Welcome to the MacNN Forums.

Tomster · Dec 18, 2003, 08:30 PM

I wondered if anyone has successfully built an external battery back for a Powerbook. I was inspired by this site. Basically, this guy built his own battery pack for his iPod from a Altoids thin, some wire, and a firewire port. HIs cost was about $5 and some time. The Belkin iPod Battery pack is about $60.

I was thinking about hooking up 8 D batteries in series - 1.5x8=12volts and connecting that to a cigarette socket. Into that, I would plug a Kensington portable power adapter. The price would be much cheaper than an extra battery plus it has the advantage of being refillable via 8 new batteries. The price of the current prebuilt external batteries are over $300.

Any advice from some EE's out there? Anyone try this yet?

Blanchard · Dec 19, 2003, 05:17 PM

Hey nice idea. So, any advice anyone? I'd be much interested in this project. I need more battery life.

Freeflyer · 12:16 AM

I built a battery pack for a himalayan trek earlier this year. Just an 8AA battery holder from radio shack, a battery connector lead and an apple thin firewire cable.

Cut the firewire cable, open up the cables and cut away the two data pairs leaving you the black and white power leads. Solder these to the battery connector leads. Install 8AA batteries into the battery holder, connnect the battery connector and plug the firewire cable into the ipod.

Oh, by the way the white lead is positive. This is important.

2 sets of AA's lasted me a month of trekking. Cost under $5 plus batteries (i had the firewire cable spare). One of the best things I ever built and gave me pink floyd at altitude with the himalayas around me. Stunning.

You might get more life out of the 2x9v + 2AA but AA batteries are the most ubiquitous batteries on the planet. I knew I could get those, I didn't see a 9v anywhere. Plus, if you could get a charger, they're easier to charge using lion or nimh. I had thought of a solar charger, but found I didn't need it.

J.

Tomster · Dec 20, 2003, 12:56 AM

Sounded like a great trip and a fantastic project. Must have some fantastic photos and memories.

I'm actually looking into building an external battery pack for a 17" Powerbook.

Here is the Apple developer page on the PMU voltage sensing. If I was feeling really bold, I could go straight in with power, mimicking aircraft/empower voltage. Not really wild about that idea just in case something shorts.

Thinking about building a 12 volt battery of some sort to power a universal/air Powerbook adapter. Right now, I'm reading up on RC battery packs. That is one hobby that takes building your own battery back very seriously.

jld · Dec 20, 2003, 04:33 AM

I don't know the inner workings for sure inside a powerbook, but I would say it would be more difficult than you might imagine.

I too built my own ipod battery pack, but the ipod has some special circuits that make it very forgiving about how much power it recieves at any one point. Ipod runs on 8-12 volts, and has a stepping power supply inside the unit. This is great because you can put in 8 batteries in and have 12 volts, and then as they run down and the batteries lose voltage, the unit can still use the power.

The powerbook (at least mine, 12" PB), uses 24.5V to power it, meaning you would need 16 or 17 batteries in series to provide enough voltage. That many batteries would weigh close to 5 pounds.

I don't think it's worth the time/weight/cost of batteries.

Plus it's a good possibility that all those D batteries might only afford you a couple hours of usage, which wouldn't really be cost efficient.

bmhome1 · Dec 20, 2003, 04:36 AM

I tried using a 7 amp hour 12V gel cell battery hooked up to a Lind 12V power adaptor for powering my Pismo Powerbook.

I found the useful life very short, the voltage drops too low very quickly and the Lind protection circuit cuts in to shut off power. Also, the 12V connector plug and sleeve gets EXTREMELY hot.

The amp draw from a running Powerbook is not small at all. Expect to need a large auto size, high amp, deep discharge 12V battery to be practical.

Also the 12V>24V convertor uses up a lot of juice.

Tomster · Dec 20, 2003, 02:30 PM

Originally posted by bmhome1:
I tried using a 7 amp hour 12V gel cell battery hooked up to a Lind 12V power adaptor for powering my Pismo Powerbook.

I found the useful life very short, the voltage drops too low very quickly and the Lind protection circuit cuts in to shut off power. Also, the 12V connector plug and sleeve gets EXTREMELY hot.

The amp draw from a running Powerbook is not small at all. Expect to need a large auto size, high amp, deep discharge 12V battery to be practical.

Also the 12V>24V convertor uses up a lot of juice.

Thank you very much for the info. It is nice to hear from someone who already implemented what I was planning to do. I was looking at a 12V gel battery on ebay but wasn't sure if it had the capacity I wanted. I guess for a bit of car camping, one of those jump start lead acid battery units would work but it wouldn't be too fun at the airport!

As for the 12v to 24v conversion, I though to avoid the whole thing by going to a 24v power source. They are in abundant supply as that is what those electric scooters use. The problem is now weight. A 3800 mAh NiMH 24v battery pack is four pounds. And for it to be useful, I have to run the power straight in. Scary.

The more I looked into this project, the more impractical it seemed.

If anyone has any suggestions for all of this, I for one, would be happy, but as it is, it seems the most practical and efficient thing is to just buy a spare battery from Apple.

spotze23 · Dec 21, 2003, 02:03 PM

did anyone try to connect the powerbook direct to a 12v car adapter? in europe there are standard 12v cigarette lighters in the cars.

my dad uses them for his pc-notebooks. it works. but i dont know if it could harm the powerbook battery.

just the ac adapter uses 24 volts. the battery itself runs at 11-12 volts. i think it would just run the powerbook but would not load the battery.

Tomster · Dec 21, 2003, 05:25 PM

Originally posted by spotze23:
did anyone try to connect the powerbook direct to a 12v car adapter? in europe there are standard 12v cigarette lighters in the cars.

my dad uses them for his pc-notebooks. it works. but i dont know if it could harm the powerbook battery.

just the ac adapter uses 24 volts. the battery itself runs at 11-12 volts. i think it would just run the powerbook but would not load the battery.

That's an out of box solution. Kensington makes a good one. This thread was about external battery packs.

romeosc · Dec 21, 2003, 07:46 PM

Just use a car adapter for your PB connected to a "jump start" or similar car starter. Sears sells them for under $40 (fairly heavy but fine for picnics or camping!

Tomster · Dec 21, 2003, 07:50 PM

Originally posted by romeosc:
Just use a car adapter for your PB connected to a "jump start" or similar car starter. Sears sells them for under $40 (fairly heavy but fine for picnics or camping!

Look a few posts up. Already mentioned. Not to fun on airplanes. But thanks!