APM 2.6 low vcc in data logs? Question how low can it go? before problems?

[Johnc]

I have just tried out a 5500 mah 3s 35c battery & 2 x 4000 3s 30c batteries in parallel on my Hex, both seem to power the hex well but I still get a low vcc in mission planner logs. Is there something I am missing or need to check?
APM 2.6 board, in line power module supplying the board with jumper 1 removed, all motor esc red wires disconnected. Board powered by PM only.
No servos, 2 axis gimbal with its own independent power supply with just the receiver controlling camera pitch angel. receiver powered from board.
Hex is running 6 x 2212 motors, 1000 KV, 30 amp esc';s. props 1038 carbon.
I felt that the 2 x 4000 batteries in parallel seemed to give smoother power yet they showed the lower vcc value?
Any ideas?
Is there something I need to calibrate, etc,
Thanks,
John
Just as a thought, what size and capacity batteries would anyone recommend?

[Revs]

I think it';s 4.5v minimum. All the info is on the APM site

[Nige8021]

I also have been having low Vcc & poor regulation problems with mine http://www.multi-rotor.co.uk/index.php?topic=12950.0

[Johnc]

Just had a quick look at your link, I am also using a Floureon 5400 35c battery and now two new zippy traxas 4000  30c in parallel, both have given a low vcc in mission planner data logs. the two in parallel slightly lower than the single battery. Apm power module clone showing 5.2 volt when checked with meter.
My question is how low can vcc go before brown out?
APM site says I can leave JP1 in place if not using board to power servos, wondering if this would make a difference?
Cheers,
John

[Nige8021]

In the second of the traces in my first post you';ll see after it went into "battery failsafe" and initiated "RTL"  there was also a "Radio failsafe" initiated yet at that time the Vcc was @ 4.8v ??

I haven';t had a chance to fly since that posting, but hopefully I';ll get a chance over this weekend, I intend to use 2x 3s 2200 35C in parallel and see if the power problem goes away