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Groups > comp.sys.raspberry-pi > #25783 > unrolled thread
| Started by | Simple Simon <please.dontspa@me.com> |
|---|---|
| First post | 2021-01-12 12:14 +0000 |
| Last post | 2021-01-17 13:53 +0000 |
| Articles | 20 on this page of 89 — 22 participants |
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Battery Powered Project Simple Simon <please.dontspa@me.com> - 2021-01-12 12:14 +0000
Re: Battery Powered Project Chris Green <cl@isbd.net> - 2021-01-12 12:40 +0000
Re: Battery Powered Project Simple Simon <please.dontspa@me.com> - 2021-01-12 12:50 +0000
Re: Battery Powered Project "A. Dumas" <alexandre@dumas.fr.invalid> - 2021-01-12 15:15 +0100
Re: Battery Powered Project Theo <theom+news@chiark.greenend.org.uk> - 2021-01-12 21:43 +0000
Re: Battery Powered Project Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2021-01-13 09:40 +0000
Re: Battery Powered Project Jim H <invalid@invalid.invalid> - 2021-01-13 18:02 +0000
Re: Battery Powered Project Joe <joe@jretrading.com> - 2021-01-13 22:04 +0000
Re: Battery Powered Project Theo <theom+news@chiark.greenend.org.uk> - 2021-01-13 23:37 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-14 00:43 +0000
Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-14 03:59 +0000
Re: Battery Powered Project Ahem A Rivet's Shot <steveo@eircom.net> - 2021-01-14 10:18 +0000
Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-14 11:04 +0000
Re: Battery Powered Project Ahem A Rivet's Shot <steveo@eircom.net> - 2021-01-14 11:46 +0000
Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-14 12:21 +0000
Re: Battery Powered Project Ahem A Rivet's Shot <steveo@eircom.net> - 2021-01-14 12:38 +0000
Re: Battery Powered Project David Higton <dave@davehigton.me.uk> - 2021-01-14 14:17 +0000
Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-14 14:28 +0000
Re: Battery Powered Project David Higton <dave@davehigton.me.uk> - 2021-01-16 20:09 +0000
Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-17 07:19 +0000
Re: Battery Powered Project David Higton <dave@davehigton.me.uk> - 2021-01-17 15:57 +0000
Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-18 07:05 +0000
Re: Battery Powered Project David Higton <dave@davehigton.me.uk> - 2021-01-18 14:14 +0000
Re: Battery Powered Project John Aldridge <jpsa@cantab.net> - 2021-01-17 17:52 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-14 12:56 +0000
Re: Battery Powered Project Theo <theom+news@chiark.greenend.org.uk> - 2021-01-14 13:46 +0000
Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-14 14:26 +0000
Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-14 03:46 +0000
Re: Battery Powered Project Folderol <general@musically.me.uk> - 2021-01-14 09:23 +0000
Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-14 11:04 +0000
Re: Battery Powered Project Folderol <general@musically.me.uk> - 2021-01-14 17:48 +0000
Re: Battery Powered Project Jim H <invalid@invalid.invalid> - 2021-01-18 17:07 +0000
Re: Battery Powered Project Joe <joe@jretrading.com> - 2021-01-18 20:33 +0000
Re: Battery Powered Project Jim H <invalid@invalid.invalid> - 2021-01-21 20:36 +0000
Battery Powered Project nospam.Vincent.Coen@f1.n250.z2.binkp.net (Vincent Coen) - 2021-01-12 14:35 +1300
Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-12 16:40 +0000
Re: Battery Powered Project The Natural Philosopher <tnp@invalid.invalid> - 2021-01-13 13:56 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-13 15:12 +0000
Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-16 12:24 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-16 17:53 +0000
Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-16 20:39 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-16 22:33 +0000
Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-16 23:30 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-16 23:52 +0000
Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-17 10:39 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-17 14:32 +0000
Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-18 13:20 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-18 13:41 +0000
Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-18 14:02 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-18 15:15 +0000
Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-19 13:46 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-19 15:24 +0000
Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-19 15:34 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-19 16:21 +0000
Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-19 17:18 +0000
Re: Battery Powered Project Richard Kettlewell <invalid@invalid.invalid> - 2021-01-19 19:31 +0000
Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-20 10:12 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-19 22:15 +0000
Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-20 10:03 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-20 10:49 +0000
Re: Battery Powered Project Chris Elvidge <chris@mshome.net> - 2021-01-20 11:29 +0000
Re: Battery Powered Project A. Dumas <alexandre@dumas.fr.invalid> - 2021-01-20 12:18 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-20 13:02 +0000
Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-20 15:49 +0000
Re: Battery Powered Project Richard Kettlewell <invalid@invalid.invalid> - 2021-01-20 16:54 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-20 17:19 +0000
Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-21 10:24 +0000
Re: Battery Powered Project A. Dumas <alexandre@dumas.fr.invalid> - 2021-01-20 12:18 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-20 13:18 +0000
Re: Battery Powered Project Chris Elvidge <chris@mshome.net> - 2021-01-20 14:14 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-20 14:51 +0000
Re: Battery Powered Project A. Dumas <alexandre@dumas.fr.invalid> - 2021-01-20 14:45 +0000
Re: Battery Powered Project A. Dumas <alexandre@dumas.fr.invalid> - 2021-01-20 14:44 +0000
Re: Battery Powered Project Richard Kettlewell <invalid@invalid.invalid> - 2021-01-20 15:07 +0000
Re: Battery Powered Project "A. Dumas" <alexandre@dumas.fr.invalid> - 2021-01-20 16:38 +0100
Re: Battery Powered Project Chris Elvidge <chris@mshome.net> - 2021-01-20 15:45 +0000
Re: Battery Powered Project druck <news@druck.org.uk> - 2021-01-21 10:07 +0000
Re: Battery Powered Project "A. Dumas" <alexandre@dumas.fr.invalid> - 2021-01-21 12:30 +0100
Re: Battery Powered Project druck <news@druck.org.uk> - 2021-01-21 13:09 +0000
Re: Battery Powered Project Anssi Saari <as@sci.fi> - 2021-01-22 10:08 +0200
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-22 10:29 +0000
Re: Battery Powered Project Chris Green <cl@isbd.net> - 2021-01-22 10:25 +0000
Re: Battery Powered Project Kees Nuyt <k.nuyt@nospam.demon.nl> - 2021-01-19 17:03 +0100
Re: Battery Powered Project A. Dumas <alexandre@dumas.fr.invalid> - 2021-01-17 01:09 +0000
Re: Battery Powered Project Chris Elvidge <chris@mshome.net> - 2021-01-17 11:48 +0000
Re: Battery Powered Project Pancho <Pancho.Dontmaileme@outlook.com> - 2021-01-17 12:11 +0000
Re: Battery Powered Project Martin Gregorie <martin@mydomain.invalid> - 2021-01-17 14:43 +0000
Re: Battery Powered Project Chris Elvidge <chris@mshome.net> - 2021-01-17 11:52 +0000
Re: Battery Powered Project Andy Burns <usenet@andyburns.uk> - 2021-01-17 13:53 +0000
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| From | Simple Simon <please.dontspa@me.com> |
|---|---|
| Date | 2021-01-12 12:14 +0000 |
| Subject | Battery Powered Project |
| Message-ID | <rtk3qv$1112$1@gioia.aioe.org> |
I am working on a battery powered car and want the Pi to shut down automatically if the battery starts to go flat to try to prevent SD card corruption. I am a beginner to bash scripts! I will run this via crontab... #!/bin/bash powerstatus=$(vcgencmd get_throttled) if [ $powerstatus="throttled=0x1" ] then echo Under Voltage Detected - Shutting Down sudo halt else echo Voltage Normal fi Obviously it is not working!! Could someone correct and explain for me please.
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| From | Chris Green <cl@isbd.net> |
|---|---|
| Date | 2021-01-12 12:40 +0000 |
| Message-ID | <nuh0dh-2vq01.ln1@esprimo.zbmc.eu> |
| In reply to | #25783 |
Simple Simon <please.dontspa@me.com> wrote:
> I am working on a battery powered car and want the Pi to shut down
> automatically if the battery starts to go flat to try to prevent SD card
> corruption. I am a beginner to bash scripts! I will run this via crontab...
>
> #!/bin/bash
> powerstatus=$(vcgencmd get_throttled)
> if [ $powerstatus="throttled=0x1" ]
> then
> echo Under Voltage Detected - Shutting Down
> sudo halt
> else
> echo Voltage Normal
> fi
>
> Obviously it is not working!! Could someone correct and explain for me
> please.
You need spaces in the test:-
if [ $powerstatus = "throttled=0x1" ]
Without the spaces you are just testing if '$powerstatus="throttled=0x1"'
is not an empty string, and it never will be an empty string.
--
Chris Green
·
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| From | Simple Simon <please.dontspa@me.com> |
|---|---|
| Date | 2021-01-12 12:50 +0000 |
| Message-ID | <rtk5ur$qi$1@gioia.aioe.org> |
| In reply to | #25784 |
Chris Green wrote: > Simple Simon <please.dontspa@me.com> wrote: >> I am working on a battery powered car and want the Pi to shut down >> automatically if the battery starts to go flat to try to prevent SD card >> corruption. I am a beginner to bash scripts! I will run this via crontab... >> >> #!/bin/bash >> powerstatus=$(vcgencmd get_throttled) >> if [ $powerstatus="throttled=0x1" ] >> then >> echo Under Voltage Detected - Shutting Down >> sudo halt >> else >> echo Voltage Normal >> fi >> >> Obviously it is not working!! Could someone correct and explain for me >> please. > > You need spaces in the test:- > > if [ $powerstatus = "throttled=0x1" ] > > Without the spaces you are just testing if '$powerstatus="throttled=0x1"' > is not an empty string, and it never will be an empty string. > > Brilliant - many thanks - works a treat - I was almost there!!
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| From | "A. Dumas" <alexandre@dumas.fr.invalid> |
|---|---|
| Date | 2021-01-12 15:15 +0100 |
| Message-ID | <5ffdaf0c$0$303$e4fe514c@news.xs4all.nl> |
| In reply to | #25785 |
On 12-01-2021 13:50, Simple Simon wrote: > Brilliant - many thanks - works a treat - I was almost there!! It won't matter here, I guess, and you needed it for debugging, but normally never output to the console from a background script. So perhaps remove the echos now that it works. Slightly more importantly, it's good practice to put variables in quotes when testing them (the part between brackets) because you never know what may be inside. If there's a space, or the variable is empty, your script will break.
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| From | Theo <theom+news@chiark.greenend.org.uk> |
|---|---|
| Date | 2021-01-12 21:43 +0000 |
| Message-ID | <7ul*5x4-x@news.chiark.greenend.org.uk> |
| In reply to | #25785 |
Simple Simon <please.dontspa@me.com> wrote: > Brilliant - many thanks - works a treat - I was almost there!! I'm curious... does this actually work for low battery detection? Unless you're wiring the Pi directly across a battery that's giving out somewhere around 5V (for example a 6v lead acid), most of the time you'll have a voltage regulator between you and the battery. That regulator will aim to keep providing 5V as the battery is going flat. When the voltage sags below 5V it means the battery is so empty it can't maintain that, which means it's in a very steep part of the voltage decline. I'd expect it to be so steep you don't get enough time to do any meaningful shutdown, but I could be wrong. What battery setup do you have and how does it work out in practice? Theo
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| From | Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> |
|---|---|
| Date | 2021-01-13 09:40 +0000 |
| Message-ID | <rtmfa7$g6o$1@gioia.aioe.org> |
| In reply to | #25812 |
On a sunny day (12 Jan 2021 21:43:03 +0000 (GMT)) it happened Theo <theom+news@chiark.greenend.org.uk> wrote in <7ul*5x4-x@news.chiark.greenend.org.uk>: >Simple Simon <please.dontspa@me.com> wrote: >> Brilliant - many thanks - works a treat - I was almost there!! > >I'm curious... does this actually work for low battery detection? > >Unless you're wiring the Pi directly across a battery that's giving out >somewhere around 5V (for example a 6v lead acid), most of the time you'll >have a voltage regulator between you and the battery. That regulator will >aim to keep providing 5V as the battery is going flat. When the voltage >sags below 5V it means the battery is so empty it can't maintain that, which >means it's in a very steep part of the voltage decline. That is a valid argument for say detecting a low mains voltage. It does not however cover a fault in the regulator itself. I like the idea as extra test for fault conditions like too much voltage drop over USB cable by high loads etc.. You can make it log the error, or switch off high load / routines first before shutdown, sound an alarm, etc. A very common error in wallwart supplies is bad filter caps on the output, causing a high ripple on the 5V, this could perhaps detect that. Did no know about the low voltage check option.
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| From | Jim H <invalid@invalid.invalid> |
|---|---|
| Date | 2021-01-13 18:02 +0000 |
| Message-ID | <ducuvf9abr4djsh1ik6svd40gjhk0diqt0@4ax.com> |
| In reply to | #25812 |
On 12 Jan 2021 21:43:03 +0000 (GMT), in <7ul*5x4-x@news.chiark.greenend.org.uk>, Theo <theom+news@chiark.greenend.org.uk> wrote: >Simple Simon <please.dontspa@me.com> wrote: >> Brilliant - many thanks - works a treat - I was almost there!! > >I'm curious... does this actually work for low battery detection? > >Unless you're wiring the Pi directly across a battery that's giving out >somewhere around 5V (for example a 6v lead acid), most of the time you'll >have a voltage regulator between you and the battery. That regulator will >aim to keep providing 5V as the battery is going flat. When the voltage >sags below 5V it means the battery is so empty it can't maintain that, which >means it's in a very steep part of the voltage decline. > >I'd expect it to be so steep you don't get enough time to do any meaningful >shutdown, but I could be wrong. What battery setup do you have and how does >it work out in practice? Yes, except... At the low current draw of the Pi, unless the battery is rather small a cutoff of 5 V for a 6 V battery is 1.67 Volts per cell (Vpc) and that's way too low if you want to prevent premature failure due to overdischarge. You might get away with this long term if the battery capacity is low to begin with because then 1.67 Vpc might be say 80 - 90% discharged. But for a larger battery, say an automotive starting battery, a voltage of 1.67 Vpc at the current rate drawn by a Pi is way overdischarged and the battery will experience short life. The upside to all of this is that there probably won't be many outages. If regular outages are expected, then a much higher cutoff voltage needs to be set to prolong battery life... the bigger the battery the higher the cutoff. -- Jim H
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| From | Joe <joe@jretrading.com> |
|---|---|
| Date | 2021-01-13 22:04 +0000 |
| Message-ID | <20210113220422.68dfdff5@jresid.jretrading.com> |
| In reply to | #25812 |
On 12 Jan 2021 21:43:03 +0000 (GMT) Theo <theom+news@chiark.greenend.org.uk> wrote: > Simple Simon <please.dontspa@me.com> wrote: > > Brilliant - many thanks - works a treat - I was almost there!! > > I'm curious... does this actually work for low battery detection? > > Unless you're wiring the Pi directly across a battery that's giving > out somewhere around 5V (for example a 6v lead acid), most of the > time you'll have a voltage regulator between you and the battery. > That regulator will aim to keep providing 5V as the battery is going > flat. When the voltage sags below 5V it means the battery is so > empty it can't maintain that, which means it's in a very steep part > of the voltage decline. > > I'd expect it to be so steep you don't get enough time to do any > meaningful shutdown, but I could be wrong. What battery setup do you > have and how does it work out in practice? > Lithium cells have a linear-ish discharge curve, from 4.2V down to around 3V. Any sensibly designed lithium battery will cut off its output at the chosen lower bound, because if it completely discharges, it's dead forever. Not a 'steep' decline, a 'fall off the wall' decline. It's a good idea to have some independent means of anticipating this point. -- Joe
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| From | Theo <theom+news@chiark.greenend.org.uk> |
|---|---|
| Date | 2021-01-13 23:37 +0000 |
| Message-ID | <6ul*le+-x@news.chiark.greenend.org.uk> |
| In reply to | #25869 |
Joe <joe@jretrading.com> wrote: > Lithium cells have a linear-ish discharge curve, from 4.2V down to > around 3V. Any sensibly designed lithium battery will cut off its > output at the chosen lower bound, because if it completely discharges, > it's dead forever. Not a 'steep' decline, a 'fall off the wall' decline. > > It's a good idea to have some independent means of anticipating this > point. But lithium ion cells don't work for this application. We need 5V. One cell is too little, two cells is too much. One cell would start at 4.2V which is too low to reliably run a Pi. Two cells would start at 8.4V which is dangerously high for the Pi, and the proposed 5V cutoff would only come in below 2.5V per cell which is bad for the cells. As mentioned 6V lead acid doesn't work for a starting battery - it might be OK for a 'leisure' battery that is fine with deep discharge, but again we're on a part of the curve where the battery is absolutely flat and declining fast. Possibly LiFePO4 might be better, but a pair of cells at 3.6V fully charged is still too dangerous for the Pi. 4x alkaline cells might just about manage it - 1.6V per cell when new, ie 6.4V total, which is a bit dangerous but maybe OK. A gradual decline - I don't know where the Pi low voltage detection is but flat would be about 1.1V per cell or 4.4V total which is probably detectable. So if you don't mind throwing away cells at 20% capacity it might just work. Theo
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| From | Martin Gregorie <martin@mydomain.invalid> |
|---|---|
| Date | 2021-01-14 00:43 +0000 |
| Message-ID | <rto43f$sl2$3@dont-email.me> |
| In reply to | #25870 |
On Wed, 13 Jan 2021 23:37:18 +0000, Theo wrote: > As mentioned 6V lead acid doesn't work for a starting battery - it might > be OK for a 'leisure' battery that is fine with deep discharge, but > again we're on a part of the curve where the battery is absolutely flat > and declining fast. > In the soaring world we use 12v SLA (sealed lead-acid) batteries to power our radios, flight recorders FLARM and and various navigation systems. Most instrument panels draw 400-800 mA when fully powered up, so a 7AH battery is good for flights of over 7 hours. I use Yuasa NP7-12 batteries. This is a 12v 7.2Ah sealed battery, so can be installed any way up and is also sold for use in small business UPSs. In my glider I use a 12v->5v 3A DC converter (under 6 quid from eBay, where they are sold for blinging up cars with festoons of LEDs) for powering instruments which want a 5v supply. Mains chargers which shut off or switch to float mode at full charge are available for these batteries. If you go this way, and want to implement low-voltage shutdown for the Pi, connect your low-voltage detector inputs across the battery and set the shut-down point to 10.5v. If the low-voltage detector is a Pi hat, make a voltage divider from a 68K and a 27K resistor, put that across the battery and connect leads from each side of the 27K resistor to the low-voltage detector: when the battery is drawn down to 10.5 volts, there will be 3 volts at the low voltage detector. Or use a 10K linear potentiometer and set it to output approximately 3 volts. -- -- Martin | martin at Gregorie | gregorie dot org
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| From | The Natural Philosopher <tnp@invalid.invalid> |
|---|---|
| Date | 2021-01-14 03:59 +0000 |
| Message-ID | <rtofim$srv$1@dont-email.me> |
| In reply to | #25870 |
On 13/01/2021 23:37, Theo wrote: > Joe <joe@jretrading.com> wrote: >> Lithium cells have a linear-ish discharge curve, from 4.2V down to >> around 3V. Any sensibly designed lithium battery will cut off its >> output at the chosen lower bound, because if it completely discharges, >> it's dead forever. Not a 'steep' decline, a 'fall off the wall' decline. >> >> It's a good idea to have some independent means of anticipating this >> point. > > But lithium ion cells don't work for this application. We need 5V. > One cell is too little, two cells is too much. > One cell would start at 4.2V which is too low to reliably run a Pi. > Two cells would start at 8.4V which is dangerously high for the Pi, and the > proposed 5V cutoff would only come in below 2.5V per cell which is bad for > the cells. > > As mentioned 6V lead acid doesn't work for a starting battery - it might be > OK for a 'leisure' battery that is fine with deep discharge, but again we're > on a part of the curve where the battery is absolutely flat and declining > fast. > > Possibly LiFePO4 might be better, but a pair of cells at 3.6V fully charged > is still too dangerous for the Pi. > > 4x alkaline cells might just about manage it - 1.6V per cell when new, ie > 6.4V total, which is a bit dangerous but maybe OK. A gradual decline - I > don't know where the Pi low voltage detection is but flat would be about > 1.1V per cell or 4.4V total which is probably detectable. So if you don't > mind throwing away cells at 20% capacity it might just work. > > Theo > switch mode regulator will work with any of them. Given that you want around a one amp capability https://hobbyking.com/en_us/turnigy-1800mah-2s-12c-lipo-receiver-pack.html is a suitable pack and https://hobbyking.com/en_us/turnigy-hv-sbec-5a-switch-regulator-8-42v-input.html is a suitable regulator. HOWEVER that is still only half the story, as, presumably, you want to run it off mains as well - or do you? My point here is that a charger that will both charge the pack correctly AND have a spare amp to drive the Pi is not so easy. If you are happy to go and change batteries every so often, well then presumably you will want a much bigger battery. Anyway hobbyking is the go-to place for chargers regulators and batteries - ship world wide, and product is good quality. -- Future generations will wonder in bemused amazement that the early twenty-first century’s developed world went into hysterical panic over a globally average temperature increase of a few tenths of a degree, and, on the basis of gross exaggerations of highly uncertain computer projections combined into implausible chains of inference, proceeded to contemplate a rollback of the industrial age. Richard Lindzen
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| From | Ahem A Rivet's Shot <steveo@eircom.net> |
|---|---|
| Date | 2021-01-14 10:18 +0000 |
| Message-ID | <20210114101857.57aca4dab56bca0a4e589a4a@eircom.net> |
| In reply to | #25870 |
On 13 Jan 2021 23:37:18 +0000 (GMT) Theo <theom+news@chiark.greenend.org.uk> wrote: > Joe <joe@jretrading.com> wrote: > > Lithium cells have a linear-ish discharge curve, from 4.2V down to > > around 3V. Any sensibly designed lithium battery will cut off its > > output at the chosen lower bound, because if it completely discharges, > > it's dead forever. Not a 'steep' decline, a 'fall off the wall' decline. > > > > It's a good idea to have some independent means of anticipating this > > point. > > But lithium ion cells don't work for this application. We need 5V. > One cell is too little, two cells is too much. One cell and a DC-DC converter to give you a regulated supply, monitor the cell so you can shut down (well) before there's too little to run the converter. -- Steve O'Hara-Smith | Directable Mirror Arrays C:\>WIN | A better way to focus the sun The computer obeys and wins. | licences available see You lose and Bill collects. | http://www.sohara.org/
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| From | The Natural Philosopher <tnp@invalid.invalid> |
|---|---|
| Date | 2021-01-14 11:04 +0000 |
| Message-ID | <rtp8gn$55d$4@dont-email.me> |
| In reply to | #25885 |
On 14/01/2021 10:18, Ahem A Rivet's Shot wrote: > On 13 Jan 2021 23:37:18 +0000 (GMT) > Theo <theom+news@chiark.greenend.org.uk> wrote: > >> Joe <joe@jretrading.com> wrote: >>> Lithium cells have a linear-ish discharge curve, from 4.2V down to >>> around 3V. Any sensibly designed lithium battery will cut off its >>> output at the chosen lower bound, because if it completely discharges, >>> it's dead forever. Not a 'steep' decline, a 'fall off the wall' decline. >>> >>> It's a good idea to have some independent means of anticipating this >>> point. >> >> But lithium ion cells don't work for this application. We need 5V. >> One cell is too little, two cells is too much. > > One cell and a DC-DC converter to give you a regulated supply, > monitor the cell so you can shut down (well) before there's too little to > run the converter. > It's slightly simpler and more efficient to use a step down from two cells. -- The theory of Communism may be summed up in one sentence: Abolish all private property. Karl Marx
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| From | Ahem A Rivet's Shot <steveo@eircom.net> |
|---|---|
| Date | 2021-01-14 11:46 +0000 |
| Message-ID | <20210114114623.0b54c475f1741b48b8f13658@eircom.net> |
| In reply to | #25888 |
On Thu, 14 Jan 2021 11:04:55 +0000 The Natural Philosopher <tnp@invalid.invalid> wrote: > On 14/01/2021 10:18, Ahem A Rivet's Shot wrote: > > On 13 Jan 2021 23:37:18 +0000 (GMT) > > Theo <theom+news@chiark.greenend.org.uk> wrote: > > > >> Joe <joe@jretrading.com> wrote: > >>> Lithium cells have a linear-ish discharge curve, from 4.2V down to > >>> around 3V. Any sensibly designed lithium battery will cut off its > >>> output at the chosen lower bound, because if it completely discharges, > >>> it's dead forever. Not a 'steep' decline, a 'fall off the wall' > >>> decline. > >>> > >>> It's a good idea to have some independent means of anticipating this > >>> point. > >> > >> But lithium ion cells don't work for this application. We need 5V. > >> One cell is too little, two cells is too much. > > > > One cell and a DC-DC converter to give you a regulated supply, > > monitor the cell so you can shut down (well) before there's too little > > to run the converter. > > > It's slightly simpler and more efficient to use a step down from two > cells. It's only simpler if you look at what's on the converter board :) -- Steve O'Hara-Smith | Directable Mirror Arrays C:\>WIN | A better way to focus the sun The computer obeys and wins. | licences available see You lose and Bill collects. | http://www.sohara.org/
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| From | The Natural Philosopher <tnp@invalid.invalid> |
|---|---|
| Date | 2021-01-14 12:21 +0000 |
| Message-ID | <rtpd10$7hp$1@dont-email.me> |
| In reply to | #25892 |
On 14/01/2021 11:46, Ahem A Rivet's Shot wrote: > On Thu, 14 Jan 2021 11:04:55 +0000 > The Natural Philosopher <tnp@invalid.invalid> wrote: > >> On 14/01/2021 10:18, Ahem A Rivet's Shot wrote: >>> On 13 Jan 2021 23:37:18 +0000 (GMT) >>> Theo <theom+news@chiark.greenend.org.uk> wrote: >>> >>>> Joe <joe@jretrading.com> wrote: >>>>> Lithium cells have a linear-ish discharge curve, from 4.2V down to >>>>> around 3V. Any sensibly designed lithium battery will cut off its >>>>> output at the chosen lower bound, because if it completely discharges, >>>>> it's dead forever. Not a 'steep' decline, a 'fall off the wall' >>>>> decline. >>>>> >>>>> It's a good idea to have some independent means of anticipating this >>>>> point. >>>> >>>> But lithium ion cells don't work for this application. We need 5V. >>>> One cell is too little, two cells is too much. >>> >>> One cell and a DC-DC converter to give you a regulated supply, >>> monitor the cell so you can shut down (well) before there's too little >>> to run the converter. >>> >> It's slightly simpler and more efficient to use a step down from two >> cells. > > It's only simpler if you look at what's on the converter board :) > No, that's not true. To step up you need to use a buck converter with a choke big enough to store energy to push the voltage up. To step down you only need a choke to smooth HF ripple, and transistor efficiency goes up with voltage and down with current, so that's a win win too. -- "Corbyn talks about equality, justice, opportunity, health care, peace, community, compassion, investment, security, housing...." "What kind of person is not interested in those things?" "Jeremy Corbyn?"
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| From | Ahem A Rivet's Shot <steveo@eircom.net> |
|---|---|
| Date | 2021-01-14 12:38 +0000 |
| Message-ID | <20210114123831.5fcccceb5cef114baa159c11@eircom.net> |
| In reply to | #25893 |
On Thu, 14 Jan 2021 12:21:52 +0000 The Natural Philosopher <tnp@invalid.invalid> wrote: > On 14/01/2021 11:46, Ahem A Rivet's Shot wrote: > > On Thu, 14 Jan 2021 11:04:55 +0000 > > It's only simpler if you look at what's on the converter > > board :) > > > No, that's not true. To step up you need to use a buck converter with a > choke big enough to store energy to push the voltage up. To step down Sure that's all on the board :) From a system perspective it's just a board with battery in and 5V out :) > you only need a choke to smooth HF ripple, and transistor efficiency > goes up with voltage and down with current, so that's a win win too. Oh I agree a step down only is a simpler board, but either way it's an off the shelf small component. -- Steve O'Hara-Smith | Directable Mirror Arrays C:\>WIN | A better way to focus the sun The computer obeys and wins. | licences available see You lose and Bill collects. | http://www.sohara.org/
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| From | David Higton <dave@davehigton.me.uk> |
|---|---|
| Date | 2021-01-14 14:17 +0000 |
| Message-ID | <609ab9ee58.DaveMeUK@BeagleBoard-xM> |
| In reply to | #25893 |
In message <rtpd10$7hp$1@dont-email.me>
The Natural Philosopher <tnp@invalid.invalid> wrote:
> No, that's not true. To step up you need to use a buck converter with a
> choke big enough to store energy to push the voltage up. To step down
> you only need a choke to smooth HF ripple
Not true. The step-down inductor needs to store energy too.
David
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| From | The Natural Philosopher <tnp@invalid.invalid> |
|---|---|
| Date | 2021-01-14 14:28 +0000 |
| Message-ID | <rtpkdt$rjp$2@dont-email.me> |
| In reply to | #25913 |
On 14/01/2021 14:17, David Higton wrote: > In message <rtpd10$7hp$1@dont-email.me> > The Natural Philosopher <tnp@invalid.invalid> wrote: > >> No, that's not true. To step up you need to use a buck converter with a >> choke big enough to store energy to push the voltage up. To step down >> you only need a choke to smooth HF ripple > > Not true. The step-down inductor needs to store energy too. It isn't a step down inductor. you just use variable PWM on the raw voltage. All you need to do is use a cap and some form of current limiter - a resistors works but dissipates power > > David > -- Those who want slavery should have the grace to name it by its proper name. They must face the full meaning of that which they are advocating or condoning; the full, exact, specific meaning of collectivism, of its logical implications, of the principles upon which it is based, and of the ultimate consequences to which these principles will lead. They must face it, then decide whether this is what they want or not. Ayn Rand.
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| From | David Higton <dave@davehigton.me.uk> |
|---|---|
| Date | 2021-01-16 20:09 +0000 |
| Message-ID | <c88de1ef58.DaveMeUK@BeagleBoard-xM> |
| In reply to | #25915 |
In message <rtpkdt$rjp$2@dont-email.me>
The Natural Philosopher <tnp@invalid.invalid> wrote:
> On 14/01/2021 14:17, David Higton wrote:
> > In message <rtpd10$7hp$1@dont-email.me>
> > The Natural Philosopher <tnp@invalid.invalid> wrote:
> >
> > > No, that's not true. To step up you need to use a buck converter with a
> > > choke big enough to store energy to push the voltage up. To step down
> > > you only need a choke to smooth HF ripple
> >
> > Not true. The step-down inductor needs to store energy too.
>
> It isn't a step down inductor.
Just a short form of words - I was referring to an inductor in a step
down regulator.
> you just use variable PWM on the raw voltage. All you need to do is use a
> cap and some form of current limiter - a resistors works but dissipates
> power
There are regulators that use capacitors, sure (commonly step up, e.g.
for EIA-232 line drivers), but they inherently require significant
resistance in the switch elements to limit the current, so they're
lossy. For a low power application the losses don't matter, but in
the case discussed here, I don't think you'd want that level of loss.
It works out the same as a linear regulator, according to my maths.
Using an inductor in a conventional step-down switching regulator is
much more efficient, and of course requires the inductor to store
energy.
(Apologies for the delay in replying - the news server I use changed
its implementation of NNTP and I have had to modify my news transport
client's code to suit.)
David
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| From | The Natural Philosopher <tnp@invalid.invalid> |
|---|---|
| Date | 2021-01-17 07:19 +0000 |
| Message-ID | <ru0oeu$f6t$1@dont-email.me> |
| In reply to | #25936 |
On 16/01/2021 20:09, David Higton wrote: > Using an inductor in a conventional step-down switching regulator is > much more efficient, and of course requires the inductor to store > energy. > No, it doesn't have to store ALL the energy - like it does in a step up And if you don't mind massive ripple, it isn't needed *at all*. Consider a 6V battery deeding a 3V lamp. Simply chop the 6V on a 50% duty cycle and there you are. No choke needed at all. Add an LC filter and the cap stores all that is necessary. All the L does is limit the peak current into the C. -- There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact. Mark Twain
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