[HomeBrew] External battery supply for laptop

[n6kyr at netzero.net]

All:
I would like to build an external power supply for my laptop (15 VDC). It needs to be rechargeable. I would like to use readily available components. So far, I have a few choices (maybe you can expand on some):

1) rechargable NiCad C cells with 2.5AH (max recharge at 1.2 VDC)
2) ditto except at 4 AH
3) a pair of 7.2 VDC 2.5 AH RC batteries hooked in series

I'd like to recharge them not only at home but also on the road via my car. I saw some special rechargers but quite frankly, $100 is not my cup o' tea. 

My plan is to get a plain jane Rat Shack multiple adaptor for the car and recharge a set of batteries (in parallel) at the 7.2-7.5 volt setting and then reconnect in series when powering the 'puter. 

Let me know and thanks. Cal, N6KYR. 


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