LiFePO4 for Moteino

[d00m178]

Hello,

Is it the good idea to use LiFePO4 rechargable battery for powering Moteino via Vcc?
For example, if I need battery with capacity about 6000 mAh, probably I can use such batteries (1500x4) connected in parallel?

https://ru.aliexpress.com/item/4-10PCS-3-2V-18650-rechargeable-LiFePO4-battery-pack-1500mah-lithium-polymer-cell-for-12V-24V/32889038385.html?spm=a2g0v.10010108.1000016%2FB.1.eeb54ba2BrSRO2&isOrigTitle=true

The main concern that LiFePO4 is about 3.2v but for powering via Vcc we need exactly 3.3v..
Also idk how to charge such battery assembly from solar panel.. Seems I need some charger with controller?
Any advices would be helpful.
Thank you.

[Felix]

Why the huge capacity?
The LiFePo4 3.2v is below the 3.3V+dropout of the LDO. You want to be around 3.5V+ or more depending on how much current the Moteino draws, but typically 3.6V+, or else the LDO quiescent current will be much more than the few uA when you're above the dropout region.

For LiFePo4 you will need a dedicated charger for their chemistry. With solar, you will probably want a MPPT charger. It gets expensive...

If your project is very low power (ie sleeps most of the time) you could just go with a Supercapacitor and small solar panel, then no worries about charging controller and extreme temperatures where batteries stop working, just size the panel according to the needs. And you can easily put Supercaps in parallel to double capacity. Perfect for year round sensing applications.

[d00m178]

Why the huge capacity?

In my project I have 11 external DS18B20 thermosensors connected to MCU.
Also there is Laser Distance module.
and LoRa radio module.
So device works about 4 month on 3x2000mAh LiPo battery pack.
powered via Vin (which means via LDO)

So I decided to check LiFePO4 battery and power MCU via Vcc.
And this way - without LDO in circuit, am I right?

But nominal voltage of LiFePO4 - the big question for me.. I'm not sure will it work or not.

[Felix]

You could use it without LDO. There is the Moteino8Mhz version which comes without LDO and should be used at less than 3.3V, but runs at 8Mhz for that reason.

Are you sleeping your sensors when not in use?

[d00m178]

You could use it without LDO. There is the Moteino8Mhz version which comes without LDO and should be used at less than 3.3V, but runs at 8Mhz for that reason.

Are you sleeping your sensors when not in use?

Can I use LiFePO4 with this Moteino with RFM95?
https://lowpowerlab.com/shop/product/99

I just disconnect power from sensors before set MCU to sleep. My sensors powered from digital pin on MCU.

[Felix]

Sure, but I would recommend removing the LDO and powering it directly through the 3v3 pin.

[d00m178]

Sure, but I would recommend removing the LDO and powering it directly through the 3v3 pin.

What if I connect LiFePO4 to Vcc and will not remove LDO? Will it work ok? Or I need definitely remove LDO if i want to power MCU via Vcc?

[d00m178]

So, why it needed to remove LDO from Moteino if I want to power it from LiFePO4 via Vcc?

[Uncle Buzz]

LifePo4 run from 3.6 to 3V or 2.7V, the LDO regul 3V3 from higher voltage, with a minimum drop out, so you need at least 3V6 to run it properly.
When running with lower voltage, the ultra low quiescent will increase a lot, the LDO will consume a lot and be useless...

Without LDO, you have to power the node by the 3V3 pin, or use VCC and replace the LDO by a short. You also need to run the node at 8MHz since you need at least 3V3 to run at 16MHz

[Felix]

LDO is not designed to feed VIN at the output 
Remove the LDO if you want to harness the low power of the Moteino/atmega328p.
You can probably still run at 16mhz with a LiFePO4, for most of its useful charge:

[d00m178]

Sorry, seems it is my mistake - I thought that Vcc pin is the second name for 3V3 pin and it designed only for powering MCU with regulated voltage 3.3V because it power MCU without LDO in circuit.

And Vin pin designed for powering with higher voltage because this circuit has LDO which drops power to 3.3v

So finally, I'm going to power my Moteino via 3v3 pin from 1S LiFePo4 battery - 18650 battery assembly like this:

https://ru.aliexpress.com/item/4-10PCS-3-2V-18650-rechargeable-LiFePO4-battery-pack-1500mah-lithium-polymer-cell-for-12V-24V/32889038385.html?spm=a2g0v.10010108.1000016%2FB.1.eeb54ba2BrSRO2&isOrigTitle=true

or different battery like this:

https://ru.aliexpress.com/item/10AH-3-2-LiFePO4-10000/32958020328.html?spm=a2g0v.10010108.1000013.4.16c42b9c5F7yYt&pvid=7d4e55cc-3eed-42ef-8077-572e6dc34f03&gps-id=pcDetailBottomMoreThisSeller&scm=1007.13339.99734.0&scm-url=1007.13339.99734.0&scm_id=1007.13339.99734.0

Do I need remove LDO in this case? I think NOT, but Im not sure..

I have another questions, but above - the main question from which I would start to order parts.
Then I need to add to my device some solar panel and charge controller to have ability charge battery during sunny days in mountains.
Also I need to know - Do I need some BMS controller for this? Or it better to have good charging controller?
Of course the price of parts also important ..

But first of all - I need to know - remove LDO or not if I want to power moteino via 3v3 pin.

[Uncle Buzz]

You have to remove the LDO if you power your node by 3V3 pin since it's the output of the LDO and there is no diode inside the LDO to prevent your voltage to turn on the LDO via its output.
This will consume a large amount of power since it's not how it should be powered.
So, with less than 3V6, you should remove the LDO because it will consume more power and it will be useless, you could replace it by a short and use VIN pin (it's how the moteino 8MHz is configured) or use 3V3 pin without LDO and no replacement.

With the short, you shall not power your moteino with more than 3V6 so don't connect the VIN pin from an FTDI with 5V !

For solar configuration, it depends of how many power you need and how efficient the charge has to be.
For very low power, a supercap and a solar pannel with a diode is sufficient.
It's not a good idea to charge your battery without a specialised charger, and you will need a solar pannel large enough to have more power than the charger needs because the charger won't regulate the charge depending of the power available but depending of the battery level and won't work correctly if there's not enough power.
While the battery is charging, you should not use the battery to power your system, so you should use the power not used of your solar pannel and use an LDO at the output of the pannel (after the input of the charger) because your panel will have an outpu higher than 3V6.

[d00m178]

thank you all for your answers.

I've deleted LDO from R6 and power it from LiFePo4 (3.5v) directly to 3v3 pin.

and I have a strange issue which seems related to the brown-out level.
some info about my setup:

R6 with RFM95 w/o LDO powered to 3v3pin from 3.5v

I'm using laser module from aliexpress:
https://ru.aliexpress.com/item/50m-164ft-Laser-Distance-Measuring-Sensor-Range-Finder-Module-Low-cost-Diastimeter-Single-Continuous-Measurement/32792768667.html?spm=a2g0s.13010208.99999999.259.5b943c00k90TW5

it connected via mosfet IRLZ44N as shown in the picture.
in the code I use

Code Select Expand

...
  pinMode(LASER_PWR, OUTPUT);
  digitalWrite(LASER_PWR, HIGH);
...

and this lead to power the laser module via mosfet.

the issue is - if I power device from FTDI adapter - moteino rebooting on this step.
And I think it is because current "settings" for brown-out level.
If I power device from battery - it works as exepected - laser works and measure distance.
BUT! sometime, usually when the battery is low - device ALSO rebooting. And I think because the same reason..

I need advice. Im stuck for many days with this issue.. What can I do in this case?

[KeithR]

I also have this laser range finder module and ran into a similar problem.  There is a brief power surge (>1A) when turning on the laser, which depending on the power source can result in a big voltage dip (in my case, down to 0.3v).  I overcame this by putting a large cap (330uf worked for me) across the power input to the range finder (and also used an AP2125 regulator with enable pin, which feeds 2.5v input to LRF).  Turn on LRF, wait 250ms, then read distance.

[d00m178]

I also have this laser range finder module and ran into a similar problem.  There is a brief power surge (>1A) when turning on the laser, which depending on the power source can result in a big voltage dip (in my case, down to 0.3v).  I overcame this by putting a large cap (330uf worked for me) across the power input to the range finder (and also used an AP2125 regulator with enable pin, which feeds 2.5v input to LRF).  Turn on LRF, wait 250ms, then read distance.

Thank you!
Can I ask you for more details about your circuit? maybe some picture?
I don't understand about AP2125 and "enable pin" - what does it means?
Also - 330uF - is it electrolytic cap or not? which place should it be installed? near power source or LRF?