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?


C

 

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.?
E

 

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.


C