The following is a question if such an alarm is desirable, feasible, and practical:
As state of charge readouts have become more and more common, the rate of people reporting problems with accuracy is increasing and I regularly come across the situation where a customer believes their battery bank of some years is fine due to reported state of charge being only 80 to 90% minimum but after assessing their battery voltage dynamic it's clear they are taking the battery into real 0% SOC territory, often daily, and unknowingly damaging the battery. Typically the battery monitor has been setup properly but something else has changed, most commonly due to aging and use the battery has lost capacity so the SOC values show as higher than they really are.
Originally I had thought surely there's a way that battery monitors could recalibrate and set themselves to the real capacity but this gets complicated... what I do think could be a real improvement and put forward for consideration is an alarm when the SOC and battery voltage seem too mismatched. Obviously the values would need to be considered and refined but the logic could work something like this:
If SOC >60% and Vbat < 0.96Vnom for 10mins with current of <3% of Bcap then report "SOC Mismatch - Please synchronise battery monitor or test battery capacity"
I think these conditions are clearly incorrect enough to avoid nuisance alarm, apply to most battery chemistries, and could prompt people to check out their system before further damage is done.
In the immediate era, this applies most to older lead acid installations, but as the large number of new lithium installs gradually lose capacity, the potential mismatch presents a significant threat where decisions based on calculated SOC may not come in at the right time, risking hitting very low real SOC or BMS cutout.
