Sonsivri

I'm looking for a circuit/project that will turn ON/OFF a laptop charger via USB based on the state of laptop battery..


Any idea will be appreciated..


TIA

what type,volt & amp battery ?
why usb controlled ?
how complicated ( spec ) ?

Hi,

I was thinking that it can be accomplished via ACPI if it has a capability to communicate with USB..


My intended application is simple..if the battery is full (usually a battery full indicator is shown in the taskbar) it will signal via USB to disconnect the AC side of the charger via relay or anything else..same with battery low..it will connect the ACautomatically via USB..





Just EXACTLY what I need!

Thanks for this info!

some info from google..
Assuming you can expose your SMBus connected accelerometer via ACPI, this may be the easiest approach.  To do this, you'd have to modify the BIOS ACPI table to expose the custom device, which Windows would then enumerate as a device node.  On this device node, you need to create a KMDF filter which would talk to the ACPI bus driver and get the custom data, which would then be exposed to the user-mode driver (something like the sensor sample driver).  This filter is essentially a bridge between the Microsoft ACPI bus driver and your user-mode sensor driver; it is necessary because the ACPI bus driver will only handle internal IO requests, which cannot be generated from user-mode.  The following resources may be useful to explain these concepts and provide sample code:


http://download.microsoft.com/download/5/b/9/5b97017b-e28a-4bae-ba48-174cf47d23cd/CPA002_WH06.ppt

 

http://www.microsoft.com/whdc/system/pnppwr/powermgmt/ACPIDriver_Vista.mspx
Lastly, you probably want to have the accelerometer be event driver.  To get the events to your user mode driver, we recommend an approach called the "inverted call" method.  This is when the user mode driver will issue an IO request down to to the filter driver, but rather than complete it immediately, the filter will save the request in a WDFQUEUE object.  Then, when the ACPI notify event arrives, you can pull the request off the queue to complete it with the data.


also read this ..

http://msdn.microsoft.com/en-us/library/windows/hardware/jj923067.aspx

also this ..

http://en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface

hardware option maybe ..

http://www.ti.com/tool/usb-to-gpio

just to get you going

Posted on: June 13, 2013, 10:32:41 10:32 - Automerged

---

what if you measured current flow and when on minimum flow then turn of relay on supply side, this way when laptop needs current, the charger will kick in anyway..

this also looks like a contender , as your I/O side to control relay..
http://jap.hu/electronic/usbio.html

I fail to see the scope of this circuit !
Life of a laptop battery is limited at about 300 cycles of charging/discharging by software in the chip inside the battery.
Life of a bare Li-Ion battery is 400 to 600 cycles, but at the end of it's life, the battery will have either a very low capacity or an explosive end. If you connect the charger to the notebook only to charge the battery and then use the notebook until battery is empty, you have just wasted a cycle from battery's life.
The scope of the battery in laptops is UPS (back-up energy source, to keep you from loosing work when AC power fails or when the power cord is accidentally removed), and that's all.

what i am saying is :
if you read the battery life via laptop (ACPI)
    then on the usb I/O controller you can use the relay you are looking for..
some of the links i have given explain the use of getting into ACPI & USB Interface
PaulC

Posted on: June 14, 2013, 11:52:31 11:52 - Automerged

---

is this any use for you ?
if not let us know and we will go down a different route..
PaulC

Do you have a source for this? I can certainly believe that some manufacturers would do this, but I don't believe they all do.

We have a number of laptops at my company would easily have been through 300 cycles and while I'm sure the battery capacity has dropped off, it still works.

I've had an Acer and a Dell (Dell was quite good, with 3-4 hours on a battery charge). For both of them the battery capacity dropped significantly after 3 years (and a mean 300 charge/discharge cycles); notebooks are still usable, with about 10 minutes on battery.
In my company there were 10 identical Dell notebooks and all of them behaved the same way.

If you want to find more about your battery, find a windows app that will read that info, or start the PC from a live Linux (on the battery tab it will show you the remaining % of the battery capacity)

But what about the chip?

You said that it was limited to 300 cycles by a chip and software inside the battery, are you just basing that on the fact that capacity seems to drop off?

I base my supposition on the fact that capacity dropped from 80% to less than 5% in a matter of weeks, and all notebooks behaved similarly. As far as I know, the battery contain an EEPROM (serial number, number of ch./disch. cycles and possible other information) and some other circuits (to prevent overcharging/overdischarging and God knows what else).
There are reports on other technical forums that after replacing all Li-ion elements in the battery (or only the faulty ones), the capacity remained at the old level. Can't be more obvious than this.

I was thinking that laptop should be powered by battery...:D

Modified the switching circuit with SSR with Zero-crossing, mechanical relay noise causes erratic behavior with the microcontroller circuit..