TK102B battery mod

 

 

Synopsis

Since my mothers car is way to easy to steal (bicycle key suffices)I figured a cheap GPS tracker with simcard could be implemented, there was just the problem with battery life for the unit.

I'll be connecting a CV source directly to the battery. LM2596 DC Step-Down will be used via a diode since the battery otherwise would discharge into the output cap when no voltage is applied to input terminals.

I'll set the CV level at about 3.8V at the battery terminals. This will keep the charge level at about 60% and also prevent plating and heating of the cell. 8-12h fantasy batterypack of 1000mAh.

 

Step by step

First disassembly, Only one screw apparently.
PCB reveals easely accessible tabs for adding wires.

 

Wires soldered in place and passed through hole melted on the side.

 

Measuring and testing

Measuring voltage to ensure polarity.Trying not to short the wires.
load test with 22ohm 1W resistance on the LM2596.
Must make sure it does not overheat or is defective.

 

1N4001 can handle 1A pulse parallelled 2x since LM2596 can deliver 3A.
It's a very unlikely scenario that the cell would reach 0V (over discharge)
always better to be safe than sorry.

 

PSU box, 3D print

Enclosure is needed for the PSU.
Quick print makes for a safe space ; )
Voltage was set to 4.5V (anode side of 1N4001) before gluing the enclosure shut.

 

 

 

Afterthougth -160915

Works and gets GPS location (±10m) from inside glove compartment
Battery only last about 2h in car, it lasted 6h outside the car.
- Installation inside dashboard next

Cont. -160920

Unit is now installed in vehicle and works just fine
I'll check it regulary and update this page if there are any issues with the build

Cont. -200626

Unit is stilll working, no problems so far.

 

 

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