Charge Controller and Inverter Longevity under varying loads

[MidniteMike]

Hi,  Is there any benefit in designing a system to run at say 50 to 70 % to gain a longer life from the unit.  I am wondering if voltage stress's are like mechanical stress's,  and as such,   cutting the feed in Watts to a Classic 150,  to around 1500 Watts,  would this be likely to give the 150 a longer life ?

Also in stacked inverters,  can you load share the load equally between units or does 1 unit pump up to the max, then bring in the next unit from " sleep " mode ?   

Load management is easy with charge controllers, but longevity factors could affect which inverters I buy.

Thanks for a great forum, and I look forward to any real life stories any one has come across.

Mike

[MidniteMike]

Further to the above,  which of the two following options would result in the longest total service life ?

a,   2 charge controllers running together, each running at half capacity.

or

b,   First one controller used at full power till it dies, then substitute in controller number 2.

Does any one have any ideas ?

Mike.

[Halfcrazy]

Mike
boB will probably reply but my understanding is the "wear items" in the Classic would be fans and capacitors both of which would work harder with more load on them. I still suspect the longest life out of 2 would be run one till it dies and swap in the other.

As for the inverters at least with the Outback you can program when the second turns on.

Ryan

[laszlo]

There was is a similar question abut longevity on the RE-wrenches mailing list this year. There was this installer who was replacing several GT inverters that failed before or shortly after their warranty period. You may want to google that. There is no statistical data on this. The consensus is that thermal breakdown is a major contributing cause of electronics failure. The takeaway was that solar installers need to do a better job of protecting of inverters chargers etc from  heat buildup -- ie don't put in the  direct  sun outside, and if possible try to put it in the shade or  indoors.   The load that you put on power electronics is going to contribute to the heat buildup, but some of the parts such as the FETs are made to run hot so it's not always y a linear cause and effect, either. If your goal is availability, you should have two of every system components.  I personally would not derate the equipment to extend MTBF - but instead I'd try to come up with cooling solutions -- fans, indoors,  a/c etc.

Hi,  Is there any benefit in designing a system to run at say 50 to 70 % to gain a longer life from the unit.  I am wondering if voltage stress's are like mechanical stress's,  and as such,   cutting the feed in Watts to a Classic 150,  to around 1500 Watts,  would this be likely to give the 150 a longer life ?

Also in stacked inverters,  can you load share the load equally between units or does 1 unit pump up to the max, then bring in the next unit from " sleep " mode ?   

Load management is easy with charge controllers, but longevity factors could affect which inverters I buy.

Thanks for a great forum, and I look forward to any real life stories any one has come across.

Mike

[MidniteMike]

Thanks Ryan,  that sounds right about the caps and fans.  The caps might dry out ( to a lessor extent ), even with no use, so buying a second spare, and putting them in the cupboard for a rainy day might also not work out as well as buying the 3rd unit when the first one becomes irreparable.  In any case,  fans and Caps would be fairly easy to replace as the units age.  A supplier that can offer a kit with a spare fan and cap pack would be nice, but I can see how it might give some customers the wrong idea.

The feature on the Outback inverters of adjustable cut in, sounds interesting.  I don't remember reading this in the manual, but will have a look around for more on this. The Outback stuff is a bit intimidating with all it's complexity, but as they say, there is no such thing as a free lunch. By the time you add all the options to other systems, both the cost and complexity increase in line with the Out back stuff.

Another lower cost inverter option I am looking at is the Victron Phoenix 24V 3000VA, 230V Sinewave Inverter, Parallelable unit. These are on the web for not much more than $ 1000.00 and don't have the battery chargers that I don't need.  Has any one had any experience with Victron gear ?  Do they also have programmable cut in points for the 2nd inverter ?

Thank you Laszlo, for the ideas about cooling.  I plan to have redundant units on hand, but putting a bit of effort into keeping the units " comfortable " and regular de-dusting is a really good point. Here in Australia, dust and direct sun light can be a killer.  I am not familiar with the RE-wrenches site, but will check it out if I can find it.

Conclusion so far.

I think I may play it safe, and design the charge controllers to run at up to 80 % per controller.  The Midnite Classic 150 is great for this, as it gives you a bit more to play with.

Thanks for your help, and if any one else has any  more to add, feel free to jump in.

Mike.

[Robin]

The bottom line is heat kills electronics. Running them cool makes them last longer. Victron is a good company. You don't find them here in the US, but they have been around a long time and are well respected.