How to Recondition (Reform) Electrolytic Capacitors and Why

[mockingbird]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

I bought an ESR meter kit based on an old design (ESR Go) so that I could proceed with this project. I started putting the kit together a while back (SMT soldering with a heat gun) and it came out pretty good. Problem is is don't work.

I ordered a PIC flasher and I'm gonna see if maybe the PIC chip's ROM got corrupted or something.

[momaka]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

If the vents are open / bulged and the cap leaked from there, consider those caps done (bad).

If the vents are not open or bulged, see if the liquid actually came from the cap. Sometimes, PCBs are cleaned with various detergents that can leave a residue on components to make it look like there was a fluid coming from these components. But if there is no WET fluid (or corrosion, as the electrolyte is usually very corrosive), the caps may be okay.

[maxbarjr]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

^ 30V should be okay, especially if you end up using those 40V caps on a device that puts even less voltage across them than that.

However, be careful if these are really old caps without safety vents. I've heard some scary stories about them exploding if they do go bad while in circuit.

Thank you momaka. Yes, they have a vent and some have signs of some fluid release.

[momaka]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

^ 30V should be okay, especially if you end up using those 40V caps on a device that puts even less voltage across them than that.

However, be careful if these are really old caps without safety vents. I've heard some scary stories about them exploding if they do go bad while in circuit.

[maxbarjr]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

I just found this thread and I have a question. I have some old 32,000uF 40V capacitors by Sangamo. I only have 30VDC bench adjustable power supply. Can I use it to reform this caps or I need to have 40VDC psu?

[barry wilkins]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

I used to reform capacitors when I was a TV engineer years ago ,but they did not last very long, so it is probably best to replace them with new ones.

[jiroy]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Indeed.
However, the degradation of the electrolytic caps is usually not that bad at all when sitting a year or two on the shelf. Past 5 years - yes, you might want to consider reforming, depending on the capacitor and how it's going to be used. And past 10 years (i.e. new-old stock, or NOS stuff), reforming is probably needed.


Nah, 1 year won't do anything.
I have lots of stuff that have been sitting unplugged for 3-5 years. Not one has ever failed on me. Even some really old stuff that I found and plugged in that haven't seen power for over 8-10 years worked fine. Again, there's a reason why electrolytic capacitors are called "self-healing" capacitors. Of course, if you do want the caps to last as long as possible, then reforming the capacitors (or plugging in the device and using it) is recommended.


That's just for inkjet printers. With laser, there are no problems like that whatsoever. The only problem you might encounter with a laser printer is if you store it somewhere with lots of quick temperature and moisture variations, especially hot places - this is a quick way to ruin a laser printer (or at least require a complete roller/fuser cleanup afterwards).

Hi Momaka; The glorious days of Telefunken and Thomson are over my friend , we're living now in what Trump labeled shithole countries era , lol ..
Although I agree with most what you've said , but the thousands and thousands of repairs i've done all the last 30 years , lead me to approve your statement 10 years ago , and contradict it today ...
Notice first of all , you put in equal all Capacitors brands , and I know , for the sake of the truth , you won't accept to equal a Panasonic with a .... you know , and secondly , you assumed that Capacitors need 5 years to start deteriorating , But that assumption takes for granted that a device was manufactured and delivered to the end customer in the same day , which is totally false in most cases .
Thirdly , Capacitors ain't the sole factor that can lead to a disastrous situation . When I wrote my reply , I was just finishing some UPS repairs damaged by non use as batteries spillage and many other factors ..
Laptops and boards in general , also loose its Bios in time due , and awaking a sleeping board was always my speciality , but never easy .

Have a nice day my friend ..

[Behemot]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Yep, ink printers like cold and wet environment for storage. The heads anyway, the metal (iron) parts may not so much

[momaka]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

It would appear that the running logic you outlined would suggest that we power stuff up regularly to avoid degradation.

Indeed.
However, the degradation of the electrolytic caps is usually not that bad at all when sitting a year or two on the shelf. Past 5 years - yes, you might want to consider reforming, depending on the capacitor and how it's going to be used. And past 10 years (i.e. new-old stock, or NOS stuff), reforming is probably needed.

Don't be surprised then if you plug a device after one year non use to hear a crackling sound ..

Nah, 1 year won't do anything.
I have lots of stuff that have been sitting unplugged for 3-5 years. Not one has ever failed on me. Even some really old stuff that I found and plugged in that haven't seen power for over 8-10 years worked fine. Again, there's a reason why electrolytic capacitors are called "self-healing" capacitors. Of course, if you do want the caps to last as long as possible, then reforming the capacitors (or plugging in the device and using it) is recommended.

By the way , In Printers too , where no one waste five minutes of his time , to read catalogues , it is recommended to print at least one paper a week , otherwise , Capillars would be damaged beyond repair ..

That's just for inkjet printers. With laser, there are no problems like that whatsoever. The only problem you might encounter with a laser printer is if you store it somewhere with lots of quick temperature and moisture variations, especially hot places - this is a quick way to ruin a laser printer (or at least require a complete roller/fuser cleanup afterwards).

[jiroy]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Interesting stuff but it made me wonder. If I have devices stirring around unplugged for months on end, well how would this evaluation or consideration play out on some old device that only gets plugged in once a year. It would appear that the running logic you outlined would suggest that we power stuff up regularly to avoid degradation.

What are your thoughts?

Don't be surprised then if you plug a device after one year non use to hear a crackling sound ..
By the way , In Printers too , where no one waste five minutes of his time , to read catalogues , it is recommended to print at least one paper a week , otherwise , Capillars would be damaged beyond repair ..

[Alex_Santos]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Interesting stuff but it made me wonder. If I have devices stirring around unplugged for months on end, well how would this evaluation or consideration play out on some old device that only gets plugged in once a year. It would appear that the running logic you outlined would suggest that we power stuff up regularly to avoid degradation.

What are your thoughts?

[montemcguire]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

I just ran this simulation in LTspice with 28 caps (two 14-pin ZIF sockets), and it's only showing a 79nA (read: nano) draw per cap. Is that right? Maybe 1kOhm is too much?



Attached is the LTSpice file if you care to take a look.

Thanks

Not really related to re-forming, but a good SPICE tip when you're trying to simulate any sort of DC charging phenomenon:

When SPICE analyzes the circuit, it first performs an operating point analysis, essentially what you get by using a .DC analysis command. Then, after that, it runs the selected analysis command around the discovered DC operating point for each node.

The problem in this simulation is that the initial .DC analysis will determine the final, settled DC operating point, and then a 1 second .tran analysis is executed, entirely skipping the capacitor charging phase of the simulation from power on to final settling.

What you can do instead is use a PULSE source instead of a simple DC source, and set the pulse to start at 0V and then a short time later (perhaps a millisecond or ten), switch to the DC value you wanted to examine initially. That way, the initial operating point will be calculated at the powered down (0V pulse source value) state, and then you can watch the circuit react to the pulse source when it switches to your desired pulse voltage.

So, instead of viewing the steady state leakage current of the charged cap model, the simulation you have now, you can see the entire charging phase of the cap in the circuit, which is what you're probably trying to see.

You can change the DC voltage source to a pulse by right clicking on it and selecting 'pulse' from the style menu.

[mockingbird]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

I've been slowly collecting parts for this project over the last two years.



1 & 2 - Amp/Voltage meters recommended for voltage measurements. I figure I'll use one before of the cap and one ahead of the cap in the circuit. I was also thinking of putting one in series to check the amperage draw.

3 - Variable voltage supply kit that I bought for next to nothing and put together. In retrospect, I should have bought a kit with a regulator that goes above 25V. I will have to look into getting something for higher voltages in the future. I would also like to get something for very high voltages for large primary caps. Mr Carlson from Youtube had an old bit of vacuum tube kit a few months ago that he said people often use to re-form caps. Can't remember exactly what it was. Either way, just generating some very high DC voltage somewhow would probably be a lot simpler.

4 & 5 - The blue PCB is something I purchased relatively recently for this project. It's made out of fiberglass and epoxy and has through-hole plating. The brown phenolic board was warped out of shape and only had eyelets which ripped off with the slightest pulling motion.

Not pictures is the wrapping wire I bought. It's the standard Chinese multi-colored one you see all over the place. Supposedly, there are two types, the regular type and the one with non-shrinkable wire (guess which one I bought by accident). It is pretty darn thin wire, in case anyone is wondering.



This is supposed to be based of the "GO" ESR Meter...

[momaka]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

3) Do not use in rapid charging/discharging circuits.
Performance would be hurt by generated heat within an aluminum electrolytic capacitor used in a circuit that repeatedly and rapidly charges and discharges the capacitor. This type of circuit could also destroy the capacitor. Please inquire with your sales or service representative regarding capacitors that can be rapidly charged and discharged for use in such circuits.

Exactly.

Only if you *rapidly* and *continuously* fully charge/discharge a capacitor, you will damage it. But for smaller caps, you can short their leads and perform the "spark" test a few times, and it won't really affecting the life that much, if at all.

[Behemot]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

I think that most caps should have the time constant dI/dt in datasheet which states how fast you can charge/discharge them. IIRC there is some simplification how much higher voltage rating you have to use for given cap if you need higher dI/dt otherwise the life durability gets very significant drop.

Ppl run into such things for example with some kind of those self-oscillating induction heaters (for metal smelting) and some have already found it is better to use more of lower-capacity caps to prolonge their life. Also Tesla transformers.

[budm]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

You need to know if the type of cap you have is made for rapid charging or discharging or not so it is better to properly discharging the unknown cap. I always use resistor.
http://www.elna.co.jp/en/capacitor/a...on/detail.html

3) Do not use in rapid charging/discharging circuits.
Performance would be hurt by generated heat within an aluminum electrolytic capacitor used in a circuit that repeatedly and rapidly charges and discharges the capacitor. This type of circuit could also destroy the capacitor. Please inquire with your sales or service representative regarding capacitors that can be rapidly charged and discharged for use in such circuits.

[momaka]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Yes, for resistors, it would be the breakdown voltage, because in order to push higher power through it, you also must increase the voltage through it. Going past the breakdown voltage can damage the resistor.

For capacitors, I think it's the amount of energy that limits this, mainly where the cap leads are riveted to the foil. If you push too much energy, that can overheat the contact points between the two and cause the cap to go open-circuit. For smaller and medium sized caps, it's not an issue. But for very big caps, it could be, depending on construction.

That said, standard electrolytic caps are not made to withstand many continuous complete charge and discharge cycles. For applications like tab welding and photo flash, Nichicon for example, recommends that special caps be used, because a standard electrolytic can only withstand about 2000-3000 charge-discharge cycles. (Though they also mention in their application notes that as long as the full charge-discharge cycles are kept under 10 per day, the capacitor life will not be affected severely).

[Behemot]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

But there is some upper limit of the maximum loading which causes irreversible damage.

[momaka]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Because you are overstepping the rated ripple current by several magnitudes?

That doesn't matter. You can apply ripple currents much larger than the cap is rated for, as long as you don't do it at such a rate that it causes the internal temperature of the cap to rise above the allowable limits.

Think of it like pushing 5 Watts of power through a resistor rated for only 1 Watt. Can you do it? The answer is YES - however, only if you limit the duration of that power level so that the AVERAGE power dissipation does not exceed the 1 Watt rating. In other words, you can dissipate 1 Watt of power through the 1-Watt resistor continuously. But if you want to dissipate 5 Watts, then you can only do it for 1/5 of a second every second... or 1/10 of a second twice a second... or 1/20 of a second four times in a second.... and etc.

[Behemot]

Re: How to Recondition (Reform) Electrolytic Capacitors and Why

Because you are overstepping the rated ripple current by several magnitudes?