September 1, 2020

18650 Battery Shield

I ordered 6 of these things from AliExpress. This list price was $1.52, but with shipping the package came to $16.90 They are adding tax now too (do you suppose sellers in China will be paying sales tax to the USA?). This brings the cost per unit up to $2.82. Even at $3 per unit, just the battery holder makes it almost worth it.

I am a little uncertain just what to call this thing. The listing calls it: 

ESP32 ESP32S Raspberry Pi 18650 Battery Shield V3 Micro
USB Port Type-A USB 0.5A For Arduino Charge Wemos Diy Kit
It holds a single 18650 battery and can supply regulated 5.0 and 3.3 volts. It claims to be able to provide 5 volts at 3 amps and 3 volts at 1 amp. Note that if you install the battery backwards, you will destroy the unit.

I bought it hoping to use it to power various ESP8266 gadgets. It remains to be seen how that will work out.

There are several different units being offered for sale that look quite similar. The above images are from the listing of the one I purchased. Note that it has what looks like a USB-C connector that is not mentioned anywhere in the listing.

I was pleased to find, after the unit arrived that the 3 volts is in fact 3.3 volts (I measure 3.31 volts on one of my units).

Several things concern me. The first is the 5 LED that light up when you push the button. These are probably consuming at least an order of magnitude more power than the devices I am hoping to use this with, so they will need to be disabled.

The second thing is the button itself. Some of my units power off after 40 seconds if no load is attached (one does not). They all seem to behave just fine with a load attached to the USB-A port, we will have to see about an ESP8266 on one of the 3.3 volt pads. The project I have in mind goes into deep sleep and runs briefly at once per minute. This may not play well with this power supply having a 40 second timeout.

The circuit

The heart of the thing is a chip marked "SW6115". Some searching yielded parts listings in Chinese along with the following diagram:

The listing says: "a super cost-effective fast charging chip, which can reach a current output of 4.5A. No agreement is required, and AAC ports can support 5V3.4A output."

Built-in USB Type-C interface logic

Some pages have links to a datasheet, but all refuse to let me download it. All in Chinese mind you.

Near the other end of the board is an 8 pin chip labeled IP3005A. It looks to be a charge management chip for if and when the battery is charged via the micro-USB connector.

It looks like the 3.3 volt supply is derived from the 5 volt supply via 3 regulators in parallel. I am unsure how this will work out for ultimate battery life with a 3.3 volt device being powered. Only some experimentation will tell the story.

On April 4, 2021, a kind person sent me the following datasheet (in Chinese) along with a translation into English. Thanks!

Have any comments? Questions? Drop me a line!

Tom's Electronics pages / tom@mmto.org