@4pyros
Re the circuit you linked to, even at the minimum (5 min) setting it is using an 8.2 meg timing resistor. That implies an intended cap charging current of ~ 1uA. At the 30 min setting the intended current is ~ 150nA !
I refer you to
**broken link removed**
That indicates that many of even the 'best' tantalum capacitors have typical leakage currents > 1uA at their rated voltage. However, if the leakage current at a lower voltage is greater than the intended charging current in the timing circuit then the cap simply won't charge. It makes me wonder if that circuit can actually work, or perhaps it's an 'ideal' one?