I have a show next week where I will need multiple pres to power around 4 pair of mics. I do have an external battery which powers both my 680 and the FP24, however, I'm planning on running my UA-5 and the 680 using the external. So how long can I expect to run the FP24 on freshly charged AA batteries powering a pair of 414 XLII's for? All other mics will be powered by tinyboxes and PIPsqueaks. Thanks for your input in advance.