diff --git a/src/main.c b/src/main.c
index a910e66..9217cb6 100644
--- a/src/main.c
+++ b/src/main.c
@@ -218,6 +218,7 @@ void calc_data(Tel *t, Bat_state *b, long now) {
 
         b->previous_ms = now;
         b->wh_used += (float)t->power.data * (float)dt / 3600000.0f;
+        if (b->wh_used > b->wh_total) b->wh_used = b->wh_total;
 }
 
 long now_ms(void) {