Battery in 2007 C5 petrol

[friarpat46]

Came out today, absolutely nothing when I turned the key. Tried a jump start, no luck. Put trickle charger on it and it showed 4.7V. I assume battery is goosed, hoping thats all. Advice please.

[GiveMeABreak]

Are sure that it showed 4.7 and not 14.7?

It’s just that 14.7 can be the charging voltage. If not then battery is probably knackered if, after you have charged it, the charge is not held or it won’t start. Also check the alternator is charging the battery - it should be about 14V+ with the car running.

[xantia_v6]

If you have the time, try charging the battery for a few hours with it disconnected from the car. 4.7V seems an unlikely value for a failed battery, as it would mean that several cells failed at the same time.

[friarpat46]

even on the jump start it still only showed 4.7

Not a flicker from flashlights or anywhere else

[friarpat46]

should read dashlights

[wheeler]

4.7V seems an unlikely value for a failed battery, as it would mean that several cells failed at the same time.

I would agree with that.
When was the car last used ? if it was in the last day or two then 4.7v is more likely to mean that something has discharged the battery. Its not to say that a battery cant fail in this way but just not as likely. Normally failed batteries show a higher voltage but then drop very low under load.