Battery operation of Wifi Lora 32 V3

[jivaro]

Being new to the Wifi Lora 32 board and having received the unit with what I understand that it’s a battery plug and a battery connection cable, I would really appreciate to know:
a) what are the limits of the acceptable battery voltage: what is the maximum voltage not damaging anything, and at what minimum voltage does the unit stop working ? Lipo batteries go from 4.2 V to 3.7 V, and I understand that these are valid voltage ranges but I would like to know what is the voltage range acceptable.
b) the charger that is supposed to be included in the Wifi Lora 32 V3 charges the battery when the unit is USB (5V) powered ? when it is 3.3 V powered ?
c) how do I have to manage to charge the battery with solar panels when no USB charging cable is available ? Do I have to provide external charging circuitry ? Does the unit already has this capability ?
Sorry to ask for such basic questions but I have not been able to find any doc related to this topic.

Thanks very much for your help

Joan

[UniquePete]

a) I can’t really answer this one except to note that the ‘power management system’ looks to be the same as that on other Heltec boards where a range of 4.2-7V is specified if providing power through the USB connector or 5V pin, which is ultimately regulated back to 3.3V, or 3.3V through the 3.3V pin, which is not regulated.

b) The board schematic diagram is probably helpful here:

HTIT-WB32LA(F)_V3.1_Schematic_Diagram.pdf

The TP4054 [battery] charging IC is driven by the 5V supply, either through the USB port, or directly through the 5V pin. The 3.3V pin does not feed into the charging circuit. The datasheet for the CE6260 regulator will probably indicate the input voltage range that will be tolerated as well.

c) To charge using a [5 - 7V] solar panel (the schematics for other Heltec boards indicate a range of 5.5V - 7V, but I have used 5V panels successfully), connect the positive terminal of the panel to the 5V pin (use of a protection diode is recommended) and the negative terminal of the solar panel to one of the GND pins. You don’t need to provide anything else [except the protection diode]. There’s a bit of discussion on this subject in the following post, which will be equally applicable to the V3 boards:

WiFi LoRa 32 V2 and solar panel management

hi, You can plug in solar energy to charge. But the charging voltage of the solar panel is best to be: 5.5V-7V. Questions about battery life: Normal charging cycle: When the Vcc pin voltage rises above the UVLO threshold level and a setting resistor with an accuracy of 1% is connected between the PROG pin and ground or when a battery is connected to the charger output, a charging cycle starts . If the BAT pin level is lower than 2.9V, the charger enters trickle charge mode. In this mode, the…

[tmmlrd]

I have the same need: powering with a solar panel and using a battery as a backup. However, there could be cases when the battery goes low e.g. in case of several cloudy days. In this case I’d like the board to switch off more than driving the battery deadly low (!)
Is this a feature offered by the charging circuit of the board or it needs an external BMS which makes the output voltage going to zero to preserve the battery safety when the battery voltage gets too low?
Thanks all

[bns]

You could read the battery voltage, and when below e.g. 2.8V, go into deepsleep with an interrupt on power from the solar panel (wire it up to a pin on the board with a voltage divider using resistors to make sure you don’t use too high voltage)… shouldn’t require any components apart from some resistors.