30 votes
Accepted

How do mobile phone chargers produce regulated voltage?

Phone chargers are indeed usually a 5 V regulated power supply. Here's an example of a simple circuit that is commonly used: Source. This is a flyback converter circuit. The output voltage is ...
Bimpelrekkie's user avatar
  • 80.8k
25 votes

Takes days to charge phone from 10W solar panel

First make sure everything is working as intended. Point the solar panel at full sun and see what kind of current you can get at 5 V. Try a 5 Ω power resistor. That should draw 1 A, which ...
Olin Lathrop's user avatar
25 votes
Accepted

Heat lost in ideal capacitor charging

The problem with these theoretical examples lies in the fact the current is assumed infinite for 0 seconds. Crudely substituting this in the conservation law: $$ \frac {\partial \rho }{\partial t} +\...
Huisman's user avatar
  • 10.7k
21 votes

Takes days to charge phone from 10W solar panel

You're hooked up wrong. The meter's big rotary switch has a legend around the outside indicating range. Obviously, there are as many range markings as there are switch positions. Only two of them ...
Harper - Reinstate Monica's user avatar
21 votes
Accepted

Why doesn't my computer USB port break when I plug in a 2A device?

To be compatible with the original standard, USB devices should not draw more than 100mA (which is plenty to power the logic interface), until they have negotiated with the host, to find out what it ...
Neil_UK's user avatar
  • 165k
20 votes

Why doesn't the capacitor fill to the maximum?

You've likely exceeded dynamic range of CH1, making measurements untrustworthy. Notice that the "zero" indicator for CH1 (lower left corner) is pointing down, indicating that the real zero ...
glen_geek's user avatar
  • 25.3k
17 votes

What does an EV "wall socket charging cable" do?

It is for safety. It can't be omitted. The box tells the car how much current is available at maximum so the car knows how much is the maximum current it can draw. The box also turns on mains voltage ...
Justme's user avatar
  • 143k
17 votes
Accepted

Windmills generate electricity by the spinning blades. Why can't EV vehicles recharge their batteries from their spinning wheels? Is that too hard?

They do. It's called regenerative braking. The only time you can practically recover energy from the wheels is during braking. Taking energy from them slows them down. If you do it while they are ...
GodJihyo's user avatar
  • 22k
16 votes

Why doesn't my computer USB port break when I plug in a 2A device?

Historically: really old mainboards connect USB power pins to the 5V power rail, with no protection power on by keypress was added, which added a jumper or a BIOS setting that decided whether USB ...
Simon Richter's user avatar
15 votes
Accepted

Can I use capacitor to measure time?

Yes, this is a well-established method of measuring with resolution in the picoseconds without requiring impossibly high clock frequencies. You switch a current source to a capacitor. The generic term ...
Spehro Pefhany's user avatar
14 votes

How do USB charging and "smart" charging ports (e.g. Anker's PowerIQ) work?

In practice, 'smart' chargers use a special chip called a Dedicated Charge Port Controller. A DCP controller can act like different chargers, and picks the mode which seems to work best. That's ...
florisla's user avatar
  • 311
14 votes
Accepted

Is this MOSFET upside down?

It is correct. You normally see PMOS connected like this to act as a reverse-polarity "diode". simulate this circuit – Schematic created using CircuitLab It has much less voltage drop ...
DKNguyen's user avatar
  • 56.4k
14 votes
Accepted

Lead Acid AGM battery testing - Why am I testing it this way?

You could do the entire discharge at the lower rate but then it would take a lot more time. When discharging at a high rate the voltage may collapse prematurely so the battery seems discharged before ...
Kevin White's user avatar
  • 32.9k
13 votes

Heat lost in ideal capacitor charging

When masses collide in an inelastic manner, momentum is conserved but energy has to be lost. It's the same with the two-capacitor paradox; charge is always conserved but, energy is lost in heat and EM ...
Andy aka's user avatar
  • 452k
13 votes

What does an EV "wall socket charging cable" do?

It is required. The charger for the car is built into the car itself and this is a weather-resistant lead with some smarts in it. The dedicated wall chargers some people have installed in their homes,...
Criggie's user avatar
  • 869
13 votes
Accepted

Are smartphone cells actually charged with 9V using QC and other techniques or does the smartphone always step down the voltage?

Your friend is right in that you cannot charge a lithium ion cell with just any old voltage. The battery university goes into some detail about it. Short form: A single lithium ion cell has a voltage ...
JRE's user avatar
  • 70.8k
12 votes
Accepted

How come charging a phone with less current is just slower?

Typically: It just monitors the voltage of the power supply. If that drops too far (typically, for USB chargers, below 4.8 V), it reduces the current sink into the battery. A smarter charger might "...
Marcus Müller's user avatar
12 votes

What is the limit for pairing batteries in series? What happens if we cross that limit?

The limit is whatever the insulation surrounding the batteries can handle. If you have one million 1.5 V batteries, then it is perfectly possible to put all of them in series, thereby creating a 1,500,...
Tanner Swett's user avatar
  • 3,315
11 votes
Accepted

Why do three series connected 1.2 V NiMH batteries read 4.16 V when charged?

No, that’s perfectly normal. See the charge curve for NiMH below. It’s about 1.45 V / cell fully charged. NiMH are tolerant to overvoltage as long as the current is kept low enough. This is commonly ...
winny's user avatar
  • 14.4k
11 votes

How do mobile phone chargers produce regulated voltage?

Complementary to main answers: It is crucial to note that attempting to charge a Li-ion cell by simply applying 4.2 V (or whatever maximum voltage is required) is an extremely bad idea because: One ...
Russell McMahon's user avatar
  • 150k
11 votes
Accepted

What does an EV "wall socket charging cable" do?

They are called EVSE, for Electric Vehicle Supply Equipment. First, it's a GFCI (human safety rated RCD). However, it's a "smart GFCI" that can self-reset at intervals - most ground faults ...
Harper - Reinstate Monica's user avatar
11 votes

Why is charging with Lithium batteries with a small load dangerous?

If your charger outputs 1 A in CC mode, and has a 500 mA constant current load connected, then 500 mA goes to battery and 500 mA to the load. So the battery will also charge slower because only half ...
Justme's user avatar
  • 143k
10 votes

Charging of capacitor in RC circuit

simulate this circuit – Schematic created using CircuitLab The current is determined by the voltage across the resistor, which is V1-Vc. As the capacitor charges, Vc increases while V1 stays the ...
Hearth's user avatar
  • 31.8k
10 votes

About the torque-free charging operation

The paper is about using the EV motor windings as a transformer or inductors as part of the charger when the vehicle is charging instead of using a separate component. A common problem of doing so is ...
Kevin White's user avatar
  • 32.9k
9 votes
Accepted

Charging a 3.7 V with a 5V usb charger

Ok, so you aren't actually asking the right question. I'm going to assume you mean you have a 5V power source (usb, battery pack, etc.) and want to charge a single cell lithium ion battery with ...
mwwalk's user avatar
  • 291
9 votes

Does the charger consume power after charged device is disconnected?

These kind of AC to DC converter will always consumme a small amout of power to maintain the control IC alive. I do not see a way around that unless your USB port has some sort of mechanical switch to ...
A. Baril's user avatar
  • 316
9 votes

Can I charge 2.7 V 500 F capacitor with 12 V car battery?

It doesn't matter what voltage your power source is, as long as the capacitor is not subjected to a higher voltage than it is rated for. You could, for example, charge the capacitor from a 12 V ...
Olin Lathrop's user avatar
9 votes
Accepted

What protocol does the data wire on an EV charger use?

In addition to the duty cycle determining the max amperage that the car can draw, there is a simple signaling protocol between the EVSE and the car which controls when the EVSE can apply AC voltage to ...
DoxyLover's user avatar
  • 8,060
8 votes
Accepted

Troubleshooting why Powerbank Doesn't Charge Cell Phone

A device (phone) gets charged at optimal (high) rate only when it recognizes "charging port signature" on charger side. For Type-A port, there are several DIFFERENT port signatures that a charger port ...
Ale..chenski's user avatar
8 votes

series charging three 18650 batteries with three chargers off the same 5V supply

No, this won't work. You can't simply daisy chain chargers but drive them off the same 5V supply. Your charger needs to be able to define both the out+ and out- rails (chances are, out- is directly ...
Marcus Müller's user avatar

Only top scored, non community-wiki answers of a minimum length are eligible