Erratic % Charge

In my campervan I have two Renogy 100w panels, a Renogy Adventurer charge controller and one 200ah Renogy battery. On the load side I have a Truckfridge 130 (supposedly uses 2 amps on average between on/off cycles), a small 12v pump (used about 5 minutes total per day) and a few small LED lights (about 0.25A each).

My problem is that the %charge reported by the charge controller is all over the place and isn't making sense. I'll give a couple examples. One day it said the battery was at 95%. We went to eat lunch and 30 minutes later when we came out it said the %charge was 60%. That's a huge drop in 30 minutes in full sunlight with only the fridge drawing power.

Another example was about an hour before dusk it said we were at 37%. An hour later, at dusk, it said were were at 85%. This was when the panels were producing virtually no electricity

Any idea what the problem could be? I've asked around and most people think it's a bad charge controller.

I know of no algorithm that could be used to determine SoC for a battery while charging or discharging.
Many a SoC vs voltage chart that give an estimate of rested battery.

To me, 100% SoC happens when the battery gets to its set pt voltage of over 14v, and is held there as the charge current tapers to nill or some small current =< 1% of battery capacity.

50% SoC would be little load and a batt volt or 12.0-12.2v.

if you can find who made the battery and the charging requirments you might read the charging section (chapter 5.4) of a lifeline battery/tech manual.
lifelinebatteries.com/wp-content/uploads/2015/12/6-0101-Rev-E-Lifeline-Technical-Manual.pdf

Battery and other components made by Renogy. I might need to call them and find out. No one else I talked to has the displayed SoC making big jumps like this.

Hello John, Did you ever find an answer to your issue. I am having the same issue. Batteries are brand new, no way they drop that fast! I tried to hook up the voltage cables they provide to the batteries and the insulation started to melt.

Your having a differen't issue than he had.... You have something hooked up backwards...