usb battery power bank recommendation

[venzi]

I've been researching different battery power banks on amazon to power my USB pump, but can't seem to find one that fits the following criteria

1. real rated capacity (reviews keep mentioning actual battery capacity is less than advertised).  I want one that's at least 20,000mah (real capacity)
2. pass through charging (so that the pump will be running when the power bank is charging or fully charged)
3. works with lower amp devices (without the power bank shutting off due to the BMS).  My pumps use 3watts at 5V so that's roughly 0.6amps.  I could connect 2 pumps to one power bank and that would theoretically increase the amp draw, but maybe that doesn't matter if the BMS threshold is set on a per port basis.

Anyone have luck recently finding one that works for you?  Older items on amazon are sometimes unavailable.

Edited August 10, 2022 by venzi

[nabokovfan87]

I can probably help you with this one! I apologize for the delayed reply.

I use one that might meet everything you're looking for, but I wish to better understand what it is you're specifically trying to find.

1. Capacity is listed, but obviously there is overhead as well as a difference in type. Some batteries hold charge for a long time, others focus on having a long lifetime, and others try to have their own advantages.  Is there a specific battery type you're after? Holding a charge without draining fast for emergency use storage? Or is this something where you would use the device and have it available when need be for the tank?

2. Pretty much everything has this now if it's decent. I will say.... You're speaking in terms of a battery backup for a pump which is a very different thing (unless I'm inferring it differently).  That being said most portable batteries will charge and drain at the same time without real issues. There is some loss there because of it. I would recommend having one that hooks up to a USB solar panel as a SOLID option to charge it as well. The added cost just being the correct wattage panel to charge it via USB.

3. No matter what, it's likely very common that you're going to run into issues with this. It's not a negative, but it's just a thing. My biggest issue was the AC to DC to AC conversion and how much that drained batteries of a good capacity. Using a DC battery to a DC based pump worked best. (My battery bank to the nano USB charger) This lasted about 4 days if I'm remembering correctly.

[venzi]

@nabokovfan87 Hi.  No need to apologize 🙂 So here's my use case, I have 2 USB pumps 5v DC (rated at 3watt).  I'd like to keep at least one (if not both) of those pumps permanently hooked into a USB battery power bank to act as a cheap UPS of sorts (for power outages).  Ideally, I want peace of mind that at least one of the pumps would be able to run for 24 hours.  I would be OK with some battery memory loss due to the pass through charging behavior and needing to replace the power bank every year or two.

cost is a factor as well b/c if the power bank(s) starts creeping up to like $50+, then I might just opt to get a portable battery power station (something like this basically for $100 range).  Although, to my knowledge, the low amp draw and auto shutting off might be an even bigger issue w/ the larger power stations.

I did a test with a 10,000mah battery power bank that I own (it's been very lightly used for 2 years) so I think it shouldn't be suffering any memory loss yet.  But the results were very disappointing.  I hooked up one of the 5v DC 3watt pumps for 7 hours and it drained from 95% down to 28%.  Obviously it's not going to be a linear draw down, but roughly extrapolating that result would yield 9.57% battery used per hour, which yields about 10.44 hours total. I did the conversion and this meant that my battery bank that's rated for 10,000mah was actually closer to 3000mah. 

For some extra info, I used a power meter to monitor the power draw using two different 5v usb phone chargers.  One rated at 2amp and one rated at 1amp.  And these were the results

2amp charger: 124v ×0.021 amp×0.72 power factor =1.87w
1amp charger: 124.1v ×0.027 amp ×0.48 power factor = 1.61w

Thanks.

[gardenman]

I bought the "Mregb Power Bank, Solar Charger, 36800mAh 5V3.1A 18W PD QC 3.0 Dual 2 USB Port Built-in Powerful Flashlight IPX7 Waterproof Dustproof Shockproof(Black)" that Amazon had on sale recently for under $20 and used it for almost two hours on my little USB air pump during a recent power outage and it still says it's fully charged. It has status lights on it instead of an LCD readout, but all four status lights are still lit indicating a full charge after two hours of use. Do I think it truly has a 36,800 mAh rating? Probably not. But it does what I need it to do, at least so far.

In your use case where you want it to come on automatically if the power goes out, you might want to look at computer UPS units. Just plug in the air pump power adapter into the UPS and when the power goes out the UPS should just take over without a hiccup. They're not especially great at powering larger air pumps long term, but since you're using a USB pump anyway, they should do fine. You're looking at $50 and up for one of those.

[TheDukeAnumber1]

@venzi

I'm not aware of a product that meets all of what you're looking for atm. My personal way of doing things is I like to use 18650 battery chargers that also have a power bank feature. That way I can vet the batteries and I have full control of the batteries that go into it. I can move or replace them if they go bad or if a power outage is extra long. I have good things to say about the Nitecore F2 Flex, Xtar PB2S, and the Efest 4213 LUC V6.

[nabokovfan87]

On 8/11/2022 at 12:57 AM, venzi said:

cost is a factor as well b/c if the power bank(s) starts creeping up to like $50+, then I might just opt to get a portable battery power station (something like this basically for $100 range).  Although, to my knowledge, the low amp draw and auto shutting off might be an even bigger issue w/ the larger power stations.

Yes, this is your biggest issue right here.  Say you take something like this and hook it up to a solar panel (they make them).  The boards on those "stations" are a lot more complex.  9 times out of 10 they are charged by plugging it into a wall. That means from the gate you're running AC power to a DC battery.  That creates issues with what type of battery you can use and issues with what specifically is driving the output.  Power circuitry itself is pretty straightforward but can get pretty complex depending on how things are designed.  Do they make everything from 120V down to a 12V rail and then break that down into smaller amperages to give you what all of the low power circuits need? If so, this is where you're spending the majority of the battery's effort doing something that you won't remotely need or use.  There is a video I'll send in DM because it links to a competitive store, but it's a very good technical analysis of one situation using the exact same batteries in 4-5 different devices.

There's a few pretty basic ground rules to minimize the impact. 
A.  A smaller batter is actually better at reducing losses on extremely low power loads.  If you're overhead is 5-10%, you're going to lose that % of the battery no matter what you're actually drawing. The draw is essentially 0 in the eyes of the battery and your loss comes moreso from resistance of the wires, the individual components on the board, and very little power is drawn from the items that you're attaching.  What does this ACTUALLY mean for you?  This means that you might be better off running a pump that is 4-5x the wattage and running multiple devices off that one pump and using a gang valve, than you are by connecting 2-3 smaller pumps.  I did the math for this on the difference between the nano pump and the ACO usb+battery pump and it was negligible.  The difference isn't anything that your circuit is going to notice. 0.6-1.5w compared to 2.5w or power draw.

This simply means.... how do you not kill the battery and keep the battery alive as long as possible under this load.

 

On 8/11/2022 at 6:46 AM, gardenman said:

It has status lights on it instead of an LCD readout, but all four status lights are still lit indicating a full charge after two hours of use. Do I think it truly has a 36,800 mAh rating? Probably not. But it does what I need it to do, at least so far.

With the majority of these things, 100% down to 50% is a pretty constant drain in rate.  This means it's a pretty consistent timing from 100% down to 75% and from 75% down to 50%.  When you start getting towards the end of the charge it might happen a lot quicker than you think.  i.e. this is why you usually don't want to fully charge lithium ion batteries over a certain % or down to a certain %.  This extends their life and the charges last a bit longer as a result.  This is also where something like "cycling the battery" every so often, especially under high use cases and retrain the batteries to work a little better longer term. 

 

On 8/11/2022 at 6:46 AM, gardenman said:

In your use case where you want it to come on automatically if the power goes out, you might want to look at computer UPS units. Just plug in the air pump power adapter into the UPS and when the power goes out the UPS should just take over without a hiccup. They're not especially great at powering larger air pumps long term, but since you're using a USB pump anyway, they should do fine. You're looking at $50 and up for one of those.

These also suffer from the above mentioned AC --> DC --> AC conversion issues and a high loss in terms of how long the power will last. 
In my use, one of those lasted about 8 hours (a big one used to power a portable "station" as well as have enough current/capacity to charge a car battery).
While my little DC-->DC battery bank lasted 4 days.

It's a crazy interesting, frustrating issue because the "best way" to create what you need is usually by making it yourself.  From my own hassle trying to set this up longer term I can only recommend what others suggested to me, wiring it yourself, or going ahead and setting it up to use solar power.

This is what I messed around with, some test results in the thread are there, but it's by no means complete. 

The "best" backup available is the ecotech stuff, but all of that is specific, proprietary connectors too.  I found out that making these for reefs is something a ton of people do, but it's not something where you get a long life of power from that device.

 

On 8/11/2022 at 12:57 AM, venzi said:

I did a test with a 10,000mah battery power bank that I own (it's been very lightly used for 2 years) so I think it shouldn't be suffering any memory loss yet.  But the results were very disappointing.  I hooked up one of the 5v DC 3watt pumps for 7 hours and it drained from 95% down to 28%.  Obviously it's not going to be a linear draw down, but roughly extrapolating that result would yield 9.57% battery used per hour, which yields about 10.44 hours total. I did the conversion and this meant that my battery bank that's rated for 10,000mah was actually closer to 3000mah. 

And the real problem is that while you start with ~10% for the yield, it's going to be 8% and then lower and lower because of it being a certain type of battery or temperature changes over time.  A lot of batteries aren't designed to be run 24/7.  Because of the change in the way we use batteries, you're even seeing cars and other devices with different battery technologies to handle the different loads a lot better.  I can't find a link with the full details, but needless to say it's being "worked on" now because LEDs are much more efficient and used in a higher rate.  Most things are USB as a standard these days, etc.

Interesting stuff for sure.  https://www.saftbatteries.com/media-resources/our-stories/three-battery-technologies-could-power-future

Edited August 11, 2022 by nabokovfan87

[venzi]

wow this is amazing feedback thank you everyone📚 @nabokovfan87 @gardenman @TheDukeAnumber1