Battery level definition

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michap
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Battery level definition

Post by michap » 19 Dec 2016 13:37

Hi,

how the battery level is defined?

I mean - is it linear? So 3.3V = 100%, 2.97V=90% and 2.475V = 75% ?
I think that not :)

Maybe linear between 2.4V (0%) and 3.3V (100%)?

Would be interesting to know for battery powered devices.

Thanks
Michael

pz1
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Re: Battery level definition

Post by pz1 » 19 Dec 2016 13:59

Battery level is the amount of energy remaining in the battery. It is defined in Wh. As an indication of the energy battery producers sometimes provide discharge curves that displays the amount of energy against voltage. This curve does have a sigmoid form.
My observation with Zwave devices are quite diverse patterns. Some of my StellaZ TRV's continued to work for well over six weeks at 0% charge, while others stopped at 10% or even more.
I guess it strongly depends on the place where the device sits. Heating systems are not designed with control with RF in mind. TRV's are stowed away in odd corners. Unfortunately you can no longer inspect the timing info in ExpertUI. But in the past I found a strong correlation between battery drain and bad figures in the timing!

michap
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Re: Battery level definition

Post by michap » 19 Dec 2016 14:08

Right. I have same experience....

That's why interesting for me how it will be defined in Z-Uno.
Here is no "battery type" defined, so that we can not take any "discharge curves".

So there are 2 questions - first about level definition itself, and second when (in what state) the actual battery level will be defined (idle process, while sending,....)

Michael

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PoltoS
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Re: Battery level definition

Post by PoltoS » 19 Dec 2016 15:47

The only way to measure battery level is via currnet Vcc voltage. But most of modern batteries do have a pretty flat curve that drops sharply on the end of battery life. This makes it pretty hard to covert Vcc -> % of energy remained.

Usually we do linear 100%-0% via 3.0V-2.4V mapping. But as you expect, this is far from real % of energy. Indeed, manu devices can work when 0% is shown for a year.

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