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Hi, I’m in the process of re engineering my home automation server.

The server is mounted within an Alarm panel box. That provides a 12v supply battery backed.

1.2Ahr Lead Acid float charged so about 13Vdc.

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The server communicates with the Z-wave transceiver via the serial port of the Raspberry pi pins 9 and 10 from memory, thus I intend to use the serial-less mode of the Strompi3.

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I need to sense the battery voltage attached to the Wide input to know when the 220Vac has failed but how? Or could I use some other method?

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Should I flash to serial-less mode?

Regards Strebor

Hello Strebor,

you would have to measure your Battery Voltage with an external ADC that can measure those high voltages. Or you need to use a voltage divider to lower the voltage if you don't have an ADC like that.

The problem is, that the StromPi will not know when you shut down your raspberry pi and will stay on as long as it gets enough power over its primary voltage supply. This also means it can not start the Raspberry Pi on its own. To start the Raspberry Pi again you either have to disconnect the voltage supply, or you need to connect GPIO3 to ground.

If you use the power off command together with shutting down your raspberry pi, the StromPi will also be switched off, but it will also not restart until all power supplies are briefly disconnected or the PowerOnButton is used.

If you need to use the serial interface for any other communication, we always recommend using the serialless mode.

Best regards[nbsp]

Tim (Joy-IT)

I don’t think I posed my question very well. I don’t need or intend to measure the AC just the float charge voltage of the lead acid battery attached to the Wide input. This will drop from 13Vdc to 12Vdc when the charge state drops to about 50%.

When I configured the Strompi3 with the python gui I got a choice of 50% or 25% charge in the configuration menu. I had expected a Voltage which I could set to 12Vdc. I now presume that the menu option is referring to the LiPo charge state is that correct?

As I don’t have a LiPo battery is there some other means of indicating to the Strompi3 that charging has stopped ? (I.e.with mains failure)

I could arrange for another input to disappear with the mains such as by running the server from a USB input as a primary and have the wide range take over, but I’d still require the shutdown script to run when the battery reaches 12V.

Any Ideas welcome on how I can meet this use case.

Regards Strebor

Hello Strebor,

Unfortunately, the battery shutdown mode is only designed for the StromPi3 Battery HAT.

To get the behavior you want, you would have to write a script that reads the voltage at the wide input and turns off the StromPi and Raspberry Pi as soon as the desired voltage is reached.

You can follow our status script and the shutdown script, there the status script already reads out the voltage at the wide input and the shutdown script shuts down everything safely.

Please note that the StromPi will only restart if either all power supplies are disconnected for a short time or the power-on button is used.

Best regards
Tim (Joy-IT)

Tim, thanks for the reply, is the status information available in serial-less mode?....S

Hello Strebor,

the status information is not available in serial-less mode.[nbsp]

You either have to disable the serial-less mode or use an external ADC to read the voltage.

Best regards

Tim (Joy-IT)

Hi Tim, thanks I'll have to have a think of a simple 'Plan B'...S

Tim, plan B is:

1. Primary set to USB direct from 230Vac power.

2. Secondary set to Wide

3. On 230Vac power fail power to the pi cuts over to Wide and initiates the shutdown timer.

4. Shutdown timer detected via gpio (Serial less mode) script begins time to shutdown countdown

Does that make sense?

Regards and thanks again for your help, Strebor

Hello Strebor,

Yes, you can do it like that.

Best regards
Tim (Joy-IT)