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1000 watt modified runs longer than 1500 pure sine

TEDthebed

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May 18, 2021
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One 100 watt 12 volt panel
Two 12 volt 100 AH Gel Batts
1500/3000 watt 12 volt to 120 volt pure sine Inverter
Or
1000/2000 watt modified sine inverter

Goal: power 11.2 amp 120 volt fridge

The 1000 watt modified sine will run the fridge for close to 8 hours, until the batteries are at minimums of 10-10.5 volts.

The 1500 pure sine shuts down after about 4 hours with the batteries around 12.5 volts.

The rub is that this is the second pure sine each from different companies exhibiting the same behavior.

What is happening here?

Batteries are connected to inverter by double 6 AWG wires (4 wires total) 18" long.

Batteries are parallel wired with 4 AWG wire (2 total wires) 18" long
 
Did you search the forums for "pure sine wave inverter" or such words? There's a whole long pissing contest about the differences in MSW and PSW and efficiencies. The idle on the MSW is way lower and there is less processing to give you something that resembles a sine wave than the PSW inverter. Go ahead, read the thread and drink yourself to sleep with regret.
 
It sounds like your MSW inverter has a 10 volt low voltage cut off and the PSW is set to a 12.5 volt LVCO.

Are they able to be adjusted?

Links to the inverters might help.
 
It sounds like your MSW inverter has a 10 volt low voltage cut off and the PSW is set to a 12.5 volt LVCO.

Are they able to be adjusted?

Links to the inverters might help.
No adjustments for low voltage cut off for the 1500 PSW, but it's 10-10.5 like the MSW. I forgot to mention this. I also forgot to mention that I power the PSW off after the shutdown for a few seconds and back on and all is back to normal with 12.5 volts batteries and 120 volt output. Thanks for your reply.
 
Did you search the forums for "pure sine wave inverter" or such words? There's a whole long pissing contest about the differences in MSW and PSW and efficiencies. The idle on the MSW is way lower and there is less processing to give you something that resembles a sine wave than the PSW inverter. Go ahead, read the thread and drink yourself to sleep with regret.
Thanks for the reply, Boondock. I will search for the PSW thread, but in the meantime, if you would be so kind, give me the Crux of the thread and just as importantly your advice in this matter. Thanks ahead of time
 
Clearly the PSW should not be shutting down at 12.5 volts then.

Two thoughts:

It could be defective, warranty?

It could be seeing a voltage below 10 volts to make it shut down.

Step one would be to double check ALL connections.
 
Perhaps the 2000W inverter has smaller lug connectors, and the connection is better to it.
The 3000W inverter may not like the small wiring on the lugs designed for larger conductors?

is ANYTHING getting hot when the PSW inverter is running?
 
Perhaps the 2000W inverter has smaller lug connectors, and the connection is better to it.
The 3000W inverter may not like the small wiring on the lugs designed for larger conductors?

is ANYTHING getting hot when the PSW inverter is running?
Super, thanks for the reply. I checked and all wiring, inverter, charge controller and batteries were cool to the touch for the PSW at shutdown and the MSW was cool as well.
My thought now is that there is a surge that the PSW can not handle and that the MSW can.
Footnote: I just shut the 1000 watt MSW down for the night after 7 hours and switched back over to the grid. The batteries were at 11.6 volts and the inverter and fridge were still running! The 1500 watt PSW or should I say POS would have stopped 3 hours ago.
Again, this is the second 1500 watt PSW each from different companies exhibiting the same behavior. Possibly, both inverters were the same, just re-labeled, who knows. Can someone please recommend a 1500/3000 watt PSW or an inverter size that would run my 11.2 amp fridge successfully?
 
Compressor. GE, side by side basic household
Monitor your battery voltage when the PSW trips out.. see if it trips at 12.x volts (defective unit), or if for some reason, the act of the compressor starting up is dragging down the bat voltage for a moment and the PSW inverter is tripping out on that momentary bat voltage sag.

Cheap Chinese inverter? There's a reason they are cheap.
 
Monitor your battery voltage when the PSW trips out.. see if it trips at 12.x volts (defective unit), or if for some reason, the act of the compressor starting up is dragging down the bat voltage for a moment and the PSW inverter is tripping out on that momentary bat voltage sag.

Cheap Chinese inverter? There's a reason they are cheap.
 
Yup, cheap Chinese inverters, all three, including the cheapest, the MSW that works(???)
Could you recommend a PSW for my needs?
 
victron is the more expensive with low standby consumption,i would rate as one of best
aims are good ,a little less expensive.
Xantrax are also great inverters .
will prowes recommends one in (Giandel) his videos that are inexpensive ,ck them out
 
Last edited:
Ok, 11.2A at 120V is 1344W... what kind of fridge is this?

Neither inverter should be running that load.

that would be a pure conversion of 112A at 12V... most inverters are poor efficiency, so, over 130A draw?
I doubt it.
More likely the fridge draws less amps during running, and the compressor surge tweaks the batteries on the psw...

And the MSW runs the compressor so poorly, it overheats, never shutting off the entire time, but never hits the starting surge...

But that is just a guess...
 
My aims 1500W inverter operates my LG full size freezer on bottom full size for a full day on my 60Ah LFP 48V battery...
 
Let's consider the "initial load, high current draw / low voltage shutting down" theory a sec. This is the same things as the "Can't start and run my AC on batts / inverter" dilemma.

The reason a household AC has a large starting or running capacitor in it, that capacitor store voltage for when the unit is shut off, and then the compressor cycles off.

To mitigate this in an RV people buy the AC quick start kits. Even people who have large well made inverters.

If this is the same principle and it's also the cause of this PSW inverter issues, a quick start kit might work.

Adding capacitors directly to the fridge compressor might work.

More likely the fridge draws less amps during running, and the compressor surge tweaks the batteries on the psw...

Let's go with that.
 
Monitor your battery voltage when the PSW trips out.. see if it trips at 12.x volts (defective unit), or if for some reason, the act of the compressor starting up is dragging down the bat voltage for a moment and the PSW inverter is tripping out on that momentary bat voltage sag.

Cheap Chinese inverter? There's a reason they are cheap.
This PSW shutsdowns at around 12.5-12.7 volts. As I recall, the previous PSW, which I returned, shutdown mid 12's as well. I do not have a way to continually monitor and log the batteries' performance, so don't know if a momentary voltage drop is causing the shutdown. I do know that the MSW does not experience this issue. So, I'm not sure if the PSW's were both defective or whether PSW's in general have a design issue with starting electric motors. Thanks for your help.
 
victron is the more expensive with low standby consumption,i would rate as one of best
aims are good ,a little less expensive.
Xantrax are also great inverters .
will prowes recommends one in (Giandel) his videos that are inexpensive ,ck them out
Thanks for the recommendations. I'll check out the inverters
 
Let's consider the "initial load, high current draw / low voltage shutting down" theory a sec. This is the same things as the "Can't start and run my AC on batts / inverter" dilemma.

The reason a household AC has a large starting or running capacitor in it, that capacitor store voltage for when the unit is shut off, and then the compressor cycles off.

To mitigate this in an RV people buy the AC quick start kits. Even people who have large well made inverters.

If this is the same principle and it's also the cause of this PSW inverter issues, a quick start kit might work.

Adding capacitors directly to the fridge compressor might work.



Let's go with that.
Thanks for the suggestion. Unfortunately, the Quick Start/Easy Start kits are all around $300 on Amazon, but you're right, I think they would work. I'll have to think about it. Just wondering though if I couldn't accomplish the same thing with a larger PSW inverter for less money.
 
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