I remember a long time ago when the Compaq IPAQ H3630 was a popular PocketPC device but the battery was short live so some people actually created their own portable charger using 4 AA batteries.
So now, is it possible to create your own Blackberry charger with 4 AA batteries?
I assume each battery will be 1.2v (rechargable) and if you put in serial, it will be 4.8v (close to USB 5v).
I have a DigiPower Power Plus 2 in 1 charger (Model #EBP-TM21) which worked great with my Bold 9000, but doesn't have enough current to charge my Bold 9930. The battery in this puts out 500ma, but I believe a minimum of 750ma is needed to charge the Bold 99x0s. I'm still looking for a replacement.
I've picked up a few external batteries from Monoprice that work great. I have the mini-usb models and just use a micro adapter with my 9900 and playbook, works great. Super cheap too as you can get a 2900mah pack for under $15, they put out 800mAh so there's no issues with providing enough current.
My project of making my own portable battery charger seems to be more possible but I dont know how to calculate the output current of these 4 batteries.
Just to share, USB maximum current output is 500ma and I always charge my phone through my USB port. This means that as long the current doesn't drop too low (below 500ma), I should be safe. But if I put 4x 1.2v rechargable batteries 2450mAh, in a series, resulting output would be 4.8v 2450mA isnt it? That seems very high isn't it (at least theoratically)
You don't need to worry about going over the mAh rating, the charging circuits in the phone will limit it to a safe level, you should be more worried about voltage being as close to 5v as possible or else the battery won't get a full charge.
Additionally the batteries do have a specified discharge rate, which is the maximum mAh that can be drawn from the battery at once, the 2450mah is the batteries total capacity.