As long as there is work the battery level check never happens. It currently only happens when an AGV arrives at a park point and then finds new work. To have the AGV start to charge whenever the battery level stops below a threshold use an independent Event-Triggered Source to listen for that. And use task sequences, so you can dispatch a charging TS to the AGV that has a higher priority than the work task sequences.
You also currently don't actually start to recharge the AGV. Which is why it gets stuck; the battery level can't increase past the threshold if it is not increasing at all.
