I want to make my own laptop battery using AA NiMH batteries. My AC adapter puts out 15V at 4A, so I figured I could run 12 in series (1.2V * 12 = 14.4V). I have a bunch of 2000mAh AA NiMH, so I thought these might work well. Then I can put blocks of 12 (i.e. 24, 36, etc) in parallel for more capacity. 24 of these batteries are $40 at Fry's Electronics, so this type of battery would be significantly cheaper than purchasing a new laptop battery, and it would provide flexibility (I can easily break the block apart and use the AA batteries individually for something else if needed). Then the block just plugs in where my AC adapter would normally go, and the laptop thinks it's running on AC.
However, this presents on problem. I have no way to efficiently charge these. Most chargers that I've seen will charge 4 at a time. I'd like to be able to charge 24 at a time, and I'd really like to be able to have the option to charge them with either 12VDC or 110VAC.
Is there an easy way to do this without purchasing a rather expensive already-built charger? Can I use a rapid charger that charges 4 batteries and plug them in parallel (so it takes longer to charge, of course), or will this screw with the electronics so it isn't able to properly detect when a battery is fully charged?
