Two nights ago i left a heated seat plugged in and now i have a flat battery. I have tried jump starting when we turn the key nothing at all dead to the world It's a focus 1388cc 2005 any help would be a great help. :(

Once a silver calcium battery is that dead its a new battery required im afraid

It should still power up when connected with jump leads. Are you sure the jump leads are connected to clean surfaces?

I jump started my silver calcium battery and it's been fine so far.

When battery in my 2.0 TDCI died, jumpstart did nothing at all, both from other car and a portable battery RAC guys are using - the car remained dead.

Think in some cases once a battery has died it also pulls down the donor battery when you're trying to jump start the car. One way to prove this would be disconnecting one or both the terminals on the flat battery and connecting jump lead directly to the wiring connector.

Not sure if this would cause any problems for the electrical systems, and of course it wouldn't be ideal to try and reconnect the original battery if you were then able to get the car started.

I wouldn't recommend connecting the donor car to the wiring terminals of the other car with the battery disconnected and try to reconnect the battery once started - if anything that will cause a spike and damage the ecu.

If the car is totally dead even with a booster or donor car, I would check the main fuses under the bonnet.

Some silver calcium batteries wont recover after a deep discharge however as above expect something from it even an attempt to start