This is the story of the evolution of an uninterruptible power supply for the likes of Raspberry Pi etc. It takes over where various posts about UPS leave off, the last (detailed) entry being “The Dog’s Breakfast” – in the search for a low-cost UPS and for individual micro boards and having been less than happy with much of what is out there. The latest video on this is on Youtube.
This started off as a simple discussion on UPS for the likes of the Raspberry Pi and other micro boards but developed into so much more. Some great conversation, some ideas – and a project at the end which could fit a lot of requirements at very low cost. Read on...
Now – you may think that isn’t enough for a Raspberry Pi or whatever but headless with no ports – should be no problem I am told.
So – a little while ago I bought a variety of little USB charger PCBs and one of the least expensive at £2.40 was this one from Banggood. Others I tested have an on-off button which has to be pressed for the output to come on – OR they won’t work when charging – or BOTH – so they’re all sitting in the bin despite one having a very nice blue LCD display.
But THIS one WORKS – you can run something on the large USB connector – while CHARGING the battery (a single 3v6 Lithium battery) – and any combination – i.e. you can plug the charger in and out and the output remains constant.
So – if your requirement is for under an AMP – you might want to get a Lithium battery and one of these. For batteries I have a boatload of these as you see in the picture on the left, from an old laptop battery – turned out when I dismantled it that ONE cell had failed and the rest were spot-on – I put them on a shelf for the day they may prove useful. Typically they are 3v6-4v2 at maybe 4.2Ah (I have some Ultrafire batteries of that capacity)
So taking step-up efficiencies into account, if you’re looking at a fully charged battery and a gadget using half an amp, you could be looking at keeping it running for maybe 6 hours with one of these? Not bad for under £3 + battery. You COULD connect more than one battery in parallel to increase capacity – and the advert even claims that – I’ll leave that to you as I’m not an expert on parallel Lithium batteries but it seems to me that to do that they should be pretty much matched.
The unit has two surface-mounted LED lights (could also be brought out as standard LEDs to a front panel) – red for charging – blue for load.
To put this to the test: I took a flat Lithium battery that had been sitting in a drawer for months – soldered it to the charger unit and plugged in a fully laden FriendlyArm NanoPiM1 complete with HDMI, wireless keyboard and mouse – this is WAY more than anything I’d considered but good for the ultimate test.
The M1 lasted about 10 seconds before the battery gave up. That’s pretty much what I’d expected as the battery was flat – what was to come next would be critical.
I plugged in a decent USB supply to the smaller charger unit. The red charge light came on. No output. About 20 seconds later – the blue light came on, the output fired up and the M1 powered up without issue.
As the battery was charging – the M1 was doing just fine. The charger unit was running HOT – but then that’s what I’d expect – it was having to power far more than I would normally give it AND charge up a totally flat Lithium battery. Not exactly a typical situation. But it was coping. Just to push my luck – I was intermittently pulling out the charger lead and the M1 continued to run rock-steadily. 6 hours later both lights were on but temperatures were now down to “pretty warm” with the battery at “just warm” with the battery sitting at 4.17v. I disconnected the mains charger at which point the battery voltage dropped to 4.11v.
I finished off this blog article and checked my mail, a process which took maybe 15 minutes at the end of which the battery was just fine sitting at 4.06v. Later this morning I took the charger off momentarily and then forgot out about it – went off to do some painting – 2 hours later the battery was still at 3.8v and the NanoP1-M1 was happily sitting there.
Overnight I left the M1 on the unit, on charge and the charge light has still not turned to green which is interesting – yet the tests show that the battery IS very much being charged. I guess the load must be pulling the voltage to just below the point where the charger considers this a full charge. During the evening last night I disconnected the mouse, keyboard and hdmi lead. This morning, the battery is cool, the charger is cool, all is well with the M1 and the battery voltage is sitting at 4.18v
Which is more than can be said for the blog which apparently came to a halt last night due to the number of people looking in!!! All fixed now thanks to a prompt response from the service provider.
I’m impressed - I have three of these units, but now I see how useful they are, I can see more of them on the way.
Update April 2017: With a really flat battery, plugging in a Raspberry Pi 2 and power, the RED light on the unit activates- but sadly the battery does not appear to charge and the Pi does not come on. If the Pi is disconnected, the battery voltage immediately starts to rise. If the PI is then reconnected, the Pi works and the battery continues to charge. Sadly, at a stroke, this makes the unit useless in the event that the battery becomes completely flat.
Update September 11 2017: A picture is emerging here of manufacturers having to content with existing chips – the lower priced ones having severe limitations. Aidan and I have been discussing the subject.
The REASON we have problems with a lot of these designs is becoming clear. Let’s say we need 1 amp – plenty of cheap voltage boost chips out there that will do the job. On the charging side, the most popular chip can charge at half an amp – and therein lies the problem.
Take a board like the one I’ve described – fully charged battery. Runs perfectly as the charger is not having to deliver much. On the other hand starting with a FLAT battery , we are expecting the charger not only to deliver a heavy current to the battery – but ALSO the full 1 amp to the unit it is powering – not going to happen. Now – you COULD say – what about simply using the input power supply, to power the load directly when there is mains power – and that’s the OBVIOUS question. DIODES is why. At heavy current even a schottky diode loses up to half a volt and you have to OR the two outputs together with diodes. So that’s no good.
So how about – using diodes to OR the battery and the input power supply to the boost converter? That’s a BETTER idea but flawed… as that also lowers the potential voltage going to the boost convertor and these chips are not that good at delivering power when the incoming voltage is below 3v (battery minus diode drop).
Another way would be TWO boost convertors – chucking out 5.5v or so – dioded together to provide power – one gets power from the battery – the other from the incoming supply. This one has merit and the likes of the MT3608 are cheap and at the output end, voltage loss is not a problem as you can simply compensate. When I say cheap – I mean REALLY cheap. Current thoughts are that one output would be maybe 0.1v or so higher than the other so that while there is mains power, the battery side is supplying nothing. As soon as power fails, the battery side takes over. This would work without any controller as the chips handle over charge and over discharge protection but I still fancy a 328 in there to warn any Pi or similar computer that a power outage is on the way.
Similarly the inexpensive charging circuits are often seen in parallel and again you could increase the charging rate that way though there is a limit to how fast you should charge 18650 batteries…
Here is some interesting reading on the subject..
If cost is not an issue, there’s a boost chip called the TPS61030 series (TPS61031) and this one is able to throw out over 2.5 amps with a 3volt input. At at 2.6volts it can STILL output over 2amps – it is however a lot more expensive than other alternatives and from a small production standpoint the chip packaging isn’t ideal.
So looking ahead I plan to play with the two-boost option – but right now a couple of Orange Pis just turned up for me to play with – priorities.
And now including - the MONSTER version. Just a short while ago, I just bought this 16750maH USB battery unit (charger) with no prior knowledge of the company - on the recommendation of my pal Aidan who does our PCBs for Esp8266.
I have a specific requirement – which many of you will recognise.
1. I don’t want to have to tpush buttons to turn it on
2. I need it to work WHILE the unit itself is being charged
3. I need lots of POWER.
Some time ago I used a similar looking cheap USB charger to power a Raspberry Pi2 and it worked well but I noted it would not really charge any higher than it already was when deployed, while running the Pi. Despite this it would not lose charge either and is still doing sterling service as a UPS for one of my older PIs.
When I wrote that original article, several people wrote in to say that many such devices will NOT simultaneously charge and discharge – and true enough – there are problems with most of the alternatives I’ve tried – some work but need a button pressing to turn them on. And that means if they run out of power due to a long outage – when the power comes back on you’ll be getting nothing!! On the web you’ll find all sorts of contraptions as alternatives for use as UPS systems – from the big monster mains uninterruptables to 12v batteries with chargers and switched down-convertors – all very, well, MESSY. And of course today the Raspberry Pi 3 for example needs peak power higher than ever before, so at least 2 amp capability per output is needed.
And so it was that I got quite excited when Aidan said he’d found an ideal candidate for the job, a heavy duty USB power pack with no less than 5 cells in it, capable of outputting up to 4 amps (one output has a maximum of 2.4amps – the other 2.1amps!! I went to Amazon and sure enough £20 inc postage – what a bargain. But I’m in Spain and so I tried Amazon.es
Sure enough – there was no free postage on this in Spain but the OVERALL price inc. postage came out to be the same as the UK overall price – around £20. Bargain.
I ordered one and amazingly it turned up the next day here in rural Spain. And… it works! When I received the unit, I took my flat phone out with me for coffee into the village along with my sparkly new supply which came with 2 short USB leads (short is GOOD). By mid-morning (despite having just taken the unit out of the box and not charged it) my phone was full and the charger was still registering 3/4 full.
When I got back I plugged my PI3 into the unit – and waited for it to boot up - rock solid red light (which on the Pi3 indicates good power). I tried putting the charge lead for the Ravpower unit in and out repeatedly – no problem. Aidan had already tested this running a Pi until the pack was flat (more than a day!!!) and then plugging a charger into the pack. The PI came back up reliably.
The unit looks good – NICE finish – and has two outputs as indicated above. The button on the top allows for a gimmick white LED – and for turning on the power level indicator LEDs – there is NO on or off and the indicators go off on their own after a while. Lovely.
In short, there appears to be no downside to this unit – it is reasonably priced – costs WAY less than other alternatives and looks rock-solid. Reading the instructions it SPECIFICALLY states that the unit will give consistent output while charging – as well as short circuit and over-current protection. What more could you want!
Here is the Amazon UK link…. I’m sure you can find other pricing where you are. Clearly you need to keep this thing charged with something able to provide what you need and more – but if it cannot handle peaks – matters not as this unit will take care of that. All-round winner it seems to me.
Summary: The RavPower 16750MaH battery unit is working just fine – over a week down the line it is happily running a pair of Raspberry Pi2 devices and I’m confident that in the event of a power cut – it will keep them going for quite some time.
Meanwhile I got in touch with the American office of SunValleyTech to see if they’d like me to write about any of their other units. They were enthusiastic but (and I’m cutting a very long story short) when I supplied my details they could not ship to Spain – and hence they put me onto their Spanish department – and this morning, despite SEUR delivery leaving the thing in the village PUB !!! I opened up a sizeable box to find…
And NOW, the 26 Ampere-hour Monster: Yes, seriously, this is not a joke like the one you’ll see me refer to lower down in the blog – but a full 26,800MaH unit – a little too big for your pocket but it would sit nicely on a car dashboard, with 3 outputs EACH of which is capable of well over 2 amps output for a total output of over 5.5 amps and capable of being charged at 2 amps. A true MONSTER. This has no gimmicky light – no on/off button just a little test button to show the battery level. When it came out of the box it was fully charged. When you plug anything in – the light comes on momentarily to show you the state of charge and then goes out! Well done!
The unit comes in a pretty box with a nice, very short USB lead and another, longer one – maybe half a metre. Quite substantial.
When I started updating this review, I plugged my HTC ONE M8 into the new unit as the phone was just about flat. It is now 80% charged and a quick check of the lights indicated it has not made a DENT in the charger’s capacity.
I can see this larger unit sitting in a corner of my office powering two of my Raspberry Pis 24/7 – a shame to hide it away but this is going to give me some SERIOUS protection against power cuts! If it works out – you’re looking at 2 Raspberry Pi units lasting maybe a day depending on what they are doing – without no mains. The smaller unit is going to sit in my car for taking to hotels etc., – I’m always running out of phone or tablet power. Just bear in mind the charging power input limit however.
Here’s the UK Amazon link. If anyone can do better - do let us know in here.
The Chinese alternative: After I wrote the first part I got into a conversation in Google+ on the subject and a couple of people mentioned solar powered boards which look like the picture on the left below. I’ve covered these before and the general consensus was that they are a con to the very last one. Here’s a comment I made on Google+
This is typical of the solar panel adverts - I don't know if Amazon simply don't check advert specs, don't understand them or are deliberately trying to deceive customers..but they are all at it - the specs are absolutely meant to trap people who can't do maths and it is not the worst by any means:
So look at the spec – this has a 20,000MAH rating (the unit IS big enough to handle 7 batteries – there are many ads claiming this and the units are just NOT big enough). That is 20 amps for one hour. That's at 5v so given that the 3v6 -4.2v cells need switching up at maybe 90% efficiency that requires 27AH capacity. If a Lithium battery does 3.5amps - that's 7 of them being generous. My new and large unit has 5 of them in there - I doubt very much if the others you see on the market have 7 batteries of that capacity.
So then there is efficiency in charging. Lets be generous and assume 100% efficiency. So assuming those units that claim 20,000MAH are real (they are not, they are a con generally but lets give them the benefit as I've not tested every one) - you need 27 amps for one hour, or 1 amp for 27 hours or any combination, to fully charge them.
Let's take a look at the CLAIMED power of that Amazon solar unit - 1.2w they claim. If we're needing 27AH at 5v that's 135WH, so you would need 112 hours of good, direct sunlight - even here in Spain who's sunlight DWARFS the UK, that is 11 DAYS to charge the battery. In the UK it would be more like several weeks.
You could argue my math either way but not by THAT much - it's a con.
So - take the unit I first blogged about above...16750mah - I'm going to call that 15AH being conservative... so VERY roughly we need to charge at 1.5amps at 5v for 10 hours. I CANNOT find powerful 6v solar panels - so assume an efficient switcher and a panel for 12v.... what.... 700ma at 12+v ??
That's 37cm by 25cm of solar panel.
And as for the phrase “Please do not place SolarJuice on or over-heated place for continuous charging.” – HELLO!!! – don’t put a solar charger in a hot place for continuous charging. Perhaps the designers don’t get out much but usually when you have decent sunshine – it’s hot! Here in Spain I can’t touch my solar panels, they are that hot.
UPS are SO never getting my business again
Absolutely predictably, after promising delivery today – UPS have once again marked the tracking system as “incorrect address” and given up. I keep sending them simple Google map links and they keep writing back to say they cannot read them – how can you not read a link to Google MAPS!!!???!?!?
Here we go again… despite telling every supplier NOT to use UPS, I’ve just received an email from UPS to say there is a parcel arriving tomorrow from China – or is it Wednesday?
So the email clearly states
Scheduled Delivery Date:
Estimated Delivery Time:
End Of Day
There you go – you don’t get any clearer than that – except that it ALSO gives a tracking number. Hopping over to the website – the tracking page says…
Of course – none of that is important because based on past history – tomorrow afternoon the tracking page will say that the address is wrong (I’ve sent them a map) and that they will try the next day…. and the next…
Well, one could be optimistic and say “third time lucky?” - I’m not getting too excited. More info later.
As some of you know, in July 2015 I was invited by Espressif to MIT in Boston, USA to be involved with their microprocessor product and how to use it. This small microprocessor has lots of uses and I've been independently blogging about the subject for some time - with some success judging by the numbers in here.
I was trying to think of something visually appealing to show people and it occurred to me that as I had written some software for serial LEDS to simulate a CLOCK, it would be nice to actually take a very bright CIRCLE of these LEDs with me - and the software and a little board so that people could visualise a nice use for the chip.
This presented me with a problem - I was moving to Spain for the summer and needed a quick fix. A Chinese company sold a LED ring for £11 which was reasonable - but it would take 2-4 weeks to deliver the little product to me. So I asked them to ship it via courier. They chose UPS. Bear in mind, while reading this the cost of the product - £11 or maybe 16 Euros.
So all in Euros - the product cost around 15.57 Euros. The postage cost 22.62 Euros - that's a total of 38.21 Euros inc delivery. YES that’s a LOT for delivery – but I was in a hurry. Normally that kind of stuff chips from China for free.
It would seem that when charging VAT, UPS charge VAT on not only the product but the delivery - which seems UTTERLY ridiculous to me - but that's life - so at 21% that would be what, around 8 EUROS?
The first time I realised something was up - was when UPS contacted the Chinese supplier for 17.20 Euros extra, bad enough after accepting a delivery job, but then it got worse - MUCH worse. Now, remember they have already contacted the SUPPLIER for more money. It turns out they also recommended he up the value of the package… reading the previous paragraph makes me wonder…
Where we live in Spain, Google maps had at the time, not caught up and the address did not show up on the maps. So I made sure that UPS had the address of a business in the village of Galera where we live (a mere 6 minutes by car from the significant main road into town and the map showed a clear path) - The people at that address speak English and Spanish - so I figured they could give directions to our place. How naive can you get.
So I missed a call from Spanish Inland Properties - UPS had called and wanted - wait for it - 38 Euros extra - half VAT, half "brokerage fee". As Spanish Inland could not contact me they quite rightly refused the package. It was never intended that the delivery would be to that address but the driver clearly thought it was appropriate – it would seem talking to others in the village that this is “normal” and they put up with this poor service. Several villagers have now said "we pick stuff up from Spanish Inland Properties as the delivery companies can't be bothered to deliver to our places".
This seems to be acceptable for some and if it works for them that's fine - but we're not getting discount for laziness here so I decided to tackle this. The postman in the village has NO problems delivering to our place - a mere 6 minutes from the main road into the village. He delivers stuff from all over the world to me no problem.
I provided UPS with photos, coordinates and even a direct Google link as by this time Google had added our place to the maps. Every now and then I would see revised instructions on the tracking note - but none of my information was passed on to them - it always came out as it I had changed the delivery address or that it was wrong – neither being correct.
I had a promise of delivery a week later - nothing - then another written promise of delivery days later - nothing.
Meanwhile because UPS systems don't like my address - when I filled in a form on the web to provide more info - it would never complete. I then receive a letter from "UPS MY CHOICE" - typical American-style bull letter to make me feel welcome - instructions - access code - the lot - I filled it all in on the website - lovely. But the very first time I tried to make ANY change, provide ANY information - this was refused as first I have to go to the user area which is not where the web form suggests (but I found it anyway) to update my info - which it will not accept. Back to square one.
On the UPS website I entered the tracking number - there is an option to add a description - so I pasted in the Google URL I made to show the directions... nothing - the ADD button did nothing - clearly intended for short, sharp responses and nothing else - but badly designed as no error message. The only option was to cancel. I could not find a way on the site even to tell UPS to put this off for another day so I could HAVE A LIFE. If you try to contact UPS - you are forced down a narrow range of operations - the nearest I could get was "receiving a package" - " InfoNotice Number" - and .... nothing - I could not get any further in contacting them. For someone having a problem - the UPS website isn't worth a light.
Anyway, several days after I was actually expecting the parcel and far too late for my trip which had come and gone, I had just about given up when... the van arrived - as it happens we'd left the house but we stopped the car just outside - sure enough 38 Euros had to be paid. So AT LEAST I proved one thing - if you stand up for what's right – it appeared at the time that they COULD deliver to the door - not without a fight and with charges that bore no relationship to the cost of the product.
So now you, dear reader, now know what to expect from UPS in rural Spain - others have already warned me - terms generally seem to focus on the word "rubbish". Another reader has warned that he too has been subject to "brokerage fees" totalling twice the value of the product... and he won't touch UPS.
I then wrote and asked for an explanation as to WHY they charged me 30 Euros more than the VAT and why they also charged or tried to charge the SUPPLIER more.
A letter came back - the VAT was the supplier's fault - for reasons WELL beyond me – on advice from UPS , he had declared a value more than twice the actual value of the goods, on the package. Why would ANYONE want to do that. But that only accounts for HALF of the ridiculous price - the rest came from "Brokerage charges" - Now I have to say, in my 60+ years I've not come across this in the UK - maybe I've just been lucky - but check this bunch of nonsense out – on the link, scroll down to "brokerage charges" - http://www.ups.com/content/es/en/shipping/cost/additional.html
It seemed there were a couple of lessons here... (a) make sure your supplier UNDERSTATES the value of goods, (b) Avoid UPS - but mainly, when buying from China - avoid couriers altogether and stick with simple airmail. It may be slower but in my experience it is reliable and there are NO charges - indeed on small packages there isn't even any VAT (and up to now that applies to both Spain and the UK).
And that was that – at least the parcel arrrived, they now knew my address. FAST FORWARD to September 2015. I’d bought a watch – a smart watch, from America and it did well for a while but got some water damage. They said no problem – we’ll ship you another straight away – you’ll have it in days.
And they chose… UPS. Too late to stop them.
On time the supplier sent me a tracking number – and the parcel would arrive Wednesday. I made sure they had the map link, that they sent the map link to UPS and I sent a copy to the guy I’d previously spoken to at UPS in Spain. What could go wrong. Eventually the tracking info updated and sure enough – LATE WEDNESDAY ARRIVAL. We were off to the coast for a couple of days (Thurs Fri) so I let everyone know. Early Wednesday afternoon – “Incorrect address” – I could not believe my eyes.
I immediately wrote to everyone involved and ensured they knew that 1. My address was correct and 2. I was NOT going to be around on Thursday or Friday.
Sure enough nothing happened on Wednesday – I sent a stream of correspondence off and we went off on our trip to the coast, with a confirmation from UPS that they’d try again Monday.
Friday, an email came in on my phone – UPS have DELIVERED YOUR PACKAGE. The address was nonsense – 2 letters – and the delivery was to “SOAN L” – not only was the address rubbish – but who on EARTH was “SOAN L” – didn’t really even sound Spanish and it certainly wasn’t English.
So after screwing up the Wednesday delivery, they sent the package on the WRONG day to the WRONG place to the WRONG person.
As it turns out – they’d just resorted to form – and delivered the package to …. Spanish Inland Properties – “SEAN L” – the very helpful chap there and on Saturday I picked up the replacement watch from him. They simply could not give a SHIT about customer requirements.
All’s well that ends well, but now I feel it is my duty to warn everyone, everywhere – DO NOT USE UPS IN SPAIN AS THEY ARE COMPLETE RUBBISH.