DIY USB power bank?

Impressive. Thanks

I also have a Tomo. It’s slow, but it’s nice that each bay is operated independently.

If you’re just trying to use your 18650’s, a case is good, but I wouldn’t go this route to save money over a prebuilt powerbank. The only problem I’ve had with powerbanks is that they cut off earlier than I’d like, so if I try using it for charging my rc batteries, the powerbank will turn off as the rc battery is in the last 10% of the charging cycle because the current draw is low enough that the powerbank shuts itself off.

Thanks everyone. I’ll check out the Tomo unit though I was really looking for something more compact that takes only a single 18650.


I have seen very portable small cables that can snap onto the end of any 18650 allowing it to be recharged from any USB port.
It would be nice if these could be used in reverse as well to charge another device.

agent80 wrote: I am looking for a 1-2 battery DIY charger with an output of 2 amps. Most seem to have an ouput of 1 amp. Can anyone suggest. Thanks

This satisfies both requests:
Mini Magnetic Emergency Charger Portable

The Xanes is very good. Unfortunately the battery is exposed. I wouldnt want to assemble the battery everytime I want to use it. Nor do I want to keep the battery connected and throw it in a pack. Without a case, the battery could be punctured.

If we consider that DIY Power banks cost $14 for a 2 cell bank, and $10 for the 2 cells the cost is $24. Now when one can get a Xiaomi 10,000 mAh power bank for $20.00 do the DIY banks make sense?

For me it made sense because I already had many 18650 batteries so no cost for cells. Also it gives me the ability to swap in charged batteries and not have to wait to charge up the powerbank. One of my daughter also carries one when she goes backpacking and there’s no ability to charge a powerbank.

Also, it is environmentally better to buy a DIY powerbank first, as you can easily replace the cells.

Also, they include nice features, like balanced parallel charging, meaning in you put in a 4V cell and a 3.5V one, one won’t dangerously charge with the other, higher efficiency, better looks, and easily swappable cells.

Which ones do ” balanced parallel charging” ?
I have to admit I never use any of mine, as I am at home or in the car. I’m curious to know if you or anyone uses the power bank often and for what?
Thanks, Jerry

There are the Tomo power banks, and the XTAR PB2 which I am using currently.

Thanks, I have the PB2 on order.
Regards, Jerry

Yes they do, for a number of reasons.

We already have the batteries, and don’t generally pay $14 for a 2 cell, I bought a 4 cell for under 10 a few months ago.

A DIY can do everyting a fixed cell can, PLUS you can charge your other batteries with it, reload it instantly, use it to reload any other 18650 device instantly, use an empty slot to store the cable and adaptors or something else, use your flashlight battery to charge your phone in an emergency.

Also, if the circuitry blows, the cells are unaffected, and immediately available, if one of the cells goes bad, the bank is unaffected and immediately available.

The reason I plan to use something like this is for travel. I carry an 18650 headlamp (skilhunt h03), so I can hot swap batteries directly between the powerbank and headlamp as needed.

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.