I have been aware of all the external battery solutions for Sota operation, and I share here with you my solution, I have always my work Laptop, and the battery is a 3S2P using the famous Samsung 18650 26f ( 11.1 v 5.2ah ) and to avoid the additional checks at the airport , I decided to build this single cable that connects the battery to the ft817 with a fuse protection , when full charged holds more than enough capacity for a sota activation.
73 all
Nuno CT2IUV
My new Dell laptop has a 2S2P battery 
Step-up switching regulator? 
Ron
VK3AFW
I had Nuno’s idea sometime back. It’s the classic teaser… where do you hide a book so nobody can find it? In a library of course. How do you get a Lithium battery in your carry on luggage without grief from security? Make it look like something they see in hundreds of business travelers bag’s every hour, a spare laptop battery!
So I now have this uber-cool Ultrabook laptop that weighs nothing (compared to my last laptop), has a fabulous screen, multitouch trackpad, big SSD, big memory, fast i7 CPU, USB3 and will run for 10-12hrs on a charge and the damn thing has a 7.4V battery. 
This is a Nuno’s great idea.
However my laptop battery is internal. So, no luck to me on this one.
Maybe on my next laptop…
BTW: Congratulations on your’s +500 SOTA points
73
Just do not know how long I have this solution , because I know that the new dell laptop models already have built-in battery like my macbook air and this is bad news 
Compatible versions of this specific battery may be available from electronics suppliers such as CPC etc (In UK). Worth checking.
73 Phil
I have been using recovered Lap Top batteries for Sota use for quite a few years. I acquired a job lot of 3s and 4s laptop batteries at a car boot sale for £1. I stripped out the internal charging arrangements and re-charge them using my usual LI balanced charger. Not as sophisticated as Nuno’s excellent scheme.
73, Frank
Me too !
I was lucky to get for free a whole stack of Dell batteries in good shape, and several laptops that used that specific type of battery.
My first SOTA-pack (using the FT857D) contained two of those in a homebrew box, to couple two of those in parallel, making a 9Ah battery @ 16V (which is OK for the FT857D , not for a KX3)
Best thing : in that model laptop, you could exchange the Floppy or CD drive for a second battery, so that’s what I do , I put two batteries in a laptop and both will be charged (one after the other).
I wrote an article about this setup in our school club magazine here : http://users.khbo.be/on4hti/boekjes/on4hti_19_2.pdf (see halfway page 16)
Happy reading if you know some Dutch, otherwise enjoy the pictures or ask Google for a translation 
73, Luc - ON7DQ/KF0CR
PS : not all laptop batteries will work by tapping into the + and - connections , most of them need to be “enabled” (in the case of those Dell batteries, they need a 10k resistor between pin 5 and 7, see schematic in that article)
An idea for 4s packs: 1 or 2 or 3 diodes in series to reduce Voltage. Check the rating if You want to go QRO!
I tried an old IBM thinkpad some time ago. That’s what I learned:
I could not figure out how to “enable” the battery. So I connected to the cells directly. This was no good idea at all. After three cycles the laptop did not charge the battery any more. All battery stats are logged unerasebly for safety reason. That’s the reason why it’s useless to change cells in an old laptop battery. (The cells are still in good working condition, no exhaustive discharge, by the way)
I use 18650 on all my sota rigs. (FT-470 and compatibles, FT-290R, KX1) 2S is sufficient on the FM handies for most of the time.
I’m still looking for a homebrew charging and deep discharge protection solution. Many cells had an honorable death in sota QSO…
73 de Martin
