LVYUAN 500W Inverter Can't Handle Mini Fridge Start Up Amps

[ForgivenCreation]

Alright, After searching and searching I figured I was time to create an account and get the down low on how this stuff works.
I Choose This Forum haha!!!

Anyhow I am just getting into solar stuff and have done LOTS of research on sizing and understanding all the lingo, none the less I am operating on bare bone for the time being.

Black Friday... or Cyber Monday I can't remember struck and I was able to score a deal through wally world and got a little LVYUAN Inverter for a awesome price, seems to have decent reviews on the internet but it is a foreign unit. I needed Pure Sine Waves to run my desktop PC as my Black and Decker Electromate 400 has a Modified wave at 400watts and my the PSU didn't sound happy as a result so I unplugged it quickly.
The Little inverter ran my PC and TV Desktop Screen without Issue off a old Group 35 car battery I got for free. The AC amp draw under heavy use was high 3's if I remember right.

NOW comes my question In regards to this Inverter. It's 500W Running, 1200W Surge. (part number is F-500P) I also need it to run a Mini fridge in my Camper.
-The mini Fridge is a HAIER HSE04WNBWW
Rated Voltage 115V
Rated Amps 1.5 A
Rated Frequency 60HZ
-The Compressor is an LG NSA36LACG
1PH
115V
60HZ

Testing via a wall outlet when first plugged in the fridges AC amp draw is 7 amps for a brief period, under or at 30 seconds then the fridge shuts off for around a minute or so. When it comes back on a Very brief 7 amps down to 1.5 amps in around 1-3 seconds occurs with normal running at around 1.5 amps.
The Inverter will surprisingly front the 7 amps for the required time, It gets a little hot... nothing a PC fan cant fix haha. The Issue occurs on the second compressor start, the Inverter seems to be pushing 3ish amps but instead of dropping to 1.5 the compressor re ramps to 7amps. It did this 3 time before the inverter was to hot for my liking. The battery draw was around 31 amps with the voltage dropping into the mid 11.5 range DC.
Now that I have all that out of the way what are my solutions? The census across forums seems to be a inrush limiter or a soft start device. Neither I which I have currently. I do however have a long extension cord and I keep reading they can be used to limit amp and voltage draw? Is this a simple and easy fix or will it not work? If I need to I can come up with another solution but cheap is best right now. What are yalls thoughts? Also Sorry for the long post, wanted to cover the bases.

 

[rodrick]

Hate to break the bad news but the surge on those cheaper inverters is rated in milliseconds if it’s a 500 watt inverter that’s about all your going to get, when your trying to start loads like motors or compressors figure 5 to 7 time the normal load for initial startup

 

[ForgivenCreation]

Another question I have is would one of those Hard start capacitors work?

 

[RCinFLA]

Another question I have is would one of those Hard start capacitors work?

The refrig already has a starter cap boost. It likely disengages start capacitor by a series PTC thermistor which takes some time to heat up.

Hard start caps do not reduce the peak startup surge current, only reduces its length of duration by increasing motor's startup torque.

You also have a defrost cycle current. Defrost heater may also exceed the inverter limit. Typically goes through a defrost cycle about every 14-18 hours.

Avoid attempting to restart compressor until you allow a few minutes of off time for refrigerant gas pressure to equalize. Attempting to startup compressor while it still has high side head pressure causes additional startup surge current on compressor motor. The start capacitor series thermistor also needs some time to cool off which may take five or ten minutes of off time.

 

[ForgivenCreation]

How about the extension cord?

 

[AlpineJoe]

The problem is also the PTC starter will cut out the start windings before the motor actually starts due to the voltage sag. The 7A you are measuring is the run winding draw when the motor isn't actually turning. The thermal cutout then saves the motor windings from burning up. As RCinFLA wrote, inverter 'surge' rating can be really poor. It's not able to get the compressor up and running fast enough before the PTC gets hot and drops out the run windings.

Lastly, I don't like what you wrote about your fridge on mains power. It sounds like your fridge isn't even starting consistently off mains power. The thermostat is likely mechanical, it is calling for the compressor to turn on, and the current draw should be very high for less than a second. The fact it is staying up that high for 30 seconds and then it cuts out and later restarts is not normal operation.

 

[RCinFLA]

How about the extension cord?

AC cord gauge probably won't help much, but battery cables and terminals series resistance, especially on a 12v inverter, do matter a lot. Check the DC voltage during startup at the DC input on inverter compared to what DC voltage is at the battery's terminals.

Most little 12v inverters will shut down when their input DC voltage drops below about 10.5 vdc. The more voltage slump you have due to cable loss, the more battery current will be required to make the AC power output requirement.

120vac x 7A = 840VA, /85% inverter efficiency at 10.5vdc input = 988 watts required from battery, / 10.5vdc at inverter input = 94 amps from battery.

With better battery cables:

120vac x 7A = 840VA, /90% inverter efficiency at 12.3vdc input = 933 watts required from battery, / 12.3vdc at inverter input = 75.9 amps from battery.

 

[ForgivenCreation]

Sorry for the late reply. Been getting my solar setup. Tried the fridge again today through a heavy duty extension cord with no avail. Upon further inspection my mini fridge has no start capacitor. Only a overload Switch and single wire start relay.
Will a hard start kit online help as there is no capacitor at all?

 

[v_green57]

Time to stop beating your head against the wall and buy a bigger inverter. My Haier 2.7 c/f which only needs 60W when running needed a 1kW to start it.

Nothing less would work.

 

[ForgivenCreation]

Hmmm, Not sure if I should start a new thread or continue here. How hard / how many Peltiers would I need to covert it over to 12volt?
It's supposedly a 4 Cubic Foot Fridge. This might also allow me to lay it on its back making it a chest fridge/freezer?
Not sure if this is even fit for this forum, If not disregard.

 

[v_green57]

The thing with Peltiers:

In most consumer applications, they cool to apx. 40 degrees F from ambient. So, if it's 80F, you can get no lower than 40 (not enuf for a freezer).

Unless there has been some advancement in that tech.

I also have an old Igloo peltier cooler. It consumes as much power as the Haier and runs constantly.

At 80F, after initial cool-down, the Haier has about a 40% duty cycle keeping the small freezer compartment at less than freezing (frosty in there and making ice for margaritas) and the main compartment at 40.

 

[RCinFLA]

Peltier junction coolers suck for electrical efficiency for btu's transferred.

 

[ForgivenCreation]

I should said fridge only, I don't plan on a freezer, while to mini fridge has one of those "Upper" freezer compartments.
I think I am going to give 3 Peltiers a try with water cooling/radiator setup.

 

[AlpineJoe]

The thing with Peltiers:

In most consumer applications, they cool to apx. 40 degrees F from ambient. So, if it's 80F, you can get no lower than 40 (not enuf for a freezer).

Unless there has been some advancement in that tech.

Peltiers have a max delta between the hot and cold side. To go colder, you can stack peltiers.

But yeah, they are not energy efficient.

 

[MattiFin]

I should said fridge only, I don't plan on a freezer, while to mini fridge has one of those "Upper" freezer compartments.
I think I am going to give 3 Peltiers a try with water cooling/radiator setup.

Peltiers are pretty horrible even for fridge use.
Compressor system can easily have 300w cooling capacity with 100w power draw.
Peltier system ends up really fast to situation where you need 300W of electricity for 100W cooling.