Capacitor Shelf Life - Brand New Inverter that was manufactured a LONG time ago

KnowledgeSponge

Hi,

Another thread just got me thinking.

I recently purchased a brand new Xantrex Inverter.

It works, I tested it briefly.

However, it is now May 2013 and this inverter has a tag indicating a manufacture date of December 2009

That means it's nearly 3.5 years old at the time I got it.

We all know capacitors degrade over time whether or not they are used. But how much?

Have I purchased an expensive device that in all likelihood will have a short service life because it has been sitting
in storage for nearly 3.5 years or more?

Anyone with sufficient electronics experience to tell me if I'm being short changed even a bit?

Or....can I expect that the time sitting has had no effect on the Capacitors or other electronics in the inverter?

It does have a 2 year warranty...but still....is it "more" likely that my unit might fail sooner in service than say a device FRESH of the
assembly line? In theory, it could fail after 2 years and one month because the capacitors etc will actually be 6 years old by then.
(Although that's rather abstract I realize. It "could" fail today. It's more of an illustration of my concern.)

Comments appreciated.

westbranch

Re: Capacitor Shelf Life - Brand New Inverter that was manufactured a LONG time ago

IIRC, John Pod BB posted a regimen as to 'reviving a stagnant inverters capacitor gently... just don't remember the thread...oldtimers..

BB.

Re: Capacitor Shelf Life - Brand New Inverter that was manufactured a LONG time ago

Basically, just power up the inverter (no heavy loads) for a while (a few hours) to reform the electrolytic capacitors. If you attempt to put them under 100%+ load right away, they may over heat and fail.

Capacitors, and all electronics, tend to age when hot... For every 10C or 18F increase in temperature (typically 20C room temperature), there is a decrease in life by 1/2... So, if they are stored cool and not operating, they should last a decade or more. (and thermal cycling--Hot/Cold cycling is very hard on components too).

-Bill

john p

Re: Capacitor Shelf Life - Brand New Inverter that was manufactured a LONG time ago

The life of capacators operating or just stored away is easily worked out.Use the following formula.
count how many caps you own.
multiply that figure by 17.6
subtract your mothers birthday year (the last 2 digits only)from that figure.
add 16.3 to the above
you now have the number of months the caps may last if either stored in a refrigerator or in use in a 386 computer.

Ihave been building audio amplifiers for band and disco use for over 40 yrs and some of the first amps Iever built are still working on the original caps.There would be other amps by others that would be ok and even older than that.
I have used with no problems caps bought new but over 10 yrs old.
Caps in switchmode power supplies and similar(inverters) usually dont last as long as caps used to audio devices.
Reason,
Caps in audio devices in the power supply only operate with a mains frequency of either 50 or 60 hz.
In switch mode supplies and inverters they operate at up to 30khz. And mostly they are not designed for that.
Some brands do cope better than others. But its all really hit and miss.
Some computer manufactures are now using caps better designed for high frequency tolerance,same with inverters, but many just use stock low frequency ones and pray.
There is no one answer fits all..
You take your chances

NorthGuy

Re: Capacitor Shelf Life - Brand New Inverter that was manufactured a LONG time ago

john p wrote: »

Ihave been building audio amplifiers for band and disco use for over 40 yrs and some of the first amps Iever built are still working on the original caps.There would be other amps by others that would be ok and even older than that.

My experiences were not that optimistic. As my old computers die, I try to salvage the parts to use them somewhere. I had several relatively big electrolytic capacitors from computer power supplies (60 Hz operation). When the time came to use them, I was very disappointed - all of them were below 50% of their rated capacity, some even below 20%. These were capacitors that worked hard in power supplies for several years.

Your model of inverter may not have any electrolytic capacitors. When I was connecting my Xantrex XW, I remember seeing big thin-film capacitors, but I don't remember seeing any electrolytic ones.

waynefromnscanada

Re: Capacitor Shelf Life - Brand New Inverter that was manufactured a LONG time ago

john p wrote: »

The life of capacators operating or just stored away is easily worked out.Use the following formula.
count how many caps you own.
multiply that figure by 17.6
subtract your mothers birthday year (the last 2 digits only)from that figure.
add 16.3 to the above
you now have the number of months the caps may last if either stored in a refrigerator or in use in a 386 computer.

Ihave been building audio amplifiers for band and disco use for over 40 yrs and some of the first amps Iever built are still working on the original caps.There would be other amps by others that would be ok and even older than that.
I have used with no problems caps bought new but over 10 yrs old.
Caps in switchmode power supplies and similar(inverters) usually dont last as long as caps used to audio devices.
Reason,
Caps in audio devices in the power supply only operate with a mains frequency of either 50 or 60 hz.
In switch mode supplies and inverters they operate at up to 30khz. And mostly they are not designed for that.
Some brands do cope better than others. But its all really hit and miss.
Some computer manufactures are now using caps better designed for high frequency tolerance,same with inverters, but many just use stock low frequency ones and pray.
There is no one answer fits all..
You take your chances

This too has been my experience in over 40 years dealing with the internal guts of electronics.

KnowledgeSponge

Re: Capacitor Shelf Life - Brand New Inverter that was manufactured a LONG time ago

So it comes down to.....

"IF it's gonna fail.....PRAY.....it does so within the warranty period"


Is Murphy's advice been dispelled yet ?

waynefromnscanada

Re: Capacitor Shelf Life - Brand New Inverter that was manufactured a LONG time ago

KnowledgeSponge wrote: »

So it comes down to.....

"IF it's gonna fail.....PRAY.....it does so within the warranty period"

Pretty much. And beyond that, if a cap does self destruct, hope there's enough left to read the values, that it hasn't spewed it's coils of aluminum foil all over the inside of the unit, causing destructive short circuits, and that it's in a place where you can replace it and get everything back together again.

NorthGuy

Re: Capacitor Shelf Life - Brand New Inverter that was manufactured a LONG time ago

waynefromnscanada wrote: »

Pretty much. And beyond that, if a cap does self destruct, hope there's enough left to read the values, that it hasn't spewed it's coils of aluminum foil all over the inside of the unit, causing destructive short circuits, and that it's in a place where you can replace it and get everything back together again.

And if you cannot read the value, chances are you have a similar capacitor in close proximity, which often will be of the same value/voltage.

mike95490

Re: Capacitor Shelf Life - Brand New Inverter that was manufactured a LONG time ago

If the caps have been formed once, and then left idle, they should not degrade too much, just sitting in storage. When you pull the inverter out to use it, fire it at half voltage for a couple minutes, then the full DC voltage. No easy way to ramp the voltage up. Let it sit idle with full DC input for a couple minutes before applying any loads.

solarix

Re: Capacitor Shelf Life - Brand New Inverter that was manufactured a LONG time ago

If properly designed, capacitors and even the electrolytic types are very long lived. And when in storage, very little aging takes place. Electrical overheating that puts stress on it by increasing its internal pressure is the danger. Within limits, its no problem, but it is easy for designers to just go by the basic electrical parameters for capacitors and get into an overstressed condition that may take years off the life of a circuit. Of course, in general consumer electronics, what manufacturer cares if their product only lasts 5 years instead of 20 when their warranty is only 1 year? Happens all the time.
In your case, I would not worry about your Xantrex. They have a good track record (apart from the factory recall replacing a couple non-electrolytic DC-input caps - they were being prepared for a company buyout at the time and went overboard with the QA folks, imho). Couple three years of storage is not a big deal on the caps.
There are plenty of other things to go wrong though - expect the worst from Murphy (but hope for the best).....