Category Archives: USB

Ravpower the ultimate Pi UPS?

RavPowerAnd 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.

https://www.amazon.co.uk/RAVPower-16750mAh-Portable-External-Technology-y/dp/B00OJXVDAU/ref=sr_1_1?ie=UTF8&qid=1465388955&sr=8-1&keywords=ravpower

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…

RavPower Monster unitAnd 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.

https://www.amazon.co.uk/RAVPower-26800mAh-Portable-Charger-External/dp/B012V9H3WA/ref=sr_1_2?ie=UTF8&qid=1466008221&sr=8-2&keywords=ravpower

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+

solar charging - notThis 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:

http://www.amazon.com/ZeroLemon-SolarJuice-20000mAh-Portable-Technology/dp/B00NIOGKL8

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 ??
http://www.ebay.co.uk/itm/10-WATT-MONOCRYSTALLINE-SOLAR-PANEL-10-WATTS-12V-PV-WITH-DIODE-/191641832274?hash=item2c9ebe4b52:g:dAkAAOSwu1VW4tgg
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.

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Memory sticks/SD and USB3

Check FlashI was just reading an article in a blog where people were slagging each other off over views about USB3 and the speed of memory sticks when a package arrived for me in the post.  A couple of USB3 32GB memory sticks (tiny ones at that).. and it occurred to me that my laptop has a USB3 socket.

So, off I went to the web and picked up CHECK FLASH for Windows – a freeby.

So – the first thing I did was to grab my favourite, fastest 32GB USB memory stick – a Duracell unit. I ran the test which took several minutes – and what did I get? 19 MB read speeds and 13MB write speeds – no errors. I know it is the fastest one I have as I often back movies up to it and when you’re backing up a 2GB movie – you soon make sure you use the quickest drive.

So bearing in mind that this was the BEST I have – and no way the machine will diminish any results as it is a very fast computer… I then went on to try the little mini-32GB USB drive.

Oh, both of these were formatted as Fat32 incidentally and so both complained that “only” a test of 4GB could be done.

Now, bearing in mind that the USB3 unit wasn’t even a super brand name – or ANY brand name for that matter, it is interesting to note that it easily managed 126GB read speed (i.e. SIX times faster read) and 36MB write (nearly THREE times faster write) – I think from now on I’ll be looking around for USB3 – I’m a convert.

THEN I remembered I had a USB card reader and a pal of mine had sent me some Samsung EVO microUSB chips – I read somewhere that these were the best for Raspberry Pi – so – I gave THAT a go too! Strangely the read speeds averaged 41/mb and the write speeds were only 13.4MB – more or less the same write as the USB 2 stick but over twice the read speed – perhaps my expensive USB3 ANKER adaptor isn’t as good as I thought it was - as the EVOs are definitely the fastest I’ve used on the Pi.

Have you come across much faster USB2 speeds that my simple test? What about USB3?

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