# Charging a 50 Farad Capacitor with Voltage Follower

1. ## Re: Charging a 50 Farad Capacitor with Voltage Follower

Hi,

You just want to charge a capacitor with 1/17 of the input voltage?

Then a simple and high efficiency solution may be:
* to generate a PWM with 1/17 duty cycle (frequency depends on some device values)
* then drive a (power) half bridge with this signal
(A simple test at this point could be to just connect a RC low pass filter and check the C voltage. It should be exactely 1/17 of the input voltage)
* further you should connect an inductor ... to your big capacitor.

Switching freqency, half bridge and inductance depend on each other.

Klaus

2. ## Re: Charging a 50 Farad Capacitor with Voltage Follower

Divider Charger Logic using real components:

@Klaus, if you can demonstrate your idea with real components based on circuit logic, it could be an option.

Capacitor - Maxwell Technologies BCAP0350 \$16.07 AUD
http://www.mouser.com/ds/2/257/Maxwe...5-4-341252.pdf
350 F
ESR 3.2 mΩ
2.85 V
Leakage Current 0.30 mA
Thermal Characteristics - Maximum Continuous Current 21A RMS @15C.
-
2x Maxwell BCAP0350 Capacitor in Series.
175 F
ESR 6.4 mΩ
5.7v
10.5A RMS
------------------------------------------

Darlington - TIP100 60v
https://www.onsemi.com/pub/Collateral/TIP100-D.PDF
Collector Current
Continuous 8A
Peak 15A

Design for 4v 10A Max.
10Amps / 4V = 0.4 ohm resistor.

Correction Note: The second Opp Amp inputs resistor divider should be connected after Darlington!!

Common Anode Dual Rectifier - MUR1620CTRG (Not sure if I need diodes or not???)
http://www.mouser.com/ds/2/308/MUR1620CTR-D-79742.pdf
Average Rectified Forward Current 8A
Peak Repetitive Surge Current 16A

Operational Amplifier (JFET-input) - TL082
Mouser Part No: 595-TL082IPE4 (not sure if this is the right version?)
http://au.mouser.com/ProductDetail/T...xFprZo7erKcw==
Datasheet: http://www.ti.com/lit/ds/symlink/tl082.pdf

I cannot workout what information to use and how to work out the maximum resistance for TL082 inputs?
Can you give me an example of resistor values for my circuit schematic?

Thanks,
Gary

3. ## Re: Charging a 50 Farad Capacitor with Voltage Follower

Hi,

I don't have the time to do this.

But it is very simple:
* pwm with 1/17 duty cycle
* feed it to a power half bridge.
* output of half bridge is LC (with damped LC resonance)
--> voltage at output "C" = 1/17 of half bridge power supply voltage

Klaus

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4. ## Re: Charging a 50 Farad Capacitor with Voltage Follower

@Klaus, please do not respond! I will request you are blocked or I will leave the forum, get over it!

The opp amp data sheet is very confusing, can someone help with the characteristics for resistance values at inputs!
Operational Amplifier (JFET-input) - TL082
Mouser Part No: 595-TL082IPE4 (not sure if this is the right version?)
http://au.mouser.com/ProductDetail/T...xFprZo7erKcw==
Datasheet: http://www.ti.com/lit/ds/symlink/tl082.pdf

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5. ## Re: Charging a 50 Farad Capacitor with Voltage Follower

Hello,

I do respond. Because your habit isn´t fair.
All we forum moderators spend a lot of our spare time to help others. We don´t get money for this.
But we don´t want to be treated like a servant.
If you just follow some discussions where I participate, then you will see that I´m no MIMIC - like you implied in your new thread.

We moderators don´t take. We only give.
But you take new information, new ideas. But don´t give nothing.

You warned to leave the forum.
To whom do you think this is the biggest loss? To me? To other forum members? For you?

So please rethink your habit and behave like a guest in this forum.

***

To the circuit:
It is done many times. For voltage and power conversion - similar in synchrounous buck converters. And it similarely is used in PWM-to-analog DA-converters.
So I think it´s your job to do an internet research or to run a simple simulation (it´s only a couple of parts) to see if this fits your needs or not.

Klaus

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6. ## Re: Charging a 50 Farad Capacitor with Voltage Follower

Originally Posted by KlausST
Hello,

I do respond. Because your habit isn´t fair.
All we forum moderators spend a lot of our spare time to help others. We don´t get money for this.
But we don´t want to be treated like a servant.
If you just follow some discussions where I participate, then you will see that I´m no MIMIC - like you implied in your new thread.

We moderators don´t take. We only give.
But you take new information, new ideas. But don´t give nothing.

You warned to leave the forum.
To whom do you think this is the biggest loss? To me? To other forum members? For you?

So please rethink your habit and behave like a guest in this forum.

***

To the circuit:
It is done many times. For voltage and power conversion - similar in synchrounous buck converters. And it similarely is used in PWM-to-analog DA-converters.
So I think it´s your job to do an internet research or to run a simple simulation (it´s only a couple of parts) to see if this fits your needs or not.

Klaus

Your using position of moderation to justify harassment.

I spend a lot of time on the detail to explain my ideas, and to help others.
I am the founder and admin of a forum.
No pay is required, I do it because I want to help people.

You seem to treat your ranking as some type of competition, and clearly fall back on the service you provide.
But offering a paper clipping and saying it is easy doesn't help.

Why is it better?
Is it cheaper?
Is it less complex?

Is it easy?

When the person you help goes off with this information and builds a circuit that self destructs, how is that easy?
I do not care what others here think, you insist on answering every question, have the decency to follow it through.

7. ## Re: Charging a 50 Farad Capacitor with Voltage Follower

Hi,

Is it easy?
Yes, I said this already.
Simple technology. Only a few parts to use.

Why is it better?
* I said it is more efficient. Less power loss.
My idea was if you wnat to charge a capacitor.. then you may use the stored energy later. As much energy as possible.
Your resistor solution dissipates power.

* it is push-pull technology.
Your circuit only works in one direction. In charging mode. When the voltage in the power rail risies.
But my circuit works even in discharge mode, when the voltage is falling.

***
My circuit is used with high power battery banks. Where many battery cells are connected in series.
The overall unbalanced energy that can be stored/harvested in a bunch (count = n) of serially connected batteriesis:
n times the energy of the weakest_battery.
--> The weakest battery determines the overall energy.
But with push-pull technology you may use almost the sum of all single stored energies.

Isn´t this better?

*****
Although you may find such information as harassment....
and you find the detailed information that you donate to the forum community of way higher quality.... your "helped" rate doesn´t show this.

Therfore an honest request:
If some user forgot to press the "helped me" button for "Constructer", please do it now.
(Mind not to do it at this post, but in any of "Constructer´s" posts.)

Klaus

8. ## Re: Charging a 50 Farad Capacitor with Voltage Follower

Lost Secrets of the H-Bridge Part III - Practical Issues of Inductor and Capacitor Ripple Current

http://docdro.id/NWM30yh

9. ## Re: Charging a 50 Farad Capacitor with Voltage Follower

Originally Posted by Constructer
Lost Secrets of the H-Bridge Part III - Practical Issues of Inductor and Capacitor Ripple Current

http://docdro.id/NWM30yh
If the article is relevant to the topic please explain instead of posting a bare link.

------------------

Klaus (post #25) made a suggestion which seems sensible:

run a simple simulation (it´s only a couple of parts) to see if this fits your needs or not.
It should be possible for you to create a simple workable circuit, by using generic components.

To illustrate the ability of an H-bridge, I was almost ready to post one of my own simulations for charging two series capacitors. Then suddenly you change your spec output to a 1/17 fraction of the supply voltage. This has the effect of rendering previous advice so it is of little purpose.

Klaus is to be thanked. However your remarks show little appreciation. Your remarks to him send a similar message to any of us who have contributed to your topic.

10. ## Re: Charging a 50 Farad Capacitor with Voltage Follower

Originally Posted by BradtheRad
If the article is relevant to the topic please explain instead of posting a bare link.

------------------

To illustrate the ability of an H-bridge, I was almost ready to post one of my own simulations for charging two series capacitors. Then suddenly you change your spec output to a 1/17 fraction of the supply voltage. This has the effect of rendering previous advice so it is of little purpose.
The bare link shows information for using H Bridge that Klaus would like to use in his design.

The 1/17th voltage divider is connected across Solar Charger for 17 Lifepo4 Cells.
This follows changes in supply rail during charging, on any set charging voltage.

The 1/17th voltage is obtained with a 1/17 voltage divider connected to Opp Amp as shown below.

I made a couple of errors drawing it up, but the logic should be clear.
The second Opp Amp divides this voltage, in order to efficiently charge 2 series capacitors.

As described earlier in thread, this equipment is to test the effect of a one-way balance system.
By design, this equipment has no effect unless the capacitor is of higher voltage then cell.

An advantage in the use of Opp Amps, is some come in Dual package that could be used for further logic.
The price is good and Logic is very simple, but people skilled in electronics could help make it a better circuit.
This is all public, people take ideas and develop them for their own use, nothing is original.

The only message I send, is respect the posters question enough to follow detail before arguing for your own curiosity.

11. ## Re: Charging a 50 Farad Capacitor with Voltage Follower

Thank you for the help.

There are a lot of people interested in the charging of Lifepo4 Cells, because they offer good value for capacity and come in large format.
Lifepo4 is in common use, but the flat charge and discharge curve makes standard balance methods unsuitable.

I wanted to build a simple piece of equipment to test any effect in one-way balance system.

The logic starts with cheap and simple.
Comparisons:
1/ Using cells in parallel incurs little imbalance. (Connected 100% of time = No imbalance)
2/ A source voltage above another dominates. (Declining over time to equalization) Re: Capacitors and cells!
3/ Work = The Cells initial state and the Capacitor decline time to equalization, and the Cells time connected to Capacitor during charging period.
4/ Different Batteries in Parallel:

My wish is to keep it simple with one-way flow from Cap to Cell.

I would appreciate any input to my circuit and the resistor values.

12. ## Re: Charging a 50 Farad Capacitor with Voltage Follower

Function After Capacitor is Charged:
The capacitor will be tapped into a cell in parallel.
During this time, any voltage it holds above the cell will transfer.
Before being disconnected from cell and charged back up to the 1/17th reference.
Repeat process for each cell.

For this Sequence of 17 outputs I am using Picaxe 28x2.

Code:
```#picaxe 28X2

symbol pulsetime = 1000
symbol gaptime = 500

do

if b0 = 0 then pause gaptime : pulsout a.0, pulsetime : pause gaptime : endif
if b0 = 1 then pause gaptime : pulsout a.1, pulsetime : pause gaptime : endif
if b0 = 2 then pause gaptime : pulsout a.2, pulsetime : pause gaptime : endif
if b0 = 3 then pause gaptime : pulsout a.3, pulsetime : pause gaptime : endif
if b0 = 4 then pause gaptime : pulsout a.4, pulsetime : pause gaptime : endif
if b0 = 5 then pause gaptime : pulsout b.0, pulsetime : pause gaptime : endif
if b0 = 6 then pause gaptime : pulsout b.1, pulsetime : pause gaptime : endif
if b0 = 7 then pause gaptime : pulsout b.2, pulsetime : pause gaptime : endif
if b0 = 8 then pause gaptime : pulsout b.3, pulsetime : pause gaptime : endif
if b0 = 9 then pause gaptime : pulsout b.4, pulsetime : pause gaptime : endif
if b0 = 10 then pause gaptime : pulsout c.0, pulsetime : pause gaptime : endif
if b0 = 11 then pause gaptime : pulsout c.1, pulsetime : pause gaptime : endif
if b0 = 12 then pause gaptime : pulsout c.2, pulsetime : pause gaptime : endif
if b0 = 13 then pause gaptime : pulsout c.3, pulsetime : pause gaptime : endif
if b0 = 14 then pause gaptime : pulsout c.4, pulsetime : pause gaptime : endif
if b0 = 15 then pause gaptime : pulsout c.5, pulsetime : pause gaptime : endif
if b0 = 16 then pause gaptime : pulsout c.6, pulsetime : pause gaptime : endif

inc b0
if b0 = 17 then
b0 = 0
endif
loop```
The individual cell sequence runs in conjunction with the banks series voltage charger 49.5 to 60v. The 1/17th voltage division is 2.9v to 3.529v.

13. ## Voltage control system for Charging Series Capacitors - Electronic Circuit Update

Voltage control system for Charging Series Capacitors - Electronic Circuit Update

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14. ## Re: Charging a 50 Farad Capacitor with Voltage Follower

Voltage control system for Charging Series Capacitors - Electronic Circuit Update2

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