Search for right battery for sensor idea with IMP002

hi guys.

I´m working on a little idea of mine, but I´m not the biggest hardware guy. Maybe somebody in this forum can help me.

I am planning a little sensor based on the IMP002 which is supposed to wake up 3 times per day. Just wake up, connect to wifi, send something (less than 1s) and go back to sleep. And the sensor should be as small as possible. It’s not supposed to be rechargeable nor do I want to change the battery. So now I am searching for the right battery.

So far my research tells me that button cells + cap don´t reach the necessary 250mA for the module. Normal batteries (like AAA or AAAA) are to large for what I have planned. My solution for now would be a LiPo-accumulator with 3,7V, 400mAh and 1C continuous discharge. In addition its also only 6x25x35, which is small enough for my Idea. Downside seems to be a self-discharge rate of 5% per month.

Am I on the right track or is the LiPo idea a stupid choice?
How long would the sensor work with this kind of power supply? Are we talking about a month or rather a year? Or even longer?

And a particularly interesting question - could a 200mAh LiPo with 1C continuous discharge handle the IMP002s worst case pulse of 250mA for some milliseconds? Most manufacturer only list the discharge rate for continuous discharge and not for a pulse. I guess the IMP002s ~4.8ms 250mA pulse can be delivered by a battery with a continuous rate smaller than 250mA. What would be the absolute minimum specs of the LiPo to handle the IMP002s worst case pulse from your experience?

thanks a lot for your help.

Li-ion should last a year if the connection time is short enough. Why not 2-4 coin cells in parallel? I feel like they can handle 250ma for a few ms. Less self-discharege.

Coin cells are not good at high currents at all - they are usually 10mA max discharge.

The LiPo would be fine for that; 2C isn’t a big issue on a pulse profile.

The other option is to use a spiral wound LiMnO2 cell (eg CR123A) which can do the current… but they’re round, which may not work for your form factor. As recommended on the Nora devwiki page, use a 220uF or higher in parallel with the battery to help with the cell’s internal resistance… but you don’t need a PSU at all to run the imp from this type of cell. The CR123A is 1500mAh but the CR2 (a bit smaller) is about 600mAh and will run the imp directly too.

These are very low self discharge too.