Hello. I'm building a water sensing device around the Arduino MKRWAN1310 and I'm powering it with an 18650 battery (3.3V). The device will be deployed in rivers, left for a month, and then retrieved to download the data and charge the battery. I'd like to use the 2-pin JST on the MKRWAN for power, but to use the same connector to charge the battery when the USB is plugged in.
Question 1. I can't get the JST connector to charge the battery when on USB. Is there a software thing I need to do?
Question 2. Is this double use of the battery connector possible?
Question 3. My device works fine with the battery connected on VIN. Can I have the battery connected to both VIN and the JST at the same time?
your USB input supply might not be delivering enough power to needed to power the board and change battery. You can try with say 5V1.5A or 5V2A USB supply.
Connect the battery only to battery port as recommended. Power via VIN and USB with the recommended input supply only. Check Arduino MKR WAN 1310
Answers to your Arduino MKRWAN1310 and JST connector questions:
Question 1: USB Charging Through JST
Unfortunately, the MKRWAN1310 doesn't have built-in functionality to charge the battery through the JST connector when marykayintouch USB is plugged in. You'll need additional circuitry to achieve this.
Possible Solutions:
External Charger: Use a separate lithium battery charger module connected to the USB and battery via the JST connector. This is the simplest solution but requires additional components.
TP4056 Module: Integrate a TP4056 lithium battery charger module between the USB and JST connector. This module automatically manages charging based on battery voltage. Requires soldering skills.
Question 2: Double Use of JST Connector (Power & Charge)
Yes, using the JST connector for both powering and charging the battery is possible. The MKRWAN1310 automatically prioritizes the USB power source when available.
Important Note: Ensure proper diode placement to prevent current backflow from the battery to the USB when charging. This can damage the MKRWAN1310.
Question 3: Battery on Both VIN and JST
No, it's not recommended to connect the battery to both VIN and JST simultaneously. This can create a short circuit and damage the board. The MKRWAN1310 should be powered from either the USB or the battery via the JST connector, not both.
Thank you so much! I've been stressing over these issues. I'm surprised that the MKRWAN doesn't have built-in charging, given that it's intended for embedded applications. I'll either go with a charging module or switch to an ESP32 board that does have a charging circuit. My problem is power consumption. The ESP32 uses more than 3X the power (60 mA) of the MKRWAN (10-20 mA), so the MKRWAN is my first choice.
Hmm... the MKRWAN1310 that I'm using does have a battery charging circuit. However, when I plug my board into a USB, I'm reading zero voltage at the battery JST. Is there something that I need to do in software to enable charging?
Solved!! The whole problem was just a bad battery. I wasted days of grief because I was testing portable power on three different MKRWAN1310’s but was using the same broken battery on all of them. Big lesson learned.