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Pugwash
(@pugwash)
Prominent Member
Joined: 1 year ago
Posts: 997
2020-03-04 8:34 am  

This is the result of testing the boards I mentioned in the following post.

https://forum.dronebotworkshop.com/power-batteries/wemos-li-ion-charging-boards/

Beware of charging boards from "diymore"!

This is the description on Amazon:

diymore 18650 Battery Shield V8 3V 5V Micro USB Type A USB with Cable for Raspberry Pi Arduino ESP32 ESP8266 WiFi

https://www.amazon.de/gp/product/B07S3H1V77/ref=ppx_yo_dt_b_asin_image_o00_s00?ie=UTF8&psc=1

Now to what happened. After charging up 2 x 18650s in the charger board, I attached one to an ESP8266 and the batteries were exhausted in 3 to 4 hours. In the meantime, I had soldered pins on to the 5V rail of the other board and when testing for continuity got a signal from my ammeter but no solder bridges were to be found.

I decided to set up a test, connecting the 3.3V rails to a green LED (3.1V forward voltage) through a 60Ω resistor. I measured the current draw at approx. 6mA. I noticed the cell voltage on both boards fell at exactly the same rate, and the batteries were completely exhausted after about 72 hours. This is not to be expected for batteries with the nominal current supply of 2 x 3500 mAh.

I have two remote sensors powered by single-cell 18650s, which appear to be working correctly, the power being pulled is about 2mA and the cell voltage is dropping about 0.7V over a 24 hour period.

Also, there is a difference between the configuration of the single-cell and dual-cell boards, on the dual-cell boards, there ?seems? to be a 60Ω power resister between 5V and Gnd.

All this has left me highly suspicious of the origin of the dual-cell boards. Knowing what I know about Quality Assurance, ISO9000 and product testing, the chances of getting two boards with exactly the same bad characteristics is almost zero, even at a low sampling rate.

As I have just thrown €20 down the drain, I can only recommend that if you buy this type of charger board, test it thoroughly before use!

By the way, the batteries I am using are genuine Samsung, not cheap clones!


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Pugwash
(@pugwash)
Prominent Member
Joined: 1 year ago
Posts: 997
2020-03-04 3:05 pm  

CORRECTION:

I POSTED ABOVE THE FOLLOWING STATEMENT:

I have two remote sensors powered by single-cell 18650s, which appear to be working correctly, the power being pulled is about 2mA and the cell voltage is dropping about 0.7V over a 24 hour period.

IT SHOULD READ:

I have two remote sensors powered by single-cell 18650s, which appear to be working correctly, the power being pulled is about 2mA and the cell voltage is dropping about 0.07V over a 24 hour period.


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Pugwash
(@pugwash)
Prominent Member
Joined: 1 year ago
Posts: 997
2020-03-05 3:22 pm  

ANOTHER CORRECTION:

After re-checking the voltage drop, it is actually <0.01V per 24 hour period. My multimeter doesn't measure less than 0.01V. This is close to what it should be, and shows that the charger board circuitry is not consuming vast amounts of current.


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