Li-ion charging

g'day folks

I'm looking at a chinese import emergency light system and am concerned at what I'm seeing. It is connected to the mains and when there is a power outage, a lithium ion cell (3V7 1300mAh) illuminates a power LED.

When I isolate the fully charged battery and put a meter across the terminals I get a reading of 4V9. AIUI, this should be ~4V2. Can anybody shed any light on this?

Steve

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Reply to
Steve B
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On a sunny day (Fri, 30 May 2014 17:46:40 +0100) it happened Steve B wrote in :

Some Li-ion cells have internal over voltage protection: Google: Varta LPP 523450 DL

From datasheet: Cell Protection

Overcurrent Detection: 2A to 4A (8 to 16msec. delay)

I have one from ebay like that, that is supposed to be a (this?) Varta, but the ink somehow washed out ;-) ebay: 181320563830 Mine works greeat, but I have never pushed it above 4.2V, am using a Microchip USB charger chip.

Reply to
Jan Panteltje

4.2v is max for the cells I've seen. Even 4.3v drastically cuts cell life. 4.9v sounds like an emergency light ready to create its own emergencies.

Cheers, James Arthur

Reply to
dagmargoodboat

My impression is that the batteries with inbuilt (pcb) protection can be used with regular chargers, whereas standard batteries need a charger that fulfils very exacting requirements. The battery that I am looking at has no external markings denoting 'pcb' protection and I shall have to dismantle it to see which type it is. The charger that comes with this unit just supplies constant current at 125mA which would be suitable for maintaining a 'float' charge on different battery types. I have a disquieting feeling that I will be having stern words with the supplier next week.

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Reply to
Steve B

yes, that is what I am concerned about. Especially as this is a ceiling mounted unit. As far as I can determine Li-ions are very particular and take exception to being overcharged - consequences can be explosive! Many cells now come with an inbuilt pcb to protect the cell from mis- adventure. I suspect that this cell doesn't have this facility and intend to dismantle it in due course.

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Reply to
Steve B

I should be impossible to get 4.9v out of a single Li ion cell, the chemistry just does not allow it.

3 possibilities:

1> Its 2 cells in series, with one nearly flat ( also very dangerous ! )

2> Its got an internal boost cct 3> Your meter tells lies.
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Reply to
Adrian Jansen

On a sunny day (Fri, 30 May 2014 22:33:05 +0100) it happened Steve B wrote in :

I decided that the Chinese use these (Varta clones? The Varta is also made in China, so it may be the same one, mine had Varta on it, printed with inkjet like dots, before it got wet and that is how I found that type number), to save on a charging chip. I have a similar battery in my solar powered ebay flashlight, I published the circuit diagram of that here a while back, and it has no charge controller either, but that battery has no model printed on it, but you can see some sort of PCB inside. Maybe your supplier knows the answer. Or you could just slightly up the voltage and see if it auto-disconnects... If in fear discharge it and see if it auto disconnects. All with the usual safety precautions like doing it outside for example.

Reply to
Jan Panteltje

Is this some newfangled Euro replacement for decimal points?

Dang, I feel old again.

Get offa my lawn, you kids.

Mark L. Fergerson

Reply to
Alien8752

On 31/05/14 13.16, snipped-for-privacy@bid.nes wrote:

Hi Mark

As you I have been of this notation. The reason why the decimal point is exchange with a letter og a symbol, is that it is more readable. I have no idea how old this notation is:

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Quote: "... It is used in many instances where the value has a decimal place i.e.

5.6 ? would be listed as 5R6. One advantage of this method is that it is relatively easy to "rub off" a decimal point symbol ".", changing the apparent value, compared to the "R" symbol, which would require more effort. ..."

A comparable notation is part of this British Standard:

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Please keep jumping at new knowledge - it is kind of fun....

-

Dang - you are using a computer! :-)

-

I am trying to grasp:

formatting link

Metamaterial have some "funny" uses e.g.:

Duke University (2014, January 10). 'Superlens' extends range of wireless power transfer. ScienceDaily:

formatting link
Quote: "... But now, Duke University researchers have demonstrated the feasibility of wireless power transfer using low-frequency magnetic fields over distances much larger than the size of the transmitter and receiver. ... The results, an outcome of a partnership with the Toyota Research Institute of North America, appear online in Scientific Reports (Nature Publishing Group) on Jan. 10. ... Yaroslav Urzhumov, assistant research professor of electrical and computer engineering at Duke University. ... "For the first time we have demonstrated that the efficiency of magneto-inductive wireless power transfer can be enhanced over distances many times larger than the size of the receiver and transmitter," said Yaroslav Urzhumov, assistant research professor of electrical and computer engineering at Duke University. ... The geometry of the coils and their repetitive nature form a metamaterial that interacts with magnetic fields in such a way that the fields are transmitted and confined into a narrow cone in which the power intensity is much higher. ... "If your electromagnet is one inch in diameter, you get almost no power just three inches away," said Urzhumov. "You only get about 0.1 percent of what's inside the coil." But with the superlens in place, he explained, the magnetic field is focused nearly a foot away with enough strength to induce noticeable electric current in an identically sized receiver coil. ... "Most materials don't absorb magnetic fields very much, making them much safer than electric fields," he said. "In fact, the FCC approves the use of 3-Tesla magnetic fields for medical imaging, which are absolutely enormous relative to what we might need for powering consumer electronics. The technology is being designed with this increased safety in mind." ... He plans to build a dynamically tunable superlens, which can control the direction of its focused power cone. ..."

American Institute of Physics (AIP) (2012, March 12). Artificially structured metamaterials may boost wireless power transfer. ScienceDaily:

formatting link
Quote: "... A superlens has a property call negative permeability. This means it can refocus a magnetic field from a source on one side of the lens to a receiving device on the other side. By running numerical calculations, the team determined that the addition of a superlens should increase system performance, even when a fraction of the energy was lost by passing through the lens. ..."

Duke University (2012, February 29). Exotic material boosts electromagnetism safely. ScienceDaily:

formatting link
Quote: "... By using exotic human-made materials, scientists from Duke University and Boston College believe they can greatly enhance the forces of electromagnetism (EM), one of the four fundamental forces of nature, without harming living beings or damaging electrical equipment. ... "While we can't suppress the electric field completely, a magnetically-active metamaterial could theoretically reduce the amount of current needed to generate a high enough magnetic field, thus reducing parasitic electric fields in the environment and making high-power EM systems safer. " ... "The metamaterial should be able to increase the magnetic force without increasing the electric current in the source coil," Urzhumov said. ..."

-

Metamaterials might enable efficient wormhole/stargate generation? :-) (

formatting link
):

Eric W. Davis, Ph.D.: Wormhole-Stargates: Tunneling Through The Cosmic Neighborhood (pdf):

formatting link
Citat: "...

2.5 Designing a Stargate ..."

-

Lower ambition level?:

Metamaterials might enable an efficient directional gravitomagnetism "beam"? :-) (

formatting link
)

European Space Agency (2006, March 25). Anti-gravity Effect? Gravitational Equivalent Of A Magnetic Field Measured In Lab. ScienceDaily:

formatting link
Quote: "... Although just 100 millionths of the acceleration due to the Earth's gravitational field, the measured field is a surprising one hundred million trillion times larger than Einstein's General Relativity predicts ... "We ran more than 250 experiments, improved the facility over 3 years and discussed the validity of the results for 8 months before making this announcement ... "If confirmed, this would be a major breakthrough," says Tajmar, "it opens up a new means of investigating general relativity and it consequences in the quantum world." ..."

Martin Tajmar:

formatting link
Citat: "... Martin Tajmar is a physicist and professor for Space Systems at the Dresden University of Technology.[1] He has research interests in advanced space propulsion systems, feep-thrusters, breakthrough propulsion physics and possible connections between gravity and superconductivity. ..."

-

Jul 18, 2011, Light propagates as if 'space is missing':

formatting link
Quote: "... Kokaman's group has designed a way to control the dispersion of light by manufacturing a metamaterial that has with a refractive index of zero. ... "What we've seen is that the light disperses through the material as if the entire space is missing," said Kocaman. "The oscillatory phase of the electromagnetic wave doesn't even advance such as in a vacuum ? this is what we term a zero-phase delay." ..."

/Glenn

Reply to
Glenn

On 31/05/14 13.16, snipped-for-privacy@bid.nes wrote:

Hello Mark

As you - I have been astonished about this notation. The reason why the decimal point is exchange with a letter or a symbol is, that it is more readable. I have no idea how old this notation is:

formatting link
Quote: "... It is used in many instances where the value has a decimal place i.e.

5.6 ? would be listed as 5R6. One advantage of this method is that it is relatively easy to "rub off" a decimal point symbol ".", changing the apparent value, compared to the "R" symbol, which would require more effort. ..."

A comparable notation is part of this British Standard:

formatting link
formatting link

Please keep jumping at new knowledge - it is kind of fun....

-

Dang - you are using a computer! :-)

-

I am trying to grasp:

formatting link

Metamaterial have some "funny" uses e.g.:

Duke University (2014, January 10). 'Superlens' extends range of wireless power transfer. ScienceDaily:

formatting link
Quote: "... But now, Duke University researchers have demonstrated the feasibility of wireless power transfer using low-frequency magnetic fields over distances much larger than the size of the transmitter and receiver. ... The results, an outcome of a partnership with the Toyota Research Institute of North America, appear online in Scientific Reports (Nature Publishing Group) on Jan. 10. ... Yaroslav Urzhumov, assistant research professor of electrical and computer engineering at Duke University. ... "For the first time we have demonstrated that the efficiency of magneto-inductive wireless power transfer can be enhanced over distances many times larger than the size of the receiver and transmitter," said Yaroslav Urzhumov, assistant research professor of electrical and computer engineering at Duke University. ... The geometry of the coils and their repetitive nature form a metamaterial that interacts with magnetic fields in such a way that the fields are transmitted and confined into a narrow cone in which the power intensity is much higher. ... "If your electromagnet is one inch in diameter, you get almost no power just three inches away," said Urzhumov. "You only get about 0.1 percent of what's inside the coil." But with the superlens in place, he explained, the magnetic field is focused nearly a foot away with enough strength to induce noticeable electric current in an identically sized receiver coil. ... "Most materials don't absorb magnetic fields very much, making them much safer than electric fields," he said. "In fact, the FCC approves the use of 3-Tesla magnetic fields for medical imaging, which are absolutely enormous relative to what we might need for powering consumer electronics. The technology is being designed with this increased safety in mind." ... He plans to build a dynamically tunable superlens, which can control the direction of its focused power cone. ..."

American Institute of Physics (AIP) (2012, March 12). Artificially structured metamaterials may boost wireless power transfer. ScienceDaily:

formatting link
Quote: "... A superlens has a property call negative permeability. This means it can refocus a magnetic field from a source on one side of the lens to a receiving device on the other side. By running numerical calculations, the team determined that the addition of a superlens should increase system performance, even when a fraction of the energy was lost by passing through the lens. ..."

Duke University (2012, February 29). Exotic material boosts electromagnetism safely. ScienceDaily:

formatting link
Quote: "... By using exotic human-made materials, scientists from Duke University and Boston College believe they can greatly enhance the forces of electromagnetism (EM), one of the four fundamental forces of nature, without harming living beings or damaging electrical equipment. ... "While we can't suppress the electric field completely, a magnetically-active metamaterial could theoretically reduce the amount of current needed to generate a high enough magnetic field, thus reducing parasitic electric fields in the environment and making high-power EM systems safer. " ... "The metamaterial should be able to increase the magnetic force without increasing the electric current in the source coil," Urzhumov said. ..."

-

Metamaterials might enable efficient wormhole/stargate generation? :-) (

formatting link
):

Eric W. Davis, Ph.D.: Wormhole-Stargates: Tunneling Through The Cosmic Neighborhood (pdf):

formatting link
Citat: "...

2.5 Designing a Stargate ..."

-

Lower ambition level?:

Metamaterials might enable an efficient directional gravitomagnetism "beam"? :-) (

formatting link
)

European Space Agency (2006, March 25). Anti-gravity Effect? Gravitational Equivalent Of A Magnetic Field Measured In Lab. ScienceDaily:

formatting link
Quote: "... Although just 100 millionths of the acceleration due to the Earth's gravitational field, the measured field is a surprising one hundred million trillion times larger than Einstein's General Relativity predicts ... "We ran more than 250 experiments, improved the facility over 3 years and discussed the validity of the results for 8 months before making this announcement ... "If confirmed, this would be a major breakthrough," says Tajmar, "it opens up a new means of investigating general relativity and it consequences in the quantum world." ..."

Martin Tajmar:

formatting link
Citat: "... Martin Tajmar is a physicist and professor for Space Systems at the Dresden University of Technology.[1] He has research interests in advanced space propulsion systems, feep-thrusters, breakthrough propulsion physics and possible connections between gravity and superconductivity. ..."

-

Jul 18, 2011, Light propagates as if 'space is missing':

formatting link
Quote: "... Kokaman's group has designed a way to control the dispersion of light by manufacturing a metamaterial that has with a refractive index of zero. ... "What we've seen is that the light disperses through the material as if the entire space is missing," said Kocaman. "The oscillatory phase of the electromagnetic wave doesn't even advance such as in a vacuum ? this is what we term a zero-phase delay." ..."

/Glenn

Reply to
Glenn

I don't find it any more readable. It's pretty easy recognize a missing decimal point. "4 7K" isn't any harder to read than 4.7K. The key is that leading zeros can't be dropped (the '0' in 0.1u is required). I don't really care much, though. I use a 'V' for voltages in schematics (5V0), mainly because the decimal point is often a forbidden character in signal names not because it's easier to read. The 'R' decimal place holder is often used in part numbers, too, so it's already "in there".

Printers are much better and it really doesn't matter. The empty space it evident.

Reply to
krw

That practice has been around since the days of all drawings (circuit diagrams etc) being hand-drawn. The DP (decimal point) size tended to be variable depending on the care taken, and was often lost in reproduction methods of the day. The two approaches that were used to address this were the unit symbol as the separator (as per O/P) or a comma.

Using the unit symbol becomes awkward to say the least when multipliers are required for sensible presentation. 4V2 looks fine, but what if that were 4.2mV you were trying to represent?

The comma had its own downside. If used as the "thousands separator" as is normal practice (i.e. 6,850) then a number like 1257.5 looked odd as 1,257,5

I readily admit that I quite often use V as the separator in voltages above 1 and below 1000. (Above 1000 I don't believe I have the need to display - or the instrumentation to resolve - parts of a Volt).

Reply to
pedro

you wouldn't use it for both, but it is still messy

here dot is thousands separator, comma is decimals at first sight it makes sense the comma is bigger and the decimal separator is more important

not so good for a comma separated file though

-Lasse

Reply to
Lasse Langwadt Christensen

V042? 4V2E-3? ;-)

Reply to
krw

OOps, make that "V0042".

Reply to
krw

Even if the cell does have an internal protection circuit, the situation would not be acceptable. There should be two means (at least) of ensuring that the cell does not get overcharged: (1) a voltage limit in the charger, and (2) the protection circuit, usually bulit into the battery pack. That way, a single component fault cannot cause a cell to be overcharged.

Also, in standby applications like this, you would want a lower float voltage, perhaps 4.0V or even lower, if the initial capacity of the cell is plenty, but you don't want to change it every year or two:

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Chris

Reply to
Chris Jones

On a sunny day (Sat, 31 May 2014 18:56:18 -0700 (PDT)) it happened Lasse Langwadt Christensen wrote in :

I use it for money:

2E22 (2 Euro 22 cents) 1$25
Reply to
Jan Panteltje

On a sunny day (Sun, 01 Jun 2014 15:13:54 +1000) it happened Chris Jones wrote in :

Well, I sort of disagree, I did power curve testing with lipo, as the GPS radiation logger I designed also logs the voltage of its lipo battery. There is a lot of scare-mongering going on, I was afraid when I first started playing with these batteries, here are some of the curves _I_ measured:

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As you can see, at the end of the capacity, then current goes way up, as the voltage converter connected tries to maintain constant output, the output voltage drops almost vertically, and the 3V to lower (I switch of at 3V) happens so fast (minute) that it makes no difference (3.2V or 2.8V switch), and that is _loaded_, at that point the open voltage (load disconnected) is likely higher, no damage done. At the high voltage end, you want full capacity in a backup situation, so the battery must be fully charged. Mine charges to about 4.15 V or so, or a bit more, or less, depends how long I put it into the USB port.. but I use a Microchip charger chip, that has all the protections. OTOH I have the small solar cell directly connected to the battery now and count on the internal battery protection if even suns nuculear reactions play up and manage to up the voltage above 4.2 That has not happened yet, and I think China's designers are aware that few people live in Sahara desert, and those that do do not buy their stuff, and those that do will not ask money back, or are killed by other means before that, its a cruel world now is it:-) Of course from an amerrican point of view you are 100% right and please remove the table ware and those pointy forks and knives, and all matches, make paddings on the side of the sidewalks, put a booklet with 'donts' with every thing you sell. Hell I bought something (PWM tester for RC servos IIRC) years ago, and it came with a 'manual' that consisted mostly of disclaimers and not a sane word about what it was and how to use it. What a world, Do not eat battery, do not dispose of in fire, do not have kid choke on it, do not give to cat, do not blah blah blah. I guess if you keep treating people like imbeciles, and allow them no practical experience with anything, then the it only takes a few generations to create imbeciles, and your enemies will walk all over you and laugh at you trying to make fire with wooden sticks. This is history, wait for it.

Reply to
Jan Panteltje

Some lithium batteries do burn very well, and overcharging them seems to make this much more likely to happen, though RC modelling enthusiasts claim that there are cases where the batteries were not charging and a fire happened anyway:

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They have come up with some ideas for storing their batteries:

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I share your wish that people would take a bit more responsibility for their own safety. Whilst for my own uses I am happy without extra battery protection circuits, this is because I charge my batteries in a place where any fire would not be able to spread. Most people have no idea about this and I often see people charging these things in a pile of papers, next to dried flowers in a wicker basket, and surrounded by curtain fabric and all manner of other kindling and combustible material.

Reply to
Chris Jones

I'm a 61 year old American. When I learned to draw diagrams by hand by co pying what was then common practice on schematics glued into the back cover s of TV and sets, in magazines etc., decimal points were the norm. I never saw units used as separators. When I later took Radio Shop (building actual toob radios) in High School (ca. 1968), same same.

I took Mechanical Drawing concurrently with Radio Shop, and you didn't kn ow my instructor. Decimal points had to be as legible as any other drawing element- a poorly indicated one would drop you a full grade on a drawing.

The only reproduction methods at the time were blueprint copiers and the mimeograph, which was part of the reason decimal points had to be easily le gible.

I think we have different ideas of when "days of yore" were...

Good reason to use decimal points by default, I'd say.

"Normal practice" varies by continent. In the U. S., thousands etc. are s eparated by commas.

Also, the phrase "decimal point" rather obviates the use of a comma to se parate integers from decimal fractions IMO.

Seriously, this is new to me. I don't like it at all (not that that shoul d impress anyone).

Mark L. Fergerson

Reply to
Alien8752

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