Today I did some more soldering with the TP4056 linear charger board and the 240mAh lipo battery pack.
Tinned the PCB and all wire prior to joining up and making the final joint. Solder joints were between stripped leads of a USB cable through the PCB’s VCC holes, and solid 22AWG wire to the battery’s stranded leads.
The lack of tools to hold the subject, together with the lack of constant heat from my soldering iron
, made for a few extra challenges. Nevertheless, I was able to get satisfactory results.
Plugging in the board and testing the charge voltage, I was able to seemingly trip the TP4056 into a charge cycle. I’m at a loss as to why my meter is registering a float voltage above the data sheet’s maximum of 4.263V. My initial assumption is that IBAT refers to the rating of the cell to be charged, I may be mistaken.
Referring to the data sheet for the TP4056
, the stock RPROG at 1.2K ohm will not provide the proper charge current for my 240mAh cell.
According to the chart, a 5K ohm RPROG will limit charge current to a 250mAh cell.
The closest and easiest match without going under is 5.1K. Now I just need to get my hot little hands on these resistors. While I still have them, of course. Fingers crossed nothing explodes on the first charge cycle. Definitely will be observing all safety precautions and charge in a fire-safe location.
After more reading
in preparing this post, it seems as though this battery is not suitable for the cat tracker project. Given the lower discharge rate (1.5C), a safer option for powering my cat tracker could be the rechargeable lithium 16340/CR123A
. These cells can be charged safely
with the TP4056, pack more of a charge at ~880mAh per cell, and are the perfect form factor for smaller projects. The 20C lipo will be more useful for a future project.
Now, to source a 16340. Any leads? 😉