Note: This was written a week ago, and for some reason kept jamming. Ironically, since I made this “professional” ipod power pack, there terrorist have been thwarted attempting to bomb aircraft from London, so I really don’t think there would be much show getting this or any commercial power pack, or even an iPod itself in carry on. (at this stage anyway)
As promised in forumosa.com/taiwan/viewtopic.php?t=52408, I thought I would put my money where my mouth is and have a go at making one of these (and as I so willingly suggested to the OP.)
The basic theory was to get a Car accessory -USB adaptor, and rip it to bits, combine it with some batteries and presto, have a power pack to charge an iPod away from any usual power source.
So I went to Guang Hua today and picked up some bits. As you will see in the photos, I got carried away with various shaped battery holders and cases, and different switches, just to make sure I had all options covered.
The final parts list (that I used) is as follows:
1 x Car Accessory-USB adaptor = 90nt
2 x 8AA battery holders = 40nt
1 x rocker switch = 12nt
16 x AA heavy duty batteries = 79nt
1 x Black plastic project case = 80nt
total price = 301nt (including batteries)
total price = 222nt (unit only)
Here is a photo of everything that I bought, including a soldering iron (80nt - and that wasn’t the cheapest!)
First step was to take the Car Adaptor to bits. A blade screwdriver in the seam and it was in bits.
Here is a photo of the bare minimum bits you’d need based on a 12v DC input (8 x 1.5 AAs)
A small sticker on the adaptor stated:
Input: DC 12V-24V
Output: DC 5.0V ± 5%
Wha,wha…what? This handles 24V input? So, after thinking about this for 2 seconds, I figured 16 AAs would be better than 8. Will last longer.
After a bit of jiggling around I found that I had to use the 2 long battery holders instead of the 2 flat ones.
I had bought a new LED so I could have a power indicator, as I presumed the one on the adaptor would be in the wrong position. After some testing, I discovered the adaptor LED was a hi-tech 2 color unit that indicated green for ‘ready’ (input ok) and red for ‘charging’. I desperately wanted to keep this feature, so I carefully bent the led around so it would sit in a hole beside the USB slot in the case.
Next step was to cut the holes for the USB slot, LED and the rock switch.
I positioned these all at one end, using the space not occupied by the battery holders
I used a drill to make some holes which I finished off with a craft knife and needle file. That took the longest time, about an hour for a decent job.
Then it was just a matter of assembling the switch and USB unit, with attached LED into the case. Due to precision hole making, these were a nice push fit.
Then it was a matter of soldering the wires from the battery holders to each other (+tve to -tve) and one to the USB unit, one to the switch, and one between the switch and the USB unit.
I should mention at this point that some web research outlined that the center pin part of those adaptors is +tve.
I melted a bit if excess plastic with the soldering iron to anchor the other end of the USB unit to the case.
Some tape tidied the only wire-to-wore soldering and it was ready for business. I packed out the battery to case void with some polystyrene wedges to stop it all rattling around.
As you can see, it works a treat and it actually looks quite professional too…
Before the lid goes on.
With the lid on, charging iPod.
Red LED indicates charging.
The complete unit is a reasonable size, but with 24V on board, I am hoping it would be good for a few charges.
220nt for a battery pack for any USB charged device is pretty cheap.
A couple of hours to make it, and I am not into electronics (no kidding, I had to even buy an iron).
Well worth the effort I reckon.
If you were a real geek:
You could put in a external DC input, and a charging circuit. Then you could use rechargable batteries which would save money in the long run, but I figure I wont actually use this unit more than a few times a year MAX so I’ll just stick with 80nt worth of once-use batteries.
Some things I’d like to know though…
What sort of safety features would be good to put in there (i.e. a fuse)?
How long will 24VDC for 16 x 1.5v AAs provide charge at 5VDC 500mA max?
What about heat?
Disclaimer: I just built this to see if it could be done, I haven’t tested it in any way, so if you want to make one, do so bearing this in mind…