Related: JIVE BEC – Support Battery?
First we need to determine: What are we speaking about? Do we speak about a support battery for a purpose as following or do we want to have a spare supply strong enough for doing an autorotation with a dead BEC?
Well… concerning the current that the BEC drives: No, not necessary. 12 amps pulsed @1kHz, symmetrical duty cycle (500/500 microseconds): Endless. 15 amp pulses @1kHz: The BEC dropped out after 5..10 seconds, came back after less than half a second (firmware version 9).
So…, okay, no support voltage at all?
No! Yes, provide a support battery! Even 4x Eneloop 800mAh will be good enough for that purpose.
Why? Because of the back-EMF voltages coming from the servos, mutual induction! They may force the processor in the JIVE, controlling the BEC, to shut it down to protect itself and other components of the ESC.
Okay, the BEC voltage will come back about two times a second with JIVE/v9. But what about your receiver and the FBL stabi?! Only Mikado’s V-Bar will fast-start without time consuming calibration – up to 10 seconds after a power fail.
In most cases the JIVE will continue to commutate, after not more than half a second at max everything is back on the bride side for the JIVE, – but for the supplied components also?… Even JLog will reboot and continue in a new log file.
Fill the dangerous gap. It’s inexpensive.
Some servos are particularly known for high reverse voltages: JR, Savöx, Align.
The BEC-monitoring responds on positive addition of BEC- and back-EMF voltage. Beginning with 6.5 volts but at least from/above 7 volts, within a certain time constant, it is the latest serious.
Thus, a lower set BEC voltage pushing the limit something down. This is not a cure, because the voltage induced by a servo depends, besides of its general properties, only on the EMF effecting angular speed.
Of course the impedance of the drain circuit plays a role (internal load capacitor at the output of the BEC), while then the resistance between the feedback voltage source (servos) and the BEC. It was observed that with lower resistance, ie, short lines and slave connection used, it may lead more often to shutdown effects by induction voltages. - In that is no solution, since we need low connection resistance for the opposite case of the BEC as a voltage source. - A backup voltage source, such as 4x800mAh Eneloop, not only fills the voltage hole, than also reduces the impedance of the voltage drain, thus the probability of harmful voltage peaks.
And, last but not least: Never accept less, fly v9!