# Power fading in and out

Registered Users Posts: 45 ✭✭
I have one circuit that is giving me problems. When I switch it from mains to my inverter, the power just fades in and out. I moved it to my other inverter, same thing. I tried changing the cord, but that didn’t work. It isn’t putting out any errors, just a slow pulsing of power. I am going to put in a new breaker on the mains panel for that circuit in case the circuit breaker Is faulty. Any other ideas?

12v inverters one is a 3000w WZRELB and the other is a 8000w Powerjack. The battery bank is 1200ah (6 200ah Renogy)

## Comments

• Super Moderators, Administrators Posts: 32,205 admin
Check your wiring and battery connections. If you are drawing a lot of current, any poor connections can be getting warm/not (be careful not to burn yourself checking).

Those are pretty large inverters for a (I guess) 12 volt @ 1,200 AH battery bank. For example:
• 3,000 Watts * 1/0.85 inverter eff * 1/10.5 battery cutoff = 336 Amps
• 8,000 Watts * 1/0.85 inverter eff * 1/10.5 battery cutoff = 896 Amps
That is a huge amount of current--Need very heavy and short cables with very good electrical connections (typically multiple heavy cables in parallel).

Measure the input voltage 12 volt terminals at the inverter and see what the voltage is under load (looking for voltage drop below ~10.5 volts).

In general, I would suggest about 1,800 Watts as the "practical maximum" for a 12 volt battery bus inverter/DC loads.

And for a 1,200 AH flooded cell battery battery bank @ 12 volts, it could reliably supply around 3,000 Watts reliably (~250 Watts per 100 AH @ 12 volt bank capacity).

The other issue can be the batteries themselves. Have you fully charged them (~120 amps nominal, 60 amps minimum) and verified that each battery is working correctly (if flooded cell, verified the specific gravity of each battery)?

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 4,495 ✭✭✭✭✭
As well as what Bill said, what (if any) AC loads are on the circuit?
Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
• Registered Users Posts: 45 ✭✭
The batteries are 6 gel 200ah in parallel, all using 1/0 cables, and each inverter has multiple cables, each with a 300amp breaker between the inverter and the battery bank. I sized it so that I don’t use more than 50% of capacity. 1500w on the smaller inverters, and I haven’t even gotten to 2000w on the larger, no plans to ever use more than about 2500-3000. At any rate, other circuits that pull more are working just fine. No overheating wires, no loose connections, and no tripped breakers. That one circuit just has normal stuff, LED lights, a ceiling fan on low, regular stuff. I had found that one of my outside receptical, which I run from mains only, was connected to an inside circuit. I plug my dogs heater and water de-icer on the same plug. Drove my usage up to almost 2000w on that one circuit, but it still powered it because I was testing each circuit at the time.  I fixed that problem. I bought new breakers for the main panel, but it didn’t fix that one pulsating circuit. It’s a real head scratcher. I am starting to think it must be in the wiring of the circuit itself. I am going to isolate it, and start checking all the switches and recepticals individually, maybe that will point out a problem. Any other ideas will be appreciated.
• Registered Users Posts: 4,495 ✭✭✭✭✭
What does "pulsating" mean, exactly (fluctuating current, voltage, what frequency - eg. 1 pulse every X seconds)?  How are you testing?
Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
• Solar Expert Posts: 3,854 ✭✭✭✭✭✭
Are there search features on the inverters to conserve idle consumption, if so, the search load threshold could  set too high, that would result in pluses. Just a thought.
1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS
Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
• Registered Users Posts: 45 ✭✭
The lights are slowly dimming and brightening. Same thing my razor does when I plug it in to charge. The pattern goes over 2-3 seconds maybe. Even if I plug in a extension cord that has the lighted plug at the end, it gets bright and goes out over about 2-3 seconds. No other circuit does it. Most individual circuits range from 200-300w unless it has a fan or something like it. My entertainment center has about 350-500w, but that’s because it has the tv, my broadband routers and the Dish Hopper. I have another circuit that includes my chest freezer, and mostly just lights. I live in a large manufactured home, so the wiring isn’t top shelf, but it works most of the time.
• Super Moderators, Administrators Posts: 32,205 admin
I am not sure but if it is "8000W LF SPLIT PHASE PURE SINE POWER INVERTER DC12V/AC 220V&110V Battery Charger", it appears to have a "power save" option.

https://www.ebay.com/itm/8000W-LF-SPLIT-PHASE-PURE-SINE-POWER-INVERTER-DC12V-AC-220V-110V-Battery-Charger-/253896711328

POWER SAVE ON :

If you only connect battery with load, ac cable unconnect, when you switch to battery charger mode, this means is power save mode on, in this moment the condition as follows: The inverter will go to sleeping mode , no load current is 0 AMP, every 3secs, the inverter will detection itself, after the 3sec, amp will go to 3amp(stand by power, time: 1sec, then back to sleep mode, amp is 0),  the inverter will repeat the situation, until you switch to power save off(inverter on, down side)
some customer need use refrigerator ，can switch to power save on mode, as refrigerator only will work every  half an hour or one hour  ,  but inverter stay in power save function, no load current is 0amp , can save power.
Basically, the inverter turns once a second for a fraction of a second to "look for an AC load", if there is an AC load > X Watts, then the inverter stays on.

For typical US inverters, the load must be >6 Watts... I could not find a specification for this inverter--But it is possible that you need a larger load?

If you are using an LED lamp (smaller ones are around 9 watts or less)... You would get a blip of light every 1 second.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 45 ✭✭
I remember reading that, and I’m not sure where I left it. That it the inverter though. I got the big one so that intermittent loads, like a toaster or microwave or whatever would have some room to surge. I don’t think I will use more than 1500-2000w at any one time. I spread that load over multiple inverters, the ATS for the larger surge items. I only have 2100w of PV, so I won’t power everything, no 220v at all. I wasn’t planning on using the ATS for its charging function. I have an iota 75amp smart charger for bad weather days, or just to start each day at 100SOC, or as close as needed. But that powersave needs more testing. Tomorrow is another day. Thanks!
• Registered Users Posts: 4,495 ✭✭✭✭✭
It certainly sounds like a search mode / power saver sort of pulse.  Putting a known higher load like a 60w filament bulb on the circuit would confirm.

As a side note, I once accidentally left my phone charging on an inverter with sleep mode.  When initially connected to power, the phone buzzes its haptic feedback so you know its properly connected to USB power.  The search pulse was enough to cause the haptic buzz, but the load was too small to start the inverter or charge the phone.  The haptic buzz drained the phone battery to the point I could only get it going by removing and reinstalling the battery!
Off-grid.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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