Charging LiPo on a Boron with 4 x AA batteries

Hello, I will be connecting a LiPo to the boron through the JST-PH LiPo connector and connecting 4 x AA NiMH batteries to VUSB. I know the Boron will step down the voltage to what is required from the AA battery setup. Is there any additional coding required to decrease power loss of AA batteries due to step down in voltage? Or should I just plug and play?

I suspect the Boron will show preference to the highest voltage source.
If so, your NiMH pack will be discharged (~1V each cell) before the Li-Po is sourced.

Thank you Rftop. So I guess I am better off using 3 x AA as voltage will be most similar to 3.7V LiPo?

Well, a “charged” 3.7V Li-Po will be begin at 4.20V but be around 4.12V - 4.14V after resting any significant amount of time.
So your 3xNiMH will be ~70% Capacity before the Li-Po is sourced.

I’m guessing both the Li-Po and the primary pack would then continue to drop voltage as the boron swaps preference back and forth, with the Li-Po never being recharged. Again, that’s just an assumption.

What are the main objectives (power) of your Project ?

Thanks for your response. I need the Boron to last 1 year on battery power waking up from standby sleep every 4 hours to publish once and go back to standby sleep. I have a 5000mAh LiPo connected and to give the device some extra buffer I wanted to introduce AA batteries to VUSB.

I read that better sleep modes are scheduled for the 1.5.0 “Final” release.

Your goal may likely be accomplished with primary batteries only (but using the Li-Po connector, not USB).
This will greatly depend on how long the Boron takes for each Cellular Connection, depending on the local signal strength.

That sounds great, excited to see what 1.5.0 has to offer.

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