Battery Widget


#1

When I transfer the following data (batt,p=50) with the MQTT API to cayenne , a battery widget automatically appears, but the data is not displayed correctly. I found out that the display of the charge state in % is converted according to the following function: [displayed_value = -3.14… * given_value + 164,…].
In order to display the desired value of 50%, it is necessary to transmit (50.0-164) / - 3.14 = 36.3.

Is this intended or a bug of the widget

.


Newbie needs help with ESP8266, HX711 and a load cell
#2

Hi @rau

I have to tell you, it looks like a bug to me. I expect the intent was to allow you to pass the battery level as a simple number and not have to do any conversion on it. I will write this up to get it fixed.


#3

Hi @rsiegel

now it works as expected. Thank you for the quick help.


#4

@rau, Do you know how can I capture the battery level connected to Raspberry Pi?

Thanks


#5

By default the Raspberry Pi does not have a battery management. So, at first you need a battery fuel gauge connected to your RasPi (e.g. over I2C). Here is an example of such a module: LiPo fuel gauge. In the next step you have to determine the charge level with your application via I2C and transfer it to cayenne.
You can use the MQTT-API to transfer the charge level to cayenne. Please read the following doc how to do it: Manually Publishing / Subscribing.


#6

I definitely will check out that LiPo fuel gauge. The built in ESP VCC function seems to be pretty inaccurate…


#7

Since the Raspi requires 5V power supply, you need the following device: PowerBoost 1000 Charger - Rechargeable 5V Lipo USB Boost @ 1A - 1000C to bring the LiPo voltage to 5V.

Install the LiPo fuel gauge between battery and PowerBoost module.


#8

Woow, thanks you a lot for the provided information. The LIPO fuel gauge looks very good. Now I am using this board:

Lithium Board

to power the Raspberry Pi.


#9

For LiPo batteries, you really need a coulomb counter like this https://learn.sparkfun.com/tutorials/ltc4150-coulomb-counter-hookup-guide, or the LiPo fuel gauge.

Very interesting technology.

Cheers,

Craig