I hope I can help shed some light on this subject.
We all want longer running times, we can either reduce power consumption (Unlikely) or we can increase storage capacity. (DUH)
I’m not an EE and I don’t pretend to be but batteries are kind of my “specialty area.”
***Disclaimer*** Below information is presented to the best of my knowledge and you are responsible in how you use it. ***Disclaimer***
The examples are all theoretical with 100% energy transfer. Sadly 100% is not the way it works in real life. 
This will take some time so get comfy.
Basics:
Hook batteries up in series = more voltage
Hook batteries up in parallel = more current
The E-pod I believe is running on 7.2V 1400mAh battery
FYI: sometime the marketing people write incorrect capacity for some batteries to make them look superior to their competitors and/or it only has that capacity under certain optimal conditions.
The mAh rating on the battery is the storage capacity it stands for milliamps an hour. The state of the art AA battery right now is 1700mAh (1.7A).
That means that you can draw 1.7A for an hour before it dies or you can draw 425mA for 4 hours before it dies, you get the point.
So, if you currently have 1400mAh battery in your e-pod and it lasts 8 hours, therefore it draws 175mAh
But if you replace it with a 1700mAh battery that means you can run your E-pod for 9.7hours, 1.7 more hours of surfing!!
Advance:
-NiHM batteries require special treatment or else they die quickly.
-Unlike NiCd batteries, which can take more of a beating, NiHM require regulated charging or else they develop hydrogen bubbles between its plates and inhibits it’s ability to hold a charge. (This is not a good thing)
-To charge NiHMs most chargers cut off the charge when it detects –DeltaV, peak voltage, and/or when it reaches the maximum time allotted for that particular battery to charge. Some battery chargers also cut off charging when it detects the temperature of the battery has reached a unsafe level (either too hot or cold)
-The problem with dropping in a battery pack with a larger capacity is that it might not reach that –DeltaV, voltage peak before the shutoff timer kicks in.
*The variable C is the Charge rate so 1C equals the current needed to charge something in 1 hour and C/4 equals the current needed to charge something in 4 hours.
Example: 1400mAh battery charges at 1C (1400mA) it takes 60min to complete so the shutoff timer is set to 61 min. The battery reaches it’s –Delta Voltage at 60 min then shuts off. if the battery doesn’t reach it’s –Delta Voltage before 61min then the timer will shut off the charge to prevent battery damage. This is normal and good.
You then drop in a replacement of a 1700mAh battery, and the charger setting stays the same. You charge the 1700mAh battery at 1400mAh so it should take 73min to complete but you run into the problem that it doesn’t reach the -delta in the allotted time of 61min so the shut off timer cuts in and you are left with at battery that’s 85.7% charged (1457mAh) This is bad and gives you only a few min of extra run time.
So, if Epod’s charging system had a timer it’s bad then we need to change its charge setting or build a whole new charging circuit before dropping in a new battery.
Some more stuff: the rate you charge the battery has an effect on it’s life. If you do a normal charge, usually 4-3 hours, and don’t abuse them you can get a good 500-1000 Cycles out of them
But if you use Fast charge, 1 hour or less, the life reduces to 450-600 charges.
Another thought. We can rip out the entire NiHM system and use Li-ion, some advantages are lighter battery, longer run time, and faster charge time. But the disadvantage is cost and the number of cycles it can go through. With 3.6V per cell for Li-ion we’ll only need 2 of them to power the E-pod.
There’s still some other stuff but I’ll leave you alone for now because most of you might be suffering from information overload.
I’m testing out right now and I will share results once they are conclusive.
There’ my 2 cents on the subject.
How much fun the simple battery can be 
I mod anything I can get my hands on!
