(Related) RC Voltage Buffering/Backup/Protection

To help to overcome usual confusion.. and as a backup of previous posts.

To be distinguished purposes, –> different/combined means.
Special conditions affecting.

From the particular to the general, more or less drag&drop.
See also:  Optipower BEC Guard, Optipower Ultra Guard
Starting with “special conditions”:
Around the BEC in a KOSMIK/JIVEpro is a design flaw: At powerup we have a race condition, a classical chicken-or-egg problem: The processor (MCU) has to control the output voltage of the BEC but it needs to be voltage supplied by that BEC itself.
Now it depends on certain conditions if it will work at all and when it comes up, if without effects. One primary factor is the electrical load during the critical time.
Critical time (after applying of battery voltage): If nothing wents wrong too much — after about 100ms the processor will be able to take control on the BEC (output voltage and regulation). The most critical time, the period of time in which it “decides” how it will proceed, is the first 10ms only.
If it wents wrong it may need much longer time, in worst case the BEC voltage starts to oscillate (sawtooth wave), forever.
That’s the point: Load. Investigation has shown that already 300mA can be too much.
An R2buffer has electronics for delimiting the charge current flowing into the supercaps (and some other means). The charge current is adjustable, at max 700..900mA. Nobody will now delimit the current to <<300mA to avoid the BEC flaw to come into effect. It would need too much time until entirely discharged caps are full.
Another problem on top may be that these electronics have minimum supply voltage requirements too. Investigation has shown that the BEC can drop below 3 volts, which is a critical threshold for most electronics.
Bottom line: Especially an R2buffer may bring the BEC flaw into effect.  (if there wouldn’t be anyway other higher load)
Note (July 2017): The next version of the “R2buffer” showed up in the shops: BufferV4.  This buffer does not contain “dumb electronics” anymore than an ARM processor (MCU) and a software-defined digital charger for the supercaps. Features: Adaptive charging depending on the value of the BEC voltage  and its behavior. As with the Ultra Guard from the beginning on: Special treatment for the BEC in “KOSMIK”, “JIVEpro”. Outcome: This R2buffer will let the BEC start-up load-free during the critical time. (Other load still may let come the flaw into effect.)
Comment: The manufacturer has NOT fixed the flaw. They use a workaround but they do not test it the right way afterwards. Also the environment temperature may can avoid the healing effect of that workaround.
Workaround (Buffer upto V3):
This BEC wants to start load-free! (The BEC in the old JIVE, btw, is almost identical, but the flaw is no “flaw” here because it starts load-free. Reason is the existence of an electronic switch (FET) behind the BEC, this switch is activated later, when the critical period is over already.)
Measures – generally:
- Backup voltage connected to the output BEFORE powerup. This voltage takes the load away. An ideal diode behind the BEC ESC-internally avoids that current can flow into the BEC output.
Voltage source: battery, Opti Ultra Guard.
- Opti BEC Guard: The Guard has many functions but one of it, the “voltage lockout”, acts automatically like the mentioned switch in the old JIVE. At least the critical 1st 10ms are load-free from the perspective of the BEC.
Now generally: Battery vs. R2buffer vs. Ultra Guard vs. BEC Guard
Fast/short voltage drops:
- BEC Guard: does not help here, only “ironing” positive/negative voltage spikes
- Ultra Guard: yes, steps in automatically, but although it is not permantly there like a battery or the buffer: it is fast enough (by far) and in the end it does better than a battery because of its lower inner resistance (voltage regulator w/ high ripple rejection)
- R2buffer: is almost the same as a battery in this case but w/ the lowest inner resistance of all possible means.
Overvoltage spikes by generative voltages:
- best “ironing” effect by supercaps (R2buffer)
- followed by the BEC Guard: voltage cutting as well as “healing effects” by capacitors in conjunction w/ its electronics
- battery and Ultra Guard are about on par in this respect. A battery may be a bit better (depends..) than the “marginal” caps in the UG.
Permanent and destructive overvoltage (BEC breakthrough):
- The BEC Guard only can protect.
Battery and imputed “nonsense of a Guard”:
Besides specific advantages of the means mentioned above: Who has no handling problem with a naked battery,
- partly discharged at time of..,
- overcharging (damaging),
- no balancing,
- higher resistance, especially at low weight (low capacitance),
may simply connect a battery to the BEC output.
-> This may absolutely be no solution for users of other BEC’s because these could be damaged by it! (the BEC Guard avoids it)

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