Often, we need to power a 5V-craving project of ours on the go. So did [Burgduino], and, unhappy with solutions available, designed their own 5V UPS! It takes a cheap powerbank design and augments it with a few parts vital for its UPS purposes.
You might be tempted to reach for a powerbank when facing such a problem, but most of them have a fatal flaw, and you can’t easily tell a flawed one apart from a functioning one before you buy it. This flaw is lack of load sharing – ability to continue powering the output when a charger is inserted. Most store-bought powerbanks just shut the output off, which precludes a project running 24/7 without powering it down, and can cause adverse consequences when something like a Raspberry Pi is involved.
Understandably, [Burgduino] wasn’t okay with that. Their UPS is based on the TP5400, a combined LiIon charging and boost chip, used a lot in simple powerbanks, but not capable of load sharing. For that, an extra LM66100 chip – an “ideal diode” controller is used. You might scoff at it being a Texas Instruments part, but it does seem to be widely available and only a tad more expensive than the TP5400 itself! The design is open hardware, with PCB files available on EasyEDA and the BOM clearly laid out for easy LCSC ordering.
We the hackers might struggle to keep our portable Pi projects powered, employing supercapacitors and modifying badly designed Chinese boards. However, once we find a proper toolkit for our purposes, battery-powered projects tend to open new frontiers – you might even go beyond your Pi and upgrade your router with an UPS addon! Of course, it’s not always smooth sailing, and sometimes seemingly portability-friendly devices can surprise you with their design quirks.
Pardon the ignorance but why would I scoff at a TI part. Chip shortage?
That, and depending on the lineup, they can be expensive, unobtainium, datasheet-less or all three. Plus, they do weird things every once in a blue moon, like DMCAing sites rehosting old datasheets that they themselves don’t host. Feel free to chalk it up to my personal bias ;-P
Huh, I’ve never found a DS-less TI part. Some of the datasheets may be cruddy old scans if they’re a part from an acquisition, but in my experience all of their PMICs have had stellar documentation. What product families have missing datasheets?
Expensive and unobtanium, though, track very well with my experience.
What springs to mind – a whole lot of the TI bq{NUMBERS} fuel gauges inside our laptops are datasheet-less! As an engineer, I understand it, but as a hacker, I don’t forgive them for that ;-P
Not only does TI have the best datasheets and most extensive application-note library, if you have a problem with it you can post on their forums and usually get a response from a US-based real-engineer. Often within a few hours. In the case of processors you might even get a bugfix diff attached to the response!
That’s the support I got just as an individual.
Oh, and if you’re sourcing all of your BOM entries from LCSC, TI and other Western parts can easily be more expensive than they would be locally, because they often have to be imported into China to be sold from there. Doesn’t just apply to TI and depends more on where you get the remainder of your BOM from, it’s just that in this case, there’s a single TI part amidst a list of non-Western ones.
I think it may be a personal thing… Somehow i know quite a few other engineers who scoff at TI. I never asked why and just used the chips of TI if fitting and available…
But i think i have to ask them why they dont like to use TI-Parts… It cant be the shortage as almost all manufacturers are hit by it in at least some parts and lines…
TI has a reputation of giving you access / responsibility to control & configure everything and the kitchen sink. Not a problem if you need to granularity, but sometimes a bit of a PITA if you just need a simple solution.
Because the TI is a higher quality part, so that’s not very hacky.
Yeah, what’s wrong with Texas Instruments parts? I was rushing here to ask the same question.
I reccon that it doesn’t do exactly what the author wanted? So a shortcoming of the chip was my thought. Ivhad the same initial run action though ;)
When I start with a product design my first decision is which TI regulator to use.
I also look quite often at analog devices. Since the bought Linear, they really are a powerhouse especially in some areas.
As a 3D-Print-DIYer i also love them as they now own trinamic as well :)
… Heck, thise trinamic-drivers still are blackmagic to me sometimes…
I do the same. I love TI. There’s a comment above that TI parts do weird things and honestly, I’ve seen that with all of the switch mode power supply ICs. There always seems to be some weird mode or transient or something that trips me up. Maybe I’ve just learned the quirks of TI and I expect them now? Anyway, I love TI parts.
A read hacker on HD builds his ideal switch from mosfet
A real hacker on HaD builds his ideal switch from a mosfet…. that he fabricated from sand himself.
There, I fixed it for ya :)
The circuit in the box in Upper left block (for USB power) in raspberry-pi-3-b-reduced-schematics.pdf is a crude form of that.
It uses discrete parts, has quite a bit of drop at about 0.1-0.2V and add quiescent load. Because of closed loop, you’ll get similar drops even if you use MOSFET with very low Rds.
If you wire multiple blocks outputs together, they can share loads. I have simulated it in LTSpice and prototyped up 3 blocks together. I simulated and got get away with non-paired transistors.
Oh! Nice, thank you ^__^
I would like to someday create a general prupose charger / discharger / stepup / stepdown / ups only using some mosfets, diodes, inductors, comparators and some MCU… possibly drive it using PIOs and ADCs on RPiPico.
A real hacker on HD buids his ideal switch from a 555
made from vacuum tubes
Okay, so now I know what I’m designing into my heterogeneous ARM micro-server rack for power supplies.
You can use another power bank board connected to the battery and share the jobs. One charges and the other manages the load ;)
Hi! Thank you all for your comments :)
If anybody is interested i have 10pcs left and no plans to make more this was more like a fun project really :)
Great write-up; I’m interested in 2 boards. Let me know cost.
Can contact me burgduino@ gmail.com
Is this project applicable to dealing with a battery in freezing temperatures? Apparently, lithium batteries don’t survive that.
No, it uses normal 18650 li-ion so will not do well in sub-zero temps
Dear Christos, I would like to buy one or two of them, if possible fully assembled and tested/working, including battery holder. The 18650 battery I have myself. how much would it cost, including shiping to germany. Peter@kammerling.de
If i ship without battery holders, shipping is 3 euro and can send several in one shipment. If i add battery holders, then shipping minimum goes to 9 euro as package exceeds 2cm height .. but then, i can ship up to 500gr :)
I need a solar/UPS for router or a small computer.
but i need no one cell but more than one and working separately like this flashlight https://www.kickstarter.com/projects/451008586/owltac-a1t-endure-flashlight-with-selective-batter?
for example my ups working 2 day or one day and i ger half power to my flashlight
What output voltage do you require?
Wish there was a spreadsheet for battery banks that don’t need this. I was looking for this exact feature a while back and gave up.
I buy Micro Center’s cheapest in house “Inland” battery bank specifically for just that. I use them for all my Wyze cameras and last about 4 hours when the power goes out ;-)
Funny enough, it made one camera stable which makes me believe its either acting as a capacitor further stabilizing the voltage
The BQ stuff was from Benchmarq, which Unitrode bought, which TI bought.