 volts going to it w/o screwing iit up...
Click to expand...
Why would I buy that and not just wire the circuit from the usb adaptor? It mentions 12 or 5 V applications, does it somehow have a voltage regulator on it?
 
Last edited:
SVTC1136 said:
Why would I buy that and not just wire the circuit from the usb adaptor? It mentions 12 or 5 V applications, does it somehow have a voltage regulator on it?
Click to expand...

The voltage out is the voltage in. So if you wire it into a 5V line, then it'll be 5V, likewise, 12V(in)=12V(out).
 
got ya, thanks.
One thing I'm still worried about is drawing too much current. Is the radio power a good source. I could always just do the current cigarette lighter line, but I would prefer it to switch off when the cars not on to prevent it draining the battery.
 
SVTC1136 said:
got ya, thanks.
One thing I'm still worried about is drawing too much current. Is the radio power a good source. I could always just do the current cigarette lighter line, but I would prefer it to switch off when the cars not on to prevent it draining the battery.
Click to expand...

Look at the fuse that the radio is connected to. See its value? (i'm not sure what it is without looking at the panel guide)

(all in amps)
Fuse - (current drawn by accesories on that line) - (current drawn by mp3 player) > 0

If that is satisfied, then you'll be fine. You mention the mp3 player draws 2A. That seems really high, you should check on that and be sure.
 
OK so to answer my own question I guess, the radio is on a 7.5A fuse and my mp3 charger draws max 2A so I am thinking its OK. Now all I need to do is execute the plan.

EDIT: thanks ibrent, I guess you were posting at the same time. since the rating says 2A I am guessing that is the max, maybe with a fully discharged battery.
 
The radio circuit is also tied in with the interior lights and IIRC the timer module (the thing that dings when you leave your keys in)... the cig lighter might also be on that circuit.

Your MP3 charger probly pulls so little amps that you could almost tap off anything.
 
I looked up the manual yesterday and I am pretty sure all those are on separate fuses. I agree though, unless the battery is nearly drained its not going to be pulling anything really to speak of.
 
Oh yeah, I think the 99+ have a different fuse box with those mini fuses.

I know the interior lights and radio are on the same circuit on a 96 because when I bought that thing they all didn't work and one fuse cured all (the one with the orange paint around it).
 
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