@83Grumman inquired about my experience with this product and suggested I write a product review.
ECO-WORTHY 200A Battery Monitor,...
https://www.amazon.com/dp/B09Y8Q1X15
I purchased it to have
something to compare the internal monitor in the Renogy Smart Lithium batteries that I use. I chose this product because having the toroid current sense is a huge deal for me in that it didn't require modifications to the high current wiring of my electrical panel. I try to minimize the high current connections as they are expensive ($ and power wise) and unreliable. That is why I chose Renogy, at the time, because the current sense was built into the BMS - one less thing for me to deal with.
I drained the batteries, then filled them up after installing the Eco-worthy monitor. Eco-worthy recorded 196 Ah whereas the Renogy reports 199.27 Ah and
my excel spreadsheet, using Renogy reported current every 15 seconds, reports ~203 Ah.
The Renogy reported SOC does some funny stuff. I think they are using some sort of life-aging model to adjust reported Ah capacity rather than actually measuring it. When charging the reported SOC rises to 90% and then sticks there until fully charged (e.g., voltage > 14.5) and then jumps to the estimated value. They also reported 0% SOC well before the terminal condition of < 10.5v. I believe others on this forum, have reported similar anomalies with Victron (and others?) battery monitors/SOC meters. It must be a simple way of dealing with varying capacity and the inevitable inaccuracy of the current measurements as integration magnifies even small errors over time.
The Eco-Worthy monitor does sort of the opposite: when close to full it shows 100% and 196Ah, yet current is still flowing into the battery. But as it drains the reported capacity generally matches the Renogy reported values. The Eco-Worthy monitor claims .1A resolution vs. 10ma for Renogy. But that is the display, I have no clue what is going on under the covers. The displayed value is significantly different at low current levels, but identical with Renogy at higher levels (4-5a)
The Eco-worthy has the option of manually setting the capacity, full and empty voltage (expert mode for more accurate results). I have not done that yet. I just let it auto calibrate. It is easily within 5% of Renogy and for a $40 product that is plenty good for me (NB: eco-worthy lists .5% measurement accuracy)
See how simple it was to install?