Need experienced Circuit designer for project, want back and forth interaction

[Spiffdandy]

I am looking to add a small bank of super capacitors to my Etrike, not to provide power, but to be charged from the batteries to give a power boost when needed. It is a 60V - 1000 W motor. I need to put a diode between the controller and the motor to prevent backflow of capacitor surge in to the controller.
So Im needing:

Selection of capacitors ( voltage 80w? 100w?) *looking for 3-10 seconds discharge time at the desired voltage
Selection of Diode ( and any installation hints I might need to know)
Look at the diagram, anything else that I might need to include or change.

Thanks in advance

 

[D.A.(Tony)Stewart]

If you know Physics 101, compute your kinetic energy at full speed and convert that to Farads with a 10% ~15% drop in Cap voltage equivalent approx to Li Ion cells dropping from 100% to 25% capacity based on voltage. Unfortunately, you cannot deplete all the initial energy stored in the caps. This is why it won't work.

If you add another identical battery bank in parallel, it will only drop 75%/2 from 100%. but then trip the breaker faster if it is already hot. Imagine how hot the motor is, or measure it.

I would imagine your motor is not a single brush pair type as shown in your bock diagram , rather it may be a multi-phase BLDC type.

 

[dick_freebird]

You probably need a better battery or a better battery
monitor. Expect both to be kind of a joke.

If battery voltage really sags on hard takeoff but
recovers immediately, that's series resistance. Slow
recovery is more like electrochemistry. But is your
complaint that the battery really depletes, or that
your indicator is just disturbing?

Energy to get to speed, should be contant-ish (believe
aerodynamics are not in play) mechanical energy.
So offhand I would not expect a much different actual
coulomb-draw unless the controller and motor become
very inefficient at high current.

I'm inclined to suspect the charge monitor is either
dumb or spoofed.

At some point your motor and controller are going
to be the ones saying "no more". If everything was
"right sized" in design the controller and motor
are not going to be able to take more than the
battery can give. Peel the onion, get more onion.

 

[D.A.(Tony)Stewart]

This question lacks good judgment on physics for a reliable power boost.
How did you get the notion this would work?

In theory, this concept works for Car 1kW audio systems for a few milliseconds before the peaks of 20 Hz woofer cycles to prevent voltage drop from 12V by shunting a lower ESR resistance in parallel with the battery 6S x 2V which is also charged by the alternator to 14.2V

A large Supercap is 10F @ 3V. Then they must string identical Caps in series and parallel to create larger ones, just like cars string 6x 2V cells in series (6S).

Then if you string 20 caps in series each being 10F in hopes of achieving a 60V string the result is only 10F / 20S = 0.5F = 500 mF. This is negligible compared with the capacity of your 60V bank. Each 18650 cell of Li Ion is approx 10,000 Farads @ 3.6V thus 60V bank ought to be 60/3.6= 16S or 17S (S for Series, P for parallel). Thus the equivalent Capacitance reduces by N cells or 10k/16= 8xx Farads or at least a thousand times more than 20 of the largest Supercaps..

Any thoughts of this working, need to understand these assumptions (which I can prove) and retune your expectations with better specs.

You will get a longer life on your eTrike by never letting it deplete more than 50% in a days use. Then using only half the capacity you may get up to 10x more charge life cycles than if you depleted all the charge every time. Go educate yourself at the Battery University website. It has lots of useful info on how to retain the energy and reliability it has now rather than trying to destroy it. Heat is the ultimate problem with energy use as every 10-degree C rise in the motor windings or battery internal junction will degrade its lifespan by at least 50% according to Arrhenius Law of Chemistry. At some threshold, it will fail catastrophically with some thermal runaway.