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

  1. #71
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    Quote Originally Posted by Jim_S-V6_2004 View Post
    I think your battery has surface charge still.
    OK, after applying a load I got 12.7V.

    I don't know its chemistry other than what I posted where it says Silver Calcium. It's not going to be lead/antimony in that case. Besides, you keep saying those cannot be bought.

    I've no idea what can or cannot be bought short of polling manufacturers but seems to me this battery has charged with 13.6V.

    I can see that various sites say to charge FASTER you want 14.4V but they don't say you NEED 14.4V and my battery apparently doesn't.

    There are probably sites which confuse wanting with needing, too.

    You can of course use a much higher voltage but at some point get fast gassing - you get gassing / more gassing anyway if you charge a full battery or nearly full battery with too high a voltage.

    As I've said before I don't see any point in discussing EFB or AGM as apparently they're not suitable and anyway cost too much.

  2. #72
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    Quote Originally Posted by Jim_S-V6_2004 View Post
    .
    OW where and what are you reading?

    Because this isn't how the L3B charging system in the 2.5-litre and post-2002 3.0-litre S Types works..........................


    ........................Have you monitored your cars closely to see what they do?

    .
    On my IDS/SDD laptop I have lots of JTIS Technical service publications, amongst which is a description of the charging system. I am only concentrating on the L3B system, & in that, it states that the PCM determines the time that the alternator charges at the higher 15.3 volts, before dropping to 13.6 volts, it also states these figures are measured with the alternator at 25 degrees C & that they will decrease with a rise in temperature or current flow &
    the time periods are variable depending upon the temperature & battery voltage. The Target voltage of the battery varies between 14 & 15 volts depending upon the ambient temperature & the vehicle operating conditions. Once this target voltage has been achieved, providing the vehicle has been operating for at least the shortest time period, the ECM will reduce the voltage regulator to the minimum setting of 13.6 volts
    That suggests to me that the ECM/PCM monitors the battery & only reduces the charge voltage when it has detected the battery has reached it's target voltage.
    I have monitored my cars battery voltage as you know from previous posts, & indeed have just checked it again on a 20 mile round trip (10 each way with a very short stop in between) using my new iCarsoft LR V2.0. From cold, having just unlocked car & connected the scanner, battery voltage was 12.3, rising to 12.5 after interior lights etc had switched off. This is measured at the data link connection. Started car & saw 15.1 max which dropped to 14.8/9 after a few moments & remained at that for about 10 min's at which point it dropped to 13.4 & remained fairly static at that for the rest of the journey there. On restarting the car, voltage was 14.9 for about a minute, maybe less & then dropped back to 13.4. It stayed at this for at least half of the return trip, but by the time I was home it had dropped to 13.2, but both engine & ambient temperatures had risen, which ties in with the description above.
    Also interesting is the battery specs I found in amongst all this. For the earlier 3.0l & 4.0l cars the spec's actually mention Lead/Antimony batteries. For the 2.5l & 3.0l cars fitted with the L3B alternator it now mentions Lead/Calcium batteries as well, suggesting Jaguar were aware of the differences. It seems to me that they changed the charging system for a reason, maybe it could just have been that they knew the old system wasn't completely suited to the voltages required for Lead/Calcium batteries, so changed to one that was. That said, in 12 years & over 160,000 miles I never had any battery issues with our old 3.0l.
    All I can really do is reitterate that I have had fairly long term experience of two different spec S types, neither has ever given me any battery related issues, I've never had to top up charge either of them & both have given very good battery life, probably beyond reasonable expectations. Time will tell with Mrs O's new 2.5.

    Regards, OW
    1999 S Type 3.0L SE, A truly lovely old girl that's served me well. Probably the best car I've had. Now retired.
    02.5MY (X202) S Type 2.5L SE, 58,000 miles, full Jag s/h, all papers, MOT's, receipts etc from new when purchased.
    2006 X type SE 2.2 Diesel. Supposed to be Mrs O's economical commuter car.
    2004 (X202) 2.5L Sport plus, to replace the 3.0L

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  4. #73
    Senior Member Jim_S-V6_2004's Avatar
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    Thanks OW.

    Yes correct, the length of the time that 15.3 volts is upheld is exactly determined by the battery voltage and ambient and coolant temperatures.

    To measure the battery voltage to be between 14 and 15 volts can only be done by turning off the charge voltage I guess. No battery is going to put out 14 volts before charging.

    Anyway, it's only 15.3 volts and 13.6 volts in the L3B charging system.

    If anyone can find new lead/antimony 017 or 019 batteries that will be icing on the cake.

    If the spiral cell Optima AGM batteries turn out to.be lead/antimony or even pure lead as they say 99% and can fully charge at 13.6 or 13.8 volts then those will be worth considering as they are even more suited to frequent starts and deep discharge, according to their propaganda.

    Battery tech is shifting sands, many "experts" disagree, and very few manufacturers are willing to specify their "secret alloy" formulae. And their sales staff are unaware of technical details and are unwilling to consult their technical or production staff.

    I believed that Varta's Silver Dynamic batteries were non-calcium (i.e. lead/antimony) because there was absolutely no info on any Varta website which mentioned calcium, until Jag_driver found a single data sheet on a blooming Vietnamese Varta website which stated that the PowerFrame contains calcium-silver alloy, hence the "Silver" Dynamic range name.

    We have no clear info on their Blue Dynamic range, only putting 2 and 2 together to make 5 - or maybe 4.

    There are new battery technologies using carbon and other materials under development and those have different requirements.

    Anyway, for our individual needs it's enough to determine our own batteries' State of Charge and if it's low, top them up on a Smart Charger.

    Note that calcium batteries will be killed (i.e. their nominal capacity dramatically reduced) if you use an old dumb charger to fully charge them if they overheat. Those chargers can be used for a couple of hours to kick-start smart charging when a calcium battery is so discharged (less than 10.0 volts?) that a Smart Charger trips out.

    The other way is to connect a good second battery in parallel with the discharged battery and charge them simultaneously with the Smart Charger until you can disconnect the good battery and continue charging the discharged one.

    By the way, those members who installed Solar Chargers, how are they performing in cloudy conditions, chaps?

    .
    Last edited by Jim_S-V6_2004; 10-01-19 at 17:27.

  5. #74
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    Rechecked and it's back to 12.8V but I don't know when it changed.

  6. #75
    Senior Member Jim_S-V6_2004's Avatar
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    Quote Originally Posted by 04str View Post
    Rechecked and it's back to 12.8V but I don't know when it changed.
    .
    Thanks 04str.

    That's normal, when there's no load, a battery's voltage will drift up again. It happens because of reversal of the internal chemical reaction which occurs when a load is applied and current is drawn.

    It's like a soft spring, when you pull it a resistance is felt and the spring is stretched beyond its natural length temporarily. Then when it's released, over time, it compresses slightly back towards its original or previous "at rest" length, but never quite gets there until it is fully charged again.

    In the same way, when it is fully charged, it is overcharged, effectively it is over-compressed to less than its natural or "at rest" length, then stretches slowly over time towards its natural or previous "at rest" length.

    Anyway, your battery is evidently in top condition and that's great.

    If it was weak it would drop to say 12.2 volts under load, then drift up to even 12.6 volts or thereabouts with no load over a few hours.

    That's why it's so important to measure a battery with a load on it. I like 3 minutes with headlamps on and measure with them still on. As I said, 10 Amps will only take about 0.16 AmpHours per minute out of the battery's 100AmpHours of capacity.

    How did/do mechies test a car battery if they don't have one of Lost One's brilliant new-fangled conductance testers?

    By putting a Great Big Fat Grik Wedding Load Tester on it which draws over 200 Amps and keeping the button pressed for 10 seconds and read the voltage and CCA measurements with the button still pressed.

    Am I right?

    Or am I spreading duff gen - yet again?

    Hopefully you can now see we're on the same side?

    .

  7. #76
    Senior Member FastEddie's Avatar
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    In the olden days it was far easier to trick an alternator in to giving you a bit more output.

    Easily done by putting a diode in series with the internal field winding wire ( D+ ) to the regulator.

    As you drop 0.6v across the diode , the regulator would then give you 14.4 instead of 13.8v

    Could retrofit with a standard alternator and fit a field winding light to IGN+ and away you go ?

    It would leave you with a battery light controlled by the PCM that you could disconnect / mod to suit.

    The field winding lamp needs to be 2.0 / 2.2w to get excited , original is probably an led in the dash.

    Interesting reading that this model slipped through the net in this way , my ST 220 sits at 15v all day long.

    I modified many in the 80's to do this , easily fitted cars universally too by moving the casing round 1 bolt.
    2009 X358 XJ LWB 2.7 Tdvi , Liquid Silver , 100k+ and going strong.
    Bumper reflectors drilled and fitted with 3W side marker lights.
    Fog lamps / DRL running with HID colour match of dipped beam.



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  9. #77
    Senior Member FastEddie's Avatar
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    Quote Originally Posted by Jim_S-V6_2004 View Post
    .
    Thanks 04str.

    That's normal, when there's no load, a battery's voltage will drift up again. It happens because of reversal of the internal chemical reaction which occurs when a load is applied and current is drawn.

    It's like a soft spring, when you pull it a resistance is felt and the spring is stretched beyond its natural length temporarily. Then when it's released, over time, it compresses slightly back towards its original or previous "at rest" length, but never quite gets there until it is fully charged again.

    In the same way, when it is fully charged, it is overcharged, effectively it is over-compressed to less than its natural or "at rest" length, then stretches slowly over time towards its natural or previous "at rest" length.

    Anyway, your battery is evidently in top condition and that's great.

    If it was weak it would drop to say 12.2 volts under load, then drift up to even 12.6 volts or thereabouts with no load over a few hours.

    That's why it's so important to measure a battery with a load on it. I like 3 minutes with headlamps on and measure with them still on. As I said, 10 Amps will only take about 0.16 AmpHours per minute out of the battery's 100AmpHours of capacity.

    How did/do mechies test a car battery if they don't have one of Lost One's brilliant new-fangled conductance testers?

    By putting a Great Big Fat Grik Wedding Load Tester on it which draws over 200 Amps and keeping the button pressed for 10 seconds and read the voltage and CCA measurements with the button still pressed.

    Am I right?

    Or am I spreading duff gen - yet again?

    Hopefully you can now see we're on the same side?

    .
    Bang on the money Jim , with a standard 500 amp discharge tester from Durite or similar. I still have one.

    Jabbing the test tips in as firmly as possible in order to not impersonate a plasma cutter on the terminals.

    Then of course , feeling the warmth from the glowing orange resistance wire between the asbestos shields

    2009 X358 XJ LWB 2.7 Tdvi , Liquid Silver , 100k+ and going strong.
    Bumper reflectors drilled and fitted with 3W side marker lights.
    Fog lamps / DRL running with HID colour match of dipped beam.



  10. #78
    Senior Member Jim_S-V6_2004's Avatar
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    Quote Originally Posted by Lost it View Post
    Missus only allows me to work on the cars one day a week because of my health, so no. last weekend was speakers.
    .
    I'm.glad she does and even more happy if you're complying with her limits bud.

    .

  11. #79
    Senior Member Jim_S-V6_2004's Avatar
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    Quote Originally Posted by FastEddie View Post
    In the olden days it was far easier to trick an alternator in to giving you a bit more output.

    Easily done by putting a diode in series with the internal field winding wire ( D+ ) to the regulator.

    As you drop 0.6v across the diode , the regulator would then give you 14.4 instead of 13.8v

    Could retrofit with a standard alternator and fit a field winding light to IGN+ and away you go ?

    It would leave you with a battery light controlled by the PCM that you could disconnect / mod to suit.

    The field winding lamp needs to be 2.0 / 2.2w to get excited , original is probably an led in the dash.

    Interesting reading that this model slipped through the net in this way , my ST 220 sits at 15v all day long.

    I modified many in the 80's to do this , easily fitted cars universally too by moving the casing round 1 bolt.
    .
    Well there are 2 or maybe 3 different charging systems here Eddie.

    I don't know anything about the 13.8 volt systems fitted to the 4.0-litre and 1999-2002.5 3.0-litre S Types yet, or if they are the same.

    The L3B looks easy to modify as it only has a single high/low control.line.

    My thought was to delay the switching on this control line, to extend the time that the 15.3 volts is generated.

    For example, I don't think a 15 or 20 minute extension would damage the battery but would restore most of the charge lost by starting, and maybe a little more each journey. And it should or might keep a fully charged calcium battery above 12.4 volts at least?

    That can be done easily with an NE555 timer, or a binary counter chip. We could also make it variable with a knob!

    We would have to test in practice to see how long we could push this delay timer.

    Since I no longer have an S Type... We would have to rope in an unsuspecting but co-operative 2.5-litre Owner??

    You see how I'm craftily sewing you and a.n. other into my web?

    .

  12. #80
    Senior Member FastEddie's Avatar
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    The quickest fix would be to use an Optima yellow top battery , these will take 15.5v up to a case temperature of 50oC

    Leaving it on 15.3v permanently with a thermostat on the battery case that drops to the low charge rate at 30oC would be fine.

    You could even do this with a Calcium battery , switching to low rate at the closest ambient differential possible in hot weather.

    The calcium batteries in both of my ST's , regardless of load / weather sit at 15 volts all day long , both originals did 8 to 9 years.
    2009 X358 XJ LWB 2.7 Tdvi , Liquid Silver , 100k+ and going strong.
    Bumper reflectors drilled and fitted with 3W side marker lights.
    Fog lamps / DRL running with HID colour match of dipped beam.



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