Monday this week I went to get in the car and found the battery completely dead, keyless won't work, I had to get in using the manual key. Tested the battery in situ and it read 2.9v.

I do on average 300 miles a week, so no reason the batt should have died, anyway tried to jump start it from another car, was surprised to see not sparking when connecting to the terminals but ok, was also surprised that nothing on the car lit up, no dash, no alarm, nothing. has a main fuse blown, a relay stuck?

Tested voltage across jump leads, 14v, tested voltage of battery terminals with jump leads in place still 2.9v. now really confused, I should see 14v right?

Left in place (30mins) to try and get some voltage in my battery but no change always 2.9v

About to give up and went to remove the leads from the other car and noticed that my headlights flashed as I removed the negative, put it back on, tested still 2.9v. Tried connect/reconnect a few times and all of a sudden my car came to life, full dash, alarm, lighting. Let it get some voltage and got my car running perfectly.

 

Is something about to go? was it just a electrical component stuck and pulling the voltage down? Im going to replace the battery but Im keen to know if anyone else has had this issue.

On your car did you connect the negative jump lead to the chassis earth point, or on to the battery negative terminal? 

I tried both, both results the same. 

Are your jump leads ok? I’ve had aluminium ones fail . Also had a battery fail internally between post and cells. Was a number of years ago though.

3 hours ago, RL123 said:

Are your jump leads ok?

Actually that is a very good point 👍

I've also had a set of jump leads that had a very poor connection to the croc clip.