USB powerbank WITHOUT auto off?

I'm hoping the collective can point me in the direction of a USB powerbank which can be permanently turned ON. I have a USB powered clock which on the lowest brightness setting draws so little power, every single USB powerbank I own, automatically shuts off. I have to set it to the highest output for the current draw to be sufficient to keep the powerbank operating.

What I'm looking for is a powerbank that will keep the USB output live regardless of the current draw (like a mains charger would). I realise this means the calls will run down even with no USB load, but need to be able to decide myself when the USB socket is live.

I'd like it to be a reasonable brand (not a no-name hope-for-the-best type product) if possible.

Any ideas?

I own this power bank:
https://www.fasttech.com/products/0/10004461/1341206-qidian-1a-1-5a-2a-4a-6-18650-mobile-power-bank
http://budgetlightforum.com/node/25609
The version without cells and accessories is way cheaper, but discontinued. It has a switch to deactivate the auto-power-off.

Not an ideal solution, because it requires some tweaking and wastes some power, but it is possible to build a dummy load that draws enough current to keep a power bank on:

http://www.dorkbotpdx.org/blog/paul/battery_pack_load

I've had the same issue in that I have these LED USB plug in boards that have a dimming circuit such that you can dim them down to very low current levels of which most power banks shut off. I've gone through a bunch of power banks and have found only a few that can manage to stay on. The following are the ones that will stay on at current levels of 1ma (or less).

1) Pocket Juice single cell power banks (Walmart) in black and neon pink
2) Ebay lipstick power banks metal cases you screw the bottom cap off to insert an 18650
3) Ebay plastic round power banks that are 2 piece white and a color
4) Ebay plastic square 2 cell power banks colors with white covers

Warning... I have found that circuit designs of power banks change often. I've found the square Ebay power banks (4) have mostly gone to circuits that don't support low current levels. It is also possible that others in my list may no longer support low current output.

I have some Pocket Juice power banks that are 2 cell and none of them support low current output. It seems any power bank with an ON switch doesn't support low current levels. I'm testing 2 Anker power banks and the first one turned off after about a minute.... the second one just turned off.... so I'm guessing the Anker power banks don't support low current as they too have ON switches. I have a few multi cell Ebay power banks (4 cells) that support low current but when I tried to buy another one I found they changed the circuit boards in them. Some power banks don't want to stay on even at 25ma current levels, some want over 100ma.
I've used these dimming LED boards and power banks in a power outage and to light up the area around my computer as they run for weeks using 18650 batteries that I've scavenged from tool batteries and laptop battery packs.

Some Xiaomi ones have a force on festure. It’s activated with a doube click of the power button.

http://www.mi.com/en/pb10000pro/

Thanks for all the suggestions. So far though, many rely on a degree of luck as ebay chargers, which are often unbranded, seem to change, making certainty of features unreliable.

maukka said:

Some Xiaomi ones have a force on festure. It’s activated with a doube click of the power button.

http://www.mi.com/en/pb10000pro/

So close, but the low power charging is for 2 hours only.

What I really want is a permanent on mode which is hard set with a slider switch, or other non-timed setting.

YZXStudio Powerbank can do it (and much much more), but it's a bit of a hassle to buy. Omnicharge as well, but it's expensive just for this purpose.

How about just a 5V boost converter from ebay connected to a bunch of 18650s in parallel?

edit: I'll go through some of my powerbanks and test them with minimal draw. Will get back to you.

Check out the Miller ML202. Been running now for an hour with minimal load. It also works as a UPS so the output doesn't cut out if you connect or remove it from a charger. HKJ's review.

Does the Miller still require an unprotected battery of a certain length without a whole lot of wiggle-room?

The 102 and 106 are in stock at the link provided.

Yes, doesn't fit long protected batteries. 102 and 106 won't work since they'll cut off power on their own.

ML202 is in stock here: https://www.aliexpress.com/item/Fre...tery-mobile-phone-IPAD-tablet/1029639250.html

Found another one that works, but this may be one of those ebay class powerbanks you don't want. I've got three and they function well though.

Here's what I have and the same one in UK but with different branding.

@maukka

Thanks for the great information. The YZX one looks fantastic, but with the issues buying it, and the amount of building required, I'm less keen. If I ended up having to update the firmware it would end up as a big fail. Too many risks.

The Powercard looks good apart from only being 2500mah.

That ML202 is looking promising, but I don't have any good unprotected cells, which then means I've got to buy more. But then again, in total price it should still be a strong contender. Maybe I missed it, but I didn't see anything in HJK's review about low power unless it was this "When overdischarge protection trips the discharge current is below 0.03mA"

I'm going to double check the power draw I need to maintain and post that as well.

EDIT: So it is 14 mA I need to keep running.

Just tried a NITECORE F1 I have, and although it did turn on automatically, it cut out after 15s.

subwoofer said:

EDIT: So it is 14 mA I need to keep running.

I tested at 12mA so you should be good. I'll let it run overnight to verify.

The ML202 was still on after 8 hours at 5mA.

Thanks, just ordered one off Aliexpress. I don't expect it to arrive for some time, but will post an update once I've tried it.

It's arrived, and none of the unprotected cells I have fit. Another order placed for some bare Samsung cells. Update once they arrive.

Strange. I measured and it looks like 65.4mm long cells should fit fine. I used a Sanyo 18650GA which are 65.25mm.

maukka said:

Strange. I measured and it looks like 65.4mm long cells should fit fine. I used a Sanyo 18650GA which are 65.25mm.

I only have button top unprotected cells as I find them more universally compatible. My recovered cells which were truly bare flat tops, all died some time ago. I'll do a few measurements once the new cells arrive.

The new Samsung bare cells arrived and just fit - no room to spare.

Onto testing it - and the results so far, is that it is no different to any of the others. It will not stay on at the required 0.014A.

I have a couple of old 'Charge Doctor' USB current meters that are quite inefficient. Each draws 0.021-0.024A on its own to light up its bright display.

0.024A does not keep the ML202 on (this is the V5.0 version of the ML202).
0.045A does not keep the ML202 on.
and adding the clock as well oddly it doesn't all quite add up as this shows as
0.052A still does not keep the ML202 on

in fact using one of the Charge Doctors on my existing USB powerbank actually does keep it on, so the ML202 I received is worse than the one I had. And it seemed so promising.

Is yours the V5.0?

That's too bad. Mine is V4.0