Low Volatage Fault

Lawrence_Hargraves

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Curious as to what ive done wrong here. Ive installed my second diy system recently and have had a low volatage fault. System is now disconnected until ive puzzled this out. Im also about 3 hours away from the equipment so ive forgotten some of the specifics.

The high level details are 2x Longi 370w panels set up in series, a renogy 60a mppt Charge controller and 3x 200ah AGM batteries in a parrallel set up.
Im using a 3000w renogy inverter. System was doing all that I expected for two days and the started getting a low voltage warning when high voltage appliances such as a toaster, a kettle or a microwave were used. These were all running well the first two days. Battery is showing 95% charge and 12.6 (or so?) V.

Hoping for some guidance as i feel as though ive missing something simple with the slightly increased complexity of the system. Use is larelgy for LED lighting, phone charging and running a small fridge but the kettle would be a nice convenience. Thanks in advancd for any help!
 

Don B. Cilly

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12.6 is more like 80%, but maybe battery health is not so good... I mean, was it showing that under load or with the loads disconnected?
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Don B. Cilly

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Right, considering that 12.6V under a 500W load is not really low voltage (for lead-acid)...
the low voltage warning was from the inverter, right? Can you see what the inverter says about voltage when it does that?
Because, if a multimeter/SOC indicator on the battery shows 12.6, but the inverter goes low-voltage (presumably the low-voltage on it is not set to 12.6, is it?) then it could be just a faulty connection/undersized cable/thatsortofthing.
Now, 3000W (or whatever your loads are pulling) at 12V is a lot of amps. Anything but perfect connections/proper-sized cables will induce big voltage drops.
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12VoltInstalls

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12.6 is more like 80%, but maybe battery health is not so good... I mean, was it showing that under load or with the loads disconnected?
Or nearly 50% of usable voltage imho on lead acid
started getting a low voltage warning when high voltage appliances such as a toaster, a kettle or a microwave were used
I get low voltage warning light often running the coffeemaker but even on cloudy days once brewed and switched off the battery voltage ‘recovers’ to about the same volts as before I turned it on.
“Voltage sag” is an occurrence that is more pronounced and noticeable with lead batteries.

That might be what you’re seeing.

An observation is that your 300Ah of usable Ah/power under high discharge loads may only be 100-or 150Ah if high amps is pulled for extended periods. You have what I think of as ‘just barely’ enough solar panels for 150Ah of usable lead acid batteries for moderate use (I have 800W of panels in the main system) and you might consider adding another panel (preferably two) for better charge/daylight performance.
 

Don B. Cilly

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Or nearly 50% of usable voltage imho on lead acid

OK, it may be that, but it should still be good enough, right?
I mean, 500W (call it 40A) on a 600Ah bank... not much is it.

Want to bet it's a bad connection somewhere? ;·)

BTW, this is what I have for lead and LFP:

Screenshot_0621_161841.pngScreenshot_0621_160808.png
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12VoltInstalls

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this is what I have for lead
Ya, I view 12.1V as 100% usable discharged. Weird fact: an engineer basically informed me that technically a 12V flooded lead acid battery is only chemically “at full charge” when over 15.2 volts but won’t hold that voltage in use or for longevity. Someone on here said something similar at one point.
mean, 500W (call it 40A) on a 600Ah bank... not much is it.
Nope. Not if you’re going to use it.
 
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