http://www.headphoneamp.co.kr/ftp/sijosae/Gallery/ - view Sijosae's Designs
Originally I was assmebling Radio Shack pre-made battery packs (2xAA or 4xAA) in Altoid tins with USB (5V) connectors. However these AA cells were large & required both frequent battery changes, low voltages, required cables and had poor charge times for a dead iPod...problems.
See Ted's excellent reviews: http://home.speedfactory.net/tcashin/ipodbattery.htm
Firewire has better potential, smaller packages and requires no cables. Newer iPods only...
Using rechargeable NiMh 9 volt batteries provide higher voltages for use with firewire than AA's, although most have only 700mAh while the AA batteries can be obtained up to 1200-2700mAh. However AA Packs of 6 or 8 can be awkward, heavy and hard to manage easily. Alkaline 9v's can be had online or at discounts as low as 55 to 99 cents ea.!
So we use 9v in series or parallel with firewire!
comments on AA vs. 9v batteries? Rechargeables vs. Alkaline dry cells
Step 1: Concept & Specifications
Working on small Cmoy amps I found many small designs online I liked. The Duracell was perfect for a single 9V solution. An Altoid tin will easily house Dual 9v (serial or parallel) and provide power similiar to the Apple AC adapter and the IEE1394 firewire output from a desktop or laptop.
Having used USB powered at 5 volts this promised to provide better performance for both old and "new" iPod's.
Firewire specs: http://www.1394ta.org/Technology/Specifications/
Step 2: Regulated or Unregulated?
Regulated - comments?
I built some regulated USB 5V battery packs and direct wired units with both USB and iPod 30 Pin Dock connectors. Using the voltage regulators waste extra voltage as heat and requires MORE voltage and battery power than required.
Higher tech and higher cost is the DC/DC converters and the IC voltage regulators "LDO" - low drop off as well as (step up) or 'step down' SIP packages...very efficient...
The iPod's have some built in voltage and current regulation. See Apple specs. Batteries tend to provide stable consistant power as it drains down. Do we really need to also regulate and clean power from dry cells? The iPod's AC adapter also supports wide ranges of inputs and outputs at up to 640mA and 12.5v. Firewire from PC/Laptops will deliver IEEE 1394 via the standard at 12-30v that the iPod must handle 'without' the AC regulator...most PC sources for 1394 are also "unregulated".
both camps have points....your position and comments welcome.
Step 3: Parts and Sources
I am considering buying bulk and reselling with discounts on some parts...what do you find hard to get or what are some reasonable prices?
Jameco - will Match or BEAT any pricing you can find...
just add "dot com" for suppliers websites...
Step 4: Next projects !
Post or email me for custom designed cable, battery packs, connectors etc...
Prototypes available for some projects...
Step 5: Future
Get smaller batteries etc...from cell phones or other "cheap" sources, gameboys, toys or other refurb or broken devices...PCB's for recharging...
New RC toys have great battery packs!