Inverter problems

[dre]

So my small off-grid solar generator setup that includes Automatic Power Transfer switch featured in one of the videos I've figured out is working fine, although when running off public power, the display turns off on the ATS. When checked with the multi-meter power is being properly routed to the output line from the house. However in the morning when it switches back to battery, the inverter trips. I have to power cycle the inverter for it to supply 120VAC. It does not like the momentary switch in draw, it sets some sort of fault that is easily reset. Need to find an inverter that doesn't do this or kinda defeats the purpose of the ATS.

 

[gnubie]

So the inverter is always running but not necessarily loaded? You might well be seeing the effect of out of phase loads being dropped onto the inverter's output. Depending on the phase difference between the mains (grid) and inverter the load could appear to be gross overcurrent when the ATS switches.

What make / model is your inverter?

 

[dre]

Sudokeji 1200Watt Pure Sine Wave. yes I leave it on all the time. Right now the only load is a couple string LED lights, but I was hoping to put a larger load later. So when the battery reaches the cutoff voltage the ATS correctly shifts power to public, now the inverter is still powered on, actually still drawing about .3 Amps, but it is not output 110. The next day when the battery reaches restored voltage the ATS switches back to the inverter, but this causes the inverter to go into a fault state. The ATS is unaware because it is only monitoring battery level and leaves the power draw on battery/inverter. Now if a I power cycle the inverter it then powers the 110 appliances.

 

[gnubie]

What is the battery voltage when your ATS switches back to the inverter?

 

[dre]

12.5V

 

[gnubie]

OK, then it sounds like its the phase of the load that is doing it. These little inverters don't have a lot of tolerance for that sort of thing. Can you manually switch your ATS? That would let you do some practical testing to see if this is the case. Put a resistive load on the inverter, an incandescent light (the old get really hot style) and then switch the ATS to mains for a bit (30 seconds is fine) then switch it back to the inverter. The inverter should be happy with that.

 

[dre]

Did some testing, definitely the inverter, which is odd. Something about the battery switching over under load. but a power cycle using the inverter power switch fixes the issue, going to have to add a relay or something to smooth things over. But while I have your attention, I've noticed a couple times the battery pack in the morning right before sunrise, the charge controller is reading 6-8 volts. Now once there's daylight it charges no problem but running it that low, is that bad for the battery? LiFePO4 50AH

 

[gnubie]

The BMS would (or should) disconnect before it gets that low so what you might be seeing is the result of the BMS disconnecting the output but leaving enough voltage on the output to allow most chargers to detect the battery and start charging. This is assuming there is a BMS.

 

[dre]

No BMS on it. The inverter has a built-in low-voltage cutoff around 10V I think, but I notice the screen and indicators stay lit even passed the LV cutoff. I'm guessing cuts power to AC loads but still monitors battery, illuminates indicators. also the LCD on the charge controller stays on. Guess I need a battery disconnect and/or BMS.

 

[MrNatural22]

Pass........?

 

[Ped]

Think a capacitor on the inverter would fix it?

 

[gnubie]

No BMS on it. The inverter has a built-in low-voltage cutoff around 10V I think, but I notice the screen and indicators stay lit even passed the LV cutoff. I'm guessing cuts power to AC loads but still monitors battery, illuminates indicators. also the LCD on the charge controller stays on. Guess I need a battery disconnect and/or BMS.

Then you are over discharging your battery. That's not good for the cells health.

 

[dre]

Then you are over discharging your battery. That's not good for the cells health.

That's what I was afraid of, looks like I need to put more equipment in the mix. also maybe not wire the battery directly to the inverter, have something else in line to ensure a true low voltage disconnect.

 

[GinoMaid]

What is the battery voltage when ATS switches are back to the inverter?