"Initial" working version, after cleanup.

s_battery.go

@@ -0,0 +1,34 @@
+package hapz2m
+
+import (
+	"github.com/brutella/hap/accessory"
+	"github.com/brutella/hap/characteristic"
+	"github.com/brutella/hap/service"
+)
+
+func createBatteryServices(dev *Device) (byte, []*service.S, []*ExposeMapping, error) {
+	var svcs []*service.S
+	var exposes []*ExposeMapping
+
+	for _, exp := range dev.Definition.Exposes {
+		if exp.Ignored() {
+			continue
+		}
+
+		switch {
+		case exp.Type == "numeric" && exp.Name == "battery":
+			exp := exp // create a copy
+			batt := service.NewBatteryService()
+			batt.ChargingState.SetValue(characteristic.ChargingStateNotChargeable)
+
+			svcs = append(svcs, batt.S)
+			exposes = append(exposes, &ExposeMapping{&exp, batt.BatteryLevel.C, nil})
+		}
+	}
+
+	return accessory.TypeUnknown, svcs, exposes, nil
+}
+
+func init() {
+	RegisterCreateServiceHandler(createBatteryServices)
+}