AiLi Battery Capacity Monitor--What Do The Numbers Really Mean?

[George Johnson]

Just installed an AiLi battery capacity monitor after our last trip in our Escape 19. The unit is inexpensive, looks good and seems to work well. As I am not conversant with electricity, and the instructions are written in Chinese English, I'm having some trouble making sense of the numbers the monitor is presenting.

Here's the situation: Batteries are Interstate lead-acid deep discharge 6 volt wired in series, purchased new in August. Rated capacity is listed as 224 amp hours. The trailer is stored on shore power, with the batteries being kept at full charge through the trailer's WIFCO controller. The initial setup of the monitor requires putting the amp hour capacity of the fully charged batteries into the monitor so it will "know" what the capacity of the batteries it is monitoring is--easy enough, and I have done that.

Next, the user initializes the "percentage reading interface" to 100%, which allows the monitor to display the percentage of amp hours from full capacity remaining. Easy enough, and I have done that. The other two functions are amperage flow (+ or -) and voltage and are automatic.

My problem is that over the past two days the amp hour (Ah) reading has drifted down and stabilized at 205.3 Ah, with a percentage reading of 91.6%. I now wonder if the batteries are only capable of holding 205 Ah of capacity, rather than the listed 224, or if the monitor is incorrect. Alternatively, might the controller not be fully charging the batteries? BTW, the voltage of the resting charged batteries is at 13.7 on both the AiLi and my multimeter.

Does anyone else reading this use the AiLi monitor, and can you tell me what is going on?

The instructions say that I can get a "true" reading of Ah capacity by fully discharging the batteries, setting the monitor % to zero, then fully recharging the batteries and then reading the resulting Ah as the actual capacity of the batteries.Everything I've read regarding lead-acid batteries says this is a bad thing to do for the longevity of the batteries, so I am not really interested in trying that.

Any help would be appreciated.

George