Hey all! I’ve read that standard switching power supplies - the kind you might buy on Amazon to power regular ol’ projects - aren’t well-suited for powering motors. From other threads, it seems like the best power supply depends on the exact needs of your motor setup. So, here’s mine - I’d like to power:
two 6.5" hoverboard motors
running at 48V
I’d like to push these to the absolute limit (tons of cooling!)
Does anyone have any recommendations specifically for these wonderful hoverboard motors? Thank you!
At that power range you’re not getting anything but switched supplys. How big are the motors, what is their power rating? From memory, those kinds of motors are 2-3kw each. Which would mean a psu around 4-5kw if you want full power, and 3-phase power since single phase isn’t enough. I don’t know if odrive can handle that much current.
Odrive can handle this.
48v*100a=4.8kw
You can get (at least where I am, germany) server psu’s for hp servers. They have up to 1.2kw at 12v.
Take 4 of them in series. They cost ~20€ each
Fantastic! That’s a crazy amount of power. Will the server PSU’s tolerate the 48v, or are they unhappy about it? If possible, do you have a link to the ones you buy? Thanks so much!
There are also other server PSUs, but they are rare in germany. Make sure, that you isolate the chassis from each other and don’t cause any other short.
Just an example. If you buy used, they can be even cheaper. They are highly reliable and can supply their power for long time. I’ve ordered my odrive but it hasn’t arrived yet. I’m going to use a high power lab bench psu for testing and 2 of those in series. In theorie, you could also use them in parell, but that’s not safe. They also usually have a second 12v rail.
But I’m not sure if they need an external signal to power up, but shouldn’t be a problem.
One thing is that you may need to dissable your grounding, which can be dangerous. You need to figgure that you when they arrive. You can also try isolating the case from negative supply or remove the case. It’s dangerous, but cheap can’t be safe.
Edir: looked it up and it can be kinda dangerous, so own risk and supply might blow up. You may need to do some research, but you need to do some things that compromise your safety, I just say it’s possible.
Please don’t go messing with power supplies and using them in ways they were not intended to. Get a good 48V old telco power supply from eBay. They were rated for that kind of power and there’s no dodgy chaining required. or at least get good PSUs that were designed for running in parallel or series. Playing with them can be dangerous and can get you killed in the worst case.
If you need to spend money, spend it on power supplies.
The board can handle it but you need to make sure your connectors can handle that too. Also a single EU phase is 230*16A = 3680W. That’s all you can get and even then, you need to make sure the wiring and connectors can actually handle that(in the board as well as in the walls of your house).
And please don’t mess with the grounding of your electrical devices.
Have done research and you have to disconnect the DC ground from the case. That’s much safer. The power supplies probably won’t be damaged, because the drop across each supply is only the rated 12V. They also can’t start to oscillate, because they can only monitor the voltage difference accross their own 12v. Just be aware that there are big cappacitors that need to be discharged.
I will do sth quite simillar, but only 2 for 24v 2400w.
Guys, as @Roiki1 said, it’s not a good idea to modify a high power PSU unless you know exactly what you are doing (i.e. you can read and understand the schematic, layout and firmware or are experienced enough to make an educated guess at it) and/or you are able to take very robust safety measures (e.g. you have a concrete blockhouse to test it in, in case it explodes and spits flames)
Two power supplies which are only designed for single operation with one side connected to ground, may go very wrong when modified to work in series. You might find that there are parts on the schematic that are still referenced to ground, and these parts end up exceeding their voltage rating and failing spectacularly. Or, you might find that there is actually some leakage between the mains supply and the output, and that the grounding of the negative output was actually there to prevent the output floating to +/- 220V, destroying any equipment and/or bodgers connected to it.
You may also find that the voltage output becomes unstable with certain loads.
It’s also very unlikely that you actually need this amount of power on your DC Bus. In nearly all cases, the DC Bus supply current is much LOWER than the motor output current. See my other post on the subject: Motor overvoltage and PSU sizing