Earlier quoted context omitted.
But if you wanted to put 30g of explosive into a device, you wouldn't just want it sat there looking out of place to any curious person with a screw-driver. My guess is that you'd want to put it inside a component like say a LiPo pouch that looks like it belongs there. Half-battery, half-explosive - and maybe hijack the BMS components to also allow it to be triggered.
My understanding is that they were extremely well concealed, and would have been difficult to detect with simple internal visual inspection.
Obviously the mistake was forgetting to sacrifice a handful of units into a bomb calorimeter.
The joules would have been way off.