My question is, what if I want to charge my iphone that uses 5volts via USB, however what if I had a powersupply that could deliver 5volts upto 10amps, if I used this to charge my phone would it ruin the phone? I thought that the phone only draws what it needs from the powersupply to charge it. Or would I be best to buy a charger to be used to charge my phone? Are phone chargers smart and turn off when phone is charged?
1228
Power supplies are available in a wide range of voltage and current ratings.  If I have a device that has specific voltage and current ratings, how do those relate to the power ratings I need to specify?  What if I don't know the device's specs, but am replacing a previous power supply with particular ratings?  Is it OK to go lower voltage, or should it always be higher?  What about current?  I don't want a 10 A supply to damage my 1 A device.
58248
Will the following situation damage or cause any harm to the battery or/and the phone:   The phone is being charging (regardless it is using the electrical outlet or via USB) and .. You are playing a game while the phone is being charging and .. You will be playing the game for 5 hours or more.   In another word, if you will be playing a android game in a android phone for 5 hours or more while the android phone is being charging, will it cause any damage or harm to the android phone and/or the battery inside the android phone?
60243
I saw a battery charger that converts 220V AC to 6V DC without a transformer.   Now I am wondering why many (if not all) power adapters are using a transformer, is it about efficiency or about drifting over time?  Update: This circuit is inside of this torch
112604
At an Not For Profit/Charity I volunteer for occasionally we were very fortunate to be provided (donated) with a brand new 3Kva APC UPS. This is total overkill for our modest server rack (four mid-range servers and a switch!) but hey, I'll take what I can get!  Pressing the TEST button on the front indicates that yes, the UPS does work. Brilliant. But it only tests it for about 15 seconds.  My question is - will I degrade the UPS by unplugging it from the wall to see how long it will last? My plan is to unplug it, and wait until the battery meter reaches its last LED before plugging it back in, so that I know about how long I will have in the event of a power outage.  Do people do this on a regular basis? I'm guessing no (Lead Acid is very different to Li-Ion batteries)... but what kind of harm would it do if this were to happen (on purpose) every 6 months?
82661
I'm designing a board that can be powered either by USB or an ATX power supply.  They can both be plugged in at the same time, independently.  I'd like the ATX to provide 5V if its plugged in, but fall back to the USB if possible.  The chips in the circuit will all be running at 5V.  Any ideas?
78704
How does a non contact voltage tester pen detect voltages and/or currents? Are they limited to voltages of a certain range or type (AC or DC)?  Here's some experiments I have conducted that lead to this question: Using a cheap pen I bought for a couple bucks, I can detect the usual 120V AC in an American outlet, but I also have been able to detect voltage in a USB cable connecting a switching power supply to a smartphone (this setup is usually referred to as charging one's phone). Here, of course, the voltage in question is DC with a negligible ripple. I also noticed that while the detector can detect the 5V of a phone charger cable, it cannot detect the voltage in a USB keyboard cable. The only difference between these two scenarios is the current level and perhaps some minor signaling differences.  A final question: In what voltage/current scenario would you have to use a current clamp sensor and not a non contact voltage detector for merely detecting the presence of power non-intrusively?
52086
If there is only the Macbook 12 inch USB-C charger nearby, can it be used to charge other USB-C devices, such as any Android phones that also use USB-C? (will it be "too powerful" and damage other devices?)  Vice versa, if there is a Quick Charge 2.0 or 3.0 USB-C charger from other devices nearby, can it be used to charge the Macbook 12 inch?  The main concern is about whether it could damage the device or battery.
82524
How much power can be drawn from the iPhone/iPad lightning connector by a external device?  Update: The use case is a audio-related device for iPhone/iPads. It would require around ~100 mA at 3,3 volts, so I'm trying to find out if we could draw this from the iPhone/iPad. (That would allow us to skip an external battery –> smaller size...)  (This question has been asked for the old 30-pin connector , but a new connector might imply new power constraints.)
57671
Answers to this question  explain how charging while phone is in use does both - charging the battery and powering the on going activities.  My question is different — Can I stop charging the battery but use the connected power for ongoing activities?  Why do I want to do this?    I want to charge the battery within ideal limits (see )    and    at the same time use the charging power to keep running the phone without any heat stress on battery, thus extending battery life.  Also the battery is not drained, enabling me to use the phone for longer time without charging   Edit : I am not looking for dedicated cables or hardware that can possibly do this
64648
I don't understand how cells behave when connected in parallel. So what if I have two Li-Ion cells: one ist "rated" at 15 amps (which means that the cell is able to discharge at 15 amps without problems , right?) The other cell ist rated to 5 amps. Now assume both have appropriate same Voltage to connect them both in parallel. What happens if you connect a load which would draw 10 amps now? Would both cells try to discharge with the same 10A (and thus the 5A-cell would overheat and fail...), or would the current be spread up eavenly? Is it actually forseeable at all what would happen, since it depends on the internal resistance of both cells, doesn't it? Does someone know what would happen?  Then another question: what if you put two cells of different capacity in parallel? Isn't the cell with the higher capacity supposed to give more current? Because the discharge curve of the high-capacity-cell is above the discharge curve of the low-capacity cell. So the high-capacity-cell would have to discharge more of its current until it decreases its voltage to the same level as the low-capacity-cell? So would that mean that the internal resistance gets lower with a higher capacity, is it proportional?  Hopefully my explanations aren't to confusing and hopefully there are people who are bothered by the same question :) Thank you!
22848
I usually disconnect my cellphone from the charger some time after it's fully charged because I'm afraid the battery could lose capacity over time if I don't. However, I believe modern electronics should be able to handle this kind of scenario and automatically stop charging the battery once it's full. Does this apply to modern Android phones? Or do I need to continue disconnecting it all the time?
33223
My friend and I both have droids and we often user each other's wall chargers out of convenience. I was told that it's possible that my phone might explode if it's charged with a charger that wasn't built specifically for my phone. How true is this across droids?
108600
I wanted to ask, what to do if MacBook Pro 2017 uses more wattage than the charger can give? Why I am asking this or thinking this might be a problem? I tried to play some games on BootCamp (playing games on MacBook is another discussion, no hate please) on settings where I got 60FPS without lag but the problem is that my battery is discharging at the time I am playing. I can not recognize the problem on macOS though.  If I bought the mac couple days ago, first they gave me fake charger which f*d up my mac and wouldn't charge at all. Still can not believe that I buy new Mac and get fake charger with it. Then I went back to the store and asked for new Original charger which I then got. I can not see any more problems than the above I described.  Can anybody tell me what to check, what to do, who to contact with? Any help is much appreciated.
86412
I have powerbank that provides 5v (presumably regulated) power, as typical of most usb interface powerbanks. I have been trying out my powerbank with different phones. It works on all except one. I have tried it with various USB cables, making sure I didn't overlook anything foolish. Then, I looked at the AC adapter of the phone that it didn't seem to be compatible with. The adapter read: 5.4v DC output. The device's official website or manual doesn't tell me what the input voltage should be. So I have the following questions   Is the fact that the device's AC adapter creates a DC 5.4v output enough to assume that, this is the correct voltage for my cell phone? If 5.4v is the input voltage, then when I attempt to power it with a 5v power bank, am I hurting it? Thus far, it just seems to be non-responsive when I try this. It seems another explanation is polarity mismatch. I'm aware that laptops have a polarity correction feature, which could explain why I can charge this phone via my laptop. Is there any other way to tell if polarity is an issue, given that I don't have access to detailed product information (unless the official website is updated, or something)   So that's the gist of it, I'm not sure why my powerbank isn't charging my phone. And I'm having difficulty troubleshooting the underlying problem by myself. Any tips big or small will be appreciated.
110926
Normal computer USB max current is much lower than needs of modern smartphone to charge while running, commonly needing ~2 amp chargers.  I want to be able to have my phone connected to my computer via usb for data purposes, but it maintain it charge.   Is it possible to do something like this to a usb cable, so instead of the 5v coming from computer, it comes from phone charger instead ?         &ndash; Schematic created using
44632
I have iPhone 5S with 10.1.1 iOS. I have experienced few situations where my battery life was about 30-40% and iPhone immediately turned off. When I tried to turn on it indicated low battery and kept doing this for about 2 hours everytime I tried to turn on. And then suddenly turned on and was back at around 30% battery life and I did not use charger in the meantime (I did not have it). Then this situation happened to me again when I had my charger with me, so plugged in and after while iPhone turned on charging but already had about 40% of battery charged. This happened to me like 5x in last 3 months. The scenario is always very similar, battery life about 30-40%.. (never happens when the battery is more than 50%) and then few hours idle until comes back. Does anyone has any suggestions? Many thanks for help
84243
I've just bought a portable battery, but the portable battery don't comes with an adapter for the house current; it only comes with a USB cable so I can charge it with my laptop. My mobile phone came with a charger, and I want to know if is safe to use that charger with the battery without problems, even though the output has a higher amperage. These are the specifications:  Battery input: 5V, 1A Charger output: 5V, 2A  Will the output only give the quantity that the input is requesting, or will the input overheat because it cannot handle all the current it receives?