TP4056 Cut Off

Im having a problem when using a TP4056 to charge a single cell 18650 3.7v li ion battery.

I have a solar panel charging. A single cell battery. Powering a wemos d1 mini pro.

The charger largely works fine, and the low voltage cut off works.

But when the battery gets fully charged 4.2v the charger cuts off like you’d expect, the red led goes blue to indicate this.

But as the battery drops the led stays blue and the charger doesn't kick back in until i put my hand over the solar panel to stop the charging then remove my hand and and the red led comes on. The blue light would just stay on draining the battery until i stop and start the charging again.

Could it just be a faulty board?

We have no idea what TP4056 module you have, so consider posting a link to it.

In general, the TP4056 modules are not designed for solar panel operation, or for load sharing. That is, you cannot connect a load to the battery and expect the charger module to work properly.

Adafruit and Sparkfun sell charger modules that are designed to work with solar panels.

Ahh I thought it could be used with a solar panel.

I basically made what is here:

The board has an in, out and battery.

Unable to post a picture of the board has my phone is saving the picture as a .jpeg and thats the one type thats not allowed :frowning:

There is a picture on the above link

The TP4056 module in the Instructable you linked specifies that the input voltage be in the range of 4.5 to 5.5V. So what happens when the solar panel is in the dark, or, as is likely, the panel output exceeds 5.5 V? The overall project design is unsafe and unreliable.

Note: the Adafruit solar charger has the same problem, but they are aware of it and caution you to use only the recommended solar panel.

Many Instructables are written by people who have no idea what they are doing, and give advice that ranges from poor to terrible. No one is allowed to post critical comments on Instructables. Forum posters often request help after destroying their Arduinos by following some Instructable, so we generally have a dim view of them.

Haha fair.

I did look into it before following that guide and it seems a lot of people use TP4056 with solar projects (that doesn’t say its correct of course).

I thought from my little knowledge of that board, that the version of the TP4056 in my link was meant to work with a load connected as well as the panel connected. As there are separate pins for the the (solar) input, separate pins for the battery and separate pins for the output which has under voltage protection (so it must expect a load on the battery to drain it while charging or it wouldn’t need the protection, right?)

But as I say the hardware side of this I have much less knowledge compared to the software side.

If you can find some documentation for that module, and it supports load sharing, fine. The TP4056 does not. Despite that, some people claim success with solar panels and TP4056 modules in similar systems. All such claims should be viewed with skepticism.

Your problem sounds like a design flaw. There is another charger module that is well known to have similar problems, but a forum member recently described modifications to make load sharing work.