2015 Vauxhall Insignia lose all electrical power without warning when attempting to open vehicle. disconnect and reconnect battery clears the fault.help

What voltage is battery from cold / lying over night ?

Battery voltage checked after standing overnight and before first start of the day. Reading was 12.08 v

12.08 is far to low for a battery and needs charging or replacing if any weak cells .

Many thanks, had already ordered a new battery

Hope that solves the problem . Needed replacing anyway so worth doing

Changing the battery unfortunately has not cured the problem. Loss of all electrics, when opening the ca, occurred 3 times today, worst ever, have not yet attempted to sort problem (disconnecting battery terminals then reconnecting usually works) on last failure yet

Was it o.k for a while after replacing battery ?

It was fine for 2 days

From what you say , you may have something taking a drain out of the battery or could also check alternator charging rate under load .

Checked battery (new) after last failure @ 12.48 volts. Have dash cam fitted but switch off when not in use, been fitted for years without problem. Disconnecting both pos and neg from battery and reconnecting immediately clears fault. Have disconnected all connections from battery and cleaned them, not disconnected neg from vehicle earth. Get the same prompt each time after power back on to open and close driver and pax windows, clock requires resetting each time. Not yet checked alternator

For a new battery that reading would give me concerns

https://www.autozik.com/how-to-test-car-battery-with-multimeter/


I would check for a parasitic drain .

On another American forum I do , we have had some 2020/2021 cars with battery drain problems that took some finding . It transpired that where the car keys were placed indoors , fairly nearby to vehicle , the key fob was continuing to communicate and would not let certain systems / modules shut down as they should after a certain time . Apparently they have now rectified this with a lot of the new vehicles fobs , just a thought , but may not apply to your car .

Sorted it myself. Problem was the short pos(+) lead from the battery to the pos(+) bus bar on top of the battery. During failure the battery voltage was 12.7v. Voltage from battery to bus bar was 5.6 v. Lead changed no problem since

Thanks for updating the forum , good you got it fixed