Member Since: 05 Feb 2006
Location: ¯\_(ツ)_/¯
Posts: 17932
drivesafe wrote:
If the voltage from the alternator was the same as it would have been from your battery charger, then the alternator would have been providing the same or more charge current.
No, not the case. The voltage provided by the alternator was higher than that provided by my charger.
drivesafe wrote:
I note how you posted up all the specific details except the most relevant one. You conveniently neglected to mention the voltages at which the battery was taking the different charges.
No, I didn't leave it out:
Robbie wrote:
From there there will be a further decline and within 3 or 4 minutes the battery will be receiving around 4 amps at 14.7v before decaying further to around 2 amps at this same voltage.
After its charge on my Ctek my battery is now at 98% SoC and I am now off to York.
Land Rover - Turning Drivers into Mechanics Since 1948
Member Since: 23 Feb 2006
Location: Gold Coast, Australia
Posts: 867
Good evening Robbie, and my apologies, your privies post did say it was about the earlier post ( which I missed ) and while you listed the alternator’s voltage, you didn’t list the battery chargers.
Anyway, going on that post, once again, you have the cart before the horse.
The alternator was not responsible for the current decreasing at the battery.
As the battery was near fully charged, the battery reduced it’s current draw from the alternator ( based on the voltage being applied to the battery at the time ).
If the battery had been in a lower SoC, then it would have continued to draw a higher current for a longer period.
In all battery charging situations, in the final 20% of the charging cycle, the battery itself governs the current draw ( again based on the voltage being applied to the battery ), not the device supplying the charge.
You could have a 1,000 amp battery charger, but if the voltage is not high enough then the battery will only draw a small amount of current.
So your post literally confirms what I have been saying, the alternator is NOT controlling the current directly, and can not do so without reducing the output voltage.
And once again, if, according to you, lowering the voltage increases the current, and therefore increases the load on the motor, why is it that Land Rover, and many other makers of vehicles, are doing everything they can to get the vehicles to operate at lower voltages, because if your theory was correct, this would all be a waste of time as it would increase fuel usage.2008 TDV8 RR Lux + 2009 D4 2.7
25th Jul 2015 11:46 am
Robbie
Member Since: 05 Feb 2006
Location: ¯\_(ツ)_/¯
Posts: 17932
Sorry about the late reply, but had a great time in York.
drivesafe wrote:
…and while you listed the alternator’s voltage, you didn’t list the battery chargers.
I took it as read that you would know the typical output voltage of a battery charger. Nevertheless, to remove all doubt I did say that it was at a lower voltage than that provided by the alternator - the key demonstrable comparison I was using. For completeness I have included a numeric screenshot towards the end of this post with the battery charger voltage as measured at the terminals.
drivesafe wrote:
The alternator was not responsible for the current decreasing at the battery.
If the current is decreasing below the level at which the battery will accept it and the SoC remains the same with the voltage at the alternator being higher there is no other plausible explanation; perhaps this is evidence to suggest the JLR technical library papers are correct.
drivesafe wrote:
As the battery was near fully charged, the battery reduced it’s current draw from the alternator ( based on the voltage being applied to the battery at the time ).
I've covered the voltage part already and the ability of a battery to absorb current as its SoC increases is basic battery charging stuff, but we can look into it in more detail:
Perhaps the first thing to note is that rate of charge is a function of voltage and available amps until the point where the battery reaches its acceptance limit. Nothing new there then and we can see the familiar graph shape of amps over SoC. So lets look at the D4 system during and after start:
Click image to enlarge
Looks textbook to me and as I covered earlier at the early part of the cycle the alternator is behaving just like a regular alternator. But the BMS is still active and has all the information required to exceed normal charging limits. As a result it has ramped up the voltage to 15v, and maintains it whilst the amps decline. As the amps decline due to the acceptance rate falling the BMS drops the voltage to 14.8v or so as the curve flattens out to just below 20 amps. Other than the BMS being able to exceed the normal limits (which can still be used if the BMS fails) this is all normal and the rate of acceptance of around 18 amps is pretty much on the money for an AGM at 87~88% SoC. Again, all as I covered earlier on this thread. So if everything continued as per a normal alternator, without BMS intervention, the amps would remain at this level and slowly decline over the next few hours of driving as the SoC increased towards 100%:
Click image to enlarge
No wait, the volts are holding steady at around 14.8v but the amps are falling fast. In fact within 2 minutes the current is down to only 4 amps.
drivesafe wrote:
In all battery charging situations, in the final 20% of the charging cycle, the battery itself governs the current draw ( again based on the voltage being applied to the battery ), not the device supplying the charge.
So has the battery has been filled in seconds and is now approaching a high state of charge? Nope, the SoC has remained at around 87~88%. Is the alternator short of power? Nope, by design it can provide enough for all conditions and only 3 minutes ago it was kicking out over 50 amps. Does the alternator need more RPM? Nope, its capable of almost full output at idle and in this case the RPM and speed is increasing. Is the voltage regulator struggling with the change in RPM? Nope, it holds steady through numerous gear changes. Is the battery overheating? Nope, it is holding at around 24ËšC. So the conditions have not demonstrably changed, the physics and battery chemistry remain unaltered. Is it possible that JLR's technical papers are correct and that they can restrict the current available to the battery and choose to do so when the BMS parameters are met and the SoC is above 75%?
But what about this regenerative power, when does that start to kick in? Well, pretty early in the journey and the BMS sort of tests the water as soon as it can. Winding back a few seconds we can see throttle being applied yet both the amps and volts take a bit of a dip. The BMS is prioritising engine power delivery over alternator output. A few seconds later there is a brief period accelerating then coming off throttle where the conditions are met for prioritising electrical power (watts = volts x amps) and both are seen to rise:
Click image to enlarge
drivesafe wrote:
You could have a 1,000 amp battery charger, but if the voltage is not high enough then the battery will only draw a small amount of current.
This is true, but it is you and not I that keeps introducing voltage control as the sole means to control current to the battery. But back to that battery charger piece; after we turned off the ignition just after the system was producing 14.8v at around 87~88% SoC but only 2 amps were being drawn through the battery terminals:
Click image to enlarge
If the SoC really has remained at around 88% and the charge rate prediction is at an amperage in double digits yet the amps at the terminal are down at just 2 amps, could we use a battery charger to double check that the battery really is capable of absorbing a higher current, even if the voltage is a bit lower? Well, that's what I did when I plugged in my Ctek:
Click image to enlarge
Hmmm, I would need a bigger battery charger to see how high the current could go and still be absorbed by the battery at 88% SoC. Indeed, my Ctek topped-out at 7.3 amps on the clamp meter and due to voltage drop only 13.2v made it to the terminals, even with the higher voltage mode selected. But even with the BCM taking 3.27 amps the current flowing into the battery was still doubled and demonstrated that it could take a higher current than the 2 amps the alternator was providing moments before. Of course, we already suspected it would as it had done so during the first few minutes after start in near identical conditions, plus the charge rate vs SoC charts predicted it.
drivesafe wrote:
So your post literally confirms what I have been saying, the alternator is NOT controlling the current directly, and can not do so without reducing the output voltage.
My posts have never confirmed this - the data is the data and none of this is revolutionary. If we wind back the clock a few years a number of us had to learn the new system rather quickly when the BMS issues started to appear. As covered earlier, back then I could only datalog all the parameters, spin them in Excel and compare them with the predictions as I could not see the sensed values at the BMS and BCM. I can now compare real-world data, sensed data and the predictions to spot the bad PCM, BCM, BMS, battery or alternator. Many a forum member has driven around with my voltage, current and battery temperature data loggers attached to their vehicles.
Click image to enlarge
drivesafe wrote:
And once again, if, according to you, lowering the voltage increases the current, and therefore increases the load on the motor, why is it that Land Rover, and many other makers of vehicles, are doing everything they can to get the vehicles to operate at lower voltages
For a given electrical load if you reduce the voltage the amperage has to increase. I feel I am repeating myself when I remind you that it is you that is claiming that reducing the voltage is the sole means by which power is being reduced. I do not recognise your statement that motor manufacturers are doing everything they can to reduce voltages and it remains un-attributed.
By contrast the desire to increase voltages to reduce the current is well published by SAE and major manufactures. Indeed, the SAE discussed an increased automobile standard voltage as early as 1988. If it was not for the march towards hybrid vehicles the 42v standard may have been adopted to power the increasingly energy-hungry electronic systems in modern vehicles. Stealing a quote from SAE the other arguments for a higher voltage included the reduction of weight in the wiring system, improved stability, and reduced voltage drop. With three times the voltage, thick conductors can be reduced to a third of the cross-section, and at the same time the relative voltage drop can also be reduced to a third. For the same cross-section, the relative voltage drop is now no more than one ninth. The voltage level resulting from these arguments was so close to three times the present voltage that 42 V became the choice for the second voltage level.
I will keep within the forum rules and I will not lower myself to your level, but I am sure you know that I found your manners and tone to be completely inappropriate for this forum as that is what you intended. Recently you have questioned my education, background, intellect and even called me irresponsible. You have pored scorn on some pretty basic physics and dug yourself some rather large holes on power equations, Ohms Law (have a quick look at my Quiescent Current Guide) and you even threw in an incandescent bulb as an example of a constant resistor so we had to cover non-Ohmic components too (see my Glowplug guide for another use of non-Ohmic filaments to increase resistance and lower current).
This is not a soulless large American forum full of internet heros. The UK is small and forum members / forum members meet each other. We drink and eat in each other's kitchens, we work on each other's cars. Quite a few members know who I am and what I do. I have even worked with some forum members in my day job and others know people I work with. Quite simply there is nowhere to hide.
That said, I have tried to help you like I would any other forum member. Indeed, it would be advantageous for you to know what the BMS system does to the voltage and current supplied to the battery as you sell dual battery controllers. It would be great if you understood how they work with the BMS and in what conditions they do not. If you have access to a standards portal I can recommend reading the supporting papers on the SAE database. I will not take offence if you utterly dismiss anything authored, contributed or originated by me. In the interim, as a free safety tip, please do not connect a tiny resistor to a high voltage. Resistors are sold with wattage limits and this is a function of volts x amps. Even if you managed to keep the amps really low the potential difference can be enough for it to overcome the insulation or just jump the gap.
A long post, but it is evidence based. DSO downloads, pass/fail waveforms and known-good CSV data is available to the technical gurus on request.
Land Rover - Turning Drivers into Mechanics Since 1948
Member Since: 23 Feb 2006
Location: Gold Coast, Australia
Posts: 867
Remember this statement of yours QUOTE “Debate the fact, physics and empirical data only†END QUOTE
Well this statement totally defies the laws of physics.
QUOTE “If the current is decreasing below the level at which the battery will accept it and the SoC remains the same with the voltage at the alternator being higher there is no other plausible explanation; perhaps this is evidence to suggest the JLR technical library papers are correct.†END QUOTE
So far you have changed your Theory so many times and it’s still the stuff of fairytales.
But just for the sake of FACTS, if according to your fairytale, and the D4’s electronics was able to restrict the current output of the alternator, and reduce the current being supplied to a battery that is not fully charged, without lowering the alternator’s voltage level, then the “LAWS OF PHYSICS†kicks in and the BATTERY, because it will try to pull more current than is being provided to it, the current being pulled by the battery will result in pulling the down the voltage level of the D4’s electrical system.
So again, if the D4’s voltage was at 14.7v and the current draw of the battery was around 2 amps, then contrary to what you mistakenly ASSUMED, the alternator’s current was not reduce by some mythical electronics in the D4, the battery was near fully charged and didn’t need a current flow of more than 2 amps to finish off it’s charge state.
BTW, having the voltage of an alternator pulled down by a vehicle's current requirements is a very common occurrence. Millions of millions of times everyday, vehicles all over the world, when stuck in slow moving traffic, at night, in rain, with the windscreen wipers going, the entertainment system on, heaters and fans running and headlights on.
With the vehicle moving slowly and the motor not turning fast enough for the alternator to be able to produce enough current to meet all the current demands of the vehicle, the alternators voltage is pulled down by the vehicle's current load, and as the LAWS OF PHYSICS causes the current to drop as the voltage drops, then eventually, the voltage will drop to a point where the current output of the alternator ( which remains constant at any voltage ) equals the current demand of the vehicle, and thats where the voltage level stays until either devices are turned off in the vehicle and/or the vehicle's speed increases, allowing the alternator to produce more current and in doing so, allows the voltage to rise again.
And further to demonstrate this point, many older drives may have come across situations where they have been stuck in traffic for long periods, and after a while they have noticed the headlights getting duller and more yellow.
This is exactly what occurs when an alternator can not produce enough current to meet the vehicle’s demands, confirms how as voltage drops so does current demand.
Robbie, you are looking different readings and having no idea what you are seeing and you are simply jumping to the wrong conclusions.
As I posted, you have the cart before the horse.
And to ask this question for the umpteenth time, if, according to you, lowering the voltage increases the current, and therefore increases the load on the motor, why is it that Land Rover, and many other makers of vehicles, are doing everything they can to get the vehicles to operate at lower voltages, because if your theory was correct, this would all be a waste of time as it would increase fuel usage.2008 TDV8 RR Lux + 2009 D4 2.7
26th Jul 2015 11:30 pm
Robbie
Member Since: 05 Feb 2006
Location: ¯\_(ツ)_/¯
Posts: 17932
I explained the methodology and how it was achieved. I explained the control system and the sensors it uses. I explained how power is volts x amps. I explained non-Ohmic components when you through yourself down another rabbit hole.
Apparently not good enough.
So I ran tests at idle, a complete journey cycle and even demonstrated that a battery at the same SoC could absorb more current.
Apparently not good enough.
I then went through your post and provided data extracts to demonstrate. I even pointed to reference material.
Apparently not good enough.
I offered digital o'scope files, CSV data and produced full data files.
Apparently not good enough.
The data is the data Drivesafe:
Click image to enlarge
I cannot wait for your data; or is the pretty much flat green line at 14.7v for around 20 minutes just the final death of your credibility?
I won't delve into your theory that a regulated voltage has to decay if the battery can accept more amps than it is being provided with. I'll leave that one to anybody who has ever used a battery charger with less than 80 amps or so available!
Land Rover - Turning Drivers into Mechanics Since 1948
Member Since: 20 Jun 2014
Location: York
Posts: 853
Hi Robbie, is that live data available on the release IID BT software, or just on the Beta version, as I can't seem to find it on mine?D4 MY14 XXV - RLD/IID BT
D4 MY13 HSE Lux - RLD/IID BT
P38 RR - Sad parting
110 - Even sadder parting
S3 88" - Still going strong after 23 years of ownership
27th Jul 2015 11:00 am
Robbie
Member Since: 05 Feb 2006
Location: ¯\_(ツ)_/¯
Posts: 17932
Hi Dudley,
It's on B2570 which is on the latest beta, but you can achieve much the same with diagnostic data loggers too. Using the sensed data from the BMS is handy though as you can see what the vehicle is seeing and a more accurate SoC.
Land Rover - Turning Drivers into Mechanics Since 1948
Member Since: 23 Feb 2006
Location: Gold Coast, Australia
Posts: 867
Robbie, when you stated “DATA is the DATAâ€, you were correct, but the problem is that you have absolutely no understanding of how batteries work and you sure as hell have no idea how an alternator operates.
As for this little gem!
Robbie wrote:
I won't delve into your theory that a regulated voltage has to decay if the battery can accept more amps than it is being provided with.
It’s not a theory, it’s how batteries and alternators have worked for the passed 70+ years.
Robbie, you have posted up all that “DATA†and you haven’t got a clew as to what you have posted up, or how to read it.
It is long over due for you to go and do a basic course in lead acid battery and alternator technologies.
And even though you are such a self proclaimed expert on DC circuits, you still have not answered this.
If, according to you, lowering the voltage increases the current, and therefore increases the load on the motor, why is it that Land Rover, and many other makers of vehicles, are doing everything they can to get the vehicles to operate at lower voltages, because if your theory was correct, this would all be a waste of time as it would increase fuel usage.
You can’t answer that question because it makes a complete fairytale of the crap you have been posting up, or are you trying to imply all the vehicle manufacturers, including Land Rover, have it wrong and you are the only one that has it right?2008 TDV8 RR Lux + 2009 D4 2.7
27th Jul 2015 11:33 am
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26769
Guys,
Could you please take your personal differences of opinion off the site, and sort it out elsewhere?
Your constant argument and counter argument is confusing to me, and all who are watching this.
27th Jul 2015 11:36 am
drivesafe
Member Since: 23 Feb 2006
Location: Gold Coast, Australia
Posts: 867
Hi Gareth and fair point, so I will leave this thread with the same question I have asked of Robbie numerous times, and this has nothing to do with any “opinions†Robbie claims I have, this is what the vehicle manufacturers are doing.
If, according to you Robbie, lowering the voltage increases the current, and therefore increases the load on the motor, why is it that Land Rover, and many other vehicle manufacturers, are doing everything they can to get the vehicles to operate at lower voltages, something you yourself have stated about D4s, because if your theory was correct, this would all be a waste of time as it would increase fuel consumption?
And Ultimately, increase exhaust emissions, something they are all out to reduce.2008 TDV8 RR Lux + 2009 D4 2.7
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