ORIGINAL: Geistware
Jim, I have heard this point mentioned often, but do not agree with it.
From No BS Tech Tips & FAQ's > http://www.hangtimes.com/rcbattery_faq.html
Q: What's the big deal about 'Impedance'? What is it and what does it do?
A: Most folks react to the 'capacity' rating alone as being the biggest part of their decision in selecting a pack for their big aggressive birds. This can lead to big trouble on board the aircraft. Just as cells are evaluated for capacity, in high load applications you need to take into consideration what the cells voltage performance will be when loads are applied. All battery technologies react to servo loads with a voltage drop while the load is applied. It's really very simple.. the higher the cells impedance rating, the greater the voltage drop will be while servo loads are applied. Rule of Thumb for cell selection: Impedance Ratings are like a Golf Score. The lower, the better. Aircraft in agressive aerobatic enviornments employing digital or high torque servos should carry a cell impedance score of 10 mOhms or less. As an example, one of the most popular lightweight packs used in IMAC aircraft is the Sanyo HR 2700AUX.. plenty of capacity, but the impedance rate on the cell is 20 mOhms. Pretty high.. but if it's used in parallel with another 2700 pack the impedance rate is cut in half to 10 mOhms (and the available capacity is doubled). This is why you usually see this pack employed in parallel in IMAC birds and used without issues as a single pack in a giant Cub.
Now who am I going to believe ?
> Jim