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(Solved) Voltage question

J

jmcook79

Android Enthusiast
I'm selling a 3 year old straight talk flip phone on eBay. You'd be surprised what people will pay for a phone that was originally only $50 and can be had refurbished for $35. I sold the last (identical) one for $40 and I want to sell the other one.

The problem is I can't find the charger and no one wants to buy it without it. The original charger was 4.7V 0.3A (it was faded and 0.3A sounds too low so I'm not really sure) I found a charger that fits in the closet and it's 5.1V 0.7 amps. I know the higher amperage doesn't matter but will the .4V difference matter or is it safe to sell it with the phone?
 
No expert here.. I would be leery of using a charger of increased voltage rating. That is the pressure the current is delivered to the device. Increased voltage could increase the heat incurred as the battery charges.

As stated, I'm not one that really knows. I hope another jumps in with a more definitive answer for you.
 
I hope someone else jumps in too, I don't want to sell something that could damage the phone or worse burn their house down!
 
I guess you could test it out over a few charge/discharge cycles, see if the phone heats up unacceptably .. just don't do it next to flammable materials ;)
 
Its one of those things,.. id use it but i wouldnt let my mum. Higher voltage=higher potential damage imo. The phone will control the current but voltage..... id wana watch it :)
 
Generally you can get away with up to 10% and sometimes 15% difference is voltage. The difference here is about 8%. I would try it out a few times first before letting anyone else use it.

Electronics is not as exact of a thing that most people think it is. Average resisters will have tolerance levels of up to 10% for film resisters and up to 20% for carbon resisters. They do make precision resisters with tolerances of 2% or less, those costing more.

Imagine making a car door with a 10% tolerance, it wouldn't work, and yet you could get away with the 10% in electronics voltage.
 
Do you know if it's USB or is it proprietary? Easiest way to tell probably, does the phone have a micro-USB charging socket. If it's USB, then pretty much any USB charger should work. Which is the whole idea of using USB, to standardise on chargers.
 
It is a micro USB, which is strange because I thought all USB chargers were a standard 5V. I wonder why this one is 5.1V and the original was 4.7? I just found the answer to my own question. From Wikipedia:

The USB 1.x and 2.0 specifications provide a 5 V supply on a single wire to power connected USB devices. The specification provides for no more than 5.25 V and no less than 4.75 V (5 V
 
Should be ok, it's the phone itself that regulates the charging voltage down to 3.6v for the battery.

In my school I see hundreds of student's cellphones being charged in the classrooms and the school shop "charging service", and don't think anyone worries about using a particular USB charger for whatever phone. They have to do this as there's no power outlets in the student dorms.
 
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