A decent Pi UPS does exist

Did you read the page you linked to?

It states bigger batteries as accessories.

Yes.

I know. How is that relevant?

The main board is out of stock at the moment and I would welcome a suggestion for a similar UPS. The query is unrelated to the fact that it accepts bigger batteries.

Incidentally, they claim that the inbuilt small battery will fit in many cases. And, if not, they have a case which takes the HAT. the Pi and one of the larger batteries. So it looks as though it is a very good, self-contained solution.

I thought to mention it as I've read the recent discussions here on UPSes and they focussed on things like mobile phone chargers. I bought one of those on the basis that the charger might allow power output while it was, itself, being charged. Unfortunately, although a video review of a similar device from the same manufacturer said that it would do both at once, the one I received did not - which makes it useless as a UPS.

Hence, I thought folks here might be interested in the PIco I mentioned at the outset.

On 01/29/18, James Harris said the following... JH> Aside from the many extras it provides I love the fact that the PIco, JH> battery and Pi can all fit in the same case. Sounds very neat. Will see JH> how it works out in practice.

Probably going to see if I can get hold of a UPS hat over here pretty soon. I am getting ready to start a car pi project and I have been concerned about how to elegantly shut down when I power down the car. All of my ideas have revolved around external batteries and having to manually shut down before I turn the car off, until I ran across this thread. While I have five or six Pi's around the house doing stuff I'm a relative newb and didn't even realize that something like this existed.

-=>Richard MilesCaptain Obviousbbs.shadowscope.com

Interesting. That's quite a full-featured solution -- it does rather more than others I've seen (it has a built-in RTC, for example).

I've never played with one, so I can't comment beyond saying that it seems to be a decently well thought-out piece of kit.

As for alternatives ... I've previously mentioned here the Adafruit Powerboost 1000C (not to be confused with the Powerboost 1000 (without the C) which is just a battery charger) and I've recently discovered the products from Alchemy Power (such as the Pi-Z UpTime for the Pi Zero).

I haven't actually played with the Alchemy products, yet, but I do have a Powerboost board and a suitable LiPo battery. That's well put together (like most Adafruit stuff) and it seems to work very nicely but I haven't yet satisfied myself that the board can't kill the battery by continuing to draw a little power for itself after it has shut down the Pi (or whatever). It may be fine, but I have seen one or two reports of people who've experienced dead batteries with this board. It may be that all that's needed is a battery with internal protection (and I need to check whether mine has, they are available both with and without).

You'll find both of these (in the UK, at least) at Pimoroni or one of the other usual suspects.

As it happens, I ordered a PIco earlier today. Delivery not expected for a month or so yet as they are due stock toward the end of Feb.

I saw a report that battery life fades after some period of use (a year or two). I decided to take the chance as the battery can be replaced.

Incidentally, I bought from CPC as they take back orders.

Aside from the many extras it provides I love the fact that the PIco, battery and Pi can all fit in the same case. Sounds very neat. Will see how it works out in practice.

On 01/30/18, Ahem A Rivet's Shot said the following... AA> There are permanently on rails in all cars, you'll find one AA> feeding the radio (as well as a switched rail that only comes on with the AA> instruments). Keeping a pi running won't matter to a car battery.

That's true. I may consider it.

-=>Richard MilesCaptain Obviousbbs.shadowscope.com

There are permanently on rails in all cars, you'll find one feeding the radio (as well as a switched rail that only comes on with the instruments). Keeping a pi running won't matter to a car battery.

off road.

So 100mA draw at 5V is enough to flatten a car battery in 2 months

Pi's draw beween 100 and 500 mA whgen idle depending on model

Its amazing what the Abilitry To Do Simple Sums can tell you when faced with handwavey statements like 'Keeping a pi running won't matter to a car battery.'

Its not true

Be warned

That depends on the car. a little petrol "tin box on wheels" may only have a 30 - 40 Ah battery. 2.5 l diesel > 100 Ah...

faced

to a

Also car batteries detest being deep discharged. Just one deep cycle can significantly reduce their abilties, two or three is very likely to kill it.

Indeed. We have all found that out the hard way...

There are some really nasty voltage spikes in automobile electrical systems.

That's a very small car battery, the one in my car has nearly three times that capacity.

Unless of course the car battery gets charged in that 2 months, like by driving a mile or two.

It shows you that I assume the car is driven from time to time, seems a reasonable assumption to make.

If it is a 'second car' its not a very long time at all.

I don't know anyone who keeps a car that they don't drive rather more often than once every couple of months, especially not one that is likely to be home to a pi car project.

How about a camper? Summer use only.

I had a luxurty fast GT saloon. Howver when I got married it didnt suit as a shopping trolley or dog carrier, so its battery went flat...

I still wouldn't let the battery go flat, it's bad for the battery.

More fool you, a car off road needs to be maintained.

I would think that any LiPo 5V power/charger system that allows you to monitor that the "UPS" is "on the battery" would work. A simple 5V LiPo add-on board would do the trick, in fact. There are probably quite a few possible solutions here.

Example:

(with 400maH battery, about US$20)

In effect, you'd use a LiPo battery charger (with a 5V boost regulator) that you can have plugged into a 5V power source 'all of the time', keeping the battery charged and powering the RPi. When the incoming power goes out, the LiPo battery kicks in, and keeps everything running.

You might need a way of detecting that the input power went out (and that you're on the battery), but that shouldn't be too difficult. Use one of the IO pins to indicate "on the battery", simple enough.

Then you could estimate capacity or measure battery voltage (an extra A:D converter or limit crossing detector of some kind) and you do a shutdown on the RPi if bat voltage gets too low. Typically you can undervolt trip at