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Renogy Shunt vs the Battery % indicator itself

joeExotic

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So I pulled the trigger and bought the Renogy 500A Battery Monitor with Shunt because I wanted to be able to read the SOC of my batteries in the percentage format and not in volts format. Now, I found out that my battery can actually show the percentage. I pushed the button by accident on my battery and now it shows the percentage. Should I still install the shunt? Is the reading on the battery reliable? Just wanted to hear your thoughts on this.

I have a 12V system with a total of 360AH LiFePO4 XUBA brand batteries
 

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If this is a lead acid battery, that's % is only going to be semi-accurate after the battery has sat completely dormant for 10+ hours with no charge or discharge. 99% certain it's voltage-based meaning it has negligible value unless you've had the battery in storage for a day or more, and you're curious to know the approximate state of charge.

The shunt Soc should be very accurate provided it is programmed properly and synchronized at least a few times a month.
 
sorry, forgot to add LiFePO4 batteries


I'm still pretty dubious because it says "Battery capacity/voltage" and looks like this:


It's just a voltage based bad approximation of the state of charge.

It's possible I'm wrong, but you should see a fairly consistent correlation between that display and your shunt if it's actually reporting BMS stated capacity.
 
I'm still pretty dubious because it says "Battery capacity/voltage" and looks like this:


It's just a voltage based bad approximation of the state of charge.

It's possible I'm wrong, but you should see a fairly consistent correlation between that display and your shunt if it's actually reporting BMS stated capacity.
So I left my system to charge my fridge and internet over night and my system turned off at 8am. The percentage showed 10% when it shut off.

I unplugged everything and let it charge up for the day and the charge controller says only 59AH was harvested for the day. It was a very cloudy day today.

But the batteries show 85% on all three batteries. Each LiFePO4 battery is 120AH so I doubt the batteries are really at 85% since only 60AH was captured.

Can someone help explain this?
I’m not using the shunt
 

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I think you are seeing the downside of using voltage to determine SOC. It doesn't work. Get the shunt installed, charge the batteries to full, set the shunt parameters and you are in business. It will count the amps in and out and doesn't care what the voltage is.
 
So I left my system to charge my fridge and internet over night and my system turned off at 8am. The percentage showed 10% when it shut off.

I unplugged everything and let it charge up for the day and the charge controller says only 59AH was harvested for the day. It was a very cloudy day today.

But the batteries show 85% on all three batteries. Each LiFePO4 battery is 120AH so I doubt the batteries are really at 85% since only 60AH was captured.

Can someone help explain this?
I’m not using the shunt

Answered here:

If this is a lead acid battery, that's % is only going to be semi-accurate after the battery has sat completely dormant for 10+ hours with no charge or discharge. 99% certain it's voltage-based meaning it has negligible value unless you've had the battery in storage for a day or more, and you're curious to know the approximate state of charge.

Since I tied it to lead-acid, you didn't make the leap.

LFP voltage in a resting battery is kinda accurate, and you don't need a long rest, but voltage in a working system is a poor.

Disconnect the battery for 15-30 minutes and report BOTH voltage and % charge.
 
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