My N900 was sold to me with a tired battery that barely made it to one day of very mild usage. Clearly this was unacceptable, so I researched aftermarket batteries - coming to the conclusion that everything available officially is either too weak or too expensive, and the only way out are homemade custom batteries.
So I decided to make one, but because I take to heart the saying "
anything worth doing is worth doing to excess", I decided to make it on steroids.
Feast thine eyes, mortals, upon my creation:
Edit:
dead links! Imageshack ate my pics and I can't be arsed setting them back up properly, so here's an imgur album.
IT'S ALIVE! IT'S ALIIIIVEEEE!!!
Ahem.
Those are three 18650 lithium-ion cells, of the kind used to make laptop battery packs. I rather doubt they have the stated capacity of 2.5 Ah, as they're Chinese cheapies (I paid about $3.5 each from DealExtreme); previous experience leads me to believe they should have anywhere from 2 to 2.2 Ah, but who knows, they might surprise me - it's happened before. I have a professional RC charger that I could use to test them properly, but with such a large pack it'd take a while and to be honest I just can't be arsed.
I'd like to find some sort of protection for the battery, but it has to be fairly resistant without making this thing even more bulky; I still have to think about that (I'll probably end up using cut-up CD cases).
Is it comfortable, you ask? Well, it depends; it's still pocketable, but whether you'll feel discomfort pocketing it depends on the depth of your pockets and how used you are to carrying lots of stuff in them. I'm used to that and I have fairly deep pockets (they're one of the essential parameters by which I choose my clothing), so I find the size and weight tradeoff to be acceptable, though a bit of a handful. Fashion victims with skintight clothing and/or tiny purses need not apply.
Runtimes? Theoretically about a week, give or take a day. It took two nights and half a day to charge the pack fully (the cells are shipped at 40% charge); since then I've topped it up at night and it makes it to the end of the day without dropping a single notch on the battery gauge.
A few more pictures of the mutat... er, modification process:
Lineup of the batteries, disassembly of original battery, JST connector soldered to battery PCB
PCB fitted then glued in place, setup tested with a spare 18650 cell.
Assembly and soldering of the big battery, melt-glued on the back casing, and a view of the casing's underside featuring the other end of the JST connector.
Edit: I'm no longer using my N900, but for the benefit of anyone who might be thinking about such a modification: three cells really are a bit too much. Since writing this the pack degraded into uselessness and I rebuilt it using only two 18650s of better quality (if I were to do it again I'd use Sanyos; 2.6Ah ones are fairly cheap on DX). It's now much less pocket-unfriendly and looks like this:
