I purchaged this module: 18650 Lithium Battery Shield V3. The module drive the power for my IoT device (Wemos D1 mini). I realized that when expernal power fails, the 5V output voltage from this module is dropped for few seconds (2-3 sec) until 5V output is re-built up. This issue causes unexpected reset to my IoT device.
Is there any known workaround for this module? any idea which alternative 18650 based power module may provide a reliable backup power for my IoT device?
Always power the Wemos D1 mini with the battery module, and plug the module into your electrical outlet.
But when wall power fails, battery module fails as well and wemos is reset!
Does the bottom of your V3 look like this?
My guess is it probably doesn't. The picture shows the original design of the V3. U2 is a TP4056 charger IC, and U7 is a boost converter. This design switches instantly when the mains supply goes out.
But newer designs save a penny by using a single chip, and a single inductor, for charging and boost conversion. When the power goes out, it takes a while for the chip to switch over to start providing boost conversion, and that causes a dropout. So all of these newer V3, V8 and V9 modules are worthless. They are supposed to function as a UPS, but don't.
If your module looks like the picture, then there's something wrong with it. But more likely it looks completely different. I don't know where you can still get the original design. You can't really depend on pictures included in listings. They will show you one thing, but ship something else.
It is similar but not the same. It seems that you are right about using a single chip. Perhaps I should look for the V3 version similar to the version you uploaded here.
I have two that look like the picture, and they both work well. No dropout when the 5V supply drops out. But I don't know of a reliable supplier of the V3 that looks like that. Banggood sells the V3, and the picture in the listing looks correct. But there's no guarantee that what they ship would look like that. The new design is cheaper than the original, so over time the original design will become more and more scarce. But the listings pictures may or may not be updated.
I cannot take a snapshot of my power module since it is integrated in my IoT device at the moment so I copied the picture from Aliexpress seller page:
Mine is slightly different since it contains a few different componenets. I may write to the manufacturor (as seen on the PCB) and hopefully I'll get a proper answer.
Does yours also have the 32-pin square chip? Can you read the part number marking on it?
Sorry for my late reply. I was busy with my project. here is a capture of my 'problematic' charger...
Eventually, I bought this one, which works very well 'UPS mode'. This one resolved the dropout issue. 18650 Lithium Battery Boost Step Up Module
On the new one, the one that works properly, can you read the marking on the 8-pin chip U1?
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