Most people are misinformed on the correct way to accurately determine their battery's level of charge.
Most RVs have a built-in battery charge readout and many have more than one. Unfortunately, almost all of the stock monitors fail to provide an accurate readout. This is due to their design and a lack of user knowledge on how to use the meter.
Battery voltage cannot be accurately read while or shortly after it has received a charge or power has been drawn from it. You can only get an accurate reading after it has been resting (no charge or draw) for a period of time. The battery industry says the rest period should be 24-hours but there is little change after about 4-hours. A fully charged flooded lead-acid or AGM battery will indicate a charge level of approximately 12.7 volts. These batteries can be used down to their 50% charge level of about 12.1 volts. Batteries drawn below 12.1 volts suffer damage that can reduce their life and efficiency.
To accurately determine your battery charge, let the battery rest for a minimum of 4-hours. then, check the voltage, at the battery, using a hydrometer, multimeter, or test light with a voltage indicator.