Why do you generally only see 7,8,or 10+cell systems?

you never seem to see motors rated at 9 cells,

Is it that ESC's fall into the "Low Voltage" or "High Voltage" catagories, or is it more fundamental than that? I can see that going to a lower current, higher voltage strategy has effeciency benefits, but I have been a bit wary of moving up to more heavily loaded models in the 10+ cell range (my inexperience)...
Your thoughts?

No rgood reason that I can see. Not ESC technology anyway. I've used 9-cell packs successfully a number of times. Ten cells is about the maximum that any cheap 400 "can" motor can stand, otherwise you'd see a lot more models with even higher cell counts. 7 cells was the max you could charge direct from a car battery, back in the dark ages. So the game has been centered around 7 to 10 cells in the last few years.

Now that we have lithium cells and brushless motor drives, the pack voltages (cell counts) will likely creep up. High voltage, low current IS more efficient. Even ten years ago the really large models were 20 or even 30 cells, using high voltage motors. Some Astro drive amps (ESCs) that have been on the market for years are rated for 40 volts.

We have more 9 cell packs than anything else right now. It turns out that 3 sticks of 3 each side by side of the 650mah NiMh batteries is a perfect fit for the GWS warbirds and Formosa. We use them for both our brushless and can motors. Although with the stock cans we are careful not to use full throttle much. We use them on the Slow Stick as well.

Jon

It's more to do with chargers than anything. You can get away with charge 7 cells (or 8 cells just about) with a cheap charger. 9 or more need extra electronics built into the charger. Once you have a good charger why stop at 9 ? BTW you rarely see 11, 13, 15, 17 etc cells. After 8 people just naturally go up in twos. The practical difference between 6 and 7 cells is quite a lot, between 8 and 9 is really very little .

Steve

if a single lipoly cell has the voltage of 3 ni-xx cells....
Aren't 3s lipos the most popular pack for brushless and other high efficiency motors?
-Michael