Make XP think it's running on batteries?

**Crispin** · 11-20-2009, 10:23 AM

Hi Folks,

Been a lurker for a while, this being my first post, be gentle :|

I've had my carputer in for a while now and mostly happy with it. I use a M3-ATX PSU and while it works well, I have a nagging tweak I want to make...

I want to make XP think it is running off a battery and detect when the "ac" is connected and battery state etc.

The above is obviously (maybe not?) to do with ACPI but how do I actually interface with it? I have thought about using the the UPS service but that is pretty limited in the sense that it only tells windows that "I am on battery", "I am on mains" etc. No details battery level etc. Not exactly what I want.
I would _like_ xp / my carputer to think it is a laptop.

I am a dab hand at electronics / arduino etc etc so don't mind delving into the bits. Has anyone done anything like this?

I know it offers little benefit overall, just something I have been pondering...

TIA

Cheers,
Crispin

**DarquePervert** · 11-21-2009, 06:59 AM

If you use an M3, then you're using desktop hardware.
Desktop hardware doesn't have the means of utilizing battery power.

With your hardware, this isn't going to happen.

**shahabmusic** · 11-21-2009, 08:14 AM

actually this is very good idea though. also you can check your car battery level by using windows(you know that little battery icon in taskbar).
may be someone expert in electronic can design a board that connects into the serial port or whatever and simulate the battery thing....

**DarquePervert** · 11-21-2009, 08:31 AM

If the hardware doesn't support battery usage in ACPI, it's simply not going to happen.

Desktop hardware isn't designed to accommodate battery power, plain and simple.

**malcom2073** · 11-21-2009, 08:51 AM

Originally Posted by DarquePervert

If the hardware doesn't support battery usage in ACPI, it's simply not going to happen.

Sorry, but you're wrong

. It would be possible to write a "fake" battery driver using the DDK, now known as the WDK, and load it at runtime. This would make the OS think there is a battery installed, and then query the driver for information relating to the battery. I believe it would also be possible to do things like make the OS think the battery is dead or at any level you want. If I ever get around to setting windows up in a VM I'll give it a shot... but don't hold your breath

**nobb** · 11-21-2009, 10:12 AM

I think an interesting idea would be that if the voltage exceeds a certain threshold (eg. when the engine is on), then it could trigger the computer into thinking it is running on AC. Then when you shut off the engine and the system is running on battery, then have the computer monitor the voltage to provide a rough estimate on state of charge. Sounds similar to what UPSes do.

One potential idea to throw in there which does not require any software modification would be to get a UPS with USB connectivity. Most APC UPSes with USB connectivity will be recognized by XP without having to install anything. But you would have to modify the hardware of the UPS somehow to trick it. Maybe remove the internal UPS battery, then hook the leads up to your electrical system. Then you would be able to monitor the voltage and approximate % left in battery. Then a rough way to trigger whether the system is on AC (engine on) or battery would be to wire an inverter that only turns on when the engine is on and hook up the AC output from the inverter to the AC input on the UPS. To prevent the UPS from charging the electrical system, you would need a diode on the UPS battery leads.

**Crispin** · 11-21-2009, 11:24 AM

I know I am using desktop hardware and I know it will not support "just plugging in a battery". But as for the other ideas, that is what I was thinking along - is there a way to fool MS into thinking it is actually running on batteries.

One thing I am busy with is to use an Arduino to send me various bits of information from various sensors. Accelerometer and inclinometer being two of them. I'll get it to send battery information as well. Like you said, anything over 13v means the car is running, anything less it's not. Anything below 12 is a low battery condition.

Still, it would be nice to make ms think this ;(

**trader007** · 11-21-2009, 11:39 AM

whats the purpose? all youre basically trying to do is simulate in software what your power supply already does in hardware?

**Crispin** · 11-21-2009, 12:11 PM

Originally Posted by trader007

whats the purpose?

Just 'cause

**justchat_1** · 11-21-2009, 02:31 PM

Originally Posted by malcom2073

Sorry, but you're wrong

. It would be possible to write a "fake" battery driver using the DDK, now known as the WDK, and load it at runtime. This would make the OS think there is a battery installed, and then query the driver for information relating to the battery. I believe it would also be possible to do things like make the OS think the battery is dead or at any level you want.

Exactly!!

I looked into this awhile ago and I think the problem I had was that windows only can use one ACPI HAL at a time....so you would need to create a replacement for the one currently used with your BIOS.

Originally Posted by Crispin

Just 'cause

Are you planning on using a front end over the OS? The better option may be to use a plugin for a front end that lets you simulate battery levels.

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