Feedback on my Battery Monitor circuit please? - Page 1
Forum section: electronics / projects

author: ElectricPower
author_rank: Frequent Contributor
timestamp: August 17, 2022, 05:09:37 am
content: I want to monitor my +12V battery in my motorcycle wireless and i use Wemos D1 Mini and Blynk app for that.Coding and connections to det Wemos D1 Mini i so not need help with, but i wan't feedback on the circuit under if there is important mistakes i have done or else.The TP4056 module will be soldered to the PCB.I want to power board with USB at the same time the 1 cell 18650 battery Charges.

author: Mr.B
author_rank: Unknown
timestamp: August 17, 2022, 06:03:27 am
content: The VCC of the 12V battery is shown as shorted to GND in the schematic.This will of course result in one or more tracks turning into small balls of flying molten copper.If you remove the short to GND it still will not work as desired.The two series resistors are wrong and will result in the analogue input of the D1 Mini seeing the actual battery voltage, a nominal 12V.The input of the analogue pin should be configured with a voltage divider. Calculating that divider should be very easy. I don’t know the analogue range of a D1 Mini, haven’t looked it up.The output of the TP4056 seems to be 5V. The output of the HT7333 is 3.3V.I don’t know how tolerant the HT7333 is of being back fed with 5V, but I would suggest it is not at all recommended.The supply voltage of the D1 Mini appears to be 3.3V, so the TP4056 supply of 5V will not be healthy for the D1 Mini.A 1000uF capacitor on the VBUS input to the HT7333 will have a massive inrush current that the USB supply is unlikely to handle very well.To make the power supply electrically work you need to cut the connection between VBUS on the USB and the VIN of the regulator (HT7333).Then, connect the output + of the TP4056 to the VIN of the regulator, not the VOUT.Change the 1000uF cap to a much smaller value, or nothing at all depending on the output filtering of the TP4056.I am pretty sure these little modules (TP4056) can charge and supply at the same time, but I may be wrong.That should satisfy the electrical requirements of the regulator and the D1 mini, however the life of your 18650 battery is going to be terrible due to the TP4056 running all the time to boost the 3.7V up to 5V.There are considerably better ways to do this.When I get home I will try to find a design I did that is very similar using an ESP8266 as the MCU…

author: ElectricPower
author_rank: Frequent Contributor
timestamp: August 17, 2022, 03:22:47 pm
content: Forst of all. Thank yoy wery mutch for good feedback!1. you are right. Thee VCC is cooected straight to ground. I will fix that. Thanks.2. actually, Wemos d1 mini has an intern voltage divider with pin A0 with 220K and 100K resistor. So that part works fine. I have testet.3. i see that with the backfeeding HT7333. I will look in to that4. yes, you are right again. The 5V is going straight to 3.3V pin. Not good. Thanks.5. yes i will change the 1000uF cap.Thanks. I really appreciate that. I look forward to see your design

author: ElectricPower
author_rank: Frequent Contributor
timestamp: August 17, 2022, 09:47:31 pm
content: I have changed my schematic now and i did som adjustments.Here i'm use an own LDO (HT7333) for battery input, and i have removed the charge board (TP4056). I just don't need it. Wemos is programmed to wake up 4 times a day, and send voltage data to my app. I can just use 3-4 AA batteries in series or and precharged 18650 etc. I don not think i have to change this battery very often.Her is my new simplified chematic and picture of the board.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 18, 2022, 02:54:25 am
content: Add pulldowns on the USB-C connector, else it won't work on some devices.https://hackaday.com/2022/08/16/usb-c-charging-mod-brings-in-the-juice/

author: ElectricPower
author_rank: Frequent Contributor
timestamp: August 18, 2022, 04:39:15 am
content: I will only use standard 5V USB power supply for powering the board. Do i still need pulldown resistors?

author: ElectricPower
author_rank: Frequent Contributor
timestamp: August 23, 2022, 08:59:02 pm
content: Some modifications since last.Some more feedback would be greatSchematic_MC BATTERY CONTROLLER_2022-08-23.png(285.12 kB. 2500x2004 - viewed 41 times.)board_3.PNG(82.52 kB. 636x1188 - viewed 40 times.)

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 24, 2022, 03:02:06 am
content: Quote from: ElectricPower on August 18, 2022, 04:39:15 amResistors are cheap, you'll need then to guarantee proper operation with all power supplies.