Battery life of sensors.

[Sweebee]

I have some sensors running for months. The sensors send their battery life to the controller. 3.3V = 100% 1.9V = 0%.

But the sensors stop working around 40-45%. The voltage is around 2.5V. I tested all the sensors on 1.9V and they all worked fine. But i think the current is the problem. The batteries can't deliver enough power to let the sensor send data with the NRF.

I used zinc chloride batteries. Don't know if Alkalines are better? All the sensors use 10-20uF capacitors.

Is there a way to improve this?

[Sparkman]

@Sweebee Most zinc-chloride batteries are marketed as "heavy duty". They are anything but that. You should get much better performance with alkaline batteries.

Cheers
Al

[Sweebee]

Thanks, I will try that.

[m26872]

@Sweebee
Perhaps you've got the BOD Level set to 2.7 V ?

[Stric]

@m26872 .. which is default for most. My battery used to cut off slightly over (readVcc-measured) 2.7V, now they're down to 2.6 after changing BOD level to 1.8 instead. Requires external programmer like USBtinyISP or so.

[Sweebee]

Bod is disabled. And the proccessor is running On 1 MHz (custom bootloader).

[Sweebee]

Opened all my pir/light sensors to look what batteries were inside. I have 1 node thats on 38% with zinc philips batteries and still work fine. the ones with panasonic zinc batteries died around 40-45%. I have some with GP alkaline that are still around 70-80% so have to wait what they will do (looks like they don't drop as quickly as the zinc batteries).

[m26872]

@Sweebee
Is the remaining charge (voltage) equal between the two discharged batteries?

[novicit]

I have heard somewhere that zinc-chloride batteries are not suitable for this kind of application. I have also been testing various batteries, all alkaline. Basically I have found you get what you pay for. I tried some local supermarket branded alkaline's and had your result. About 45% they just died. Then I tested a different 'cheap' brand, same result. Upgraded to more expensive brand name and got to ~20% consistently. Then tried top of the line (price wise) brand name - and they have been excellent! I have one node - DS18B20 temperature node in the attic for 6 months - exposed to 0 deg. F to 118 deg. F from winter to summer - and it shows 11% left. Key information is they are AAA, and the BATT_MIN is set to 1.65V! Hope this experience helps.

[5546dug]

@m26872 what does BOD stand for?

[hek]

@5546dug

Brown out detection
http://www.scienceprog.com/microcontroller-brown-out-detection/