USB car phone charger - Page 1
Forum section: electronics / projects

author: j.a.mcguire
author_rank: Contributor
timestamp: April 19, 2015, 05:16:26 pm
content: If I put 6, 0.5a 5v regulators in parallel could I make a (up to) 3a phone charger? Why would this be a bad idea?Want to make something better than the crappy cigarette lighter chargers that claim 2a or more but seem to struggle to keep my phone charged when I'm using it as a sat nav.

author: SeanB
author_rank: Super Contributor
timestamp: April 19, 2015, 05:32:04 pm
content: Would be better to buy on eBay a proper step down converter that can do 3A, and then put it in a small case with leads in and out, using the one dead car lighter unit simply as the power lead, removing the little 500mA converter inside and then having the USB lead for the phone soldered to the output.That way you will have a more reliable supply, as the smaller ones do not like being connected in parallel, the one with the highest voltage output will try to supply all the current while the rest will stay switched off as the output is above the reference voltage setpoint.When ordering the converter also get a small USB charger doctor, which you can put in line and which will give a good idea as to the voltage and current used on the phone while charging. Mlorton had a review of a niceYZXstudio unit on his channel.

author: Isad
author_rank: Frequent Contributor
timestamp: April 19, 2015, 05:35:13 pm
content: Quote from: j.a.mcguire on April 19, 2015, 05:16:26 pmYou totally could i do that sometimes and it kinda workbut u get some loses involtage and some in current fromah i might be what i have seen.And with all of those reagulator u mightget some heat out of them but totally wrong.

author: kurt
author_rank: Contributor
timestamp: April 19, 2015, 07:03:19 pm
content: Most likely your problem is that the phone do not know that your charger can deliver 2A. So it will be very conservative to not fry it. It does not seems to be a proper standard for how the chargers tell the phones how much current it can pull. Or it might be now?I had the same problem with my HTC Desire HD a few years ago. I had a third party car USB charger capable of delivering 2A. But still I could not use the phone as a GPS in the car without draining the battery. Even when on the charger. I read somewhere that some phone manufacturers shorted the two data lines in the charger to tell the phone that it was on a high-current capable charger. So I tried to do that in the car charger.And after that it would charge just as quick as the original HTC charger and would have no problem running the GPS and charge the battery at the same time. I later replaced the Desire HD with a Samsung S3 that I again replaced with a Samsung Note 4. And all those phones seems to take the shorted data lines as a sign that they can pull high currents.What "high currents" means I'm not sure. But given the capability of a micro USB connector I doudt it is more than 2A.Another thing to be aware of, is that many cheap eBay USB cables seems to have to thin wires to be usable. I guess the phone is again being very conservative and if the voltage drop more than it expect when it start pulling, it will back off and do a slow charge to not risk blowing up the charger.Wether shorting the data wires in the charger is correct, or even safe, I do not know. It might risk blowing up your phone. But at least it has worked very well for me. And if your charger have unconnected data wires, it is very unlikely that increasing the current capability of the charger will give any shorter charge times unless something else is done to.