DIY USB power bank?

1 to 2 cell and 2 amp charging

good reasons, thanks for the info.

I would not recommend the Tomo power banks.

They have problems with self discharging the cells too quickly.

What are the best at a reasonable price?

For a 2 cells powerbank, I would recommend the XTAR PB2. Best one yet.

For a much bigger powerbank, I would recommend:

I’ve tested it, and it is the only one which cuts off charging at always 4.19-4.21V. Never goes higher, and never goes lower. It can also charge at up to 1.95A(confirmed by my USB tester), and can output up to 4A before shutting down. Out of many other DIY chinese powerbanks that I bought and tested, it is the only one I actually trust my life with it, and sold it to many of my friends with tested cells.

It also has a reasonable efficiency of 88% at 5V 1A, and 86% at 5V2A, as per advertised specs and per port. You can’t easily remove cells though, but if something dies, you can actually remove it without any tools, unlike sealed powerbanks

For the ultimate DIY powerbank, I would recommend this monster, if you can easily buy it though, and can stomach the price:

I have a couple of the Tomo’s and I just put a piece of cardboard on the positive ends of the batteries until I need to use it.