Powering Notecard with 2 Alkaline batteries

Hardware
1

Does anyone have any thoughts on a custom pcb M.2 connector powering VModem_P and VIO_P directly using 2 D Alkaline Batteries? Pros, Cons?
Voltage is monitored by notehub.io.
Couldn’t it run for many years with D size Batteries.

2

The answer is yes. We have devices that run for years on three AA cells. Although they are not blues modems, the technique is general. Isolate the modem from the “scheduler”. It also helps to connect to the tower only once a day

1 Like
3

Hello @Poem ,

Thanks for your information. Good to know.
My question is more about powering Notecard VIO_P directly without any voltage regulation from 2 alkaline (3-3.3 v).
If the microcontroller connected to Notecard IO’s work can from 2 to 5.5v, does the voltage going to VIO_P have to specifically be 1.8 or 3.3v. Or can it be whatever the Host Micro can tolerate? Say between 2.5 and 3.3v?

4

I guess this is a question for Greg. However, if your external digital logic tolerates being pulled up to the battery voltage even as it decreases over time, I don’t see a problem.

5

@Poem

That is what I was thinking too.

Thanks

6

We do not recommend using 2 alkaline batteries to power the Notecard
To be clear, I’m assuming you mean having two ~1.5 V alkaline batteries in series.

There are 3 primary reasons for this:

  1. We do not test this configuration
    Since the use of 2 alkaline batteries technically falls outside the bounds of the Notecard specification, we do not test this configuration.

  2. The modem requires at least 2.5v power, which is close to the ~3.0 volts supplied by the batteries. As the batteries drain (or the temperature changes) the available voltage will drop. When the modem powers on, the extra current draw can cause the voltage to drop below the 2.5 volt minimum.

With the 2 batteries, there is not much extra voltage potential to allow for the decrease in battery voltage and still enable one of Notecard’s primary functions.

  1. Recommending the use of voltages outside of our datasheet specifications could result in future hardware revisions not working in your design.

If using 2 batteries works today with the current Notecard hardware, but for some reason the Notecard on-board hardware components must be changed, it is possible it could result in a design that meets the datasheet specifications, but not work in your device design.

7

@gwolff

Thank you for your noted reply.

8

You could use a AAT1217 from 0.85 volt and 3.3V out to power the Notecard for 2 AA batteries.

1 Like
9

Thank you. @robouden