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Increased battery discharge while connected to power source!!
21-11-2017, 09:47 AM (This post was last modified: 21-11-2017 09:54 AM by Node.)
Post: #31
XZBMW RE: Increased battery discharge while connected to power source!!
So you say that I who has a masters degree in physics does not understand physics? That is very funny rofl I laughed hard and long. I personally think that you yourself is too ignorant to try to see the whole picture.

OK, then lesson in physics and chemistry begins (for those who do want to understand why I’m telling what I am telling here in this thread)…

HOW BATTERIES DIE

To understand that first you need to understand why and how batteries die. Almost always the reason is shorted cells. Shorts can be strong when battery voltage is decreased in multiples of 2.15V immediately (but such failure mode is much better than another because such cell can pass high current and you can start a car with one cell dead) or weak when one or more of cells self-discharge (and then you can’t start a car, because discharged cell can’t pass high current killing battery as a whole).
First let’s talk about low quality batteries where lead plates bend and touch or dissolve into acid so that holes appear in them. And why they bend is all physics again: electrostatic charge attracts opposites so plates will always bend towards each other and if they are too thin or otherwise weak mechanically – it is a question of time (for flooded batteries). AGM batteries as their name suggests have absorbent glass mat between them so they can’t physically touch because of bending. But they still die! And you yourself are saying that voltage higher than 14.8V will kill them. So how does that happen? Do you have any clue? I think not.

HOLES IN LEAD PLATES (AS EXTREME CASE)

Why holes do appear in them? It is chemistry here as lead ions from plates dissolve into the acid when battery is charged and are supposed to set back onto plates when it is discharged. In perfect world, this would be happening forever and battery would never die. But they die in real world so why?

LIGHTNING ROD

Here you need to remember from the school how and why lightning rod works. You probably don’t have a clue why I began talking about this, but this is very general physics again. And EXACTLY same physics is causing batteries to die. So. Lightning rod has a sharp end. Sharp end causes nearby electrostatic field to bend, because field direction is always perpendicular to conductive material. Bent field concentrates the energy of the lightning and helps ionize the gas so path of least resistance forms and lightning strikes into the rod.

LIGHTNING RODS IN BATTERIES

Now, what that has to do with batteries? They are not supposed to have any sharp things on their plates. Yes, they are not. BUT. Due to various reasons (like impurities in lead or just statistical nature of the process) lead does not dissolve equally from the whole surface of the plate. Some places dissolve more easily than others. This leads to microscopic mountains on the plates and their tops work THE SAME as lightning rod. The bent field causes the path of least resistance and current begins to concentrate in those places where those mountains formed. This causes both increased deposit of lead when discharging the battery and increase dissolve from around those mountains when charging.

So AS SOON as such mountain BEGAN to form – it has self-amplification properties and its growth rate only increases from that point.

So the cheaper the battery, the more impurities are in the plates and they are produced less flat and that causes battery to die much faster than quality ones. And this does not apply to lead-acid batteries only, it more of less applies to batteries based on any other chemistry.

WHY I TELL THAT OVERCHARGING IS KILLING THEM

Those mountains on the plates will begin to form sooner or later on any battery. But there are two well-known reasons for them to begin forming excessively: over voltage and over current. Charging with too high voltage or too high current causes violent process of dissolving but not only that. It also causes acid to evaporate and form bubbles (very microscopic in AGM case). Bubbles on the plate IMMEDIATELY cause mountains to appear as they change conductivity of the acid at that spot. Again those mountains will not cause battery to die immediately as they need time to grow, but you already made a good start for the process.

CONCLUSION

Now yes, when programming the car the current rarely drops below 2.5A. BUT. First: 2.5A is just an estimate to when excessive bubbling begins. It happens long before that. Second: it DOES as ignition is switched on and off and some control units are programmed when ignition is off. Even when it’s on and current is higher than 2.5A this is the total amount of current. You don’t know how much of it is flowing through the battery and slowly starting to kill it.

P.S. And you also tell that “Larger 70-90Ah battery requires higher voltage than 14V”: that is absolutely bullshit. Voltage depends on the chemistry and composition of the acid and lead plates. In lead-acid batteries the electrochemical potential is around 2.15V and is not dependent on the capacity of the battery. It depends on the temperature of a battery. That is why I say, that charging voltage must be adjusted according to temperature of a battery.

To compensate for that, manufacturers fill batteries with different concentration of acid depending on a potential market for a battery: batteries made for Africa have different concentration of acid than batteries made for North Europe. So anything higher than 2.15V at 25°C is dissipated as heat IMMEDIATELY and causes bubbling. Which causes mountains. Which causes good start for a death.

Now if you still think I do not understand physics, please explain what is wrong with my understanding wink

P.P.S. willisodhiambo, sorry for hijacking your thread, but I do not want you to be killing batteries of your customers.
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22-11-2017, 00:07 AM (This post was last modified: 22-11-2017 18:00 PM by DNK76.)
Post: #32
RE: Increased battery discharge while connected to power source!!
You did not have to put up with it
and prescribe from the physics textbook at school
I have access to the encyclopedia and it's in my language, I've read long ago,
https://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery
Write to BMW AG that damages AGM batteries
Using 14.8V in their chargers
a to old models 14.2V
lithium ion batteries 14V
for workshop work and programming
read ISTA documents / Workshop Operatng fluids
[Image: f7cef188db7c.jpg]
[Image: 80354253f38f.jpg]
[Image: 84e9ff56e9fe.jpg]
Good luck I did not want to be malicious,
like you .

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22-11-2017, 08:30 AM (This post was last modified: 22-11-2017 08:32 AM by willisodhiambo.)
Post: #33
RE: Increased battery discharge while connected to power source!!
(21-11-2017 09:47 AM)Node Wrote:  So you say that I who has a masters degree in physics does not understand physics? That is very funny rofl I laughed hard and long. I personally think that you yourself is too ignorant to try to see the whole picture.

OK, then lesson in physics and chemistry begins (for those who do want to understand why I’m telling what I am telling here in this thread)…

HOW BATTERIES DIE

To understand that first you need to understand why and how batteries die. Almost always the reason is shorted cells. Shorts can be strong when battery voltage is decreased in multiples of 2.15V immediately (but such failure mode is much better than another because such cell can pass high current and you can start a car with one cell dead) or weak when one or more of cells self-discharge (and then you can’t start a car, because discharged cell can’t pass high current killing battery as a whole).
First let’s talk about low quality batteries where lead plates bend and touch or dissolve into acid so that holes appear in them. And why they bend is all physics again: electrostatic charge attracts opposites so plates will always bend towards each other and if they are too thin or otherwise weak mechanically – it is a question of time (for flooded batteries). AGM batteries as their name suggests have absorbent glass mat between them so they can’t physically touch because of bending. But they still die! And you yourself are saying that voltage higher than 14.8V will kill them. So how does that happen? Do you have any clue? I think not.

HOLES IN LEAD PLATES (AS EXTREME CASE)

Why holes do appear in them? It is chemistry here as lead ions from plates dissolve into the acid when battery is charged and are supposed to set back onto plates when it is discharged. In perfect world, this would be happening forever and battery would never die. But they die in real world so why?

LIGHTNING ROD

Here you need to remember from the school how and why lightning rod works. You probably don’t have a clue why I began talking about this, but this is very general physics again. And EXACTLY same physics is causing batteries to die. So. Lightning rod has a sharp end. Sharp end causes nearby electrostatic field to bend, because field direction is always perpendicular to conductive material. Bent field concentrates the energy of the lightning and helps ionize the gas so path of least resistance forms and lightning strikes into the rod.

LIGHTNING RODS IN BATTERIES

Now, what that has to do with batteries? They are not supposed to have any sharp things on their plates. Yes, they are not. BUT. Due to various reasons (like impurities in lead or just statistical nature of the process) lead does not dissolve equally from the whole surface of the plate. Some places dissolve more easily than others. This leads to microscopic mountains on the plates and their tops work THE SAME as lightning rod. The bent field causes the path of least resistance and current begins to concentrate in those places where those mountains formed. This causes both increased deposit of lead when discharging the battery and increase dissolve from around those mountains when charging.

So AS SOON as such mountain BEGAN to form – it has self-amplification properties and its growth rate only increases from that point.

So the cheaper the battery, the more impurities are in the plates and they are produced less flat and that causes battery to die much faster than quality ones. And this does not apply to lead-acid batteries only, it more of less applies to batteries based on any other chemistry.

WHY I TELL THAT OVERCHARGING IS KILLING THEM

Those mountains on the plates will begin to form sooner or later on any battery. But there are two well-known reasons for them to begin forming excessively: over voltage and over current. Charging with too high voltage or too high current causes violent process of dissolving but not only that. It also causes acid to evaporate and form bubbles (very microscopic in AGM case). Bubbles on the plate IMMEDIATELY cause mountains to appear as they change conductivity of the acid at that spot. Again those mountains will not cause battery to die immediately as they need time to grow, but you already made a good start for the process.

CONCLUSION

Now yes, when programming the car the current rarely drops below 2.5A. BUT. First: 2.5A is just an estimate to when excessive bubbling begins. It happens long before that. Second: it DOES as ignition is switched on and off and some control units are programmed when ignition is off. Even when it’s on and current is higher than 2.5A this is the total amount of current. You don’t know how much of it is flowing through the battery and slowly starting to kill it.

P.S. And you also tell that “Larger 70-90Ah battery requires higher voltage than 14V”: that is absolutely bullshit. Voltage depends on the chemistry and composition of the acid and lead plates. In lead-acid batteries the electrochemical potential is around 2.15V and is not dependent on the capacity of the battery. It depends on the temperature of a battery. That is why I say, that charging voltage must be adjusted according to temperature of a battery.

To compensate for that, manufacturers fill batteries with different concentration of acid depending on a potential market for a battery: batteries made for Africa have different concentration of acid than batteries made for North Europe. So anything higher than 2.15V at 25°C is dissipated as heat IMMEDIATELY and causes bubbling. Which causes mountains. Which causes good start for a death.

Now if you still think I do not understand physics, please explain what is wrong with my understanding wink

P.P.S. willisodhiambo, sorry for hijacking your thread, but I do not want you to be killing batteries of your customers.

happyhappy This is serious discourse! Very enlightening. So because voltage between plates is 2.15v, 6 cells as is the norm is 12.9volts fully charged. Why is it that a battery is said to be discharges on loss of only 1volt? That is not even one cell taken out!

Second question. In the can bus, at what voltage is communication sent through the bus? 12volts? If so can I just measure voltages between the bus and ground to know whether a communication line is broken or is poor?
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