[deep_bang]

To give a short answer to someone who wants a absolute no-risk solution - DONT use other chargers.

However, if i myself would be in the same situation, i would go ahead and use the other charger, but knowing the risks.

First, like others mentioned here, using a charger of a higher ampere rating is fine. Since the original charger was 3.4amps, it means the laptop by design NEVER consumes more than 3.4 A. Since the other charger supplies more than that (remember 4.5 is MAX current - not the ACTUAL current).
I am myself using a HP charger that has a higher rating than the one that came originally with the laptop.

Second, the voltage mismatch is not good. This is certainly a risk. However, if the laptop is old, I would go ahead and use it - small risk - old laptop.

Your biggest problem is to find a connector that converts from one type to another. I had problems finding for my HP adapters which were not the same connectors - finally got it in SP road, but the converter is also made by HP. So, for you, i dont think you will get that converter that easily.

[SirAlec]

Originally Posted by it_inspector

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

that was a nice explanation. But you are confusing power with current.
components need a specific voltage with specific current. I know the equation is still P=I*V.

Similar in the case of computer SMPS. you can use smps as low as 275watt and as high as 600 watt. But the specific voltages and current at the ATX 24v and molex connector does not vary (red 5volt, yellow 12volt. If it does vary due to faulty smps the caps at the mobo leaks and fattens.

Same goes with lappy charger. charger do has wattage rating like 65 watt, 48 watt etc. that is just fine. Same goes here higher the better.

[amitk26]

Originally Posted by SirAlec

that was a nice explanation. But you are confusing power with current.
components need a specific voltage with specific current. I know the equation is still P=I*V.

In any kind of DC regulated power supply ( SMPS or Laptop Charger or anyother) If you fix the voltage 19.5 ( out of charger) or 5V or 12V ( in SMPS) in the equation P= I*V ,
With a fixed voltage P is directly proportional to I so increase in power means increase in current as well.

[SirAlec]

You misunderstood again. So you mean the 750 watt smps used in gaming pc will supply more voltages? than say standard 400 watt smps.

I am enjoying this. this is fun.

[amitk26]

Originally Posted by SirAlec

You misunderstood again. So you mean the 750 watt smps used in gaming pc will supply more voltages? than say standard 400 watt smps.

I am enjoying this. this is fun.

I hope you understand that 750 Watts is max power capacity , In case you choose to use only 12V lines ( for simplicity) you can draw maximum 62.5 Amp Current that does not you can not choose to draw 33.3 Amps which is the max a 400W SMPS could have provided from 12V line.

The current drawn on 12V line depends on the load placed , For a High load ( low value of R) the current will be higher. The load value depends on what all peripherals are turned on and the clock speed of processor and bus.

what is the confusion or misunderstanding here ?

[tsk1979]

LOL even if I put a 100,0000 Watt SMPS with 5V output voltage on just 1 W load, it will give 5V only.
Only as you start reaching its capacity, voltage will drop.
For example, take a 1.5V battery and measure current across its terminals, it will show 1.5V
Then put a LED, it will show 1.5V again, and if you have sensitive instrumentations, it will show 1.49996 or something like that.
Now if you put a high power bulb, the voltage will drop.

A perfect voltage source has infinite power. No matter what you drive with it, it will always give V volts.
When you take a 700W SMPS, and run just 200W with it, it will give you rated voltages.
Only when power consumption approaches 700W, it will show degradation. Good SMPS will hold quite well till 750W or so, after which it won't be able to cope up.

[it_inspector]

Originally Posted by SirAlec

1 amp makes a lot of difference and will certainly ruin your mobo and battery in the long run

Originally Posted by SirAlec

that was a nice explanation. But you are confusing power with current.
components need a specific voltage with specific current. I know the equation is still P=I*V.

Similar in the case of computer SMPS. you can use smps as low as 275watt and as high as 600 watt. But the specific voltages and current at the ATX 24v and molex connector does not vary (red 5volt, yellow 12volt. If it does vary due to faulty smps the caps at the mobo leaks and fattens.

Same goes with lappy charger. charger do has wattage rating like 65 watt, 48 watt etc. that is just fine. Same goes here higher the better.

So hold on a sec here, What are we arguing over here??? And for that matter what point are you trying to make, seems like your confused???

Leaking caps are not only caused due to voltage variations, there is a huge list of other factors affecting it.

About a Desktop SMPS, well just get a proper voltage monitoring utility and none of the voltages will be accurate on pretty much any CONSUMER smps.

Hence the reason there are Regulators built into each Motherboards and variation of 10% in voltage is expected and the regulators are meant to correct it.

Cheers

[SirAlec]

Originally Posted by tsk1979

LOL even if I put a 100,0000 Watt SMPS with 5V output voltage on just 1 W load, it will give 5V only.
Only when power consumption approaches 700W, it will show degradation. Good SMPS will hold quite well till 750W or so, after which it won't be able to cope up.

Exactly my point. Hence my friend in a charger you can charge a lappy with a 65 watt charger or a 35 watt charger but it should be rated at a particular voltage and amps rating.

thats why we don't have a fixed 5 amp or 6 amp charger. its even designated to its decimal places like 3.25, or 4.75 amps.

I am not confused, just tired of typing all the explanation.

[it_inspector]

Originally Posted by SirAlec

Exactly my point. Hence my friend in a charger you can charge a lappy with a 65 watt charger or a 35 watt charger but it should be rated at a particular voltage and amps rating.

thats why we don't have a fixed 5 amp or 6 amp charger. its even designated to its decimal places like 3.25, or 4.75 amps.

I am not confused, just tired of typing all the explanation.

Hold on, you say your not confused, yet you are suggesting that different wattage is okay but at the same time Volts and Amperes cannot vary.

How does wattage vary then ?????

As far as i know, 1Watt = 1V x 1A

Originally Posted by it_inspector

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

As i said before, IBM/Lenovo itself manufactured different chargers for its laptops and these are all usable with all of the IBM/Lenovo range. Voltage is kept same at 20V and Amperes changes accordingly:

60W = 20v x 3A
65W = 20v x 3.25A
90W = 20v x 4.5A

I would love to read your explanation tough.

Cheers

[amitk26]

Originally Posted by SirAlec

thats why we don't have a fixed 5 amp or 6 amp charger. its even designated to its decimal places like 3.25, or 4.75 amps.

It is designated to decimal places because Voltage is fixed and Wattage is decided by peak power requirement .

P/V = I therefore
65 W /20 V = 3.25 A
90 W / 20 V = 4.5 A

Originally Posted by SirAlec

I am not confused, just tired of typing all the explanation.

Indeed you are , Please take some time to understand which parameter is regulated in a DC regulated power supply and that will clarify a lot of things.

PS :

SMPS is another kind of Regulated power supply which uses a Power transistor in saturated region so that it acts as a switch and it is used as a Switch at very high frequency ( 50KHz upwards) and the switched output is filtered using an LC circuit to get smooth DC. SMPS used in desktop consists of multiple Switching circuits internally to derive various DC output lines with different voltages.

So nothing changes if you draw example from either a laptop power adapter ( more appropriate word then Charger) or SMPS used in desktop PC.

Also both SMPS and Laptop power adaptor are essentially different from a Ni-CD or Ni-Mh battery charger which keeps both current and Voltage regulated, The current rating is determined by Amp-Hr of battery and how long charger should take to charge the battery. In your previous posts you keep referring to batteries which gives a hint that you are essentially confused between a Laptop power adapter and a battery charging circuit.


I think we are coming back to same thing in circles so I will refrain from posting here until there is something new.

[tsk1979]

Originally Posted by it_inspector

As i said before, IBM/Lenovo itself manufactured different chargers for its laptops and these are all usable with all of the IBM/Lenovo range. Voltage is kept same at 20V and Amperes changes accordingly:

60W = 20v x 3A
65W = 20v x 3.25A
90W = 20v x 4.5A

I would love to read your explanation tough.

Cheers

it_inspector you are right. However when you say 90W charger it basically means that the max output is 4.5A. If you power a device which requires lower than 4.5A, lets say a 5W 20V device, it will output less current.
Battery chargers are constant voltage devices, and are designed to give constant voltage upto the max wattage.
So if the load is 10W, 20W, 30W or 90W, the charger voltage will show 20V(whereabouts), however, the moment you put a higher load , the voltage will drop.

[it_inspector]

Originally Posted by tsk1979

it_inspector you are right. However when you say 90W charger it basically means that the max output is 4.5A. If you power a device which requires lower than 4.5A, lets say a 5W 20V device, it will output less current.
Battery chargers are constant voltage devices, and are designed to give constant voltage upto the max wattage.
So if the load is 10W, 20W, 30W or 90W, the charger voltage will show 20V(whereabouts), however, the moment you put a higher load , the voltage will drop.

I agree with u.

I should stop calling charger.

Cheers

[SirAlec]

Originally Posted by tsk1979

it_inspector you are right. However when you say 90W charger it basically means that the max output is 4.5A. If you power a device which requires lower than 4.5A, lets say a 5W 20V device, it will output less current.
Battery chargers are constant voltage devices, and are designed to give constant voltage upto the max wattage.
So if the load is 10W, 20W, 30W or 90W, the charger voltage will show 20V(whereabouts), however, the moment you put a higher load , the voltage will drop.

thanks man! i couldn't have explained it better than you.

[amitk26]

Originally Posted by tsk1979

it_inspector you are right. However when you say 90W charger it basically means that the max output is 4.5A. If you power a device which requires lower than 4.5A, lets say a 5W 20V device, it will output less current.
Battery chargers are constant voltage devices, and are designed to give constant voltage upto the max wattage.
So if the load is 10W, 20W, 30W or 90W, the charger voltage will show 20V(whereabouts), however, the moment you put a higher load , the voltage will drop.

Well that is how a regulated DC power supply behaves that is voltage is constant up to the max load and moment more current is drawn then the max voltage will drop.

Battery charger is little different in a battery charger the current is regulated at fixed voltage and there is a cutoff either based on time or the measured voltage drop ( smart charger / micro controller based charger).

The word Charger in case of laptop is misnomer , I just noticed that my HP laptop uses the word power adapter and so does office Dell Vostro

[SirAlec]

after three pages and 40+ posts facts remains the same.
One should not mix and match charger in case of such sensitive equipment as lappy.

thats the reason they haven't standardized it like desktop smps, all have different battery its memory circuit and hence to prevent this they have different pins at the end.