Thanks Steve! That was helpful, sometimes I need things explained in lamen's terms. I appreciate the link, it's informative, but I don't think I'll be running this on AC power.
You're welcome, glad to help.
So I take it 7W isn't going to somehow overload the recorder? Or 1.5 or 2A? My primary concern is powering the 70d for as long as possible, but I also don't want to break the recorder with an insufficient battery.
That's right...the amp rating on the supply side needs to exceed the amps needed by the device...and the DR70D should have fuses and such in the design to protect in case of shorts/exteme overcurrent situations.
I'm a mechanical engineer so it helps me to think of electricity like water flowing through a garden hose...volts is like the pressure in the hose, current is the flowrate through the hose, and resistance is the number of twists/turns/kinks in the hose (as well as how rough the hose is on the inside surface).
So, if your DR70D needs 1 amp and your 'pump' supplies you with more flow/current than that, you're good.
An analogy is your house which probably has 200amp supply. Each circuit comes off either 15 or 30 amp breaker. If only one circuit is energized in the house because only one appliance is on, you don't destroy the appliance even though the house has 200 amps at the circuit breaker. The circuit breaker is like a fuse in your recorder to protect in the case of shorts/overcurrent, so the breakers are set to trip at 15 or 30amps of total current flow...or before the short causes the wires in the house heat up and start a fire!!! (The analogy would be trying to force a zillion gallons of water through a 1/2 inch garden hose in a ridiculously short amount of time...in this case friction would cause the hose to heat up and fail.)
The other thing you don't want to do is put a 'pump' on your hose that outputs alot of pressure (volts) into your garden hose because then it will exceed the strength of the hose and the hose will split/crack (note that this is a different failure than heating up). So, match your voltage output to what your device needs and you're fine.
And it seems like I could successfully run the 70d with my 3200mAh battery. But, it probably wouldn't last too long, especially if running 4ch. I'll buy one of these ~18000 mah batteries in the ~25 USD range.
The manual says the DR70D pulls 5W peak. Since it operates at 5V, that's 1amp or 1000ma. Assuming the 3200mah rating on your battery is at 5V, that means you should get 3.2 hours of run time from that battery and 18 hours from the 18000mah battery. I think you can probably assume slightly longer times since 5W is the stated as the max.