flashbang

I was once told that capacitors on flash units will 'deform' if the unit is not used regularly, so it is necessary to power up a flash periodically even if it is not being used. I still do this with any of my lights that I have not used for a month or so, but doing it today (on a rainy afternoon) I realized that I never really checked out the benefit. Or even if it is necessary. Anybody know for sure?

ejones0310 Loc: Tulsa, OK

Eventually, the capacitors will fail if left idle for an extended period of time. Some time ago, I remember reading in a flash manual, that you should load batteries in the flash, let it cycle to ready and discharge the flash with the test flash button. They recommended doing this once a month, a dozen times and then removing the batteries if you're putting it back in storage.

From my electronics training 40 years ago, I remember that the oxide coating inside deteriorates if the capacitor is not used. Reforming the capacitor periodically keeps the oxide layer healthy.

TriX Loc: Raleigh, NC

Depends on the type of capacitor. for Electrolytic capacitors (with a positive and negative polarity), it is good practice to charge them periodically. You may find this article useful: http://www.qsl.net/g3oou/reform.html
Oil filled capacitors (non polarized) typically are fine even after long periods of non-use. I have a large 8KV 16MFD oil filled that was originally a photoflash capacitor in my ham radio high voltage (4KV) power supply, and it was probably unused for 10-20 years when I first charged it, and it works fine.

Longshadow Loc: Audubon, PA, United States

Yup.
YEARS ago we used to call it drying out.
It's from lack of use.

BHC Loc: Strawberry Valley, JF, USA

Excellent answer. I would like to note, however, that "wet" capacitors can leak if not properly sealed. I had an entire pack of, I believe, .1μμf capacitors that were bad and leaked. The ultimate repairs weren't expensive, but the were time consuming, and, since six happened with one client, embarrassing. I've also seen one flash head crack because a power regulation failed and caused the capacitor to "explode" and double its size. So yes, capacitors should not only be charged regularly (I prefer every 3-6 months), but they should be fully cycled several times when charging. Also, be aware of any oily or grainy discharge, particularly INTO the battery compartment (as opposed to leaky batteries).

speters Loc: Grangeville/Idaho

I still do it too with my older speedlights ( Metz units), because I believe it is still a valued thing to do, but I have not done it with any of my newest speedlights. So I guess it is a thing of the past that one does not need to do anymore ( I think, that companies would still suggest doing it on a regular basis, if that would still be the case!

dpullum Loc: Tampa Florida

I do not want to confuse the my Aunt Sally opining with a dull scientific reference, but it appears that if you store your flash for 20-30 years or leave in your car on the dash and park in Death Valley you my have a problem.... however for normal storage the following my provide the information to answer for Mr Flashbang ... who should never listen to his Aunt Sally's opinion as she bakes cookies:
"Long storage periods for aluminum electrolytic capacitors .... For the series of aluminum electrolytic capacitors listed below, which are suitable for automotive applications, EPCOS specifies in regard to the leakage current a storage period of up to 15 years at a temperature below 40°C. After the storage period, the expected leakage current is still in the order of magnitude of the original limit."
http://www.powerguru.org/long-term-stability-of-aluminum-electrolytic-capacitors/

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

Once every two months I reform my capacitors, it is very easy, load batteries, hit the red button and fire off about 10 flashes letting the flash fully recharge between flashes, leave flash fully charged, take out batteries, store flash. I have very only units that are still humming along.

bobmcculloch Loc: NYC, NY

Exercising a flash is a good idea, back when I used flash a lot I could tell the difference in recycle time and number of flashes from a charge/ set of batteries, newer flashes not so much but then I'm not using flash as much Now.

DaveC1 Loc: South East US

If you look in any one of the electronic supply catalogs on line you will find modern electrolytic caps are rated for their life expectancy in hours of usage, read that hours of charged time, in the case of a flash unit. There is no mention of shelf life, so to speak.

TriX Loc: Raleigh, NC

From Cornell Dubelier (who is one of the oldest capacitor manufacturers):

“Aluminum electrolytic capacitors stored for more than 5 to 10 years may have increased levels of DC leakage current. Check if DCL meets application requirements before placing in service. Recondition high DCL units by applying rated voltage through 1,000 Ω resistor for 30 minutes. Shelf life is a measure of how the capacitors will withstand storage for long times especially at high temperature. To test shelf life place the capacitors in an oven set to the shelf-life test tem- perature –0 +3 oC for the shelf-life test period. Upon completion of the test stabilize the capacitors at 25 oC for 24 h or more. Apply the rated voltage for 30 minutes, then verify the post test limits.”

And from Nichicon:

“When an aluminum electrolytic capacitor is stored under no load conditions for a long period of time, its leakage current tends to increase slightly. This is due to a drop in the withstand voltage of the dielectric caused by the reaction of the anode oxide layer with the electrolyte. When the voltage is applied to the capacitor, the leakage current returns to its initial level because of the re-forming action of the electrolyte (called voltage treatment). If the storage temperature is high, the leakage current will increase substantially. Therefore, it is desirable to store capacitors at normal temperature level with no direct sunlight. A voltage treatment is recommended when using a capacitor stored for a long period of time. The treatment for an individual capacitor is accomplished by charging up to its rated voltage through a resistance of about 1 kΩ and applying the voltage for approximately 30 minutes.”

The consensus from manufacturers seems to be that there is a small, but measurable degradation in performance from long shelf life, but unless the electrolyte has dried out completely, the capacitor may be “re formed” by applying the rated voltage through a current limiting resistor for approximately 30 minutes. LONG answer to a short question 😂

DaveC1 Loc: South East US

Would you mind posting the URL for those two statements from the manufactures?

TriX Loc: Raleigh, NC

Sure:

http://www.nichicon.co.jp/english/products/pdf/aluminum.pdf

http://www.cde.com/resources/catalogs/AEappGUIDE.pdf

And if you REALLY want to get into it:

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.823.6133&rep=rep1&type=pdf

RRS Loc: Not sure

Forgot how I did it, I'll check my notes but I used a Powerstat and brought the voltage up slowly to reform my bigger caps and also to run the filament voltage at a reduced voltage on high power vacuum transmitting tubes that had not been used for years.

BebuLamar

Applying rated voltage through a current limiting resistor is a condition similar to when the flash capacitor is fully charged and was charged only very low current to keep the flash ready. So if I take this advice then I would turn the flash on a leave it on for 30 minutes.