Inverter Problems/Head scratcher

LesVos98 · January 2016

Hi All,

I have a little bit of a head scratcher. I have 600w of PV array going done through an 40amp MPPT to a battery bank of 558 A/H. From there it runs a 3000w Mod sine wave to run my fridge and soon hopefully my freezer as well.

This all works well except for this part (Here come the head scratcher part).

Over the last couple of months, the fridge has worked well, the small ice compartment making enough ice for the whiskey (all just the essentials) .. but we have had some serious hot and bright days lately and now the fridge will only run at night when the voltage drops to below 13.5v, it starts and almost immediately switches off again. I thought that maybe a voltage regulator in the form of an old PC UPS would help but no luck..

Any Ideas.. (I can't drink whiskey with out ice, that is just cruel and unusual punishment) :

Raj174 · January 2016

Hello LesVos98,
I think there may be a good chance that the problem is the modified sine wave inverter. They generally do not get along with motors, compressors, florescent lights, microwave ovens and some other devices. The modified sine wave causes inefficiencies that create heating and sometimes odd noises in these devices. This heat may be damaging the windings in the compressor of the refrigerator. The only way I have heard of to test this is to borrow or buy a pure sine wave inverter to verify the problem and replace the old one. A 2000 watt should be large enough for a refrigerator and a freezer. 1500 watt for just the fridge. Hopefully, other forum members will give you their thoughts on this problem also.
Good luck

LesVos98 · January 2016

Raj174 said:

Hello LesVos98,
I think there may be a good chance that the problem is the modified sine wave inverter. They generally do not get along with motors, compressors, florescent lights, microwave ovens and some other devices. The modified sine wave causes inefficiencies that create heating and sometimes odd noises in these devices. This heat may be damaging the windings in the compressor of the refrigerator. The only way I have heard of to test this is to borrow or buy a pure sine wave inverter to verify the problem and replace the old one. A 2000 watt should be large enough for a refrigerator and a freezer. 1500 watt for just the fridge. Hopefully, other forum members will give you their thoughts on this problem also.
Good luck

Thanks buddy.. My biggest concern is that it works well at night, ice and every thing, its just during the day.. I will / am trying to borrow a pure sinewave to test with so I will give that a bash as well..

vtmaps · January 2016

Does the inverter work at all during the day, or is it just the fridge that doesn't work? --vtMaps

LesVos98 · January 2016

vtmaps said:

Does the inverter work at all during the day, or is it just the fridge that doesn't work? --vtMaps

The inverter works fine. TV phones ect.. just the fridge wont work during the day..

LesVos98 · January 2016

oops not ect lol etc

vtmaps · January 2016

LesVos98 said:

vtmaps said:

Does the inverter work at all during the day, or is it just the fridge that doesn't work? --vtMaps

The inverter works fine. TV phones ect.. just the fridge wont work during the day..

The only thing I can think of is that the inverter's waveform is different during the day when the input voltage is higher, and that your fridge can't tolerate the daytime waveform ????

--vtMaps

Brock · January 2016

I wonder if the inverter isn't regulated and stepping the voltage up say 10 times and pushing the top end of the fridge's limit?

Raj174 · January 2016

Lesvos98,
If you have a meter check the AC output of the inverter to see if the voltage is what it should be during daytime verses night. If the voltage is the same then vtmaps may be on to the problem. Of course you would need an oscilloscope to see the waveform.

mike95490 · January 2016

most meters are not going to give a good reading of a mod sine waveform. I suspect the problem is your mod sine inverter and poor interaction with the motor in the fridge.
If you are going to go to a pure sine inverter, consider also upgrading to a 24V battery bank. instead of all the parallel batteries I know you have now.

LesVos98 · January 2016

Mike95490,

Thanks Mike, but I have a series of 2v cells lol. A forklift battery pack (actually a part of one- they run 48v). but I agree with the comments that the Mod sine is pushing out a different waveform when the battery is over 13.5v. And as RAJ174 pointed out I would need an oscilloscope.

OH well.. Thanks to all for the comments and suggestions.. Seems like I will have to fork over for a pure sine wave..

Brock · January 2016

They are more expensive but then things run more efficiently and everything will work without thinking about it. I have a Xantrex prowatt 2000 for remote work and as a back up and it has been great, handled any single item you can plug in, including some larger tools. I picked it up for under $400.

Estragon · January 2016

Just a thought, but could it be the temp of the fridge itself - starting the compressor being just a bit harder in the heat enough to overwhelm the inverter?. I've found the output ratings on the cheaper mod sine wave inverters to be pretty optimistic.

LesVos98 · January 2016

Estragon said:

Just a thought, but could it be the temp of the fridge itself - starting the compressor being just a bit harder in the heat enough to overwhelm the inverter?. I've found the output ratings on the cheaper mod sine wave inverters to be pretty optimistic.

I had thought of that, but it turned out that it wasn't the case. If I plugged in one of the power tools and used it until the voltage dropped to under 13.5v the fridge ran like a dream.. seems as though I will have to go the PSW route.. or get a regulator that will only allow 13v and under thru to the MSW..

SoloSolar · January 2016

I'd say 600w is the bare minimum you're going to need to run an AC fridge. You might not have enough of a solar panel input to charge the batteries and run the appliance at the same time. I'd increase array size for sure (200w more at least) and maybe the battery bank, not 100% on that. Just a heads up that you wouldn't be able to run an AC fridge and freezer off that array, let alone one of them (as I suspect that is the problem).

LesVos98 · January 2016

SoloSolar said:

I'd say 600w is the bare minimum you're going to need to run an AC fridge. You might not have enough of a solar panel input to charge the batteries and run the appliance at the same time. I'd increase array size for sure (200w more at least) and maybe the battery bank, not 100% on that. Just a heads up that you wouldn't be able to run an AC fridge and freezer off that array, let alone one of them (as I suspect that is the problem).T\

Thanks for the input. Just to clarify, the fridge and freezer sips power and are HUGELY efficient, 300w and 600w per day respectively. The charge is no problem.. I live in sunny South Africa and we get huge usable daylight. Winter I am getting > 6.5 hours and summer is well over 10 hours on average. Normally by 10:00 am the battery is fully charged. I borrowed a small PSW, and the fridge is running well now, and the batteries are still over 13.5, and sometimes over 14v, at any given time, even when running my old camping fridge at the same time. (Its one of those gas/12v/220v thermo types).

I have enough spare capacity to add to the system if I need to. This is a learning curve for me as well, one that I must say, has proved to be interesting.

zoneblue · January 2016

Interested in what kind of fridge is it? 300Wh/d in high ambeint south africa is impressive.

South Africa · January 2016

So am I LesVos98.
Make and models please.

While ago I went for a Hisense to try it out. Small fridge, wife is moaning but marketing material says it uses 150kwh per year!
It is running beautifully on a pure sine wave inverter, 24/7/365 on solar only. Batts do not even feel it at night.

But I need a bigger fridge, or another wife.

Suspect a bigger fridge will be the cheaper option.

SoloSolar · January 2016

LesVos98 said:

SoloSolar said:

I'd say 600w is the bare minimum you're going to need to run an AC fridge. You might not have enough of a solar panel input to charge the batteries and run the appliance at the same time. I'd increase array size for sure (200w more at least) and maybe the battery bank, not 100% on that. Just a heads up that you wouldn't be able to run an AC fridge and freezer off that array, let alone one of them (as I suspect that is the problem).T\

Thanks for the input. Just to clarify, the fridge and freezer sips power and are HUGELY efficient, 300w and 600w per day respectively. The charge is no problem.. I live in sunny South Africa and we get huge usable daylight. Winter I am getting > 6.5 hours and summer is well over 10 hours on average. Normally by 10:00 am the battery is fully charged. I borrowed a small PSW, and the fridge is running well now, and the batteries are still over 13.5, and sometimes over 14v, at any given time, even when running my old camping fridge at the same time. (Its one of those gas/12v/220v thermo types).
I have enough spare capacity to add to the system if I need to. This is a learning curve for me as well, one that I must say, has proved to be interesting.

I'm also in on the group that wants to know the make/model of it. I've got the 6.1cf here: http://www.c4pinc.com/solar/solar-refrigerator/ which runs at ~380wh/d and I don't have as high of an ambient temperature as you would.

Inverter Problems/Head scratcher

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