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Off Grid System, Questions!

Hillbilly Dave

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Jul 26, 2022
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Out in the sticks
I’m building a small off grid system and have a few questions, and am open to suggestions. (I’m kind of newish to solar.)

Panels:

12 - 300w ran in two series of 6 in parallel.

Inverter/Charge Controller:

MPP LVX 6048

Batteries:

2-EG4 LifePower4 (Planning to add more when I expand the system in the future.)

So my question is about what size fuse to use on the battery input, the manual for the LVX6048 says typical amperage is 137A does that mean I need the next step up and fuse it for 150A?

Also, the manual recommended specific wire gauges, I’ve heard of folks stepping up a size in order to reduce any likelihood of heat issues and to over build their system. What do you all recommend from your experience?

Thanks!
 
LVX 6048 is going to burn at least 60W idle power 24/7.

That's 1.44kWh/day. That will burn about 14% of your total battery capacity and consume about 300-400W of your array replacing it every day.

Fuse for 1.25X wire rating.

Recommended wire sizes are a minimum. You can always go thicker. Sometimes you have to if your installation requires longer wire runs.
 
Yeah, I saw that idle consumption issue on Will’s review of the LVX 6048 after I already had picked one up.

My main draw to the 6048 was the ability to use it without batteries, but now I definitely see a 6 slot server rack in my future.

Right now I only really need to run a chest freezer and the occasional tools.

Where is a online good source for purchasing fuses?
 
So, I hooked up the panels to the inverter today, it was raining really hard, but the Inverter was reading the PV input as 240v 75w, but then would jump to 575w, then back down and back up repeatedly.

Is that normal to see a large variation?

I don’t have anything hooked up to it, no load or batteries, I was just checking the panels and the inverter to run it and make sure everything would fire up.
 
Sounds weird to me. With nothing hooked up, I would expect a relatively consistent ~100W draw.

Total SWAG: It is possible that the poor solar conditions were marginal for operation, and it was causing some "surging" as the capacitors depleted and recharged?
 
My EG4 batteries were back ordered so I picked up a couple of Pytes 5.14KWH batteries.

I noticed that their battery wires are all 4AWG, even the line in to the inverter. A lot of folks were recommending running 00 cables.

Should I run the 4AWG cables to a bus bar or fuse then bridge them into the breaker at 00 size and then to the inverter?
 
causing some "surging" as the capacitors depleted and recharged?
Any input should keep them charged at the 100W low he mentioned wouldn’t it?
was reading the PV input as 240v 75w, but then would jump to 575w, then back down and back up repeatedly.
That can happen in two conditions I know of:
1) low light conditions the mppt is trying hard to make a charge output based on the voltage it sees; it’s hunting and pecking because as soon as it applies voltage to the load it sucks it to below mppt range- over and over and over and over until it gets dark or sun breaks through. This has been observed mostly at sunup.
2) the exact scenario as above except sometimes in full sun the mppt will spike and zero, or just suddenly collapse and disconnect altogether with a ‘not charging’ error. Then reset and act fine for a while.
This is nearly always a poor connection in the solar array wiring, something corroded, a bad crimp- something in the primary voltage circuit ahead of the SCC terminals.
 
Small update for those interested. Hooked everything up and has been running flawlessly.

The Pytes batteries BMS communicates with the MPP LVX 6048 using the Pylontech battery settings.

Interestingly the LVX 6048 has only been drawing around 5W when it is idling. I did turn off some of the features such as the annoying beep and the backlight. Not sure if that contributes much.

Overall I am very pleased thus far.
 
Small update for those interested. Hooked everything up and has been running flawlessly.

The Pytes batteries BMS communicates with the MPP LVX 6048 using the Pylontech battery settings.

Interestingly the LVX 6048 has only been drawing around 5W when it is idling. I did turn off some of the features such as the annoying beep and the backlight. Not sure if that contributes much.

How did you measure this?
 
During the initial start-up and initial charging of the batteries the Inverter was drawing 70-100w, but once the system started running for a few days the idle consumption dropped very low.

Unless I’m measuring it incorrectly.
 
Okay. It seems you're not measuring anything. You're looking at a display.

Does the display report current from each battery?

Do the batteries independently report voltage and current?

Is the inverter running in power saving mode?

A measurement would entail using an independent battery monitor or other instrument to look at battery voltage and current passing between the batteries and the inverter.

The simplest way is to get a clamp DC ammeter and measure the current passing through one of the main cables between battery bank and inverter. Will does this regularly in his videos.
 
Power saving mode is going to be much lower than idle. You said "5W when it is idling." If you need ANY AC power continuously from a system, the power saving mode isn't an option.

Idle means the unit is not actively powering any loads but full power is available at all times, i.e., if you measure the output, you will see 120V/leg and 60Hz. In power-saving mode, it's not actually providing AC power. it's just looking for a load by periodically making power available. In many cases, that load has to be as high as 500W before it will even turn on. If the load drops below 500W, it will turn off. Pretty undesirable for most people.

What do the individual batteries report for current and voltage? Not what the inverter says, but what the batteries themselves report.

If your multimeter has a clamp DC ammeter, then you can measure it. If your multimeter does not have this feature, you can't measure current with it.
 
The LVX 6048 doesn’t have a power saving mode, but I disabled the features I wasn’t using.

Actually the batteries don’t have an independent reading, I’ll have to pull out the multimeter and check.

But, Battery 1 was putting out 5W and Battery 2 was putting out 0W with 120/240 being output.
 
The LVX 6048 doesn’t have a power saving mode, but I disabled the features I wasn’t using.

Actually the batteries don’t have an independent reading, I’ll have to pull out the multimeter and check.

But, Battery 1 was putting out 5W and Battery 2 was putting out 0W with 120/240 being output.

One thing about Chinese hardware is they tend to get pretty lax about low current draw. MANY BMS simply don't acknowledge low current. My JBD BMS won't register anything below 0.2A meaning I can charge to full or drain it flat at less than 0.2A, and it will never budge in its SoC. IIRC, at one point, the Chargery BMS was notably higher than 0.2A in what it would simply ignore.

My one prejudice against this family of inverters is the high idle draw and the associated costs. Many find that their setup is consuming 50% of one of their rackmount batteries. When you consider that the choice of inverter renders $750 worth of one of their batteries as unusable due to self consumption, then they're not as cheap as their price suggests. If that can be rectified, I'll change my tune. If you've stumbled on a configuration that can reduce idle power consumption, it's worth getting it out there for other's benefit.

Yes. Please measure with a clamp DC ammeter. Set to the lowest scale you can (many have 60A/600A options or similar) and zero it out before you measure.
 
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