Added battery module, cal factor refresh bug

src/data/general_store.cpp

@@ -0,0 +1,14 @@
+// Copyright (C) 2026 Hector van der Aa <hector@h3cx.dev>
+// Copyright (C) 2026 Association Exergie <association.exergie@gmail.com>
+// SPDX-License-Identifier: GPL-3.0-or-later
+#include "general_store.h"
+
+ volatile double vbat_global = 0;
+
+ void vbat_global_read(double& out) {
+     out = vbat_global;
+ }
+
+ void vbat_global_write(const double& in) {
+     vbat_global = in;
+ }