Juice to Hot-Swap 12" PBG4 Batteries

You can do this while the computer is asleep: there is a capacitor already in the computer that holds a charge to preserve RAM contents for 30 seconds after you take the battery out.

That's only the 15 and 17" Powerbooks.

Are you sure? Old iBooks and my Powerbook G3 will do this, too. I don't remember if the 12" shuts down when you do this or not.

Maybe it goes into safe-sleep...I'm on my 12" pb, I'll post back in a few more minutes with the results of putting the machine to sleep, popping out the battery for 10 seconds, and seeing what happens.

Nope, I am mistaken.
http://docs.info.apple.com/article.html?artnum=58445

Check out this url http://www.andrewescobar.com/archive/2005/11/11/how-to-safe-sleep-your-mac/. I'll test it on mine after dinner, but it looks like this might do what the fellow needs.

I appreciate all the input, thank you. However, Safe Sleep will not let me accomplsh what I want. On my PowerBook 2400, I could put it to sleep, swap batteries, and simply wake it up. I am (and was) aware that the 12"G4 does not have this capability (like the 15 "& 17" do), and I must be able to *quickly* swap batteries-no time to unwrap the power adaptor cord, find an ac outlet (I work always on the road, and am always in a hurry), plug it in, make the swap, then put away the power adaptor. And the LAST thing I have time for is rebooting.

What I am looking for is a small (home made) alkaline battery powered device (perhaps the size of an iPod Shuffle-you know, tiny & light), which when plugged into the power adaptor jack, would just supply enough to keep the computer asleep for a few seconds while I swap the main battery for a fresh one, which would allow a normal (and fast) wake up.

It would be possible to make a battery pack for this, but it would have to output between 12 and 19 volts@ ~500mah, so it could get pretty large.

Thanks, moosemanmoo. How large would it have to be? Would a couple of 9v's wired in series do it for the 20? or so seconds needed? Or would the amperage be way to low?Other thing, where could I find a plug that will fit the power adaptor jack?

I think it's a 2.5mm minijack plug with positive on the end and ground torwards the cable, but do not take my word for it! With some searching for replacing or repairing the powerbook plugs, I'm sure you'll find the info. Using 4 (yes, 4) 9v batteries wired so they output 18v should work, but just to be safe you should use a 16v resistor. Ideally, AAs should be used, but you would need 12 of them for 18v, which would be a rather large battery pack.

Do you mean 16 ohm resister? Where would this go?

I don't mean 16 ohms or a resistor at all, I suppose. You would need a voltage regulator to keep the current at 16v. It would go between the cable and the batteries.

sourcing the dang connector is gonna be tough. Only sources are existing power supplies or airline adapters or similar. Nobody sells just the connectors. I've fabbed a connector using a mini stereo plug, but it was a major PITA. I'll never do that again, not worth the hassle. Just FYI, positive is the furthest from the tip, ground is the middle band and the tip is not connected.

In any case, I figure a pair of 9v batteries in series ought to work just fine for the few seconds it takes to swap the battery.

good luck, let us know how it goes.

Edit: Example one, a Kensington adapter for $21 and Example two, a VST/SmartDisk adapter for $17, though shipping is kinda high for these examples.

dan k

Or, get the 12vc car adapter, then get a small motorcycle lead acid battery, and attache a 12v lighter socket to it. Then jack the above adapter into the socket, and voila, it works. Ok, it's not as small as a Shuffle, but it'd be dead simple, and it'd be almost guaranteed to work. I know ax0n had a pakc from Target that had a small 12v battery and a low wattage 120v inverter on it. You could eitehr use the 120v or plug straight into the 12v socket if you had an adapter. Great for portable 12v/120V power on the go, away from the vehicle.

While I like this idea, the car chargers are not cheap. You can get even smaller, completely sealed lead acid batteries from any specialist battery supplier (round here the largest chain of those is called Battery World). They're often sold as backups for fire alarms and emergency lighting, so you might be able to pick up some used for nix or close to it from one of those firms. The smallest I've seen are about 2" x 3" x 3", but there might be more.

Get 3 x 6V in series to make 18V (well, more like 21V in real life). You can also get small DC step up modules that will double your voltage, as an alternative to more batteries, although you'll want to check they can handle enough current. A charger to keep them topped up (although your Apple charger might work), a voltage regulator, and a plug, and you're good to go. Note the regulator will likely need a heatsink as well.

....... all for the input. I'll let you know if I can get any of this up and running.