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Topic: Button cells vs 9V headache  (Read 386 times) previous topic - next topic

gduffy

I am working on an arduino controller project with a few attached components returning data e.g. gps and mini camera. All works fine with usb power or 9V battery. I tried using button cells in parallel creating approx. 9V (to save space) but the resulting battery does not seem to be able to power the components... is it a max current problem? The button batteries are in three pairs connected in parallel. Any ideas?

bos1714

Hello there!

What specific coin cell battery are you using?

Are you sure placing the batteries in parallel is going to increase voltage?
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DrAzzy

#2
Jun 22, 2018, 10:37 pm Last Edit: Jun 22, 2018, 10:38 pm by DrAzzy
Please describe the wiring in more detail; I don't see how 3 pairs of button batteries in parallel could get 9v.


Button cells have lousy current handling. The 2032 coin cells are okay for powering a barebones arduino that's kept in sleep almost all the time and has no power led. The smaller button cells, probably no good at all.

9v batteries are also pretty lousy in terms of current handling / capacity.... and GPS is usually a major power hog; I suspect the mini camera is probably power hungry too (though you've given no specs on either, so who knows?). You're lucky it works on a 9v battery, imo. Why do you need 9v, anyway? Isn't it a 5v or 3.3v board?
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gduffy

Thanks for the speedy responses :-)
You are right my arrangement provides 6V rather than 9V. I did not explain well sorry. Each cell is 3V. A pair of cells in series gives 6V. Three pairs in parallel; in an attempt to extend the time the system can run for before changing cells. I hope that helps clarify. Any ideas chaps?

gduffy

The 9V battery was recommended for the project. I'd happily use a smaller battery if that would work.

DrAzzy

Recommending a 9v battery for an arduino project is a red flag that someone's advice may be bad, and you should be cautious about their advice until you've determined whether they know what they're doing. There are appropriate times to use one, but most of the cases where people use them with Arduino are not. The current handling and battery life are lousy, and you're wasting at least

To assess the suitability of a specific battery we would need to know what the expected peak load and required battery life would be - at a minimum, what board, and what will be connected to it (ie, part numbers, not just a description like "GPS and mini camera")
ATtiny core for 841+1634+828 and x313/x4/x5/x61/x7/x8 series Board Manager:
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts (some assembled), mosfets and awesome prototyping board in my store http://tindie.com/stores/DrAzzy

jremington

#6
Jun 22, 2018, 11:45 pm Last Edit: Jun 22, 2018, 11:45 pm by jremington
Quote
with a few attached components returning data e.g. gps and mini camera.
Those are power hungry components. Plan on using rechargeable cells, for example AA NiMH or larger.

ReverseEMF

#7
Jun 22, 2018, 11:50 pm Last Edit: Jun 22, 2018, 11:51 pm by ReverseEMF
You might consider one of those rechargeable battery packs designed to charge cell phones or run USB powered devices.  I'm not sure how noisey they are [some may be better than others], so there is that to consider.
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DVDdoug

#8
Jun 23, 2018, 12:26 am Last Edit: Jun 23, 2018, 12:26 am by DVDdoug
Quote
is it a max current problem?
Probably yes.   If you have a multimeter,* check the voltage under load.  If the batteries can't supply the current, the voltage will drop.     

For this particular problem it's actually better to measure/monitor voltage than to measure current.   (And it's kind-of a pain to measure current, and you burn stuff up if you measure current incorrectly.)

Batteries in parallel will increase the current capability but it's probably still not enough, and batteries in parallel are generally a bad idea anyway.





* If electronics is going to be your hobby you should get a multimeter.  And if cost is an issue, a cheap meter is better than no meter.    (If this is a one-time project you may be able to get-by without one.)

gduffy

Thankyou. Here is the documentation for the project:

http://doc.open-cosmos.com/Qbcan_modular#Power
Including
BMP180 temperature and pressure sensor
RFM69 transceiver
Low Level Converter

Also added are:
Adafruit Ultimate gps
https://www.adafruit.com/product/746
Adafruit tiny spy camera
https://www.adafruit.com/product/3202

Not sure about peak load...



https://www.adafruit.com/product/3202

jremington

#10
Jun 23, 2018, 01:32 am Last Edit: Jun 23, 2018, 01:33 am by jremington
Quote
Not sure about peak load...
Time to get out your multimeter!
Studying the data sheets goes a long way, too.

vinceherman

Why are you trying to use button batteries?  Those are usually only considered if you are going for the smallest size possible.  Are you?

If absolute smallest size is not important, go with a bigger battery.  Then let the device run.  Measure battery voltage over time.  Stop the experiment when the battery has reached minimum voltage.

Now you have the data you need to decide if you have more battery than you need, or if you need more battery to reach your duration goals.

MarkT

3V coin cells are primary lithium batteries which are rated at 10 years shelf life, but only upto a
few mA of current.   They are calculator batteries, completely unsuitable for anything taking more than
perhaps 3mA.

The 1.5V button cells are alkaline and have a much higher max current.  Those are the sort you want perhaps?

Why use 9V though?  What are the peripherals you want to power?
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TomGeorge

Hi,
Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html .

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Thanks.. Tom.... :)
Everything runs on smoke, let the smoke out, it stops running....

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