Ian2861

Out of interest, if the headlights of a car were left on for an hour with the engine off could it ruin a perfectly good battery?

The car in question was a 1.7 Puma.

After the above incident the car refused to start wih jump leads. We were told the battery was kaput and would need replacing.

There had been many other things wrong with the car, which we had only got in November, and in the end we sold it, but I wondered if the battery was another dud thing on it?!

steanlol

I have left my kc daylighters on once on my range rover and they flattened the battery in 30 min but just charge it up and as good as new

Leaving lights on will not kill a battery

Must have other issues

Ian2861

Many thanks. Suspected as much!

tabetha

Not as simple as that, if the battery is old, and has broken cell plates it could indeed spell the end, as the remaining plates heat up having to supply for the lost parts, which are not only lost but usually short cicuiting in the bottom of the battery case, by bridging the neg/pos plates.
I've known it happen a few times, where after no matter what charge was put back in they just wouldn't play ball, but battery was obviously crap as 1 hour of headlights, will only consume around 10 amps over an hour, so taking a 40ah battery to about 3/4 charged, which is more than enough to start the car, but that's assuming fully charged if duff it won't have that much in there to start with.
Everytime a normal lead acid battery or calcium is flattened damage occurs, but if AGM it doesn't affect it.
tabetha