Xantia V6 dead battery

[xantiagreen]

@ Simon,

Glad the new battery has solved the issues. The voltages you quote seem to suggest the alternator's doing it's bit so "All good to go" What battery did you get in the end?


@ Faz,

64ah/640cca would that be ok for a 110 hdi Exide premium 027 246mm length, 190mm height, 175mm width £66 at ECP

I think that should do you fine. The 027 doesn't quite have the power of the 096 as it's 35mm shorter, but Exide Premium has 4 yr guarantee. I'm using Exide Premium 075 battery on my TD which is 3 years old, and it's only a touch down (8%) on it's nominal Cold Cranking Amps when new. ECP want a lot for an 096 don't they!

Just done a quick reading off multimeter:
Car hasn't been driven since Monday after 6pm, wan't used over weekend and only driven under 10 miles Monday.

Standing reading 11.96v
Ignition on 11.66v
Whilst cranking over dropped to 7.4v - 8.5v (took approx 12 seconds to start this was at 2pm today)
Idling No load 14.3v - 14.4v
Idling (With all electrics on, air con, rear/front fogs/full lights with main beam/hazards/rear window demister) 13.9v - 14v

Cheers.

[Xantidote]

Hi Faz, & apologies to Simon for the hijack,

I'm no expert on low battery state, but surprised your car started with the 11.96v you quoted. Presumably the "ignition on" did not include the glowplugs. That's the bad news, and perhaps confirms you could do with a new battery.

Good news is your alternator seems to be developing the correct charging voltage.

[MikeT]

12.0v is generally considered "half-charged" and that's not good for optimum battery life. You say you fitted and used the battery off-the-shelf, which is fine for emergencies but I would have gotten it fully charged (I'm talking at least overnight connected to a 5-6A automatic charger) at the earliest opportunity.

Although your charging system is working as it should (as shown by the 14v output), it does take a fair amount of time/driving to replenish the cranking energy used on starting. My rule of thumb is 10miles per startup but you also say yours required extended cranking (appx 12 seconds) to fire up, which of course used even more (possibly 4 times more) energy which by my thumb makes it 40miles driving to recharge the battery. Also, if you're driving using heavy electrical loads such as lights, blower fans, rear-demisters etc, you can extend that recharging estimated time even further.

[RichardW]

Pretty sure it's a lot less than that Mike - we touched on this some time back (or was that another forum, where certain members were talking about regular charging of batteries.... ). A modern Alt can put out >100A - the one on the HDi with AC is 150A. So if the battery is rated say 700CCA, let's say it takes 500A cranking. Even if the crank time is 12s, this only accounts for 1.6 Ah (12/3600*500). Assuming only half the Alt's output goes back into the battery 1.6/75=0.02h to recharge, ie 1.2 minutes. So it will be recharged by the time you get to the end of the road. Unless you drive REALLY fast

If the volt figures above are correct, and taken at the battery posts, then either the volt meter is out of calibration, or the battery is shot. If the figures are taken elsewhere, then you can add in poor connections to the meter / battery problems.

[Dommo]

Carparts4less are very good for batteries, free delivery too!

This is mine

http://www.carparts4less.co.uk/cp4l/c/C ... 6fd&000020

[MikeT]

Yes, I was over-generalising as I'm unsure of the technical understanding of the OP - I may be read as being patronising/over-cautious but hope it's taken in the context it was meant - better safe than sorry, so to speak.

To clarify - off the shelf batteries are rarely (if ever) fully charged before sale. (this didn't use to be the case as the shop owner usually had a sense of duty to precharge them for the customer once bought) and for optimum life (as per the instructions) should be fully recharged before use.

While an alternator/regulator maybe can push up to 150A (at which rpm?) the car is constantly using some of that; the more loads on, the more is used for running, therefore less to recharge, and as you say Richard, the recharing process is not 100% effecient and more of that charge goes to resistance and wasted heat etc.

I think the best "layman way" to gauge it is to read the voltage before starting and read it again several hours after stopping (to allow the misleading "surface charge" to dissipate). I'd be very surprised if a battery used for 12seconds cranking is fully recharged within a couple of miles (of traffic free driving) but happy to be proved wrong.

However, my main concern would be the calcifying of the battery plates which happens when batteries are discharged for extended periods, which seems to be the case here.

[sparksie]

Hi
Something to be borne in mind is that an alternator that's rated for 100A will only deliver that output when the voltage at the alternator is far enough above that at the battery to overcome the internal resistance of said battery. Ohms law will always govern this and you will VERY RARELY see 100A charging current for more than a couple of seconds.
In normal use, a discharged battery will have a voltage of 12.1V and the alternator will aim to generate 14.4V. This means that, for the first few seconds, until the battery voltage starts rising, we have a 2.3V charging potential. This has to overcome the resistance in the cables, connectors, clamps etc AND the theoretical "internal resistance" of the battery itself. The latter is hard to quantify, as it changes with temperature, state of charge, degree of sulphation and electrolyte level, but 0.05 ohms would be pretty good. This gives us a current of 46A from our 100A alternator, (assuming all leads and connectors are made of superconductive materials and not liable to cause resistive conditions)! Even this will only be for a moment, because the battery voltage will rapidly rise, reducing the charging potential and consequently the current.
This is why it's important to maintain clean contacts in the starter cables and to always use the correct size fittings for both the cable and the stud. With such low voltage you need to maximise contact area in order to minimise resistance. A very small resistance can half the charging current and may be nearly impossible to detect, unless you're lucky enough to notice a warm joint.
In the real world, it takes roughly 10 minutes at >1500rpm to replace the current taken by the starter, assuming no extended cranking and no faults in the starter itself.
Sorry for long boring speech, but this is my area...

[Hell Razor5543]

Not a boring long speech, but a useful lecture imparting important knowledge. For a boring long speech ask a politician a question!

[MikeT]

Sorry for long boring speech, but this is my area...

I found it quite the opposite - clear, concise and (presumably) very accurate. WAY better than our laymans efforts imo, and a much welcome addition.

Appreciated

[myglaren]

Sorry for long boring speech, but this is my area...

I found it quite the opposite - clear, concise and (presumably) very accurate. WAY better than our laymans efforts imo, and a much welcome addition.

Appreciated

Agreed!
Although I knew this in a very unformulated way it is always helpful to have a clear and informed description.

Boringness=0

[momag46]

Moving back a bit..

The other week my V6 alarm went off at 2 in the morning - the car was locked up in the garage. I just unlocked it to stop the alarm (it had been going for only about 5 minutes). a week later the car wouldn't start until I topped up the battery, it's now aok.

Am I right is thinking that if the car is left unlocked, the system keeps checking to see if anyone is getting in or out, therefore it uses more battery than if it was locked and the alarm was activated

Maurice

[harryp]

Good post and two penneth from me...
Don't forget, max charge should not exceed the 10 hour rating - i.e 65 amp Hr batt = 6.5 amps.
(Massively exceed this and small bits get blasted off the plates)
As the batt voltage rises, the charging current reduces.
It takes very approx 50% more to charge a car battery than it uses.
Despite what it says on the battery, it's always best to trickle charge a new (or especially a flat) battery for at least 24 hours, preferably over the weekend. HTH