UPS for the Raspberry Pi

There are a number of reports of the Raspberry Pi not being able to
reboot immediately after a short power outage, but only a few minutes
later. I have seen this happen myself.
To reduce the frequency of power outages, one would add a UPS and I see
several on the market. Can anyone recommend a reasonable priced UPS
from their own direct, personal experience?
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Thanks, 
David 
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Reply to
David Taylor
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At present I have one pi PSU and a bunch of other stuff supplied by an Eaton 3105 UPS, but what I am planning to do is to is run the Pi directly from a LM2596 dc-dc converter run from (say) a 12V float charged battery.
It seems silly to convert 12V DC to "mains" AC and then to convert again to 5V DC for something like a Pi.
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Graham. 

%Profound_observation%
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Reply to
Graham.
Not seen this myself, however I do have one Pi (my very first) that sometimes won't reboot and needs a power-cycle...
What about one of the USB battery charger devices? I have a 15,000mAh one - really intended for charging phones - which itself is charged via USB and it powered a B+ for about 36 hours.
Obviously something smaller would also work.
Gordon
Reply to
Gordon Henderson
I use these:
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and I have some of these which are a bit cheaper, but not tried them out yet:
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Might be more expensive than making your own lm2596 SMPS, or buying one off ebay, but these are 7805 drop-in replacements and just work..
Only 1 amp though - ok for a Pi, but not so OK for power hungry peripherals (so use use another ;-)
Gordon
Reply to
Gordon Henderson
Not a UPS, as such, but I use one of these:
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for my pi heating controller. It lasts for about 10 hours on a B+.
There are smaller/cheaper onesusing the same technology.
One slight drawback: If the battery is exhausted before the power is restored, it needs to be manually reset.
Reply to
Tony van der Hoff
Parts for a "real" UPS:
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LiPo Charger/Booster
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- Polymer Lithium Ion Battery - 6Ah
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- USB Micro-B Cable
The Booster can supply 5V @ 600mA max, may be just enough to run the Pi.
Reply to
hamilton
I use one of these to run an Arduino + reflective LCD from a PP3 battery :) With that load, it holds the voltage right down to 6V in (the PP3 endpoint). It'll only run for a couple of hours but that fine for the unit's purpose.
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W J G
Reply to
Folderol
Thanks for all the suggestions for the RPi UPS. I was thinking more of a board which connects directly to the RPI as a number have been mentioned here before, but the ideas you came up with are useful and I will pass them on to the end user.
If anyone still has comments on an integrated solution that would still be of interest....
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Cheers, 
David 
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Reply to
David Taylor
Just buy one then:
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and there are others..
Gordon
Reply to
Gordon Henderson
Beware: Neither of those recharge (or even float-charge) the batteries. Totally useless IMHO.
Reply to
Tony van der Hoff
Exactly the reason I originally asked for users who had practical experience of such devices! Thanks!
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Cheers, 
David 
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Reply to
David Taylor
This connected board does.
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Also provides on/off switch, real time clock, temperature sensor and some other bits. The mAh/? ratio is not so good, though.
Reply to
A. Dumas
Hm. There's a chap in sheffield designed one that does - in my naivety I guess I just assumed they all did ...
Ah, here it is:
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Looks like a bit of a rolls royce solution though, but it seems to have all bases covered...
Gordon
Reply to
Gordon Henderson
This is such a trivial problem to solve.
You need a cheap switching regulator like this:
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There are cheaper ones about, but I have one of these and it works well, doesn't get red hot and doesn't produce lots of RF noise. The connector provider plugs directly onto the GPIO header on a B.
You need a battery, if portability is not an issue then a SLAB is best as they are ideal for this application and can stand float charging indefinitely. A 12V 2Ahr SLAB (burglar alarm type) should provide 5hrs battery running time.
You need a power supply of about 15V to charge the SLAB and some silicon diodes 1N5401. You can get regulated laptop PSUs from eBay for around
drop of about 0.75V at 300mA.
You connect the PSU across the SLAB with 2x 1n5401 in series in the positive supply and you connect the UBEC across the battery. The two diodes drop the voltage to about 13.5V on load which is plenty to float charge the SLAB and run the UBEC and hence the Pi. The diodes also isolate the battery from trying to back drive the PSU.
When the power is on the PSU float charges the SLAB through the diodes, the UBEC powers the Pi and everything in the garden is rosy. When the mains power fails, the battery voltages drops slightly but as the UBEC will run as long as the input from the SLAB is greater than 5.5V and your Pi will keep going. The Pi is always powered from the SLAB and there are no switch over glitches to worry about. When the power comes back on, the PSU has to power the Pi (300mA) and charge the battery. The current will be up around 2-3A when first applied to a discharged battery but this will soon drop. The diode leads should be left at least 1cm long each end so they can dissipate the heat of passing several amps.
You can get used SLABS from your local commercial burglar alarm company. They are changed every 2-3 years even if perfect. The alarm company needs to pay commercial disposal charges so will give you as many as you can take away for free as long as you promise to dispose of them correctly. Well my local company does.
Dave, as you are GM8ARV, this will be easy to put together for someone with such a venerable call! :-)
Reply to
mm0fmf
A big advantage of the RS ones is that they will power through while charging, so they do make a UPS. None of the others I have seen will do that.
Reply to
Steve Drain
Folks,
Thanks for your comments.
Gordon, the "MoPi: Hot-Swap Mobile Power for the Pi" seems not to be ready as yet, and may be not quite what my friend wants.
mm0fmf: Yes, I could build something like that, but I don't know whether the end-user who asked could. I think a ready-made solution is what is wanted.
A. Dumas: Rather cumbersome and expensive, but I suppose it can shut the RPi down cleanly if needed.
Tony van der Hoff & Steve Drain: This feedback on the RS device is very helpful. Checking on Amazon there are dozens of similar devices, but will they power-through? Hardly ever seems to be mentioned in the product descriptions. I think either the 5200 or 10400 mAh devices would suit, and I will pass that along as a recommendation. Might even get one myself to have a play! That device, with a USB to micro lead for the RPi, appears to be ideal to cover a power outage for up to ten hours depending on the device and the peripherals attached to the RPi.
Many thanks to you all for your responses!
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Cheers, 
David 
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David Taylor

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