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Old 23rd December 2009, 20:15   #16
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Originally Posted by AbhiJ View Post
I have an old inspiron 8500 chrger lying around un used... You can have it, if its compatible with your laptop.

I think this is the best suggestion, I have been with Dell from past 6 years and this would be the best way, than cutting wires and reattaching the charger.
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Old 23rd December 2009, 22:21   #17
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Sure why not ? Battery and charger are not exactly analogous but keeping space constraint aside why not ?
will it not burn the low amperage alternator.
how hard is it to understand. Sigh!!

BTW main aim of my response to was simple to the thread starter, you should not in the long run.
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Old 24th December 2009, 10:24   #18
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Originally Posted by SirAlec View Post
will it not burn the low amperage alternator.


No fundamental laws of physics never change , Charge flow ( current) is always from higher potential to lower potential.
So as long as your low Amperage alternator is higher then 14.3 V and battery is 12 V.
The current will always flow from alternator to battery , Battery will take ages to charge but it can not damage the alternator, It is fully possible that due to non-charging of battery the battery may get damaged.

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Originally Posted by SirAlec View Post
how hard is it to understand. Sigh!!
Sigh!! yes fully agree why it is so hard to understand

PS: the analogy in just reverse in case of original poster , He wants to connect higher ampere rating charger ( source) as long as total load on the charger does not exceed the source these is no harm , Please note that the Ampere rating is always max current that can be drawn without distorting the waveform any laptop always draws a fraction of maximum rating even with full load that is CPU at max clock and all peripherals turned on.

Last edited by amitk26 : 24th December 2009 at 10:30.
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Old 24th December 2009, 14:06   #19
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Originally Posted by tsk1979 View Post
AMP rating is not that important. It just means the maximum current the charger is able to put out.
For example, in case of dell, there are multiple charger models, which can out out from 3-6A, but voltage is same.

Now having 20V given to MB instead of 19.5V, again a very minor difference.
From an electrical standpoint, there are not going to be any issues.
Infact, If you take 10 different chargers from dell, and attach a voltmeter, not all of them will show 19.5 V. The voltage given out will range from 19-20V.

However if your thinkpad charger gives out something like 21 volts instead of 20V(5% error can happen in case charger is very old etc.,) you have an issue.
So just put a multimeter to the terminals, and if voltage is in range of 19.5-20.5V, you can go ahead without any issues.

Now coming to the point of the FUD spread by companies that third party chargers can damage devices. This is not actually true unless you are using a cheap charger which does not fully remove the "AC component" from the output. So instead of a stable DC pulse, you are getting an AC pulse which has its mean at 20V. Digital multimeter will still show 20V, but the spikes will kill your equipment.

That said, since your other charger is also from a reliable source, you can go for it.
Ditto, 100% correct


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Originally Posted by SirAlec View Post
i will have to disagree on that.

Say your cam uses a 3 volt li-on battery. or your mobile phone. Can you drive the cam or mobile with a 3volt button cell.
yes you can but the mobile phone will power on only for a brief moment and when the charge finishes it will die, in this scenario well before one even sees the actual LCD turn on.

You can put a 3.7v 1600ma battery in nokia or u can change it with a 3.7v, 1200ma or 1800ma or a 2000ma or 4000ma battery.


Quote:
Originally Posted by SirAlec View Post
no you can't.

can you use a truck battery (12volt) on a Maruti also a 12 volt.
Yes one can use a truck battery in a Maruti800 and it will run fine. Just that the Truck battery will not be charged as alternator will still have lower Amps outputting that battery needs to charge itself.


Quote:
Originally Posted by amitk26 View Post
No fundamental laws of physics never change , Charge flow ( current) is always from higher potential to lower potential.
So as long as your low Amperage alternator is higher then 14.3 V and battery is 12 V.
The current will always flow from alternator to battery , Battery will take ages to charge but it can not damage the alternator, It is fully possible that due to non-charging of battery the battery may get damaged.


Sigh!! yes fully agree why it is so hard to understand

PS: the analogy in just reverse in case of original poster , He wants to connect higher ampere rating charger ( source) as long as total load on the charger does not exceed the source these is no harm , Please note that the Ampere rating is always max current that can be drawn without distorting the waveform any laptop always draws a fraction of maximum rating even with full load that is CPU at max clock and all peripherals turned on.
Again 100% correct.

Cheers
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Old 24th December 2009, 18:33   #20
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^^^
Dude try it and i would be surprise if you managed to run a mobile which need minimum 250ma to start.
Well don't bother, i have news for you, I have done that in past

You know what, people really do use our advice which is posted here. One should be careful what we say in a public forum.

i am not saying that it will not charge, it will definitely charge but in the long run will damage the battery, which is an expensive affair.
So why take chance with a 1200/- charger which may spoil a rs.5000/- battery.

above analogy is simple common sense which may save money in the long run to our esteem thread starter.

well i can go technical if you want, but its out of scope. who can forget high school physics and ohms law.

Last edited by SirAlec : 24th December 2009 at 18:37.
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Old 24th December 2009, 23:29   #21
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Whats the Model # of your Dell Charger?
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Old 25th December 2009, 04:18   #22
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Originally Posted by SirAlec View Post

You know what, people really do use our advice which is posted here. One should be careful what we say in a public forum.

i am not saying that it will not charge, it will definitely charge but in the long run will damage the battery, which is an expensive affair.
So why take chance with a 1200/- charger which may spoil a rs.5000/- battery.

above analogy is simple common sense which may save money in the long run to our esteem thread starter.

well i can go technical if you want, but its out of scope. who can forget high school physics and ohms law.
Please go technical , Analogy is not correct as explained earlier.
Lets stick to the laptop charger keeping mobiles and car battery aside as the analogy is converse in that case
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Old 25th December 2009, 23:45   #23
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yeah! lets stick to charger. Its no use who can't understand a simple solution.

and yeah analogy is correct, all electronics follow the ohms law. and its the simplest and very first law of electronics that you learn if you are into electronics.

and my answer is still as before, you should not use charger that is not rated for your laptop. be warned you will destroy your battery in the long run. Li-ons are very particular and sensitive about the way they are charged.
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Old 26th December 2009, 06:00   #24
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Originally Posted by SirAlec View Post
and my answer is still as before, you should not use charger that is not rated for your laptop. be warned you will destroy your battery in the long run. Li-ons are very particular and sensitive about the way they are charged.
Not a single laptop directly charges the battery from the charger there is always a secondary circuit there to charge the battery and because lithium ion batteries are so fraglie, this is the reason they come with secondary circuit inside the battery.

We can argue ohms law and physics here whole day long. But the fact is as long as voltage is within 10% margin and charger has higher amp, it will be fine. I can give many examples. But lets stick to IBM/Lenovo

IBM used to and Lenovo currently provides many different Laptop chargers but these three are mainly available 60W, 65W and 90W chargers put out 20V but at 3A, 3.25A, and 4.5A

Ohm's Law is still there but remember with a computer R is varying and not a static load. One of the reason using Switchable Power Supplies and secondary Regulatory Circuits inside the laptop.

I do agree with you as it would hold perfectly for an older charger with a transformer with 4 diodes and a capacitors, where a spike will just fry the whole laptop but its a different scenario here, we are talking about a Switchable Power Supply with regulators built in.

Cheers
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Old 26th December 2009, 16:49   #25
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same hold for the SMPS. the laws of physics will never change.

To cut the long story short, i have found a perfect quote.
Lithium-ion battery - Wikipedia, the free encyclopedia

go through the charging section.

Quote:
For safety reasons it is recommended to stay within the manufacturer's stated voltage and current ratings during both charge and discharge cycles.
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Old 26th December 2009, 19:23   #26
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Originally Posted by SirAlec View Post
same hold for the SMPS. the laws of physics will never change.

To cut the long story short, i have found a perfect quote.
Lithium-ion battery - Wikipedia, the free encyclopedia

go through the charging section.
That is by assuming laptop is not regulating the voltage and charger is charging the battery directly while is frankly wrong assumption for any decent laptop.

And yes ohm's law does true but think it yourself R varies and so does I

Cheers
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Old 28th December 2009, 10:56   #27
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Originally Posted by SirAlec View Post
yeah! lets stick to charger. Its no use who can't understand a simple solution.
Lets keep the discussion and tone civil please
Quote:
Originally Posted by SirAlec View Post
and yeah analogy is correct, all electronics follow the ohms law. and its the simplest and very first law of electronics that you learn if you are into electronics.
In this Case a charger with high load capacity is being attached to a laptop so correct analogy drawing from your example wold be attaching a higher rating alternator in the car.

Quote:
Originally Posted by SirAlec View Post
and my answer is still as before, you should not use charger that is not rated for your laptop. be warned you will destroy your battery in the long run. Li-ons are very particular and sensitive about the way they are charged.
Do you know that laptop and cellphone batteries do not directly attach to the +ve and -ve terminals of charger ? The charging process is controlled by microprocessor and there are distinct battery charging algorithms. It is not trivial on for instance in case of mobiles for an new BSP ( board support package) charging algorithms development and commercialization may be approx 0.5 to 1 person year effort out of total 100 man year (approx) to do a commercial mobile on a new platform.

Also if you know how chargers are rated then it is not that a 3.5 Amp charger will provide 3.5 Amps fixed. A charger is basically a DC regulated power supply.

The current flow depends on the load in the circuit and a 3.5 Amp 19.5V charger actually means that it will keep the voltage constant at 19.5 V ( +/- 5% depending on tolerance) as long as current drawn is up to 3.5 Amp.

Last edited by amitk26 : 28th December 2009 at 10:59.
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Old 28th December 2009, 11:11   #28
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Ohm's Law is still there but remember with a computer R is varying and not a static load.
Exactly this is shortest and best possible explanation.
The number of Amp given is maximum rated current not fixed current V is fixed parameter in an DC RPS
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Old 28th December 2009, 19:47   #29
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Its people's choice man, if somebody want to use it who am i to stop. It was my recommendation with my personal experience.

Quote:
Ohm's Law is still there but remember with a computer R is varying and not a static load.
Exactly this is shortest and best possible explanation.
The number of Amp given is maximum rated current not fixed current V is fixed parameter in an DC RPS
Explain this to me please. . i would really like to know your theory on this
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Old 29th December 2009, 00:48   #30
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Explain this to me please. . i would really like to know your theory on this
As everyone knows computers do not draw a set amount of Power and it varies with the load.

For example, A C2D cpu can draw as little as 7Watts when slowed and can jump upto 21W when under load (approx TDP, each Cpu changes and even then they are not 100% solid figures). Similarily HDD's when idle or spun down can draw as little as 0.7W and can jump to 5-6W when spinning up(as it reaches set spinning speed power usage again comes down).

So what does that have to do with Ohm's Law????

Well According to Ohm's Law I = V/R Where R is Resistance or Load, V is Voltage and I is Amperes.

So V = I/R

But Since R is varying due to the load on the computer, something else needs to vary to compensate. Cpu's/Gpu's/Ram/Micro-controllers are very sensitive to change in V, early C2D cpu would simply die with variation of 0.1v, please don't confuse this with over-clocking as during over-clocking when voltage is changes, system gets restarted except where Cpu's are able to vary voltage on the fly, even then its recommended that voltage changes are made at BIOS level and system is restarted each time.

Only thing left that can vary to compensate is I. Which makes sense as with the implementation of Micro-controllers and Regulators, voltage can be kept static while I varies.

In Lay-mens terms, System takes power as it requires and not 100% at once.

Cheers
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