Xantia car Battery question please?

[falling-out-with-my-car]

Does anybody Know how many amp hours a Citroen Xantia 1.9TD battery should be from new please?

I have been trying to recover a battery that has had a number of short charges and had obtained a memory refusing to charge above 12.96 volts and 10 amp hours.

I have used a Graupner Ultramat charger (these are quite expensive chargers £100+) to discharge the battery several times and recharge at 500mah over several days. the charge rate can be adjusted between 5amps and 0.01 mah if required.

The voltage now stands at 14 volts and the amp hours at 45. 597 the most accurate way to get the amp hour rate is to discharge the battery. The graupner ultramat charger does this automatically setting the discharge rate and has a built in fan to cool the charger to prevent it overheating.

It has taken five discharge/charge cyckles to reach 45 amp hours from the initial 10 amp hours.

the part number on the battery is 096 if this helps.

Thanks in advance Nigel.

[Xaccers]

Had a look on Google and many are showing over 70Ah
Sounds like your battery is knackered

[Old-Guy]

The Ah capacity recommended by various battery suppliers can easily be checked on line for any car.

Lead-acid batteries don't suffer from 'memory effects' like NiCad or NiMH batteries; though one that has been sitting 'near-flat' for a long time can sometimes be persuaded to take and hold a reasonable charge by several gentle charge-discharge cycles with a proper charger - that said, it will likely to then be a rather sickly battery.

You don't say under what circumstances your 'fully-charged' voltage of 12.96V was measured, if rested overnight then that's a good charge. If immediately after charging then it's not taken anything like a full charge. The maximum charge voltage of 14V doesn't really indicate anything as you are using a constant-current charger (at a very low setting). The maximum theoretical charge voltage is 14.4V - continued charging in excess of this simply causes the battery to gas (converting distilled water into Hydrogen and Oxygen). Immediately after charging stops, a more-or-less fully charged battery will show a voltage of something like 13.6V (or more), dropping very rapidly initially and slowly levelling out over 10+ hours to something like 12.8V. If you take a small percentage of the charge out (headlights for 5 minutes), the voltage will drop more than you would expect ("blowing the surface charge of the plates").

The charging of lead-acid batteries and battery voltages is a very complex subject.

If we assume that it was nominally something like a 70Ah battery, at your 5A setting, it would take 14h to charge fully; at 500mA, 140hours!

Automotive batteries are designed to be charged (from 1/4+ capacity) at several tens of Amps - IIRC the Xantia alternators are 60A jobs - so charge it at the maximum 5A for 14 hours, wait 10 hours for the voltage to settle and then see what voltage it shows.

It's not necessary to 'fully' discharge a battery (not kind to it anyway) to determine its actual capacity - see this explanation.

[falling-out-with-my-car]

it seems to be recovering nicely the battery was mains charged several times after only using it to start a xantia and travel very short distances less than a mile.
regular mains charging seemed to reduce its capacity.
the battery is now at 48 amp hours and the capacity climbs at every charge providing I discharge it properly. my charger holds down the voltage and builds the capacity reducing the charging rate as capacity climbs to prevent over gassing.

cheers Nigel.