Battery voltage too low - top disabled

  • HI all,

    I keep getting the message "Voltage too low - top disabled" after the car has stood for a couple of days and cannot understand why as the car is charging ok (do about 250 miles a week) and had a new AGM battery last year.

    Has anyone had this problem before? If so what was the fix, could it be a bad bettery sensor?

  • Did you mount additional electrical parts that have a canbus interface e.g. a tow-bar or a happyblue module or a throttle control box? If it is like this have you disconnected the battery afterwards? It seems like disconnecting the battery do some kind of reset of all interfaces.

  • Do you have a measuring device to measure the standby current? When you want to measure it lock the car and then wait a few minutes until all control devices in the car are in standby. Probably we can then compare your standby current with the standby current of my car.

  • Hi Fighter1968,

    I haven't tried locking the car and testing it so will try it tomorrow whilst i'm changing the rear brakes and suspension.

    The tests I have done without locking the car are:

    Engine off: 12.44V

    Engine on at idle: 13.64V

    I did one test at both battery terminals and one test at the positive terminal and body earth, both tests came out the same.

  • Let me explain:

    assuming your standby current is 0,5 ampere.

    After 10 hours this is 0,5 ampere x 10 hours = 5 ampere per hour = 5Ah

    After 100 hours this is 0,5 ampere x 100 hours = 50 ampere per hour = 50Ah

    When your battery has 70Ah capacity the battery is empty after about 140 hours.

  • No. Of course not.

    You have to untighten the screw of the neagtive battery terminal clamp. Now disconnect the negative battery terminal clamp from the negative battery terminal itself. Now put the ampere meter between the neagtive battery terminal clamp and the negative battery terminal itself. Now you see the current. When you now lock the car and wait a few minutes you should see the current is going down (more and more) because the control devices of the car are going in standby.