PSU's cutting out on motor reverse, now dead

Ever since I first made my rig over a year ago, the PSU's have tended to lose power when the motion of the motors became more violent... mostly due to quick motor direction changes (afaict). I believe this to be one of the protections offered by these psu's. I have two of these 24v 25a psu's driving 2x IBT2's, driving 2x 24v 75rpm 250w wheelchair motors from ali. CTC was around 55mm.



Very rarely if ever did I experience these conditions in flight however. Only when using the manual slider in SMC3, which is kinda jumpy if you know what I mean, or using the "motion" mode, which is quite violent.

If you've seen my other thread about bumpy motion, I've be redesigning the drive system to a rack and pinion system to try to smooth out the motion by allowing the motor to use more degrees of rotation. However, even without load, I'm noticing that the PSU's have been experiencing this power loss much more often. One motor did it just in the SMC3 sine wave, the other motor did it with the sine wave if I pushed down on the rack (creating a load) while it was descending. Strangely it tended to cut out only when I pushed in the direction of the movement, and not against.

EDIT: I also noticed when I ran a sine wave in Flypt, the motors would be fine if the sine wave was very slow and shallow. However, if I decreased the period of the wave, at some point, one of the psu's would start losing power and result in motion in the video posted at the bottom of this post.

My initial thought was I'm pulling more amps than the psu can provide, so I bought a TRMS clamp meter. The "poorer" motor was showing no more than 5 amps with me pushing against the motor with my hand. The "better" motor is only showing 3 amps. The motors are too powerful for me to stall them with my hand so I don't know the stall current. But considering these PSU's are 25a, and the power-off is during motion, I can't imagine that's the actual problem.

I think (not know) the problem might be worse now because the motor is running at a higher rpm (much shorter "CTC" of about 17mm but using a gear instead of a lever) than before and takes longer to stop and reverse direction.

Yesterday I was trying to get different amp readings and ended up frying both PSU's (not at the same time). I had already ordered 50a versions that will be here Tuesday, but after seeing how little current is even under load, I'm thinking these won't change anything.

How likely is it that this is back EMF? Or could my ibt2's be damaged? Or the motors? How would I know? I swapped one ibt2 out with an extra one I had but no change. Not sure how to proceed. My electronic knowledge is insufficient unfortunately. I've been reading a bit about the basics but not sure it's helping me in a practical way yet.

This is a video of the worse motor that was pulling 5a before the psu failed. This is supposed to be a sine wave in smc3, but notice it gets to the ends of the wave and lose power and backs up a ways, coasting to a stop, before regaining power and continuing. I'd not seen this behavior before. The other motor wasn't behaving this way yet, but did at the end right before its psu died.

https://youtube.com/shorts/_4x6mbRrKhI

EDIT: Also, I purchased one of the 100A ebay controllers mentioned on another thread and it'll be here at some point. I'm just trying to prevent damaging more electronics!

I can recommend reading this thread: https://www.xsimulator.net/communit...-reverse-curreng-regenerative-breaking.19060/

That was a good read and sounds like exactly my problem. My gears do not want to stop when I move them by hand, like the friction motor monster truck toys that you wind up and let go. They seem to take as much energy to get them to stop as to start when I'm manually moving the rack (or ctc lever). I'm sad that Ronan didn't come come back with the results of the LED test.

So the reason to use batteries instead of rectifier diodes is that the battery actually absorbs the energy safely, whereas the rectifier just blocks it from going into the PSU, leaving the driver to "deal with it" which would eventually damage the driver? Could I not use a capacitor instead of a battery? Trying to save space and money...

Yes, exactly.

A normal electrolytic capacitor like those used in the power supplies (several 1000µF) is not sufficient. It has to store energy in the range around 100J or more. A supercapacitor like those used to buffer big car audio systems could work. But they are equally expensive as a (new) battery.

You can take a used car battery. Even old ones that don't have enough power to start the engine in winter are still good enough.

Use diode KBPC5010
Power supply 24V connect to both AC pin , + pin KBPC5010 connect to + motor driver, - pin KBPC5010 not used

Does Amp hour matter much? How about a

24V 6Ah Rechargeable Lifepo4 Battery Pack Built-in 6A BMS, 2000+ Deep Cycle Lithium Iron Phosphate Battery

Would that work? Should I use this in conjunction with the diode or is that even necessary with the battery?

Final question (hopefully), how do I hook the battery up? Across the psu +/- terminals (parallel?)?

PSU + to battery -, battery + to PSU -, and then battery + to driver + and battery - to driver - ?

EDIT: Oops, just noticed that battery can only do 6A... but if it was, say, 25A, would tat work? Or does the amp not matter because the battery doesn't need to drive the motor? Although my ammeter only showed a max of 5a with a partial load, but I'm not sure how accurate that is.

What is the second red wire connected to the second AC pin? Another output with the same polarity? Why would that be used?

yes, from the power supply connect 2 times the power supply to the AC pin

I doubt it would work. Those LiFePo batteries have an internal battery management system to protect the battery. So it has to limit voltage and current and that's not what we want. A "good old" lead acid battery can take a lot of abuse. If the PSU voltage is in the range of 12 to 13V it self-regulates and can run in parallel to the driver without further protection (except for a fuse).

If the voltage never goes above what the PSU can take (usually there are caps rated 16V) the diode is no longer necessary.

It's a 24V system, a 12v battery would still work?

Ah, no. You need 2 of them, of course. Sorry

So would this be the proper way to connect? And I believe I read in the other post that I won't need a fuse if the PSU amperage is close to the motor's stall current?

I updated the diagram to include the rectifier... could you please let me know if this is correct? I have all the components and am ready to assemble and test, but I want to make sure I don't blow something up. Does it matter which side of the PSU the diode is on?

Got impatient and gave it the ole' college try. Everything is working! Now to strap the other motor back on and rig up some push rods.