24" iMac self-contained battery mod

Posted by: endosage

24" iMac self-contained battery mod - 04/12/08 11:25 PM

First post here, so if I do anything against conventions, don't kill me. I'm just looking for help with an idea that I had.

So, I just bought a 24" iMac (like... 30 mins ago) and I'm going to mod it with a touch screen from these guys: http://www.trolltouch.com . Since I'll basically have a semi-portable form factor to work with I was wondering if it wasn't at all possible to do away with the power cable on this thing and use some type of laptop battery to keep it on. I'll be using it for musical performance as well as production. I'll be using Reason 4, Pro Tools (when connected to a power supply of course), and MAX/MSP on it for the performances.

So, usable battery in a 24" iMac. Possible? If so, how?

Thanks in advance

-Zack Isaacs
Posted by: soundmann18

Re: 24" iMac self-contained battery mod - 04/14/08 07:16 AM

I can't imagine that a laptop battery would be able to power it, and if it could, you'd have to put it after the power supply that converts the 120v AC into the proper DC voltages. Maybe you could get a big car battery or similar to run the thing after an AC converter.

But I don't really know, this is just my intuition.
Posted by: BigO

Re: 24" iMac self-contained battery mod - 04/14/08 07:21 AM

There's really not much room left in the cases of those things so if you're wanting it to sit inside without modding the case you may be out of luck.

But getting a desktop to run off a battery is totally possible. There's an example of someone doing something like that to a Mac Mini here:

http://hardware.slashdot.org/comments.pl?sid=149912&cid=12566236

--O
Posted by: flippy10

Re: 24" iMac self-contained battery mod - 04/14/08 08:42 AM

The biggest problem I can see being current consumption. The iMac has got a 24" screen which means it's driving inverters, it's got dedicated graphics and should be quite a power hungry beast. However, the 24 inch screen also allows a large space to mount the batteries behind the case/screen.
Posted by: oojacoboo

Re: 24" iMac self-contained battery mod - 04/14/08 01:25 PM

welcome first of all!

The problem I see is the amount of battery this thing will drain. Its gonna be a lot more than a laptop for sure. If you are gonna do this, I am going to recommend the deep cycle marine battery or two. But, that really puts a damper on the portability factor... The imac just isn't a great candidate.
Posted by: Waragainstsleep

Re: 24" iMac self-contained battery mod - 04/14/08 01:42 PM

Think of it like this:
A small, cheap UPS has enough batteries to run maybe a few of these units but only for a few minutes. So if you are running one, you might get half an hour at best. This is fairly useless for your purposes unless your performances are very short. And to get this much run time you have had to install the guts from something the size of several bricks into your case, probably tripling the weight of it.
This would have been the simplest method, since you are merely re-housing some stuff.
Simplest in terms of work at least, but what you are doing there is converting DC from the batteries to AC via the UPS circuitry into the iMac PSU which converts it back into various DC signals for the logic board.
You could opt to bypass the the UPS bit and the iMac PSU, but you would need to know all the pinouts from the PSU. Also you are then short on the power management front. The iMac has no drivers for the battery. Modern laptops have complex power management systems to deal with the battery and its interaction with the rest of the system.
I would say the only way to go would be to use a UPS but choose your own batteries. Or a car battery with an inverter (and a surge protector).
Posted by: endosage

Re: 24" iMac self-contained battery mod - 04/14/08 03:22 PM

Well, alright. I can see that this isn't possible in the way that I've thought that it was. I was thinking modding the case to accommodate 2 17" Macbook Pro batteries would be enough, but deep cycle marine batteries? Yeah, can't do that.

Well, thanks. I'll be sure to post my touch mod and what all I'll be doing with it here when it's done. I'll be getting the touch screen component some time in September, so it'll be a while, but the end result should be pretty badass. laugh

Thanks all for the help! laugh
Posted by: BigO

Re: 24" iMac self-contained battery mod - 04/14/08 05:55 PM

Originally Posted By: "endosage"
I'll be sure to post my touch mod and what all I'll be doing with it here when it's done.


Yeah, please do that. I'd love to see video of the process and lots of pics. I think the site could really benefit from it because I know a lot of people (including me) are interested in touch screens on the mac.

--O
Posted by: Tigaernach

Re: 24" iMac self-contained battery mod - 04/15/08 05:56 AM

Hmm... Interesting project. Problem would be, as far as I can see, that the iMac has indeed a very huge screen that is in no way optimised for power savings, as is the rest of the computer. The hard disk, too, is a standard desktop 3.5" SATA drive, very hot and hungry.
It *might* however be possible with a reasonably big battery and if you would be satisfied with short battery life (mayba an hour, tops?). The problems with using 2 MBP batteries would be twofold:

1. The batteries (being Lithium-Ion in design) require internal electronics that interface with the MBP to keep them from overcharging, undercharging and overheating. Simply rigging the batteries together would not only shorten the lifespan of the batteries, it could be downright dangerous.

2. Because the power draw on an iMac is pretty high (up to 220W!), much higher than any MBP, the batteries would drain too deep too quickly, bringing swift death to their charge-holding capacity. That's where those deep-cycle accus would come in, as they are built for this sort of use. They are, however, not only bulky and immobile, but also pretty expensive, especially if you would want 140V (unless you would devise a way to connect directly to the motherboard...

It WOULD however be one of the sweeter mods I have ever seen, so if you could at least succeed at doing the touchsreen, the machine gods will be very pleased. Keep us posted!