diff -r 10d208fa6c74 -r cf75e6fadcb1 src/DetailiSpindel.cpp
--- a/src/DetailiSpindel.cpp	Sat Aug 19 18:50:22 2023 +0200
+++ b/src/DetailiSpindel.cpp	Sun Aug 20 11:08:05 2023 +0200
@@ -140,10 +140,12 @@
 		ui->batVal->setText("");
 	    }
 
-	    double batt = query.value("battery").toDouble() - 3.064;	// 0% voltage
+	    const float battery_max = 4.13;
+	    const float battery_min = 3.43;
+
+	    double batt = ((query.value("battery").toDouble() - battery_min) / (battery_max - battery_min)) * 100;
 	    if (batt < 0)
 		batt = 0;
-	    batt = round(batt / 1.05 * 1000.0) / 10;	// 100% range. Was 1.17875
 	    if (batt > 100)
 		batt = 100;
 	    ui->batVal->setText(QString("%1%").arg(batt, 2, 'f', 1, '0'));