Solar weather station. TP4056, Li-Ion constant failure

Thread Starter


Joined Jul 4, 2011
Hi folks,

Wonder if someone could help me diagnose a problem I keep running into.
I have a number of weather stations / pool temperature monitors / soil monitors / water tank monitors etc which use the following:
  1. 5.5V Solar panel (fleabay options, around 1W)
  2. TP4056 module - ones with battery protection included
  3. 2-4 18650 in parallel
  4. esp8266 doing funky stuff

The code I have on the esp8266 logs on to wifi, then mqtt, sends some data and logs off. My normal runtime is around 300-450ms. Sleep is mostly around 10-15 minutes with my sleep current being in the 10-20uA range (given what my fluke can do).

Everything works well for a few days and the battery remains at 100% or near it (I send back the voltage as part of the readings)
Then, all of a sudden my device stops charging and the battery quickly depletes over a couple of days.
When I venture out to collect the device, the battery module is normally broken. i.e. adding a known 5V source to it does not charge the battery.

The modules are bought from fleabay or Aliexpress in from various suppliers and periods so unless I am really unlucky, there should be a good batch.
The PV panels never go over 5.5/6V under no load, full sun so not breaking the 8V max of the 4056.

Am I just doing it wrong? Are these modules really rubbish? Anything better I should try?

Last edited:


Joined Jan 29, 2010
hi Crispin,
As you say it sounds as though the TP4056 is failing and taking out the batteries.?
Is this video of the TP any help.?

Thread Starter


Joined Jul 4, 2011
HI Eric,

Yes, that is the module and everything in the vid is familiar.

What I am struggling with is seemingly broken modules where they just stop charging or do a really bad job of charging from a small solar panel.

Is there a better way to do something like top up a 18650 from a solar panel than a 4056? They seem to be pretty generic and commonly used for that purpose.