Regenerative power

[Jerry Carducci]

I've read somewhere here on the forum that either the motors or the ESCs are 'regenerative' meaning under some conditions power will be returned to the batteries.

How? Under what conditions? If I have a graphing or logging power measuring instrument inline with the battery during operation how will this
regenerative power manifest itself?

I ask because I've begun to use inline current and voltage telemetry sensors and 1) I don't want to cause damage to either the sensors
or other electronic components and 2) want 'pure' results - no skewing of readings.

Jerry

[Armortek]

Regenerative power can occur under the following circumstances:
1. Abrupt stopping oft he motors
2. When the tank is being driven but one motor is not being used or is being used less than the other one.
3. When tank is being pushed or towed.

Constant regenerative current will be low, but there will be short term spikes (for example when the motor is abruptly stopped).

[John Clarke]

Lovely equipment you've got there Gerry, I shouldn't worry about regen spikes, these occur all the time from equipment generating back EMF (Electro motive force) such as dc electrical motors, (a short time dynamo effect if you like) weather you've got regen recipient equipment or not.
A very short time once you take your fingers off the gas, that's because the tanks don't roll very easily. (Steep slope maybe) So they don't generate very much back EMF, and it's all because the of the type gearboxes used in the models tanks from Armortek.
On wheeled models, a lot of ESC's use this Back EMF force to act as a " Electrical Brake" to the motors, injecting this energy into a reverse direction to slow the model when a reduction of power is applied, Sophisticated electronics' can do both regen and brake in various setups.

As long as your sensors and BMS for that matter are not too sensitive to expected Back EMF peaks you should be fine.

Ps, I wouldn't push a Armortek model tank, it could put your back out.
Disconnect the track and push it on the road wheels.

[Gerhard Michel]

Besides my Armortek Jagdpanther I'm using also some non-AT-tanks, and they all are equipped with smooth-running spur-gear motors. So the models can be pushed with one finger or towed by a simple rope! These motors then produce some EMF which flows back to the ESC. My ESC uses this effect for an efficient motor brake, controllable by a transmitter channel. I had no damage from this effect at any time till now!

Armortek's Spiradrives are nearly self-locking and don't need a motor brake effect by EMF, and so they don't produce EMF besides very short moments when stopping by R/C. But also motors with more EMF don't harm the ESC. Charging the battery by EMF is not a feature of my ESC, and only long downhill movements would cause a significant charging. I think we may forget those effects.....

[Jerry Carducci]

I agree with all of the comments. The core reason I posed this question was not as much for the sensors but rather for another component.

While testing the fpv video I encountered a complete failure of the OSD (on screen display and attached vtx (video transmitter). I initially thought only the OSD was impacted but it seems the VTX was as well. The exact series of events is murky at this point but the OSD is an inline component which feeds
power to the VTX. During my last test the OSD failed at some point. I did increase and decrease the motor power as part of the test and saw current demands as high as 8+ amps while the motor were running up and then taper when top speed was reached. I may have cut power abruptly at one point.
It was so unexpected that trying to play the events back in my mind, who knows? I'll assume it was one of the things I did and not do it again.

Not being sure what caused this I'm going to power the video resources separately and avoid the inline aspect. The normal full 24 volt supply is within the capability of these components as per their specifications but I'm uncertain about any feedback or spikes so to proceed the cautious (and less costly) route, separate sources it will be. I really do like the video feed!

Jerry

[Gian Marco Menozzi]

Hi Jerry,
regenerative charging requires dedicated electronics,
both the ESC and the BMS,
lithium batteries do not tolerate uncontrolled regenerative charges,
but we are talking about wheeled vehicles with strong acceleration/braking.
depending on the armortek ESC model,
some regenerative recharge may arrive,
with the first 2 series no (the 4QDs or those in the silver-colored aluminum container) are the only ones I have used,
in the Dimension Engineering Sabertooth ESCs it can be activated ,
I used some but not from Armortek,
bought directly from Dimensio Engineering (the smallest 12A version) I mounted them on a Stuart M5A1.
however don't worry, the regenerative recharge is very minimal on the Tanks.
We towed a Jagdtiger for over a kilometer and nothing happened, the batteries were flat .
Ciao
Marco
P.S.
if it's not a suitable ESC, the ESC prevents current from going from the motor to the battery

[Gian Marco Menozzi]

HI Jerry,
I read after posting the answer of the problems you had,
a simple system to block the regenerative current is to mount a 150/200 Ampere power diode at least 100 Volt,
between the ESC and the batteries,
taking the power supply from the other electronics directly on the batteries, t
hey are protected from extra voltages and extra currents,
specific anti-emi filters could also be used,
but I don't know if there are any ready for 24 Volts and high currents.
Ciao
Marco