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I have a solar powered project which includes an Arduino Nano and a cellular module.

At the moment the Arduino is powered via the USB port and the cellular module is powered by a small 3.7V battery (to cope with the brief 2A spikes during data transmission.) I want to power both of these elements from the same 11.1V lithium-ion battery which I can keep topped up with a solar panel and a charge controller.

To do this, I’ll need to regulate the voltage from the battery down to two different voltage levels – 7-12V for the Arduino and 3.7-4V for the cellular module. The battery needs to be 11.1V as it will occasionally be used to directly power a solenoid.

A lot of people seem to opt for the LM2596 regulator, but it seems a bit overkill for this since the battery voltage will actually be between 8.25V and 12.6V. Regulating 8.25V down to 7V isn’t much of a drop and the LM2596 is designed for higher voltages I believe.

I’ve found some dual output step down converters, such as the TPS54395.

I’m wondering if anyone has any other suggestions which may be easier to implement?

I don’t mind SMT components either as I’m looking to fabricate a PCB for the project anyway. The device should also be able to supply at least 3A.

JRE
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RM429
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  • A confusion of requirements. Fix on a specification please. – Andy aka Jan 07 '21 at 17:26
  • The newer Arduinos like the Nano 33 IoT have a DC/DC converter on board that will take an input of up to 21V. Would using one of those be an option? Saves you one external DC/DC converter. Also, your battery charger may not like having a load connected when charging. – ocrdu Jan 07 '21 at 17:38
  • I would stick to a battery for low ESR for the Tx and keep it on float at 3.8V use a MPT BMS charger for Li Ion or keep on float at 11.4V otherwise, extended CV at 12.6 V will significantly reduce lifespan – Tony Stewart EE75 Jan 07 '21 at 17:44
  • @ocrdu That's not a bad idea, thanks. Although I've already fabricated my own standard Nano from the open source schematic and so I'd rather use that. With regards to charging the battery with a load, I assumed the charge controller would solve that (correct me if I'm wrong). – RM429 Jan 07 '21 at 17:47
  • The charge controller does not know of load so cutoff current may never be reached or as I said, extended times during load and charge – Tony Stewart EE75 Jan 07 '21 at 17:48
  • @zt42: You're wrong 8-). Some chargers can do what you want; they implement load sharing; I don't know if yours does. Also see this question and answers: https://electronics.stackexchange.com/questions/539946/recharging-a-lipo-battery-while-using-it – ocrdu Jan 07 '21 at 18:00

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