Home  |  Contents 
Electronics
  Forum Index : Electronics         Section
Subject Topic: Ultra Capacitors "Boost-Caps" Post ReplyPost New Topic
<< Prev Page of 6 Next >>
Author
Message << Prev Topic | Next Topic >>
Tinker
Guru
Guru
Avatar

Joined: 07 November 2007
Location: Australia
Online Status: Offline
Posts: 864
Posted: 12 December 2011 at 11:15pm | IP Logged Quote Tinker

Regarding active super cap balancing I got a reply today from hlandis@hotmail.com who says he'd built one but thinks the added complexity is not worth the effort to get a small improvement in leakage. He's doing fine with just LED/diode balancers.

In light what Yahoo2 posted above what I will do once my caps arrive is wire in a rotary switch & multimeter so its simple to check the state of charge of each individual capacitor in my bank of 11.
If there is no worrying variation over some time I might not even bother to fit a balancing indicator.
As I intend to hook up the caps straight to my 24v battery bank they would automatically charge up to the bank voltage. What I want the caps to do is:
1. supply the heavy current peak when the fridges connected to the inverters cycle on.
2. absorb sudden current increases from the solar panels and - when its finally going - the VAWT.

__________________
Klaus


Back to Top View Tinker's Profile Search for other posts by Tinker
 
VK4AYQ
Guru
Guru


Joined: 02 December 2009
Location: Australia
Online Status: Offline
Posts: 2328
Posted: 13 December 2011 at 12:05am | IP Logged Quote VK4AYQ

Hi Tinker it sounds like a passive system would be OK for our application provided the caps are matched evenly, so a initial charge to a set voltage say 2.5 and a timed discharge to 2 volts should give a good idea then recharge and let sit for a week and measure the amount of discharge internal leakage, I think that would show up any faulty or out spec item.

I must get a set to fool around with.

All the best

Bob

__________________
Foolin Around
Back to Top View VK4AYQ's Profile Search for other posts by VK4AYQ
 
fillm
Guru
Guru
Avatar

Joined: 10 February 2007
Location: Australia
Online Status: Offline
Posts: 613
Posted: 13 December 2011 at 12:36pm | IP Logged Quote fillm

Tinker;Bob,

I have my bank in paralell with a 48V /225Ahr Batt bank , and connected with a slightly higher resistance of 5m of 6mm cable , all other loads and inputs are connected to the U/Cap +&- bus bars .

It only took slightly over a week for 3 caps to become quite out of balance with one at 1v low as previously stated .

The problem that could arise is as caps go out of balance then the others of course are compensating at higher volts which compounds with cycling, if a sudden rise of power is absorbed then it could push the higher Ucaps voltage past their recomended high limit causing damage in a severly out of balance situation .
In lower voltage banks that are closely matched to the upper voltage limit would be more at risk but adding extra caps to increase the safety margin then reduces capacity.

Because of the LEDs different brightness levels I would not have had a visual check to see the problem I had, and I still have not fully investigated whether it is in the balancers or internal leakage.

Tinker , I like your idea with the rotary switch to be able to easily check voltages which would also make it easy to manual equalize if needed, but I would think the need for reliable auto balancing is a must have.





__________________
PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits
Back to Top View fillm's Profile Search for other posts by fillm Visit fillm's Homepage
 
VK4AYQ
Guru
Guru


Joined: 02 December 2009
Location: Australia
Online Status: Offline
Posts: 2328
Posted: 13 December 2011 at 1:43pm | IP Logged Quote VK4AYQ

Hi Phil

Roberts set up with zener diodes would be one way of monitoring the cell voltage as it wouldn't cut in till the 2.5 volt is across the cell. That would mean that if the led is out the voltage on that cell is low, and when on the brightness of the led would indicate the amount of equalisation taking place, There is quite a range of LED powers available so that could be varied to alter the equalisation current.

Just waffling on trying to get an easy way, as I looked at the active circuit in the manual and it is a bit to complicated and hard to build in the numbers we would need.

I ordered some little 4 F ones to have a play with they are rated 5.5 volts and only $20 for 10.

4 Farad Super Capacitor Electric Double Layer 10 pcs (250939558232) (fleabay)

I was thinking about a very low power float charge system with a separate leg for each cap. It would use a bit of power but most of it is being fed into the cap. A three terminal reg across each cap with a led in series.

Let me know what you think.

All the best

Bob

__________________
Foolin Around
Back to Top View VK4AYQ's Profile Search for other posts by VK4AYQ
 
yahoo2
Guru
Guru
Avatar

Joined: 05 April 2011
Location: Australia
Online Status: Offline
Posts: 584
Posted: 13 December 2011 at 2:18pm | IP Logged Quote yahoo2

The Maxwell paper I quoted was published in April 2009 and was an update from 2007. I doubt they would have imagined the variety of uses and the fact that individuals are buying cap banks now. My guess is that it was aimed at larger companies that are changing out expensive custom made batteries very frequently, as a lower cost option.
Phill has hit the nail on the head, the reduction in capacity by lowering the voltage is just too much of a sacrifice.
I am glad it's you guys that are experimenting, capacitors seem to commit hare-kari around me.

I got a bit exited about LiPo batteries 12 months ago and found a similar thing, most of the positive info I found on the internet was outdated stuff that was rehashed. the forums on the other hand seemed to be full of tales of battery management modules not doing what they are supposed to do, and banks getting out of sync.
Back to Top View yahoo2's Profile Search for other posts by yahoo2
 
MrDelanco
Regular Member
Regular Member
Avatar

Joined: 12 November 2011
Location: United States
Online Status: Offline
Posts: 99
Posted: 13 December 2011 at 4:39pm | IP Logged Quote MrDelanco

Hello everyone;

This is an update ;I found the resistance in the system coming from the store bought controllers causing the build-up of current up the line in the system overheating the power resistor's. They are not designed to work with a positive grounded setup.

I found the cause of the build-up when voltage was increased and the current increased on the positive side into the charge controllers was caused by the store bought charge controllers not allowing the current to pass without restrictions. The balance circuit stabilized the negative side of the system to a constant 2.5 voltage. On the scope I do see the tunneling start and the readings are normal the reverse voltage stays at 2.5 volts even during the increase in voltage on the pos side and the operating current remains stable.

I installed some used sealed cell electric lawnmower batteries into the line after the ultra-capacitor's before the charge controllers too act as a buffer for the controllers. When the current increases on the positive side the batteries absorb the increase so the controllers don't over regulate the flow. They now have a stable constant current to work with. The lawnmower batteries were a quick-fix in the circuit. The system is working as it should.
When I get some extra time I will design and build a new controller to replace the store bought ones and remove the shunt batteries.

Cheers Robert.


__________________
MrDelanco:Project Videos
It is not only too know what it does but to understand how it does what it does.
Back to Top View MrDelanco's Profile Search for other posts by MrDelanco Visit MrDelanco's Homepage
 
fillm
Guru
Guru
Avatar

Joined: 10 February 2007
Location: Australia
Online Status: Offline
Posts: 613
Posted: 13 December 2011 at 8:23pm | IP Logged Quote fillm

MrDelanco wrote:


This is an update ;I found the resistance in the system coming from the store bought controllers the circuit causing the build-up of current up the line in the system overheating the power resistor's. They are not designed to work with a positive grounded setup.



Robert , which balancers do you have, as am a bit confused , it now seems like you have a active balance system that is store bought and not as you claimed as quoted below in your first post that showed the passive balance LED / Diode diagram that you built and modified to suit your application.

MrDelanco wrote:


To keep the Maxwell ultra capacitors "Boostcaps" from charging over 2.5 volts in the center of the stack, I built a charge equalization circuit for each row in each bank.





__________________
PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits
Back to Top View fillm's Profile Search for other posts by fillm Visit fillm's Homepage
 
Tinker
Guru
Guru
Avatar

Joined: 07 November 2007
Location: Australia
Online Status: Offline
Posts: 864
Posted: 13 December 2011 at 11:13pm | IP Logged Quote Tinker

VK4AYQ wrote:
Hi Phil

Roberts set up with zener diodes would be one way of monitoring the cell voltage as it wouldn't cut in till the 2.5 volt is across the cell. That would mean that if the led is out the voltage on that cell is low, and when on the brightness of the led would indicate the amount of equalisation taking place, There is quite a range of LED powers available so that could be varied to alter the equalisation current.



Bob


Bob, the problem with using "zener" diodes (and the fact that Robert does not seem to grasp) is that the lowest available zener voltage is 2.2V.
Now, when you put a LED in series with it, and the LED itself requires about 2V across it to light up, its never going to light when connected across a 2.5V super capacitor.

Just an ordinary silicon diode has a 0.5V drop across it so combined with a LED it would do as expected. I just wish the word "zener" would disappear from this topic.

Years ago ( about 30 ) I built a digital clock that used a circle of 60 LED's for the minutes and 12 LED's for the hours. I quickly found out that all LED's are not equal and there was a significant brightness difference even when they had lo tolerance series resistors. I ended up matching LED's for brightness individually against a chosen sample and required about a hundred LED's for a neat brightness match. LED's were expensive back then .
Anyway, to build a LED equalisation/ charge indicator its worthwhile to match the LED's and series silicon diodes on a breadboard first, something I will definitely do when I build one. I might even incorporate it in that DMM idea I mentioned above.

__________________
Klaus
Back to Top View Tinker's Profile Search for other posts by Tinker
 
VK4AYQ
Guru
Guru


Joined: 02 December 2009
Location: Australia
Online Status: Offline
Posts: 2328
Posted: 13 December 2011 at 11:31pm | IP Logged Quote VK4AYQ

Hi Tinker

I have never used them for anything this low in voltage before, so I see what you mean now. If I decide to go ahead with these caps I was thinking on a balancer like in my model battery lipo balancer, for final top up it sends a controlled voltage to each cell for 30 minutes at reduced current.

All the best

Bob

__________________
Foolin Around
Back to Top View VK4AYQ's Profile Search for other posts by VK4AYQ
 
MrDelanco
Regular Member
Regular Member
Avatar

Joined: 12 November 2011
Location: United States
Online Status: Offline
Posts: 99
Posted: 14 December 2011 at 2:34am | IP Logged Quote MrDelanco

fillm wrote:


Robert , which balancers do you have, as am a bit confused , it now seems like you have a active balance system that is store bought and not as you claimed as quoted below in your first post that showed the passive balance LED / Diode diagram that you built and modified to suit your application.



Phill

I am talking about the charge controllers after the ultra caps that regulate the input into the 24 volt battery bank not the charge balance circuit.

Regards Robert.


__________________
MrDelanco:Project Videos
It is not only too know what it does but to understand how it does what it does.
Back to Top View MrDelanco's Profile Search for other posts by MrDelanco Visit MrDelanco's Homepage
 
MrDelanco
Regular Member
Regular Member
Avatar

Joined: 12 November 2011
Location: United States
Online Status: Offline
Posts: 99
Posted: 14 December 2011 at 3:28am | IP Logged Quote MrDelanco

Tinker wrote:


Bob, the problem with using "zener" diodes (and the fact that Robert does not seem to grasp) is that the lowest available zener voltage is 2.2V.
Now, when you put a LED in series with it, and the LED itself requires about 2V across it to light up, its never going to light when connected across a 2.5V super capacitor.

Just an ordinary silicon diode has a 0.5V drop across it so combined with a LED it would do as expected. I just wish the word "zener" would disappear from this topic.


A Zener 1N3718 Germanium tunnel diode 0.3v drop.

In a conventional semiconductor diode, conduction takes place while the p–n junction is forward biased and blocks current flow when the junction is reverse biased. In the tunnel diode, the dopant concentration in the p and n layers are increased to the point where the reverse breakdown voltage becomes zero and the diode conducts in the reverse direction. However, when forward-biased, an odd effect occurs called “quantum mechanical tunnelling” which gives rise to a region where an increase in forward voltage is accompanied by a decrease in forward current.
Ref;Wikipedia

Tinker wrote:


Years ago ( about 30 ) I built a digital clock that used a circle of 60 LED's for the minutes and 12 LED's for the hours.


Years ago I also built an led clock using 60 led's in a circle for the seconds and an led digital numeric readout for H/M's, still working today . would you like a photo?

Regards Robert.

__________________
MrDelanco:Project Videos
It is not only too know what it does but to understand how it does what it does.
Back to Top View MrDelanco's Profile Search for other posts by MrDelanco Visit MrDelanco's Homepage
 
Warpspeed
Guru
Guru


Joined: 09 August 2007
Location: Australia
Online Status: Offline
Posts: 574
Posted: 14 December 2011 at 8:33am | IP Logged Quote Warpspeed

How about a TL431 ?



This is a proper shunt voltage regulator with an accurate 2.5v internal voltage reference.
No need for either R1 or R2, just connect Vref direct to Vi and it will regulate Vi to 2.5 volts.
A series resistor is required to limit the current through the TL431 to below it's maximum safe rating of 100mA when it turns hard on.
Maybe 27 ohms 1 watt should do it.

Only two components wired directly across the cap, enclosed inside a bit of heat shrink tube is about as simple as it gets.



Edited by Warpspeed on 14 December 2011 at 9:52am


__________________
Cheers, Tony.
Back to Top View Warpspeed's Profile Search for other posts by Warpspeed
 


<< Prev Page of 6 Next >>
In the news...
 
Post ReplyPost New Topic
Printable version Printable version
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot delete your posts in this forum
You cannot edit your posts in this forum
You cannot create polls in this forum
You cannot vote in polls in this forum

Powered by Web Wiz Forums version 7.8
Copyright ©2001-2004 Web Wiz Guide

This page was generated in 0.1250 seconds.
Privacy Policy     Process times : 0, 0.02, 0, 0.11