Super Caps, Servos and surge protection/reserve

Using Arduino Motors, Mechanics, Power and CNC
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I'm making a small quadruped with a dozen or so standard (55g 10kg/cm) hobby servos. Power is a 7.2V 5300 mAH NiMH battery.

From what I gather, NiMH source about 1.2 times the AH rating. What I think I want to do is isolate the Arduino from the servos and have a surge cap on the servo bus.

The isolation for the Arduino seems simple enough, a diode and a capacitor. Similarly a capacitor across the servo bus to ground.

In the old school days all we had was caps rated in microfarads, now we have super caps. I have on order some 1F 5.5V caps (I assume two 2F caps in series in one package).

So, two of these in series could yield a .5F at ~ 11V.

Questions:

Are the super caps well enough matched that the voltage will divide more or less evenly enough to get at least a 7.2V rating? Or will I need some bleeder resistors across the caps to do some balancing?

What happens when I connect my NiMH battery to a Farad or so? Seems like quite a surge...

I'm considering a switch with .5 ohm 5W resistor in series to slow the charge down a bit, then a direct connection.

Am I making too big a deal on this? Should I just use smaller caps to filter the transients? Or something else?

2

Supercaps are usually intended as memory chip backups, etc., have high ESR and are not suited for large currents. There are exceptions. What do you have on order?

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http://www.ebay.com/itm/131493677827?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

I've got tons of 16V power supply caps of a few thousand uF I could use instead.

4

That is a NEC FA or FE series capacitor. Read about it here: http://www.nec-tokin.com/english/product/pdf_dl/supercapacitors.pdf

Recommended maximum current draw for FA, for a 30 minute period is 1.5 mA, although for short periods you can get a couple of hundred mA.

Part 3 in the introduction states:

Super Capacitor can not be used for applications in AC circuit such as ripple absorption because it has high internal resistance (several hundred mΩ to a hundred Ω) compared to aluminum electrolysis capacitor

I wouldn't buy a used supercap.

5

jremington:
That is a NEC FA or FE series capacitor. Read about it here: http://www.nec-tokin.com/english/product/pdf_dl/supercapacitors.pdf

Recommended maximum current draw for FA, for a 30 minute period is 1.5 mA, although for short periods you can get a couple of hundred mA.

Part 3 in the introduction states:
I wouldn't buy a used supercap.

Thanks, that's all I need to know.

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