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Can I combine 2 Laptop power supplies (65W-19V) to provide 90W - 19V for PC?

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lv2eof

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Hi,

I have a laptop which is powered @ 65W-19V and I have two power supplys of 65W-19V to feed it. Everything is fine. In one place I use one and in other I use the other, so I don't have to carry them.
Now, I bought another laptop which is powered @ 90W-19V. I can't use the power supplys I have because they are only 65W.
So I ask, can I just connect the two power supplys in order to feed the new laptop?
Thanks in advance for your help.
 

hkBattousai

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Re: Laptop Power Supply

You can connect those two power supplies if they are exactly same. Even a small output voltage difference between them may cause serious problems in the long term.

On the other hand, I don't believe that using a 65W supply instead of a 90W supply would create such a big problem. A PC or say a laptop drains maximum power only when you use it with maximum screen brightness, all white screen, %100 CPU usage, full hard drive and optical drive usage, ... etc. All those occurring at the same moment is impossible.
 

    lv2eof

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malcolmst

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Re: Laptop Power Supply

I wouldn't recommend connecting them together, any difference in voltage is a dead short between the two supplies, and could cause damage to any regulators, etc... as well as possibly draining a lot of extra current. It probably wouldn't hurt to try it with one 65W supply, to see if 95W really is more than it needs. Laptop power supplies are definitely overpriced, but it might be worth getting a new one so it will have the right rating.
 

    lv2eof

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nguyennam

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Re: Laptop Power Supply

One 65W PSU can supply your new laptop with no problem. The only thing you should pay attention is it takes the longer time to fully charge your battery, or you need to switch off the laptop to charge the battery fully.

In case you want to connect the two (2) 65W AC adapters in parallel to supply the new laptop, you should modify the circuit as following:
- Connect 2 minus (-) output wires of 2 PSUs together and to the minus (-) power input terminal of the laptop.
- You need 2 rectifiers of about 5...10A each, high speed or Schottky type is preferrable. Connect each positive (+) output wires of 2 PSUs to the anodes of 2 rectifiers. Then connect together 2 cathodes of the 2 rectifiers and now to the positive (+) power input terminal of the laptop. These 2 rectifiers are used to protect each PSU from drawing current from other PSU that may lead PSUs to be damaged.

Warning: - You should check with your local electronics components vendors about the available rectifiers.
- You should, after connect 2 PSUs together via rectifiers, check carefully new power system with any dummy load, for example, several lamps of 24V-50W, and with a multimeter. Be sure it is good before using with your new laptop.

However, I suggest you not get risk with your laptop, which is very important for your job/work, especially the inside informations/documents. The AC adapter for laptop is not expensive, while the laptop+document are really worth, buy a new one, if you need 2 AC adapters at home and work.

Goodluck
nguyennam
 

    lv2eof

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lv2eof

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Re: Laptop Power Supply

Hi,

Thanks to all that viewed my post and especially to those who had reply.
Although forums are one of the oldest things in the Intenet culture, they are still one of the best.
 

sunnyhere

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Re: Laptop Power Supply

Hi,
You can use both adapter in parallel. there won't be any problem.
as for the as the concern thing is voltage as they are equal, you can use the adapter parallel up to 65+65W applications. but your requirement is lower than that 90W.
for the protection purpose you should add to diodes in their series with the +ve or -ve line according to direction, so that it won't allow a circulating current in case of a voltage mismatch.

-\rhd$^b$ \mid-

-\mid\lhd$^b$ -

Regards,
Sujit\]
 

grittinjames

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Re: Laptop Power Supply

its spoil ur smps powersupply,becouse. eventhough it is mensioned as 19v, practically there will be a some difference. due to feedback of ur smps one having slight less voltage will move to stand by stage assuming there is no load is connected due to more voltage of other power supply.
and full load will be driven by ur powersupply having more voltage . but i thing 65 watt power supply can drive ur new laptop safly




sunnyhere said:
Hi,
You can use both adapter in parallel. there won't be any problem.
as for the as the concern thing is voltage as they are equal, you can use the adapter parallel up to 65+65W applications. but your requirement is lower than that 90W.
for the protection purpose you should add to diodes in their series with the +ve or -ve line according to direction, so that it won't allow a circulating current in case of a voltage mismatch.

-\rhd$^b$ \mid-

-\mid\lhd$^b$ -

Regards,
Sujit\]
 

sunnyhere

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Re: Laptop Power Supply

why will there be a major difference in voltage? normally it don't vary more than 1%.
to protect all kind of these things you are using diodes in series so that it won't allow the current to lop back it will allow it only in one direction.if there will be any voltage mismatch only one of them will operate.[/img]
 

Meridian

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Re: Laptop Power Supply

lv2eof said:
Hi,

So I ask, can I just connect the two power supplys in order to feed the new laptop?
Thanks in advance for your help.

I agree with sunnyhere. It shouldn't cause any problems putting them in parallel to double your wattage. Using the 65 watt type in your new laptop will still work but the risk of fire is there since it will run very hot (over a period of time).
 

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