no charger

[5LY]

Can a laptop battery be charged through a USB port? Left my charger behind. It's an HP Pavlion.

Tks

[M.Mouse]

Not that I am aware.

[A A Gruntpuddock]

Doubt it - usb only provides about 5v and most laptop chargers supply about 3x that.

Usb charging works for gps, phones and the like because they are electronics only so need 5v or less. Laptops need higher voltages for mechanical operation of disk drives. Hope you can read this before your batte .......

[west lakes]

If in a hotel check with reception, it's often mentioned on here that they may have one left behind by previous customers

[Booglebox]

Nope. Ask the reception of the hotel though, they are a very commonly left behind item and they should let you borrow / have one (or just say you left yours last time you were there), and while "finding" it get the right voltage. Remember - less volts is fine, more is not! (and amps... and all that stuff)

[mike-wsm]

Sorry, nope. Each usb port is a regulated power output. There is no way that power can be injected through them. And usb leads are one-way, power out to peripheral only.

Laptop batteries are fiendishly complicated units with all sorts of interfaces to the databus. Never ever try to do anything but use the proper charger unit from the original manufacturer.

[mixture]

Mike-WSM,

And usb leads are one-way, power out to peripheral only.

Would you care to enlighten us as to which particular law of physics you are invoking to transform a physical (non-optical) cable into a one way medium ?

[west lakes]

I would suggest the addition of a couple of diodes prior to the socket on the computer would fit the bill

[hellsbrink]

Is there an electronics store nearby, SLY?

You might be able to buy a "universal" laptop charger

[green granite]

and while "finding" it get the right voltage. Remember - less volts is fine, more is not!

errrrrrr how do you charge, say, an 11V battery with a 9V charger?

[mike-wsm]

Originally Posted by mixture

Would you care to enlighten us as to which particular law of physics you are invoking to transform a physical (non-optical) cable into a one way medium ?

It is not the cable itself that is one-way, it is the interface at the computer end, which is designed to supply power, not receive it. You can't poke power back through a regulator. Check out some reg chip designs.
http://www.datasheetcatalog.org/data...s/tl780-05.pdf

The specification for usb says very clearly that the power flow in the cable is one-way, taking power from a computer to a peripheral.
USB.org - Documents

Originally Posted by hellsbrink

You might be able to buy a "universal" laptop charger

Avoid these like the plague. I found they really mess up the electronic innards of the laptop battery. Always use the correct charger from the oem.

If you can't carry the charger one solution is to carry a spare fully charged battery of the correct type for that computer. Expensive items but easily affordable on pilot pay, and prossibly tax-deductable. Edit: Take care to carry in an appropriate container with protection against shorting of contacts. Li-ion batteries present a major fire hazard if mis-handled.

When caught short use a public access terminal at a library or internet cafe. And enjoy the excellent coffee.

If there is private information you need in transit the best way is to email it to yourself, then you can pick it up from any terminal anywhere.

[srobarts]

Be careful with a universal charger. Some are too easy to get the polarity wrong on. My daughter managed to plug the tip needed for her laptop in the wrong way round and bye bye motherboard

[mike-wsm]

Originally Posted by green_granite

errrrrrr how do you charge, say, an 11V battery with a 9V charger?

I would not recommend using the wrong charger. However the question here derives from a misunderstanding of how battery chargers work. An 11V battery would be just that, a battery with a nominal output of 11 volts. But a 9V battery charger would be a charger designed to charge 9V batteries. Its open-circuit output voltage will be considerably greater than 9 volts and it will adjust to match whatever battery is connected, over quite a wide range.

There are significant differences between laptop chargers and, say, car battery chargers.

The car battery charger contains the limited intelligence of what current to apply and what voltage to stop at, whilst the battery is dumb. It is advisable to use the appropriate charger so that it charges at the right current and stops charging at the right voltage for that battery. But it is possible to use the wrong charger provided you know what you are doing and do not over-stress the battery.

The laptop charger is dumb but the battery, in conjunction with the laptop itself, is very, very smart. The battery has an internal circuit board that contains a lot of smarts (se diagram in post above)and it communicates with the laptop down the data bus (individual types may vary). Li-ion batteries on fast charge need a lot of attention to keep them safe, and this is why so much smart stuff is built in. It is possible to charge a laptop from the wrong charger (higher or lower voltage) because the battery and laptop will tend to work together to protect the battery from catching fire. But in my experience the use of the wrong charger can permanently affect the logic within the battery and may cause problems even when the correct charger is reconnected. I would advise using the correct charger from the oem (original equipment manufacturer).

[mixture]

hi mike

which is designed to supply power, not receive it.

Sure, I'm not debating that what the OP was hoping to do is not possible, I was just pulling your leg on the wording of your reply...

[green granite]

However the question here derives from a misunderstanding of how battery chargers work.

Oh dear mike-wsm, I'm an retired electronic service engineer, and know perfectly well how to charge batteries, my question was a sarcastic comment on the previous post that said "Remember - less volts is fine, more is not!"


The charger (bad term really) required to run and also charge up the battery is, for an HP Pavlion, one that supplies 19VDC @ 4.74A
The battery charging parameters will be handled by the laptop circuitry.

[mike-wsm]

mixture, green granite

Ho-Ho!!!!

But it's so much funnier to take you guys seriously!!!

[Booglebox]

I had a feeling that would cause guys who know about electronics slap their hands to their faces. Sorry guys...

[5LY]

Thanks all. I've been talked out of any creative notions and will chase down the right quipment. Cheers & beers.