the draw of the unit also depends on the draw of the mics. looks like your mics only draw 100mA each of the 4 mics so that is a total of 400mA
http://digital.schoeps.de/en/products/cmd2based on the 788t draw which is found here:
http://www.sounddevices.com/notes/recorders/ssd-current-draw/It draws 1.15A when Recording (24-bit, 48 kHz, 8-track) + mic draw 400mA (or .4A) = 1.55A
so the chart was based off 13V DC power so 13V x 1.55A = 20.15 Watts per hour
Also, other 788T usage factors have larger affect on power consumption and battery runtime, including:
Inputs – active inputs increase power consumption. If recording solely to one or two inputs, disable unused inputs to reduce power consumption. Analog inputs and their microphone preamps draw current whether they are idle or active.
Inputs draw 1.5 W versus to deactivated inputs.<<< so for every channel deactivated you get that much more run time Drive Activity – when the unit is recording to or playing back from the internal drive, power consumption raises by approximately 2 W.
Recording to CF only reduces power consumption.
Microphone Powering - phantom powered microphones draw power for operation.
Up to 4 W can be drawn from the phantom supply. <<< we already determined the consumption of the mics with 13V DC as .4 amps or 5.2 Watts for all 4 mics being powered, which is great.
now to your batteries: Tekkeon 3450 specs found here:
http://www.tekkeon.com/downloads/dtasht_MP3450.pdfeach is equal to 50Wh, the piggy back is 58Wh so, paired together you get 108Wh
The 788 draws 20.15 Watt per hour so divide the dual
Tekekon108Wh capacity by 20.15 = 5.35hours x 70% efficiency = ~3.74 hoursremember if you record to the internal hard drive or run your LED's/Backlight bright, this will also cut down on the run time.
If it were me, I would buy this
300 Watt Hour battery for $400
http://www.bixnet.com/bp300.html 70%eff = 10.42 hours run timein regards to it needing to jumpstart the 788:
Continuous Discharge Current 12 A <<this is the max that you can pull at one time continuously
or I would at least get the
153 Watt Hour battery for $200
http://www.bixnet.com/unpowbat.html 70%eff = 5.31 hours run timeContinuous Discharge Current is 4.75A <<this is the max that you can pull at one time continuously
Someone please correct me if I am wrong, as I am not an electrical engineer