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Thread: At rest Voltages. Post start voltages on a 1999 S type 4.0 V8.

  1. #1
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    At rest Voltages. Post start voltages on a 1999 S type 4.0 V8.

    Battery is a three year old Lucas LPO 19.

    https://www.tayna.co.uk/car-batteries/lucas/lp019/

    Meter used is a Fluke 116 true rms multimeter.

    Battery voltage after an over night of 12 hours at approx 4 degrees C:

    12.36V

    Battery Voltage as soon as car starts:

    13.72V

    Battery voltage after engine goes "Off choke" and revs settle down to normal tickover:

    13.77V

    Battery voltage after 10 minutes at tick over:

    13.45V

    Battery voltage with every electrical thing turned on, except power windows as I couldnt reach the switches, engine at tickover:

    12.75V With a lot of whistling from the alternator...

    Hope this is what you needed Jim.

    Actually, looking at the pre start voltage, either I have something pulling on the battery or it's about ready for a new one?
    2001 3.0 SE Auto, Satnav, winter pack. Dark Blue, all the toys.
    2004 3.0 Sovereign Estate. Winter pack. Fixed. For Sale.
    2005 Estate X type 2.2 Sport.
    2000 V8 3.2 XJ8 LWB. "Prom" car. Lovely. Should sell this one too really...
    2005 "AllyCat", 3.0 XJ6 SE.
    2000 S type 4.0 V8. Latest toy.
    VFR800A and a VFR 800F

    Still beating cancer. Trevor 2, Cancer 0.

    Sure I took the Red pill....

  2. #2
    Senior Member Jim_S-V6_2004's Avatar
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    Yep that's great, very many thanks Lost One, much appreciated, this completes my research on S Type charging systems.

    ...


    So for your car, as per the 3.0-litre and the 2.5-litre S Types too, it cannot fully charge the battery because modern batteries are calcium alloy plated and need constant 14.4 volts to reach full charge.

    From your values, your 4.0-litre has the same charging system as the pre-2002.5 3.0-litre S Type, which outputs a nominal 13.8 volts continually.

    The post-2002.5 3.0-litre and 2.5-litre S Types have the same L3B charging system which outputs 15.3 volts for 5 to 6 minutes then 13.6 volts for the rest of each journey.

    (Note: the 4.2-litre V8 and the STR have SC1 and the 2.7-litre Diesel S Types have SC2 charging systems, which provide variable 14-15 volts according to the battery's state of charge, so they do fully charge calcium and AGM batteries).

    Therefore, like my 2.5-litre S Type, the battery charges to around 12.2 to 12.4 volts, which equates to 75% to 80% of full capacity.

    So... Yours is bang in range.

    It's not a problem in frequent use but needs a charge on a home charger now and then in winter or if it's infrequently used or only does short journeys.

    If the car is difficult to start, the battery can go flat in 6 to 10 tries. If headlamps are left on unintentionally, it can go flat in a couple of hours. If there's a boot light or courtesy light left on it can go flat overnight.

    So charge your battery overnight on a house charger, preferably a smart charger like the C-Tek MXS 5. It should show 12.7+ volts after you reconnect it in the car.

    To check its condition after charging, turn on your headlights with the engine off and measure the voltage at the battery terminals after 3 minutes with the headlamps still on.

    It should be 12.6 volts. 12.5 volts is acceptable, less is weak.

    If you don't have access to a load tester you can make one with 4x 55 Watt headlamp bulbs - connect them in parallel, and connect them across the battery after disconnecting the battery positive cable.

    Together they draw about 18 Amps.

    After one hour a good fully charged 100A/h battery from 12.7+ volts should still read 12.3 to 12.5 volts, 80% charge. It should recover within a few minutes to 12.5 to 12.6 volts. Don't leave the battery for more than an hour with 4 bulbs, it could go dead flat if it's weak. And don't let it go below 12.0 volts, and recharge it immediately after this load test.

    I tested my Merc's battery on the bench with only one 55 Watt bulb (4.5 Amps) and it took about 20 hours to go flat as expected, drawing 90Amp/hours, from 100Amp/hours to 10%, still dimly glowing, and measured 12.1 volts if I remember.

    If you do this don't forget to stop at 20 hours or 12.1 volts, and recharge the battery or it can be damaged.

    Remember the S Type's control modules start to misbehave below 12.2 volts. So at 12.0 volts a battery is technically dead flat even though it can still start the car.

    Thanks again bud.

    .
    Last edited by Jim_S-V6_2004; 24-12-18 at 09:29.

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    Looks like they used the same or a similar "charging solution" through the full range of S type cars then. What were Jaguar's engineers thinking?

    So the solution is to put a conventional Lead/Acid type battery on it? Because I'll go that route if necessary. I'm not always in a position to give the car battery a trickle charge.

    Also kind of confirms my thoughts on why the car cigar lighter was completely incapable of recharging the lithium booster pack I used to start derv engined light tower.

    I have a Ctek 5, I also have a very low current one that I use to keep my bike topped up, that's designed for lead acid batteries but only gives about .4amp output.

    I have a "conventional" load tester, the one with two prongs and a big lump of resistance between the cables. Basically puts a dead short across the battery, very useful in the days when you could check for dead cells as they used to bubble when you used the tester.
    Last edited by Lost it; 24-12-18 at 10:21.
    2001 3.0 SE Auto, Satnav, winter pack. Dark Blue, all the toys.
    2004 3.0 Sovereign Estate. Winter pack. Fixed. For Sale.
    2005 Estate X type 2.2 Sport.
    2000 V8 3.2 XJ8 LWB. "Prom" car. Lovely. Should sell this one too really...
    2005 "AllyCat", 3.0 XJ6 SE.
    2000 S type 4.0 V8. Latest toy.
    VFR800A and a VFR 800F

    Still beating cancer. Trevor 2, Cancer 0.

    Sure I took the Red pill....

  4. #4
    Senior Member Jim_S-V6_2004's Avatar
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    No, bud, I hadn't finished my post, reread it.

    The different models have 4 different charging systems.

    Your battery is fine, just charge it and test it as I've described.

    Read my post again and edit yours, then I'll edit this one to match.
    Don't believe anything I say - Alzheimer's is setting in!
    Links:
    The Coffee Shop Thread: http://www.jaguarforum.com/showthread.php?t=65758
    S Type Stickies: http://www.jaguarforum.com/forumdisplay.php?f=104[/SIZE]

  5. #5
    Senior Member Jim_S-V6_2004's Avatar
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    It's not possible to find a "non-calcium" battery except on a scrap heap.

    .

  6. #6
    Senior Member Lost it's Avatar
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    I accept the challenge! I happen to know someone who used to build them to order for the classic car market... Not cheap though.
    2001 3.0 SE Auto, Satnav, winter pack. Dark Blue, all the toys.
    2004 3.0 Sovereign Estate. Winter pack. Fixed. For Sale.
    2005 Estate X type 2.2 Sport.
    2000 V8 3.2 XJ8 LWB. "Prom" car. Lovely. Should sell this one too really...
    2005 "AllyCat", 3.0 XJ6 SE.
    2000 S type 4.0 V8. Latest toy.
    VFR800A and a VFR 800F

    Still beating cancer. Trevor 2, Cancer 0.

    Sure I took the Red pill....

  7. #7
    Senior Member Jim_S-V6_2004's Avatar
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    Quote Originally Posted by Lost it View Post
    I accept the challenge! I happen to know someone who used to build them to order for the classic car market... Not cheap though.
    .
    So that you know and for anyone else who is reading...

    The old batteries from when I started driving in the 60s are lead/acid.

    Calcium batteries are also lead/acid too.

    The difference is in the alloys used to make the electrodes (plates): the old batteries used lead & antimony and charge fully to 12.6 volts on 13.6 volts from the alternator, but the calcium ones use lead & calcium, or some use lead & calcium & silver. Those need 14.4 volts to fully charge to 12.7 volts.

    "Calcium/calcium" means both the positive and the negative plates inside are made of lead & calcium alloy. Those batteries need a bit more, 14.8 volts, to fully charge.

    Some people call them all "Flooded wet cell", or "lead/acid" or EFB (Enhanced Flooded Battery). The term "SLI" means the purpose of the battery is Start, Lighting, and Ignition.

    They all have at least a vent hole if not cell caps.

    The ones with cell caps need to have the electrolyte level checked periodically and topped up with distilled water if it's lower than 1/4 inch above the plates. The ones without cell caps are "sealed and maintenance free". But the vent hole is to connect a vent tube which leads outside the car for the acid vapour to vent safely if the battery gets hot.

    Some manufacturers like Varta strictly forbid the owner from checking and topping up the electrolyte, and insist that we go to a mechie!

    We're better than that.

    Then there are AGM ("Absorbed Glass Matting") batteries, which are sealed, maintenance free. Those have a fibreglass mat wrapped around the plates and the acid is semi-solid or solid, not liquid. Those need 14.4 to 14.8 volts to fully charge

    "Start/Stop" batteries can be of either type.

    Then there are Gel (jellified acid) batteries but those are for other applications, not for cars.

    .

  8. #8
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    I have "gel" batteries on my bike. Because the battery isn't mounted level.
    2001 3.0 SE Auto, Satnav, winter pack. Dark Blue, all the toys.
    2004 3.0 Sovereign Estate. Winter pack. Fixed. For Sale.
    2005 Estate X type 2.2 Sport.
    2000 V8 3.2 XJ8 LWB. "Prom" car. Lovely. Should sell this one too really...
    2005 "AllyCat", 3.0 XJ6 SE.
    2000 S type 4.0 V8. Latest toy.
    VFR800A and a VFR 800F

    Still beating cancer. Trevor 2, Cancer 0.

    Sure I took the Red pill....

  9. #9
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    Do the voltages (as measured at the battery) on the various cars (except the ones with SC1/SC2) rise with engine revs at (say) 2000rpm?

  10. #10
    Senior Member Jim_S-V6_2004's Avatar
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    Quote Originally Posted by 04str View Post
    Do the voltages (as measured at the battery) on the various cars (except the ones with SC1/SC2) rise with engine revs at (say) 2000rpm?
    .
    Just slightly on my 2.5 litre, 04str.

    L3B charging system.

    From 13.6 to 13.7 or 13.8 but not to 14 volts.

    It came down to 13.5 or 13.4 as the battery charged, then varied between these high and low values according to the car's current demand.

    It starts off at 15.3 to 15.1 for the first few minutes from starting the engine, 5 to 6 minutes when cold, less when the engine was already warm.

    I documented it accurately in a thread in our Stickies long ago but I asked Ian D to delete it when it became a long dragged out dispute with jag_driver saying I was wrong and misinforming members.

    I think the two related "Project Electron" threads still exist somewhere.

    .

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