Flushing out an idea

raydias · August 2011

I have been reading about running specific loads off of solar/battery and one of the challenges is that certain loads like refrigerators, air conditioners, etc that have motors end up surging beyond the inverters capability. It seems to be the main issue a lot of people experience (not having an inverter that can handle the surge, not enough batter and solar is common also).

So her is my thought, what if you put a UPS between the load like a fridge and the inverter? Would the surge be handled by the UPS while the inverter would just resupply the UPS battery on a more even rate?

Just a thought. you'd still need to ensure that the solar/battery can handle the load for the period of time needed.

would this work? and would using the UPS mean that the inverter does not need to be a pure sine wave?

thanks for all the great information provided here.

Cariboocoot · August 2011

Re: Flushing out an idea

The question would be: Which UPS?
If it's capable of handling the surge load, it would work. If it were non-continuous it may not switch "in time".

Most UPS units are just MSW inverters and a small battery anyway, and the over-all efficiency of a system with such in line would be less than without it.

Probably better to spend the money on getting a bigger inverter or investigating the possibilities of some soft-start circuitry.

techntrek · August 2011

Re: Flushing out an idea

I agree, better to size the inverter correctly the first time, including splitting your loads over more than one inverter if you have several large surge loads that could occur at one time.

PhilS · August 2011

Re: Flushing out an idea

A UPS is constantly charging (unless it's providing power). So almost all of the time it would be an load on the system itself. Whether it could provide for a "surge" is questionable as it's designed to provide power when the main supply disappears. SO... if the surge shuts down the main inverter, the UPS would quickly kick in. Then, would the overloaded inverter automatically reset and the UPS would go back into "charge" mode? There are operational questions that would depend on the individual units but IMO not worth further contemplation.

As other's said, those funds would be better spent on improving the main power source.

Phil

Seven · August 2011

Re: Flushing out an idea

I have been wondering about the small UPS. Why do they recommend them for computer backups if they are MSW? Is it because they are limited time runs? We have several of those, and rack mount units in our IT and land line room.

Cariboocoot · August 2011

Re: Flushing out an idea

Seven wrote: »

I have been wondering about the small UPS. Why do they recommend them for computer backups if they are MSW? Is it because they are limited time runs? We have several of those, and rack mount units in our IT and land line room.

Contrary to popular opinion, computers are not affected by MSW. People think they should be because of the highly sensitive circuitry inside. It is precisely because of that circuitry that they are not: the need for a really, really good power supply is there to begin with. You'd be amazed at the poor quality power input a typical computer will put up with and not complain. Many of the newer laptops have auto-switching input that can take 110 VAC 60Hz up to 240 VAC 60Hz or 230 VAC 50Hz and only require the right plug adapter to hook it up.

I've run our computers on MSW for years before we got the Outback inverter, and none of them ever so much as blinked.

Seven · August 2011

Re: Flushing out an idea

That is really good to know.

techntrek · August 2011

Re: Flushing out an idea

Cariboocoot wrote: »

Contrary to popular opinion, computers are not affected by MSW. People think they should be because of the highly sensitive circuitry inside. It is precisely because of that circuitry that they are not: the need for a really, really good power supply is there to begin with.

+1

"Back in the day" I subscribed to a popular computer magazine, and they would occasionally run tests on power supplies. It was amazing how much abuse those things took while keeping the 12 & 5 volt lines steady (not sure if the 3.3 volt line existed yet back then) - through massive spikes, steady over/undervoltage and sags. I'm sure this is why so many companies have offered high-dollar-guarantee-low-dollar-price "surge" protectors. They can just build them to clamp down on the really big spikes and let the computer's power supply handle the rest! Then only pay out a handful of claims a year, partly because most people forget about the guarantee and then let their insurance company replace everything after a direct lightning strike.

While most other electronic devices don't have such robust internal power supplies (excluding stereos), MSW vs. PSW still isn't an issue for most since they convert it all to DC anyway.

techntrek · August 2011

Re: Flushing out an idea

Seven wrote: »

I have been wondering about the small UPS. Why do they recommend them for computer backups if they are MSW? Is it because they are limited time runs? We have several of those, and rack mount units in our IT and land line room.

MSW = cheap, at least for the small ones on the floor. Most rack-mount UPSs (and larger, like the ones that can take up an entire wall or room) are PSW. Not that they need to be as Cariboocoot said. I guess once you get to that size companies are willing to pay for "the best" to protect their big servers and wouldn't be willing to settle for MSW.

Flushing out an idea

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