External flash power-on time/battery life without power-save function

Question

I am looking for cheap external flash for my wildlife camera trap (Canon EOS 40D). I got cheap Metz 44 AF-1 But unfortunately- it has built in power-safe function which can not be disabled in Manual/TTL mode (only by waking the flash and camera every X minutes which will drain the camera battery quickly).

I am now looking for an older Canon SpeedLite flash, where power-saving function can be disabled and flash will be continuously ready for triggering. My question is: does somebody have any experience, how long the batteries in flash will last until fully drained in such "constantly ready" operation? E.g. in Canon SpeedLite 430 EX, but I have no idea if there are some model-specific differences. Are we talking about hours, days, or weeks?

The only think I was able to test with my current Metz is to set it to Slave mode (power-saving disabled). It lasted over 2 days, but I am not sure if this is comparable with manual/TTL operation. Thanks.

Answer 1

Slave mode would be comparable to manual/TTL operation. It needs more logic than the latter, but since a flash capable of slave mode will use the same kind of logic for implementing manual/TTL, you don't save a lot.

The bulk of energy use will go into keeping the flash capacitor topped up, and that's just the same either way. The quality of the circuitry for that and the leakage of the flash capacitor may wildly diverge between different flashes, so it's perfectly possible that a smarter flash will use less current than a dumb flash, even if the latter has some advantage out the gate.