my car charger can charge my HP IPAQ 4150 5V 2A

or my GPS - Leadtek 9553( which I will replace for one with antenna support)
5V and less than 1A power.
source- http://www.pocketgpsworld.com/leadtek-9553-bt-gps-review.php

I can use a USB Hub and power both. I'm wondering what the limit is though.

My car charger has a USB connector. I think USB is 5V, 6 amps ? (so I won't
be trying to charge my laptop!)

How does the electronics work? In terms of finding what the limit is. Does
it mean I could have as many 5V devices as I want, totalling 6A. (so
they'll all share that current).

If a device is - say - 3V will it blow? or if a device is 10V will not power
up properly ?

At 01 Feb 2007 02:23:50 +0000 jameshanley39@yahoo.co.uk wrote:

> My car charger has a USB connector. I think USB is 5V, 6 amps ? (so I
> won't be trying to charge my laptop!)

I have a few USB-output car crgers and none off them put out anything
close to 6 amps! My "biggest" is 850mA (0.85A.)


> How does the electronics work? In terms of finding what the limit is.
> Does it mean I could have as many 5V devices as I want, totalling 6A.
> (so they'll all share that current).

Yes, if your charger actually puts out that much current. Unless it has
a "boilerplate" (sticker with it's specifications) actually saying that,
however, I wouldn't assume it's anywhere close.

>
> If a device is - say - 3V will it blow?

Depends on how well built it's regulator is. It might blow, or it
just might get really hot.

> or if a device is 10V will not power
> up properly ?

Probably won't power up at all.

It's pretty simple- the adapter you're using for power should be the
correct voltage- not lower or higher- and the current (amps) must be
equal or greater than what the device draws. (The device will draw what
it wants- if it needs 500mA, you could plug it into a 1A, 2A or even a
20A supply- it will only draw it's 500mA.)

>> How does the electronics work? <<

With respect to amperage (current) and assuming that the voltage is
correct, the device will draw the current it needs and the supply will
simply provide what it can.

In other words, if the device draws a maximum of 1 amp, and the power
supply can only supply 500ma, the device will accept that and simply
charge at a slower rate.

The voltage is the critical value.

Beverly Howard [MS MVP-Mobile Devices]

"Beverly Howard [Ms-MVP/MobileDev]" <BevNoSpamBevHoward.com> wrote in
message news:eUxPdTbRHHA.412@TK2MSFTNGP02.phx.gbl...
> In other words, if the device draws a maximum of 1 amp, and the power
> supply can only supply 500ma, the device will accept that and simply
> charge at a slower rate.

Or overheat the charger.

Note that the output of a standard USB port on a PC is supposed to be 5v at
500ma ( 0.5A). PPCs will charge at that rate, and the PC USB ports are
regulated enough to not supply more. The car chargers and wall chargers are
typicaly rated at a higher current and can usually charge the device faster.
I regularly run/charge both my PPC and a BT GPS (which is designed to work
off of 5v conveniently) off of a car charger with a power splitter.

--
Sven
MVP - Mobile Devices

jameshanley39@yahoo.co.uk wrote:
> my car charger can charge my HP IPAQ 4150 5V 2A
>
> or my GPS - Leadtek 9553( which I will replace for one with antenna support)
> 5V and less than 1A power.
> source- http://www.pocketgpsworld.com/leadtek-9553-bt-gps-review.php
>
> I can use a USB Hub and power both. I'm wondering what the limit is though.
>
> My car charger has a USB connector. I think USB is 5V, 6 amps ? (so I won't
> be trying to charge my laptop!)

I am not aware of any laptops that will accept 5 V input. They generally
need much more than that.
>
> How does the electronics work? In terms of finding what the limit is. Does
> it mean I could have as many 5V devices as I want, totalling 6A. (so
> they'll all share that current).

Generally this is true so long as all are attached to the same power
source. In the case of the USB Hub you mentioned about there may be some
logic in the various HUB connections to isolate one from another and
this may limit the amount of current that can be funneled through a
given connector. You will need to check the Hub specifications for
details on this.
>
> If a device is - say - 3V will it blow? or if a device is 10V will not power
> up properly ?

Yes, you are likely to blow up a 3 V device. Generally the regulator
built into the device will not take kindly to 5 V input but some may be
able to do so. There are regulators designed for different voltages on
input and output, some are even adjustable.

10 Volt devices will not work and may in fact attempt to pull more
current (amps) than you have available depending on the design.
Particularly if they are designed to work off batteries.

A device really needs Watts as a measure of power to work. Watts for DC
is just Volts times Amps. As the Volts go down the Amps go up for a
particular Watt rating. Devices designed to work on batteries still need
a constant Watt value to work properly.

Dale

--
_ _ Dale DePriest
/`) _ // http://users.cwnet.com/dalede
o/_/ (_(_X_(` For GPS and GPS/PDAs