Inverter Kicking Off

[Gabrielle]

Alright so I've been tinkering with my system for two weeks now and finally seem to have everything working properly. Except- the inverter is kicking off after a few hours of running. This is my setup

2x 100 watt panels
SOK 100 amp battery
Epever 40 amp charge controller
Gowise 1000 watt inverter
2AWG from batteries to busbars
4AWG from bus bars to inverter
8AWG from bus bars to controller
Solar panels in parallel

I haven't wired in my DC appliances but they'll be very low wattage.

I'm only running my fridge and a string of lights from the inverter. The string of lights is 10 watts and I just got a kill-a-watt meter to check the freezer-to-fridge conversion and its showing 50-70 watts when the compressor kicks on, which is not very often! I haven't been able to get a good kWh reading because the inverter is turning off after a couple hours of running these two things.

Anyone know what the deal here could be? With my understanding this shouldn't be overloading the system. The batteries were fully charged when I plugged things in tonight.

 

[12VoltInstalls]

batteries were fully charged when I plugged things in tonight.

What is the voltage for ‘fully charged?” It sounds like low battery or poor amperage or not enough startup headroom.
Is that a pure sine inverter?

 

[Gabrielle]

Voltage was 13.4
What do you mean poor amperage or not enough startup headroom?
It is a pure sine inverter

 

[John Frum]

The string of lights is 10 watts and I just got a kill-a-watt meter to check the freezer-to-fridge conversion and its showing 50-70 watts when the compressor kicks on, which is not very often!

70 watts in nothing.
Do you mean amps?
Please post a picture of the core of your system.
By core I means batteries, busbars and inverter and everything in between.

 

[Zil]

Have you measured the voltage at the inverter positive/negative terminals while it is on load? It sounds like a voltage drop condition as the battery gets low.
That is not much battery for a few hours of inverter.
The fridge has a data plate. What is the listed watts of the fridge?

 

[12VoltInstalls]

70 watts

That is possible running watts. My 60W-running surges 800W+ for a second on startup.

You’re right; something is wonky here

 

[12VoltInstalls]

What do you mean poor amperage or not enough startup headroom?

When the fridge starts it will pull a LOT of watts for a few seconds, somewhat higher than running watts for 5-30 seconds, and then settle to its running watts. A frost-free cycle can vary on brand and age and could be a few hundred watts.

2AWG from batteries to busbars
4AWG from bus bars to inverter

For 1000W those are probably “fine” though I didn’t look them up.
However I think they are way too small as I overcable stuff on purpose. Like I would use 2/0 gauge- WAY bigger than 2ga or 4ga

But you have one or two other things going imho and the questions people are asking will discover what is going on eventually

 

[SparkyJJO]

I'm guessing a voltage slump is occurring when the batteries are lower and the freezer attempts to start, triggering a low voltage cutoff.

 

[acdoctor]

For LFP 13.4 is not fully charged resting. I wouldn’t think 5.5 amps DC would not pull it down to that either. Have you babysit it to figure out if it trips at a start up or during a run cycle? What is the voltage at the inverter input just before tripping?
I have ran a fridge from a 3000 watt inverter and 1 100 amp hour 12 volt FLA battery for 24 hours regularly without a problem.

 

[TomC4306]

When the fridge starts it will pull a LOT of watts for a few seconds, somewhat higher than running watts for 5-30 seconds,

Have you actually measured this?
I have been running Kenmore residential fridge, sanyo mini fridge, and Frigidaire upright freezer and I don't see this magical surge. Once the units are cold, that magical locked rotor amp startup doesn't happen. At least not here.

 

[John Frum]

4 awg is right on the ragged edge for a 1000 watt inverter at 12 volts nominal.

1000 ac watts / .85 inverter efficiency / 10 volts low cutoff = 117.647058824 service amps
117.647058824 service amps / .8 fuse headroom = 147.058823529 fault amps

117.647058824 service amps is out of spec high for a single 100ah sok battery.

 

[John Frum]

Have you actually measured this?
I have been running Kenmore residential fridge, sanyo mini fridge, and Frigidaire upright freezer and I don't see this magical surge. Once the units are cold, that magical locked rotor amp startup doesn't happen. At least not here.

How are you measuring?
If you don't have a clamp meter with the in-rush feature you may miss it.

 

[wmgeorge]

1000 watt invertor ignoring losses is 77 amps on the low voltage side, #4 is fine for that. How many 100 Ah batteries?

 

[John Frum]

1000 watt invertor ignoring losses is 77 amps on the low voltage side, #4 is fine for that. How many 100 Ah batteries?

I showed my math, please show yours.

 

[wmgeorge]

I showed my math, please show yours.

1000 watts / 13 volts = 76.92 amps. The wattage is the same on both sides.

 

[John Frum]

1000 watts / 13 volts = 76.92 amps. The wattage is the same on both sides.

13 volts is arbitrary, no?
I chose 10 volts as that is the voltage at which the bms will disconnect.
Its extreme but I prefer to be conservative.
Also inverters are not 100% efficient.
My experience shows that 85% is a good plug-in here, especially for low end high frequency inverters.

 

[wmgeorge]

13 volts is arbitrary, no?
I chose 10 volts as that is the voltage at which the bms will disconnect.
Its extreme but I prefer to be conservative.
Also inverters are not 100% efficient.
My experience shows that 85% is a good plug-in here, especially for low end high frequency inverters.

She is using a LiFePO battery correct? I think 12 or 13 vdc is the recommended limit. Amps do not increase as battery voltage drops. Most modern inverters run over 95% efficiency.

 

[SparkyJJO]

Uh, yes amps do increase when voltage drops to maintain the same power output. P = I x V

 

[John Frum]

She is using a LiFePO battery correct? I think 12 or 13 vdc is the recommended limit. Amps do not increase as battery voltage drops.

OP is using LFP.
12.8 volts is the nominal voltage of LFP.
12.0 volts is going over the waterfall.
10.0 volts is typical BMS disconnect.
Amps do increase as voltage drops.

Most modern inverters run over 95% efficiency.

My Samlex PST is ~89% efficient and its one of the better high frequency inverters.
I'm skeptical of your claim.

 

[John Frum]

Most modern inverters run over 95% efficiency.

What does modern mean in the context of a discrete high frequency inverter?
I doubt much RnD money has gone into the base of the platforms in the last 5 years, probably more like 10.