I'm using the FMA CellPro 4S, and it automatically uses a balancing function as does the OEM charging devices (Black and Decker and DeWalt both use smart charging circuitry). Don't know if we "need" to balance, but since my setup does it automatically, I just let it go the way it's setup.

The diode in series is suggested by the RC Excell instructions, and I've verified that it SHOULD be done when using ignitions with sensors that can't tolerate higher than 6v sources. I've also verified that the v.2 RC Excell does not "need" the diode. Other brands *may* benefit from having the lower voltage, and it is definitely a cheap and super-reliable way to drop the .7 volts. You can use TWO and drop 1.4 volts for the ignitions that are REALLY finicky about input voltage.