Nigel Goodwin said:
Isn't it just for checking how well charged the battery is?, I would call that "VERY non-critical".
No Nigel, it's used to monitor the battery voltage during use, and when the voltage drop because of low battey level, the unit needs to activate and brake the car. If the voltage gets too low, or rather the batteries get too depleted, the throttle/brake and steering servo will stop working, and if this happens at WOT (Wide Open Throttle) the car will be completely out of control and dangerous.