# Tag Info

30

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 regulated even though it's not immediately obvious how that's done. But note the winding "Na" on the left, it is one of the transformer's windings. This ...

11

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 normal charging method is to use CCCV (constant current / constant voltage) charging where a constant current is applied while Vbat is under 4.2 V and then a ...

8

I have not yet been able to find a good visual representation of the saturation stage of the charging and how it is different from the constant current stage of charging. Does anyone have/know of a good visual representation of this? The 'saturation' stage isn't any different as far as the cell is concerned, it's just a result of the charger having to limit ...

8

To answer one point ... Moreover, why can't we simply provide a 4.1 volts input to batteries instead of using 5 volts power supply with an overcharge protection circuit? Because to get current to flow you need a higher voltage than your target. With your approach the current would quickly fall to a very low value when the battery terminal voltage reached 4....

7

I don't see any voltage regulator or a zener diode inside. In all of the phone chargers I have examined, there is a very small switching regulator chip. The chip often has an internal Zener diode to provide a bootstrap supply for the chip. The chip is a switchmode regulator and sends modulated width pulses through an inductor / flyback transformer to get a ...

4

I am somehow creating energy. For example for one cycle, It took 600 seconds to charge but it took 640 seconds to discharge, since the current is constant, that means the battery is somehow discharging more current than it was charged with! Charge is not energy - you have to consider the voltage of the battery as well as the current. When I charge at a ...

3

They self-balance based on voltage. Not charge. Because things in parallel want to have the same voltage. Your example of 50% and 100% balancing out to 75% doesn't work like that as a result. Because battery voltage vs remaining capacity is not linear, and even if it were linear the 50%||100% = 75% would only happen for batteries with identical capacities. ...

3

Since you do not know how much charge is already in each battery you cant actually find the state of charge, how do you overcome this problem? Fully charge the battery, then 'count coulombs' until voltage shows it is nearly empty. This can be used as a reference for future partial charge and discharge, but may have to be repeated occasionally if the battery ...

3

what does PMID actually stands for? It stands for "power-middle" as per this explanation from TI: -

2

But what exactly happens as operationB is done? When you perform operation B you are eliminating the charge on C2. The electrons on one side of the capacitor flow to the other side and combine with the positive charges there. The total net charge on cap is reduced to 0. Assume C1 and C2 have the same capacitance and the system starts with Q charge on C1 and ...

2

It is unsafe to rapidly charge a deeply discharged li-ion battery, and so many li-ion charging chips will use a pre-set trickle charge if the battery is below a certain voltage. In the datasheet this is usually indicated by V_TRIKL and I_TRIKL. As another safety precaution, most charging ICs will refuse to charge a battery which is lower than a certain ...

2

Almost everyone dislikes 'proprietary' chargers Why can't we simply provide a 4.1 volts input to batteries instead of using 5 volts power supply with an overcharge protection circuit? You're talking about putting the battery charge-control circuitry in the wall-wart instead of the phone. That's the same idea, really, as putting the Electric Vehicle ...

2

The problem with this is that the batteries are charged using PV cells which means I am employing an MPPT algorithm to adjust the voltage to deliver the most power to the batteries so this is not an option. MPPT is only useful when the load can take all the power being harvested. If the battery has already reached its maximum permitted voltage then you have ...

1

I am somehow creating energy. For example for one cycle, It took 600 seconds to charge but it took 640 seconds to discharge, since the current is constant, that means the battery is somehow discharging more current than it was charged with! You don't know whether you are 'creating' energy unless you also take the voltage into account. But you do seem to be '...

1

From what I understand, Constant current charging is when you fix the current supplied to a battery and the voltage would vary depending on the battery. Constant Voltage charging is when you connect a certain Voltage across the terminals of a battery Not quite. True 'Constant Voltage' charging would risk blowing up the battery or charger, because there is ...

1

I have read previously that it is possible to fully charge a battery to 3.6V by switching to constant voltage charging after 3.4V and just watching it until the battery draws very small amounts of current which would mean it is fully charged. Is this true? Yes that is true. If I was somehow able to implement this, what constant voltage should be chosen? ...

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