no electrical power

[white exec]

Check also the main battery connectors. If either one gets at all warm (or hot) after trying to crank, there is a bad connection there.

[wheeler]

A cold diesel engine will draw roughly around 250-300 amps from the starter motor but as said above the headlamps will probably draw less than 10 amps so your knackered battery may have enough capacity to operate lights, wipers, radio etc but nowhere near enough to start the engine
You’ve not answered the previous questions about the voltage dropping under load & attempting to jump start?

[hoppington]

why do you think the lights and wippers are comming on then?

I tried putting a 15 volt small battery charger on it for a week this time as it has more voltage then the other one.
I put the multi meters on the battery and turn the key and all I can hear is a relay clicking under the dash (no wippers or lights this time) and the voltage on the battery drops to something like 5V

[hoppington]

& attempting to jump start?

not possible

[white exec]

A jump start from a known-good battery, or another vehicle, will tell you whether your battery is dead or not.
If the jump start is successful, buy a new battery.

[admiral51]

Just to add my issues to this thread .
Yesterday my Xantia decided it would not start, i have been doing 70 miles a day for the last 18 months in it, yesterday it refused to start, jump started it from the C5 no issues, but battery was showing 12.4 v and could not pull the skin off a rice pudding. New battery aquired today and fitted fired up like a new baby and she is 20 years old

[admiral51]

Voltage and Amps are very different animals and live within the battery

[Hell Razor5543]

Voltage and Amps are very different animals and live within the battery

A scruffy analogy is that the volts carry the load, but the amps are the load.

[wheeler]

why do you think the lights and wippers are comming on then?

I tried putting a 15 volt small battery charger on it for a week this time as it has more voltage then the other one.
I put the multi meters on the battery and turn the key and all I can hear is a relay clicking under the dash (no wippers or lights this time) and the voltage on the battery drops to something like 5V

You need a new battery.

[hoppington]

A jump start from a known-good battery, or another vehicle, will tell you whether your battery is dead or not.
If the jump start is successful, buy a new battery.

I dont know anyone with a motor car round hear

why do you think the lights and wippers are comming on then?

I tried putting a 15 volt small battery charger on it for a week this time as it has more voltage then the other one.
I put the multi meters on the battery and turn the key and all I can hear is a relay clicking under the dash (no wippers or lights this time) and the voltage on the battery drops to something like 5V

You need a new battery.

Well if you defo think it the battery then I will go out and buy a new one

[white exec]

That is probably the best option.
When you fit the new one, thoroughly clean the main battery connectors where they clamp on the battery terminals.

If either battery connector gets at all warm (or hot) when cranking the engine, there is a bad connection there. If they are the original lead (Pb) lumps, these deteriorate with age and are best replaced with new solid brass clamp-type connectors.

[wheeler]

Im pretty sure Xsara Picassos never used lead type battery clamps.

[GiveMeABreak]

They're not lead on my Sister's XP and being inside under the passenger seat have a little more protection from the elements.