It might actually last longer 'cuz typically UBEC efficiency goes up with increased voltage. Depending on the UBEC you can get something like 5% increase in efficiency!
SH Z-Car, Custom Crawler, 8s Savage, 12s XTM XLB 1/7 buggy, 4wd 4-link rear/IFS Pro4 truck, Custom Hyper 10 Short Course, Belt-Drive Mammoth ST 1/8 truggy, 4s 17.5 MM Pro HPI Blitz
It should last longer. You have a battery with, say, 148 watts vs a battery with 296w. I remember a guy running a 12s 2650mah setup and he got similar/better runtimes then a person with a 6s 5000mah setup.
Can't really compare watt output capabilities here 'cuz they mean nothing to the usage of a BEC that won't draw more than a few amps from the battery. And in this case, provided the batteries are made up of the same cells, they have the same power output capability.
I'm surprised Brian hasn't chimed in yet?
SH Z-Car, Custom Crawler, 8s Savage, 12s XTM XLB 1/7 buggy, 4wd 4-link rear/IFS Pro4 truck, Custom Hyper 10 Short Course, Belt-Drive Mammoth ST 1/8 truggy, 4s 17.5 MM Pro HPI Blitz
I guess I got myself a little confused. More realisticly it would be a 3s lipo pack as the receiver pack. I used a 4s as an example to see if it would get twice the amount of time. Easier math for me.
I was thinking that a 4s 14.8v on a bec that provided 6v to the rx would take longer to reach the lvc then it would a 2s 7.4v doing the same job. Just to round the numbers off with a 3v lvc a 4s would be 12v (2.8v) and a 2s would be 6v (1.4v). It should take longer to used 2.8v. I know there's an amp thing going on here. I am just trying to avoid understanding that part of it.