What to do when one battery is not enough for T520?

Hi guys,
I have a 9-cell battery for my T520. It is obviously in the laptop all the time. Unfortunately, most of my classes do not have power outlets readily available, so I have to charge my laptop every other day during the classes. We do some intensive calculations on our laptops that are hungry for battery power, that's why one 9-cell battery sometimes isn't enough (it depends on activity, but usually every other day I have to charge during the lunch time, instead of having a lunch - which is very uncomfortable).

So I have several options:

Option 1. Buy 2nd 9-cell battery and charge both batteries at home during the evening, so that next day I have both of them ready. Sometimes, I have so many things to do, that I have a hard time to keep track of the charge in my batteries. I have to charge one battery and then take it out and insert another one in the laptop and wait for it to be charged. During this time I obviously can't unplug my laptop to go to different room or sofa and e.t.c. So I imaging it could be very annoying sometimes.

Option 2. Buy a 2nd battery and an external battery charger for Lenovo, but that thing requires own power adapter, so I end up buying that too. Plus I've read some reviews on that external charger and most people complain about flimsy connectors. So I'm not sure if this option will be the best. The only good thing is that in this scenario I don't have to worry about switching my batteries to charge them, since one will be charging in laptop and another one in external battery charger.

Option 3. Buy a slice battery that attaches underneath the laptop. That way I don't have to save all my work and power down my laptop or hibernate while I switch batteries as in case if I go with Options 1 or 2. That saves me time and is more convenient, but my laptop overall becomes too heavy and bulky with 9-cell battery and another 9-cell slice battery attached. BTW, will I be able to charge slice battery attached to laptop at home or I'll end up buying another external charger? So I'm confused about this one too.

Maybe there is some other way to manage this issue? Do I have to power down completely before I change my batteries?

So what do you think guys is the best way?
I appreciate your patience in reading this long post and all advices are welcome. Thanks.

 

Slice.. you can charge it from your laptop no need for external charger

 

I believe there's another battery that goes in the Ultrabay, thus giving you two batteries in the machine. I have never used one so I don't know the pros and cons, but it's another option.

 

For your usage, I'd imagine the slice is most suitable. Sure, it'll make your T520 heavier, but you could always detach it and leave it at home if you don't happen to need it. Also, it takes away the problem with the 2 x 9 cell battery arrangement, allowing you to charge both batteries at once.

I think the Ultrabay battery is sadly not compatible with the Tx10 and Tx20 generations, other than the T4x0s series.

 

Thinking outside the box:
a) Get a desktop, remote in.
b) Long extension cord.

 

Slice battery, if you are already carrying a t520 the extra weight and size wont bother you after a few days.

 

i have t520 with slice battery. i used it for a few days but i do not use it any longer. it raises the laptop fairly high so u definitely need to keep that in mind. for me, it became too awkward to type. is it something i can eventually adjust? maybe. but i hardly need more than what i can do with 6-cell battery i have with T520...

with any luck, the ivy-bridge powered t530 with 9 cell battery might last as long as t520 with both 9-cell and slice battery. here u go, ur option #4

 

Surely other people in the class are having the same issue as you? I realize that having multiple classes in one day is a lot to ask of a battery, but perhaps some optimization of your computer might save you from having to pay for additional batteries. Are you sure you are minimizing power consumption, aside from the necessary computations?

 

Thanks everyone!
For now it looks like my best choice is to go with slice battery plus try to optimize my power consumption.
I very much appreciate your help.