As Shane said, a first step is to make sure they are fully charged initially. Charge them up using a garage-stye charger or the TM built-in charger. Then disconnect them. Wait at least 30 minutes, and then measure the voltage. The voltage after the delay is their true state of charge.
When a battery is being charged, most of the charging takes place on the surface of the lead plates. It takes a while for the so-called "surface charge" to equalize with the bulk material below it. If you don't wait, you will get an artificially high reading.
https://batteryuniversity.com/articl...surface-charge
Bill