USB Power bank that doesn't switch itself off

[jc101]

I have a USB device which draws around 150ma which I need to power from a battery pack, for up to 4 days. A 20,000 mAh power bank ought to be able to do capacity wise. I've tried a few, but they all seem to switch off after a couple of hours. Which is really annoying.

Whilst I could make something, I need something off the shelf. Not least as I'm looking at needing around 50 of them.

Anyone know of a power bank that has a USB-C output that doesn't have an auto-off?

[thm_w]

Switching off after a few hours is odd, unless you are saying the device draws 150mA and then sometimes decreases that current low enough to the point the power bank shuts off. Usually it has to be >100-200mA or the power bank will switch off after ~30s.

You can either:
- add a dummy load resistor
- add a smart pulsed dummy load
- find a model that has an override to not shutoff

https://www.reddit.com/r/batteries/comments/14jqoso/preventing_powerbank_from_shutting_down/
https://www.reddit.com/r/camping/comments/1ac05at/any_portable_handheld_power_banks_that_dont_shut/
https://voltaicsystems.com/always-on-batteries/

[Peabody]

I agree that the first thing to do is add a resistor across the load to increase current flow, and then see if it still switches off after a few hours.  If it does, then something else is going on.  Anyway, you need to answer that question before you order power banks you don't need.

It sounds like what you need is more of a UPS device than a powerbank.  Powerbanks are more for charging batteries, not powering circuits.  Hence that obnoxious auto-off on low current.  But I don't know of a mini UPS with a USB-C output.

[Nusa]

Search for "Always on USB power bank"....there are some out there. (He said USB-C, but clearly that isn't mandatory unless he needs a PD voltage other than the 5V default. A different cable or adapter is cheap for the right solution.)

Of course, your application suggests something simpler and cheaper, if money matters. A battery pack in your preferred chemistry and size, no smarts at all. "RC battery pack", which can be had in many sizes or made to order. The right cabling is a detail...having them made for you is practical if you need 50+ of them. No need for a charger in the field...you can swap batteries when required and have a separate charging solution (wall wart and cable).

[Peabody]

I was thinking of something like this:

https://www.amazon.com/DWEII-Lithium-Battery-Charger-Converter/dp/B0DCVRXTW8

Boards like these come in 1, 2 or 4 18650s in parallel.  They combine a charger with a boost converter.  But the output would just be header pins, not a USB-C port.  You would need to test something like this to make sure there is no dropout when charging power is suddenly removed.  Most of the money here would be in the batteries.

Also, there's apparently no on/off switch between the batteries and the boost regulator, so the only way to completely stop battery drainage is to remove the batteries, which you generally don't want to do, particularly if they are in parallel.

[jc101]

Thanks for the suggestions.

All I need is 5V, the devices have USB-C connectors and the two 5.1k resistors to trigger a USB-PD supply to activate. Drawing more power isn't ideal as larger batteries would then be needed.

The Voltaic ones seem ideal, but are expensive. I will see what my google-fu can uncover.

[Peabody]

It looks like some of the Anker power banks have a "trickle charge" mode, which makes them stay on all the time.  Anker would probably be a good bit less expensive than Voltaic Systems.

Anyway, I hope you will report back on what you tried that worked or didn't work.

Edit: But it looks like the Anker switches back to normal auto-off mode after a few hours.  Rats.

[DaneLaw]

Most modern power banks have trickle charge mode, a mode optimised for charge low current devices, like earpods etc
You tend to enter it, by pushing a few times on the button or holding it in for a few seconds... it varies from device to device.
I dont think any of the power banks I have, dont have it, so its very common

[JimKnopf]

In 2020 I used this one https://www.ramser-elektro.at/shop/bausaetze-und-platinen/powerbank-anti-off/ which is a pulsed dummy load.
Can be programmed with different dutycycles to emulate different loads.
Another solution was to plug a USB-C to USB-A adapter in the USB-C Port of my ugreen PB178 10000mAh Powerbank and use the USB-A connector for the device i wanted to power. I guess the (probably 56k) resistor on the CC pin kept the Powerbank active.

[Psi]

LTT will be releasing their USBC power pack at some point this year.
We don't really know much specs yet or if it will be 20,000mAh, but i'm sure it will be well designed and I cant imaging it having an annoying auto-off.
It's also going to have removable 18650's so you can replace them if they wear out.
And is firmware upgradable.

[jc101]

I'm still looking.

I would have thought that USB-C with the resistors to tell the supply "I'm here, keep on" would be the norm. Sadly, no. The "best" I've found so far is a 24,000 mAh version of a Fresh'n'Rebel bank. But only the this capacity, larger or smaller, they turn off. Plus you must use the USB-A port.

Some with low power or trickle mode seem to work, but after a number of hours they auto disable the feature and turn off.

[JimKnopf]

Just checked it again. CC1 5,11k, CC2 2,55k. Still active after 4 hours with the USB-C to USB-A adapter.

[jc101]

I've tested a 20,000 mAh UGREEN supply, it shuts off after around 30 mins on using either the Type A or C ports.

Not heard of a 2.55k on the CC pins, is that part of the USB-C PD specs? The devices have 5.1k on both CC pins, no chance to modify them.

[DaneLaw]

LTT will be releasing their USBC power pack at some point this year.
We don't really know much specs yet or if it will be 20,000mAh, but i'm sure it will be well designed and I cant imaging it having an annoying auto-off.
It's also going to have removable 18650's so you can replace them if they wear out.
And is firmware upgradable.

Sadly not many with high-wattage powerbanks (+100W) tends to have exchangeable 18650 cells..  were a few models from a Chinese maker around a decade back.. they were quite advance powerbanks.
They also got a dedicated "always on" that the user needs to manually activate, but it will obviously drain the battery, as it won't turn off no matter the load or time, and display always on.

Have quite a few of them as it was some of the first back  around 2015/2016 that could do +100Watt, but they are around a decade old, so not even sure they are still on the market.. Were around 30 bucks, without batteries.
8x 18650 bay, fitted them with LG HG2 3000mAh, so around 24k mAh.
Adjustable DC out. 3.0v to 24.3v
Power delivery (PD up to 20V / 5A)
2x USB A with fast charge, Qualcomm.

Pretty much use them for anything.
Charge DJI batteries out in the field before PD was implemented on DJI drones, easy to dial in the correct voltage and with a good high wattage output
Been quite handy over the years for everyday things like laptops, tablets, scope,  pretty much all items that runs on DC.
Surprised going through imgur, and to see how many various things I been using them for, even induction modules.
A dedicated adjustable DC output. Definitely a plus, as trying to dial it in on modern power banks with fx a USB meter.. gets tedious fast.

[Psi]

Always on isn't really needed, just always on while the load is above X mA.
Unless the connected device is something with its own battery that may draw 0mA once fully charged until it drops to 90% or something, in which case yes, that is annoying and always on is needed.

You could of course fool it with some extra timed load that periodically turns on to prevent <XmA for longer than the timeout.

[DaneLaw]

Always on isn't really needed, just always on while the load is above X mA.
Unless the connected device is something with its own battery that may draw 0mA once fully charged until it drops to 90% or something, in which case yes, that is annoying and always on is needed.

You could of course fool it with some extra timed load that periodically turns on to prevent <XmA for longer than the timeout.

The benefits of always-on power banks versus low-current mode (aka trickle charge) and the reason why I, in certain cases, pursued "always on" power banks, like the units highlighted above from around a decade back, is that it opens up for a lot more use cases.
Most low-current modes (often activated by double-clicking the power bank's button or holding it in) are often trickle-charge timers that turn of after a given time fx 2 hours, where always on, will work a little like an AC input source until its depleated.

If you have a device that has its own battery, and you wanna subsidize it with a powerbank with low current mode, the moment that battery is full on the unit, the powerbank turns off, and when the unit's own battery depletes, its difficult to get the powerbank to source it again, as the device aint gonna knock & holla "wake up, pls source me again", even though the powerbank is almost full.

* Power Bank with low current mode, for fx devices that consume very little ampere: Charges the device once, shuts off, and lets the device eventually drain and die.
* Power Bank with Always-On: Keeps the device locked at 100% indefinitely until the power bank itself runs completely dry.

I don't know if things have changed over the years, though I kind of doubt it. Previously, trickle charge units (aka low-current mode) were often locked to a timing aspect, like 2 hours.
However, having the ability to attach an always-on power source that can subsidize a device with a limited internal battery can be quite useful in certain scenarios.