Tech has moved along since these articles were written, with many off the shelf LiFePO4 options available. (Though if you do go lead acid, use an AGM; it will save you from many HCL acid spills.) E.g.:

https://ww2.cpapaustralia.com.au/blog/cpap-batteries

If you want more endurance or just want to DIY:

Big LiFePO4s: https://www.bioennopower.com/collections/lifepo4-batteries-f...

Portable: https://youtu.be/SJGKuriGRok https://www.youtube.com/watch?v=erS3b22FgmU

http://www.siliconchip.com.au/Issue/2016/March/Battery-Pack+... http://www.ebikeschool.com/how-to-build-a-diy-electric-bicyc...