Battery/starting issue

So a funny thing happened to me today. I took my Metro to work and on the way home stopped off to pick up some dinner. When I got back to the car and turned the key in the ignition, the panel lights were very weak and went out completely trying to start it. The car would not crank at all.I tired a few more times and in the end took a look inside the engine bay.

Now about one year ago one of the battery terminls came loose so I installed a new terminal. I thought that may have also come loose and pulled on it and ended up pulling out the wires out of the terminal - obviously it was not being held on very well.

So in the end I called AAA - the guy came out and fixed the terminal so that it could at least be used but the car still would not crank. He then connected up his jump start pack and suprisingly the car started up. So I made it home without further incident but when I got home and turned the engine off and then tried to restart it was dead again. I turned on the headlamps and measured the voltage across the battery terminals - it was about 7V - clearly very low. I connected my own jump start pack which I have in my toolkit and was able to start the car again.

Now the funny thing is there was no sign of the battery failing until today. I'm almost inclined to think the problem may be a wiriing issue or a bad earth execpt for the fact that a jump start can start the car. I also notice that now with the flat battery the lights are no only very dim but also flickers (without the engine running). Also the lights get quite dim unless the engine is being revved up.

So my question is - am I dealing with a possible bad electrical connection, a flat battery or both. Can a battery suddenly fail wthout warning. I've never had it happen but I suppose it is possible.

Battery can fail without warning and yours probably hasn't been getting a good charge for a while. I'd replace the battery and both cables, couldn't hurt to add a ground cable from where the stock one connects to the transmission to the firewall.

Yes, you're probably correct about the charging - I don;t use the Metro much since it is my second car - it sometimes sits around for weeks without begin driven (for the last 2 years). I think the battery is about 5 years old now.

5 years is typically as long as a battery is going to last anyway. What I meant by not charging is that your bad cables prevent the alternator from charging the battery properly, hastening it's demise.