For now there are a few issues to resolve, namely:
- Make the seal on the top cover air tight - even though the container was bought under the premise that it would be air tight, in practice is was verified that it was not;
- Control circuit FET transistor is heating up too much under a 4 Amps load - must check if the gate voltage is being enough to cause it to switch from cutoff to saturation and not somewhere in between. According to the device datasheet, it dissipates up to 150 Watts of power. In this case it has to dissipate around 40-50 Watts of power (10 to 12 Volts at 4 Amps), which is probably too much for the 25 cm^2 heat sink installed.
4 Amp run (12 V):
No load applied:
Typical signal applied to the cell (10 ms/div, 5 V/div):