Can I use my 3-phase e-bike motor as a generator with rectifier?

[magnusvr]

I'll try to keep it short! I want to DIY a 230v Gasoline Generator with pure sine output, to power my air-heat-inverter-pump thing, which peaks at 2500W@230v. I have a bunch of junk at home and I'm not afraid to get my hands dirty, I have and know how to use a welder, cabling sizes and proper connections, oscilloscope, Arduino etc. I work in server/compute/datacenter tech and have built electric gocarts and etc.
Where I live, we are expecting power cuts to be more common, and we have no heating other than electric. Modern urban house etc.
The Daikin heat exchanger/inverter is brand new state of the art, and I'd hate to risk it using anything but a controlled full Sine-wave inverter. So I was thinking that a Server UPS would be sweet. Doesn't get more professional that than, in terms of the inverter.

Countless people on Youtube have built very nice lawmower-powered-car-generator-generators with an expensive Inverter attached to them. Fine, but such an inverter is way out of budget for this project, since I hope and expect that I'll never have to use it. It's a fun project that I can actually justify to my wife, she likes the idea of having power.

So I thought I'd get a huge but cheap UPS and hook up to my bank of 12v batteries, and charge from the motor which drives tha Volvo Generator... great. Until I realized that the UPS's that size have their batteries in serial, runnung 72 or 192 volts... Hm. So I need to charge/run them at 72 volts while the UPS is also consuming the same power, using the batteries as a buffer if I momentarily exceed what the mowerengine/generator can generate.

I have at my disposal:
* 5.5 HP lawnmower engine that runs great, but the rest of the mower expired.
* 12 x 12v, 12 Ah AGM UPS batteries from a previous project.
* 12 (14.5?) volt car generator, 140Amp, from a Volvo S80.
* A compressor that leaks air, but with a good 240v single phase motor (2500Watt?) (I'm in Europe). Can that motor be used as a genny? I don't think so?)
* A 24-72 volt 3000Watt Brushless E-bike type motor, new in box. Also from abandoned project. Can that be used with some sort of controller/rectifier? That would be awesome since it's 72 volt.

Can get for no och few money:
* APC UPS, 6000XL (6000 VA) one-phase with bad batteries. It takes 16 x 5Ah in 192v batterypack, and the current one is dead..
* Eaton 3000 UPS (~2800W peak), which I believe has 72 volt packs. This would be the best with my current battery stock.

Crazy but feasible ideas welcome. TIA!
Magnus, Sweden

 

[magnusvr]

Hi,
I have a brand new e-bike/gocart chinese motorkit left over from a project. It's up to 72 volts 3000W and has a controller for using it as a motor. Like this one:
https://www.aliexpress.com/item/1005004224314512.html?spm=a2g0o.productlist.main.3.693f6d375vhtpV&algo_pvid=3eae79f1-de72-404b-b850-7104b9ce2d40&algo_exp_id=3eae79f1-de72-404b-b850-7104b9ce2d40-1&pdp_ext_f=%7B%22sku_id%22%3A%2212000028444787150%22%7D&pdp_npi=2%40dis%21USD%21304.05%21212.84%21%21%21%21%21%402102110316724235386583200d06fe%2112000028444787150%21sea&curPageLogUid=wYdtUoMWs2OF

Can I "just" get a "MDS200A 3-Phase Diode Bridge Rectifier 200A Amp 1600V" from Ebay, and couple it to my 72 volt battery bank made up of 12v AGM batteries?

Or is that type of motor not effective as a generator?

The full plan is to simultaneously hook said battery bank up to a UPS that uses 72v battery banks, and both charge the batteries and power the UPS in order to get the inverter function of the UPS.

Thanks,
Magnus

 

[eee291]

You would need a charge controller that limits the current/voltage as well, and perhaps boost the voltage in case it doesn't reach 80V+.
The easier way would be to just connect a programmable 72V BLDC controller to it.
With it, you can limit current, voltage and even charge when the motor is turning very slowly (this is less efficient though)

 

[CONSIDERABLE SHOUTING]

First, look at the specs on the motors for the compressor and e-bike motor to see what their working RPM is; it's very possible their working RPM for ~80 volts is higher than what your lawnmower engine can physically do. Try to find it's working RPM and redline as well, you want it in a happy range.

That S80 Alternator is likely useless for the project unless there's something unique about it's rectifier.

The Low-Tech Magazine may have some insight into building a generator as well. I'm afraid that's the extent of the knowledge I can offer.

 

[amberwolf]

First, look at the specs on the motors for the compressor and e-bike motor to see what their working RPM is; it's very possible their working RPM for ~80 volts is higher than what your lawnmower engine can physically do. Try to find it's working RPM and redline as well, you want it in a happy range.

Belt and pulleys or chain and sprockets, change ratio as needed.

 

[crossbreak]

There are ready made generator controllers exactly for this pupose. Have a look here: https://dcautogen.com/product/v7-autogen-auto-start-generator-controller/