This is what I refer to as a traditional Ah/Coulomb counter. In order to display the SOC correctly, as seen here, requires proper programming, the battery temperature the battery was rated at 77F -80F (or a temp sensor and some Ah counters offer this), known accurate 20 hour Ah capacity and shunt wiring with no sneaker wires bypassing it.


Can these be made to be pretty accurate? Yes they can but certainly not to the tenth of a percent. If they are accurate today they will not be accurate three months or a year from now unless YOU program them for that.


What I am getting at is that Coulomb / Ah counters are only as accurate as you the owner make them. They are NOT plug and play and do require human intervention.


BULLET POINT: Ah counters, pretty much all of them can Coulomb count EXTREMELY accurately this is very, very simple stuff to do. Where they miss the mark is that this Ah counting rarely if ever matches your battery due to Peukert, temperature, rate of discharge etc. etc. etc..


Looking at a screen that says -50Ah on a 100Ah rated battery tells you little to nothing about the actual SOC of the battery because the rate at which that -50Ah's was drawn, the battery case temperature and actual capacity of the battery may not have been drawn at exactly the 20 hour rate, at 75-80F and your batteries capacity is rarely going to be 100Ah for very long.


Coulomb counting and looking at only the Ah counted/consumed screen is not the best and most accurate way to use a Coulomb counter. Programming for actual capacity, Peukert and temp or using a temp sensor, will get you the most accurate SOC readings with an Ah counter.