VV Explained

[exo72069]

Can someone please point me to an explanation of how a Ego Twist style battery controls the voltage? Not too technical but a little deeper than "Twist the dial dummy.".

 

[Eitje]

If im nog mistaken, ego batteries with VV use PWM, pulse width modulation.
Say your fully charged battery can provide 4.2v
Now to lower the voltage, it rapidly switches the power on and off for x miliseconds. Taking the 4.2v: on for 5ms, off for 5ms, on for 5ms, etc will give a 2.1v output.
Varying the timings on and off (you turning the dial) you can get different output voltages.

 

[Rabbit Slayer]

A potentiometer controls how much power goes to the atty

 

[Ryedan]

Can someone please point me to an explanation of how a Ego Twist style battery controls the voltage? Not too technical but a little deeper than "Twist the dial dummy.".

They use a voltage regulator to push the output voltage up to 4.8V and then as Eitje said, they use PWM to lower the voltage to what you set.

 

[exo72069]

Thank you very much for the information. The curse/blessing of knowledge is that answers, invariably lead to more questions. What electronic wizardry allows boosting the voltage up to 4.8? I presume this same technique is used on the cheaper removable battery mods while the more expensive mods uses a variable boost?

 

[Ryedan]

Thank you very much for the information. The curse/blessing of knowledge is that answers, invariably lead to more questions. What electronic wizardry allows boosting the voltage up to 4.8? I presume this same technique is used on the cheaper removable battery mods while the more expensive mods uses a variable boost?

You're welcome

The circuit is called a boost dc-dc power converter. I have also seen it referred to as a boost dc-dc voltage regulator, or a boost dc-dc converter. Here is how it works.

There is also a buck dc-dc converter which lowers the voltage. They can be combined into a buck-boost dc-dc converter which does both.

Here is some info on PWM.

Hope that helps.

 

[exo72069]

Many thanks Ryedan. This is exactly what I was looking for. Once I figured out that that in the circuit diagrams the circle was the source and the rectangle meant the load, it all began to make sense. I'm used to circuit diagrams where a battery is represented by a stack of alternating long and short lines and a resistance is represented by a zigzag line.

The way I understand it is that a Buck Converter works by switching off the source before the coil is fully saturated so the load sees a lower voltage than the source. It seems to me that there would still be a bit of ripple in the output voltage but a lot smoother that the "all on/all off" of pulse width modulation.

Apparently a Boost Converter works by storing energy in the coil/capacitor array, then switching the circuit so that the battery and the coil/capacitor are in series, thus the load sees a voltage that in theory could be almost double that of the battery alone.

Please let me know if I've gotten it wrong.