Had to use my backup / spare AB the other day and running on 3 x AA eneloops had me a bit twitchy - I've heard the AB can be a bit power hungry. My other AB runs of a large SLA battery but has developed a fault over the lockdown somehow. So yesterday I fitted 4 x 18650 Lion cells, a Mini USB charging port, and a small inexpensive single cell charger. Below - the 4 cells in a parallel battery holder (giving 16AH / 16,000Mah of capacity at 4.1v) and also the charger at the bottom Below - Mini USB charging port. I like mini USB - much more robust than micro and much easier to see which way round to put it in! I'd use USB-C if it were commonly available for the charger parts. Below - I drilled a 2mm hole so you can see the charging status LED. Red = charging, green = full. I've just powered it up and it shows P7 in the control panel software, and I'm plotting the voltage over time - we'll which lasts longer, the AB, the tablet, or the 18R2 (powered by a bit lithium powerbank)! In all seriousness - I'll pop back out shortly and plug the tablet and powerbank on charge so they last the test Easy mod and costs very little. I'm going to attach one of these when it arrives: Though it won't be needed in all reality. The 18650s should last a loooong time. I've got better quality ones on order. This is the charger : (well, mine is very slightly different - a single dual colour LED, not two seperate ones, and mini, not micro usb) It will happily still run with three AA batteries installed too, as a backup. Prob not ideal, but it works. Very similar voltages.