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USB charger connected to Fuse Box, Low Power Output Problem....

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RDTK

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Hello,

I am a brand new user at this forum and I was hoping for some guidance.

I recently fabricated a Micro USB charging cable which taps into my Cigarette Lighter Fuse, and is hidden behind my dash. This was done with a Blackberry Micro USB cable, a 5 volt regulator, and a 3 amp fuse, then grounded to metal body.

But the power output can't give the phone enough power to keep up with the power consumption. The battery is drained about 1% every 3 minutes.

Also to make it a little more confusing, If I were to plug the same model blackberry USB charger into my USB adapter which is then plugged into my cigarette lighter, the phone charges perfectly. The adapter in question has a 1 amp and 2 amp USB outlet. Both work just fine.

At first I thought the cable was to long, since while fabricating it, i was not sure how much length I needed. But just yesterday I tore apart my dash and took atleast 4 feet off the length of the cable, shortening it to around 4 ft. But this did not resolve the problem.

I with much embarrassment, I posted a how to on another car forum before doing any type of long term tests. Show here:
https://www.mazda3forums.com/showthread.php?t=642466

Does anyone know what I have been doing wrong??
The soldering is tight.
 
Sounds like you have a short-circuit somewhere if your circuit can drain a car battery in 5 hrs (1% per 3 mins):eek:.
BTW, shortening the cable would actually increase the fault current (albeit only slightly), because there would then be less wiring resistance.
 
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Ah, that makes more sense :).
In that case I'm guessing your dual-outlet USB adapter is a switched-mode type for efficiently converting 12V to 5V with little power wastage as heat. If the 5V regulator in your home-built adapter is a linear type it will waste considerable power as heat. If we assume the charging current is 0.5A then the reg has to dissipate 0.5 x (12-5) = 3.5W. It may be that internal protection circuits in the regulator cause it to shut down when hot, thus limiting the useful charging current.
 
Presumably part of your problem is down to not fitting the required components round the regulator IC, you can't just use it on it's own. Also, as alec_t mentioned, you would need a substantial heatsink to get 0.5A out of one, even if wired correctly.
 
That makes sense. Is there any markings on the regulator that would confirm it is switched-mode or linear-type. No longer have packaging. Would like to confirm before I dismantle my working adapter to reuse the circuitry.
 
That makes sense. Is there any markings on the regulator that would confirm it is switched-mode or linear-type. No longer have packaging. Would like to confirm before I dismantle my working adapter to reuse the circuitry.

It will have a number on it, the most common is 7805, a linear 1A 5V positive regulator - which still needs a number of external parts to work correctly. A switch-mode one requires considerably more external parts.
 
You have an enumeration problem. The best way to handle this is to buy a cigarette lighter adapter and hide it. USB power is limed to 0.1A UNLESS more power is requested. "Charge Ports" can supply more. 0.1, 0.5 and 1A were the original specs. You can now draw up to 2A. Resistors on the data lines were used. Check your OEM charger for these reistances.

Findin the chips are hard. TI has an application note that builds a lighter charger.
 
Thank you all for your feed back. I have decided to tare apart a very good working cigarette lighter to usb port adapter which will give me 2 usb ports, 1 rated as 1am the second rated as 2, which will go nicely with the 3 amp fuse which I will be re-using. Hiding it is no problem, as I have become very good at take apart the dash of the car in question. Will be doing this in a couple hours.

Thanks Again!
 
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