What is my shunt measuring

[Sneruh]

I have a Basement Watchdog sump pump with sump pump controller and charger connected to a 12V AGM battery. The charger is rated for 1.6A and does a bulk charge to 14.4V. I want to monitor the SOC of the battery but also the voltage across the battery terminals. If I connect the shunt (on the -ve side of the battery) with the + wire from the meter to the +battery terminal, what voltage is the shunt reading? When my charger is recharging, is it reading the "recharge voltage"? When the charger is not charging is it reading the battery voltage? The reason for all this is that my battery specs say to recharge at 14.7V while the charger for the BW controller charges at 14.4V. The battery manufacturer indicates that if the battery is consistently undercharged, it will sulficate and fail prematurely. This is a well known and reputable battery manufacturer that produces deep cycle AGM batteries.

 

[sunshine_eggo]

Shunts measure open circuit voltage (OCV). This is the voltage at the battery terminals where the measurement is not affected by current flow.

The charger will "see" 14.4V battery voltage before the shunt would report 14.4V because of the resistance in the wires between the charger and battery. This assumes that both instruments are calibrated and correlated.

If the charger also floats the battery at 13.6-13.8, the battery should get fully charged after a couple of days.

1.6A is a low charge rate. If your battery is larger than 16Ah, then the charger may be undersized. Charging with too low a current is also a factor in reduced service life.