Express RTK Battery Charging Circuit Failure

GPS/GNSS
1

I have an Express RTK and its been working great. However recently after a while of not using it, and I believe a period of having antenna and boards plugged into it but nothing powered on, the battery circuit has failed.
When no cable is plugged in to charge the unit, pressing the power button does absolutely nothing.
When a cable is connected to charge/power the unit, pressing the power button brings up the boot flame, then version Number, then the screen says “Charge Battery” and shuts off. Additionally, having the cord plugged in to charge does not turn on the charging LED.
I have tried several different methods of charging, wall outlet, computer port, power bank. Regardless of time or method, it does not charge.

After looking for solutions online, it was mentioned to check the PCB. Upon visual inspection of the PCB with cross reference to the Board Schematics and PCB Design, there does not appear to be anything physically wrong with the board.

To test if the battery is the issue, I checked the voltage of the battery, 2.9 V, obviously dead. Since I couldn’t traditionally charge the battery, I charged it with current limiting power supply at 3.7V and 0.05 A for several hours to manually charge it up. After several hours, the battery was plugged back in and the unit powered up.

HOWEVER, the real kicker is that the battery status indicator states that the battery is 100% empty, with it being fully charged. The next day after not being used past checking to see if it turns on, the system is back to the original “Charge Battery” instruction and no LED>

What if any solutions are available for this sort of this issue? Is the issue the MCP73833 roached or is the unit a lost cause?

2

It sounds like it is just a dead battery; you can easily replace it with this’n Lithium Ion Battery - 1250mAh (IEC62133 Certified) - PRT-18286 - SparkFun Electronics and be good to go (it’s the exact same one as in the RTK Express…the 50mAh discrepancy of title vs label is the real-world rating of 1250 instead of 1300)

3

Just a point of reference here:
A Li-Po at 3.7V fresh off a charger is basically still empty. I would be surprised if any fuelgauge responded with an SOC over 10-20% or so in that condition.

Since this battery was discharged to 2.9V, that’s right at the threshold that’s considered to be potentially damaging. Safest choice is as @TS-Russell says, and replace it.

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